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1.
  • Gross, C. P., et al. (författare)
  • The biogeography of community assembly: latitude and predation drive variation in community trait distribution in a guild of epifaunal crustaceans
  • 2022
  • Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2954 .- 0962-8452. ; 289:1969
  • Tidskriftsartikel (refereegranskat)abstract
    • While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.
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2.
  • Reynolds, P., et al. (författare)
  • Latitude, temperature and habitat complexity predict predation pressure in eelgrass beds across the Northern Hemisphere
  • 2018
  • Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 99:1, s. 29-35
  • Tidskriftsartikel (refereegranskat)abstract
    • Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 370 of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas in situ water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simple increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.
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3.
  • Alonso Aller, Elisa, 1984- (författare)
  • Effects of Marine Protected Areas on Tropical Seagrass Ecosystems
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Seagrass beds are highly productive coastal ecosystems that sustain a rich and diverse associated fauna and flora. Increasing anthropogenic pressures threaten seagrass ecosystems and have already led to major seagrass losses across the world. Marine Protected Areas (MPAs) have become one of the key strategies to manage coastal ecosystems and associated resources worldwide and have been often shown to successfully protect marine ecosystems. However, relatively few studies have assessed the effects of MPAs on seagrass ecosystems, and there are indications that MPAs may not be able to fully protect seagrasses, especially from disturbances originating outside their boundaries. Within this context, this thesis aimed to investigate the direct and indirect effects (those mediated by biotic interactions) of MPAs on tropical seagrasses, associated fish communities, and ecosystem processes.The thesis consists of three parts. First, we used 10-years of seagrass monitoring data within a MPA to evaluate the temporal variability in seagrass cover and species composition in relation to changes in environmental conditions (Paper I). Second, we investigated the potential of MPAs to enhance the temporal stability of seagrass ecosystems using a 10-month field study. We surveyed seagrass-associated fish communities (Paper II) and estimated seagrass growth and herbivory rates (Paper III) during three different seasons within MPAs and unprotected sites. Finally, to evaluate the effects of MPAs and land-use on seagrass ecosystems we surveyed seagrass species and trait composition within government-managed MPAs, community-managed MPAs, and unprotected sites (Paper IV).The seagrass bed monitored in Paper I showed a high temporal and spatial variability, with a temporal decline in cover and change in species composition, followed by a period of recovery. This pattern could not be associated with any of the climate and tidal variables considered, suggesting that potential drivers of decline may have originated outside MPA boundaries. The results from the seasonal field study showed that MPAs increased the temporal stability of seagrass-associated fish communities, particularly juvenile fish (Paper II), and strengthened a positive link between herbivorous fish, herbivory rates, and seagrass growth (Paper III), suggesting the presence of a positive feedback that promotes stability. Finally, MPAs affected seagrass species and trait composition (by selecting for more stress-sensitive species) but did not seem to be able to protect seagrasses from land-use effects, with seagrasses showing similar changes in species and trait composition within and outside MPAs (Paper IV). Considering these results, this thesis builds to a body of literature indicating that MPAs alone may not be sufficient to protect seagrass ecosystems and that improved management strategies may be necessary to preserve these important coastal habitats.
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4.
  • Alonso Aller, Elisa, et al. (författare)
  • Fishing weakens a positive link between herbivore abundance and plant growth in tropical seagrass beds
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Herbivory is a key process influencing the structure and function of both terrestrial and aquatic systems. In seagrass ecosystems, moderate levels of herbivory may stimulate plant growth, compensating for the loss of eaten tissue. However, the relationship between herbivory and seagrass growth can be influenced by an array of factors, such as seasonality, herbivore abundance, and presence of epiphytes, many of which can be directly or indirectly affected by human activities like fishing. Here, we used data from a multi-season field survey in fished and protected seagrass beds to assess how fishing and seasonality affect the link between herbivores, herbivory, and plant growth in seagrasses. Path analyses revealed an interactive effect of seasonality and protection. In protected seagrass beds, seasonally high herbivore abundance positively affected herbivory rates, which in turn enhanced seagrass growth. This link was however not apparent in seagrass beds subjected to fishing activities. At the same time, seasonality effects seemed stronger in fished areas, suggesting that in addition to weakening a positive herbivory-plant growth interaction, fishing increases temporal instability of ecosystems. Our results highlight the need for evaluating not only the direct effects of fisheries exploitation on fish populations, but also the potential indirect effects on ecosystems, to improve fisheries management.
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5.
  • Alonso Aller, Elisa, et al. (författare)
  • Marine protected areas increase temporal stability of community structure, but not density or diversity, of tropical seagrass fish communities
  • 2017
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Marine protected areas (MPAs) have been shown to increase long-term temporal stability of fish communities and enhance ecosystem resilience to anthropogenic disturbance. Yet, the potential ability of MPAs to buffer effects of environmental variability at shorter time scales remains widely unknown. In the tropics, the yearly monsoon cycle is a major natural force affecting marine organisms in tropical regions, and its timing and severity are predicted to change over the coming century, with potentially severe effects on marine organisms, ecosystems and ecosystem services. Here, we assessed the ability of MPAs to buffer effects of monsoon seasonality on seagrass-associated fish communities, using a field survey in two MPAs (no-take zones) and two unprotected (open-access) sites around Zanzibar (Tanzania). We assessed the temporal stability of fish density and community structure within and outside MPAs during three monsoon seasons in 2014-2015, and investigated several possible mechanisms that could regulate temporal stability. Our results show that MPAs did not affect fish density and diversity, but that juvenile fish densities were temporally more stable within MPAs. Second, fish community structure was more stable within MPAs for juvenile and adult fish, but not for subadult fish or the total fish community. Third, the observed effects may be due to a combination of direct and indirect (seagrass-mediated) effects of seasonality and, potentially, fluctuating fishing pressure outside MPAs. In summary, these MPAs may not have the ability to enhance fish density and diversity and to buffer effects of monsoon seasonality on the whole fish community. However, they may increase the temporal stability of certain groups, such as juvenile fish. Consequently, our results question whether MPAs play a general role in the maintenance of biodiversity and ecosystem functioning under changing environmental conditions in tropical seagrass fish communities.
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6.
  • Alonso Aller, Elisa, et al. (författare)
  • Monitoring of a protected multi-specific tropical seagrass meadow reveals a pattern of decline and recovery
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • In a changing environment, there is an increasing interest to monitor ecosystems to understand their responses to environmental change. Seagrass meadows are highly important ecosystems, but at the same time they are under a constant threat from human activities, as well as climate impacts, and marked declines have been observed worldwide. Despite increasing efforts, monitoring of multi-specific tropical seagrass meadows is scarce, particularly in developing regions. Here we analysed data from the first 10 years of a monitoring programme in a marine protected area in Zanzibar (Tanzania) to assess temporal changes in seagrass cover and species composition and to detect potential drivers of change. The seagrass meadow experienced a strong gradual decline in seagrass cover and changes in species composition, followed by a period of recovery. However, the timing and length of these temporal patterns varied in space (between transects). Of the climate variables considered, cloud cover, temperature, storm occurrence, sunspot activity and the height of the diurnal low tide seemed to influence seagrass cover, although only to a small extent, suggesting that the monitored seagrass meadow may be influenced by other unmeasured factors. Considering our results, seagrass meadows seem to be highly dynamic at small spatial scales even in the absence of major local anthropogenic impacts. Further monitoring programmes should be developed in the region to gain a better understanding of seagrass temporal variability and causes of change.
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7.
  • Alonso Aller, Elisa, et al. (författare)
  • Single and joint effects of regional- and local-scale variables on tropical seagrass fish assemblages
  • 2014
  • Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 161:10, s. 2395-2405
  • Tidskriftsartikel (refereegranskat)abstract
    • Seagrass beds are highly important for tropical ecosystems by supporting abundant and diverse fish assemblages that form the basis for artisanal fisheries. Although a number of local- and regional-scale variables are known to influence the abundance, diversity and assemblage structure of seagrass-associated fish assemblages, few studies have evaluated the relative and joint (interacting) influences of variables, especially those acting at different scales. Here, we examined the relative importance of local- and regional-scale factors structuring seagrass-associated fish assemblages, using a field survey in six seagrass (Thalassodendron ciliatum) areas around Unguja Island (Zanzibar, Tanzania). Fish density and assemblage structure were mostly affected by two regional-scale variables; distance to coral reefs, which positively affected fish density, and level of human development, which negatively affected fish density. On the local scale, seagrass biomass had a positive (but weaker) influence on fish density. However, the positive effect of seagrass biomass decreased with increasing level of human development. In summary, our results highlight the importance of assessing how multiple local and regional variables, alone and together, influence fish communities, in order to improve management of seagrass ecosystems and their services.
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8.
  • Alonso Aller, Elisa, et al. (författare)
  • Temporal variability of a protected multispecific tropical seagrass meadow in response to environmental change
  • 2019
  • Ingår i: Environmental Monitoring and Assessment. - : Springer Science and Business Media LLC. - 0167-6369 .- 1573-2959. ; 191
  • Tidskriftsartikel (refereegranskat)abstract
    • In a changing environment, there is an increasing interest to monitor ecosystems to understand their responses to environmental change. Seagrass meadows are highly important ecosystems that are under constant pressure from human activities and climate impacts, with marked declines observed worldwide. Despite increasing efforts, monitoring of multispecific tropical seagrass meadows is scarce, particularly in low-income regions. Based on data from a monitoring programme in a marine protected area in Zanzibar (Tanzania), we assessed temporal changes in seagrass cover and species composition during a 10-year period in relation to local variability in environmental variables. We observed a strong, gradual decline in seagrass cover and changes in species composition, followed by a period of recovery. However, the timing and length of these temporal patterns varied in space (between transects). Multiple environmental variables—cloud cover, temperature, storm occurrence, sunspot activity, and tidal amplitude and height—influenced seagrass cover, although only to a minor extent, suggesting that the monitored seagrass meadow may be influenced by other unmeasured factors (e.g. water currents and sediment movement). Our results show that seagrass meadows can be highly dynamic at small (10–50m) spatial scales, even in the absence of major local anthropogenic impacts. Our findings suggest that high-resolution monitoring programmes can be highly valuable for the detection of temporal changes in multispecific seagrass meadows; however, to understand the causes of change, there is a need of long-term (> 10years) data series that include direct measurements of environmental variables and extreme events.
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9.
  • Alsterberg, Christian, 1982, et al. (författare)
  • Consumers mediate the effects of experimental ocean acidification and warming on primary producers.
  • 2013
  • Ingår i: Proceedings of the National Academy of Science of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 110:21, s. 8603-8608
  • Tidskriftsartikel (refereegranskat)abstract
    • It is well known that ocean acidification can have profound impacts on marine organisms. However, we know little about the direct and indirect effects of ocean acidification and also how these effects interact with other features of environmental change such as warming and declining consumer pressure. In this study, we tested whether the presence of consumers (invertebrate mesograzers) influenced the interactive effects of ocean acidification and warming on benthic microalgae in a seagrass community mesocosm experiment. Net effects of acidification and warming on benthic microalgal biomass and production, as assessed by analysis of variance, were relatively weak regardless of grazer presence. However, partitioning these net effects into direct and indirect effects using structural equation modeling revealed several strong relationships. In the absence of grazers, benthic microalgae were negatively and indirectly affected by sediment-associated microalgal grazers and macroalgal shading, but directly and positively affected by acidification and warming. Combining indirect and direct effects yielded no or weak net effects. In the presence of grazers, almost all direct and indirect climate effects were nonsignificant. Our analyses highlight that (i) indirect effects of climate change may be at least as strong as direct effects, (ii) grazers are crucial in mediating these effects, and (iii) effects of ocean acidification may be apparent only through indirect effects and in combination with other variables (e.g., warming). These findings highlight the importance of experimental designs and statistical analyses that allow us to separate and quantify the direct and indirect effects of multiple climate variables on natural communities.
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10.
  • Ammar, Yosr, 1992- (författare)
  • Novelty in social-ecological systems: understanding the past to plan the future
  • 2020
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Human activities are shaping the Earth system and creating novel properties in the intertwined Social-Ecological Systems (SES). Although novelty is acknowledged in SES theories, the concept of novelty is not well understood, and little mathematical formalization and empirical foundations have been made. Building on the theoretical frameworks of Complex Adaptive Systems (CAS) and concepts of novelty in ecology, this licentiate thesis suggests a first attempt to quantify novelty in a marine ecosystem, in a SES context. Here, I focus on the past emergence of novelty in a marine SES to better understand when and where novelty has emerged and which drivers affect this emergence. Novelty emerges in a CAS when it has moved beyond its historical range of variation. The historical state depends on the temporal and spatial scale as well as the context of the study. Building on the characteristics of CAS, novelty is multidimensional, emerges on a continuum, can be nonlinear, and follows baseline specific trajectories. It has been quantified as the degree of dissimilarity of a system relative to a specific baseline. I used the case of the Baltic Sea SES, where long-term data exists, and many ecological, political, and economic changes have been recorded. Here, I focus on structural changes of the system rather than interactions and feedbacks. Paper 1 focuses on the ecological novelty in the Baltic Sea and contributes as the first study that quantifies novelty in marine ecosystems and across different trophic levels. Results reveal that over the 35-year study-period (1980-2015), novelty has emerged following the pattern of change, but at a slower pace. It has emerged in complex temporal and spatial pattern of the tested abiotic and biotic components. Both abiotic and biotic novelty showed a higher rate of novelty in confined northern basins than in the Central Baltic Sea, which indicated that some areas are more susceptible to the rise of novelty than others. Temperature and salinity were identified as the main abiotic drivers of biotic novelty in the Baltic Sea. Paper 2 contributes as the first study to quantify socio-economic novelty in a marine SES. Socio-economic novelty in the Baltic Sea showed a change in the contribution to novelty from factors linked to local and regional management levels, i.e., fishing gears and commercial groups, to trades which are linked to international level. A high increase in imports and exports in recent years marked the fastest increase in novelty over the period studied. In the latter, novelty in terms of economic value of fishery products was higher than their novelty in quantity. Sweden, Denmark, and Poland have been the countries contributing most to the emergence of novelty in the studied period. This paper illustrates that understanding socio-economic novelty together with ecological novelty, may provide a better understanding of the complexity of marine SES. Although not all the characteristics of CAS could be captured by the methodological approach used in Paper 1 and 2, many have been identified and considered. However, this highlights the need for more methods that can capture different characteristics of CAS, such as interactions and feedbacks, and more knowledge on the emergence of novelty in SES. Understanding how novelty emerges, its processes in different SES components and across-scales, may reduce the risk of missing opportunities for biodiversity conservation, and of unintended management outcomes for long-term sustainability.
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11.
  • Austin, Åsa, 1988- (författare)
  • Aquatic vegetation in coastal ecosystems : The role of biotic interactions and environmental change for ecosystem functions and resilience in the Baltic Sea
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Coastal ecosystems are among the most productive on Earth but subjected to many human pressures. In shallow coastal areas, aquatic vegetation constitutes foundation species that sustain secondary production and act as a nutrient filter, which may buffer human impacts. But little is known about how anthropogenic factors alter biotic interactions in aquatic vegetation, and how these changes affect ecosystem functions and resilience.The aim of this thesis was to investigate how natural and anthropogenic factors alter aquatic vegetation communities and biotic interactions, and how these in turn affect ecosystem functions and resilience to common stressors. Shallow coastal bays in the Baltic Sea were used as model system. A large field survey was conducted to investigate effects of natural and anthropogenic gradients, including bay topographic openness and nutrient runoff, on vegetation communities and ecosystem functions. Results suggest that high vegetation cover can improve water clarity, whereas sediment-driven turbidity can negatively affect vegetation by decreasing the light penetration of the water (Paper I). This dual relationship indicates the potential for two alternative, self-sustaining states in shallow bays; with or without vegetation.Using data from the same survey I investigated the influence of species richness and cover of rooted aquatic vegetation and drift wrack (Fucus vesiculosus), for ecosystem multifunctionality (MF) (Paper II). MF was estimated as the mean of four variables used as proxies for key functions; large predatory fish recruitment, grazer biomass, inverted ‘nuisance’ algal biomass and water clarity. MF was highest when the two functionally different vegetation types (rooted and drifting) co-occurred at high covers, and high species richness increased multifunctionality by increasing rooted vegetation cover.To understand in greater detail if and how interactions within and between vegetation species mediate the effects of environmental change, I conducted two experiments. First, a cage experiment to test if intraspecific plant facilitation may buffer effects of altered top-down and bottom-up control (Paper III), then a mesocosm experiment to test if shading alters interspecific interactions between three common plant species (Paper IV). The cage experiment showed that high shoot density of a common plant (Myriophyllum spicatum) increased individual shoot performance, but only when subjected to both fertilization and large predatory fish exclusion (Paper III). The mesocosm experiment showed that individual species’ traits had stronger effect than shading on interspecific competition and community yield (Paper IV).In conclusion, my thesis shows that single and multiple ecosystem functions benefit from high vegetation cover, with direct and indirect effects of diversity, but are sensitive to anthropogenic stressors (Papers I, II). Further, shading alters biotic interactions among vegetation species in a eutrophic coastal ecosystem by increasing the competitive advantage of dominant species (Paper IV), while intraspecific facilitation increases resilience to interacting stressors (Paper III). Together, the results highlight the need for ecosystem-based management where efforts to reduce anthropogenic influence (e.g. by nutrient reduction and fishing restrictions) are combined with improved protection and restoration of the ecologically and economically valuable aquatic vegetation communities.
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12.
  • Austin, Åsa N., et al. (författare)
  • Relationships between aquatic vegetation and water turbidity : A field survey across seasons and spatial scales
  • 2017
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Field surveys often show that high water turbidity limits cover of aquatic vegetation, while many small-scale experiments show that vegetation can reduce turbidity by decreasing water flow, stabilizing sediments, and competing with phytoplankton for nutrients. Here we bridged these two views by exploring the direction and strength of causal relationships between aquatic vegetation and turbidity across seasons (spring and late summer) and spatial scales (local and regional), using causal modeling based on data from a field survey along the central Swedish Baltic Sea coast. The two best-fitting regional-scale models both suggested that in spring, high cover of vegetation reduces water turbidity. In summer, the relationships differed between the two models; in the first model high vegetation cover reduced turbidity; while in the second model reduction of summer turbidity by high vegetation cover in spring had a positive effect on summer vegetation which suggests a positive feedback of vegetation on itself. Nitrogen load had a positive effect on turbidity in both seasons, which was comparable in strength to the effect of vegetation on turbidity. To assess whether the effect of vegetation was primarily caused by sediment stabilization or a reduction of phytoplankton, we also tested models where turbidity was replaced by phytoplankton fluorescence or sediment-driven turbidity. The best-fitting regional-scale models suggested that high sediment-driven turbidity in spring reduces vegetation cover in summer, which in turn has a negative effect on sediment-driven turbidity in summer, indicating a potential positive feedback of sediment-driven turbidity on itself. Using data at the local scale, few relationships were significant, likely due to the influence of unmeasured variables and/or spatial heterogeneity. In summary, causal modeling based on data from a large-scale field survey suggested that aquatic vegetation can reduce turbidity at regional scales, and that high vegetation cover vs. high sediment-driven turbidity may represent two self-enhancing, alternative states of shallow bay ecosystems.
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13.
  • Austin, Åsa N., 1988-, et al. (författare)
  • Stronger effect of individual species’ traits than shading on aquatic plant community productivity and interspecific competition
  • 2023
  • Ingår i: Aquatic Botany. - : Elsevier BV. - 0304-3770 .- 1879-1522. ; 187
  • Tidskriftsartikel (refereegranskat)abstract
    • Competition is one of the major factors structuring plant communities. Species with similar traits generally compete more intensely and have more similar yield than functionally dissimilar species, which often respond differently to environmental change. Little is known about how the interacting species’ traits influence the effect of environmental change on interspecific competition. However, theory predicts that environmental change should lead to more asymmetric competition, by favouring the species best adapted to the particular environmental change. Here we used a mesocosm experiment with three common aquatic plant species from the Baltic Sea (Northern Europe), to test how community productivity and competition asymmetry were affected by functional dissimilarity, individual species’ traits and a common stressor: shading. Competition asymmetry was defined as the absolute difference in reductions in yield relative to monocultures of two interacting species. Community productivity decreased and competition asymmetry increased with functional dissimilarity of the interacting species, possibly explained by the traits of the superior species, which had higher specific leaf area, maximum canopy height and primary production rate than the subordinate species. Community productivity was not affected by shading, contrary to our expectation, while competition asymmetry was higher in shaded than ambient conditions. Individual species yield depended on species identity and species combination. Only the shortest species was negatively affected by shading. Thus, by favouring tall-growing species, shading can alter interspecific competition. Together, these findings suggest that non-random species loss following environmental change can be caused by competitive exclusion, in addition to a direct effect of abiotic filtering.
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14.
  • Austin, Åsa N., et al. (författare)
  • Synergistic Effects of Rooted Aquatic Vegetation and Drift Wrack on Ecosystem Multifunctionality
  • 2021
  • Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 24:7, s. 1670-1686
  • Tidskriftsartikel (refereegranskat)abstract
    • Ecosystem multifunctionality is an increasingly popular concept used to approximate multifaceted ecosystem functioning, which in turn may help advance ecosystem-based management. However, while experimental studies have shown a positive effect of diversity on multifunctionality, observational studies from natural systems-particularly aquatic-are scarce. Here, we tested the relative importance of species richness and cover of rooted aquatic vegetation, as well as cover of the loose-lying form of the macroalgae bladderwrack (Fucus vesiculosus), for ecosystem multifunctionality in shallow bays along the western Baltic Sea coast. We estimated multifunctionality based on four indicators of functions that support ecosystem services: recruitment of large predatory fish, grazer biomass, inverted 'nuisance' algal biomass, and water clarity. Piecewise path analysis showed that multifunctionality was driven by high cover of rooted aquatic vegetation and bladderwrack, particularly when the two co-occurred. This synergistic effect was nearly three times as strong as a negative effect of land-derived nitrogen loading. Species richness of aquatic vegetation indirectly benefitted multifunctionality by increasing vegetation cover. Meanwhile, high bladderwrack cover tended to decrease vegetation species richness, indicating that bladderwrack has both positive and negative effects on multifunctionality. We conclude that managing for dense and diverse vegetation assemblages may mitigate effects of anthropogenic pressures (for example, eutrophication) and support healthy coastal ecosystems that provide a range of benefits. To balance the exploitation of coastal ecosystems and maintain their multiple processes and services, management therefore needs to go beyond estimation of vegetation cover and consider the diversity and functional types of aquatic vegetation.
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15.
  • Bergström, Ulf, et al. (författare)
  • Inför fler fiskefria områden för att skydda bestånd och ekosystem
  • 2024
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Fiskefria områden kan vara ett effektivt verktyg för att skydda både fisk- och kräftdjursbestånd och marina ekosystem. Men det är viktigt att områdena utformas på rätt sätt och är tillräckligt stora. Lektidsfredade områden kan vara enklare att driva igenom, men ger inte lika goda effekter.
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16.
  • Chirico, Angelica A. D., et al. (författare)
  • Community- and government-managed marine protected areas increase fish size, biomass and potential value
  • 2017
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Government-managed marine protected areas (MPAs) can restore small fish stocks, but have been heavily criticized for excluding resource users and creating conflicts. A promising but less studied alternative are community-managed MPAs, where resource users are more involved in MPA design, implementation and enforcement. Here we evaluated effects of government-and community-managed MPAs on the density, size and biomass of seagrass- and coral reef-associated fish, using field surveys in Kenyan coastal lagoons. We also assessed protection effects on the potential monetary value of fish; a variable that increases non-linearly with fish body mass and is particularly important from a fishery perspective. We found that two recently established community MPAs (< 1 km(2) in size, <= 5 years of protection) harbored larger fish and greater total fish biomass than two fished (open access) areas, in both seagrass beds and coral reefs. As expected, protection effects were considerably stronger in the older and larger government MPAs. Importantly, across management and habitat types, the protection effect on the potential monetary value of the fish was much stronger than the effects on fish biomass and size (6.7 vs. 2.6 and 1.3 times higher value in community MPAs than in fished areas, respectively). This strong effect on potential value was partly explained by presence of larger (and therefore more valuable) individual fish, and partly by higher densities of high-value taxa (e.g. rabbitfish). In summary, we show that i) small and recently established community-managed MPAs can, just like larger and older government-managed MPAs, play an important role for local conservation of high-value fish, and that ii) these effects are equally strong in coral reefs as in seagrass beds; an important habitat too rarely included in formal management. Consequently, community-managed MPAs could benefit both coral reef and seagrass ecosystems and provide spillover of valuable fish to nearby fisheries.
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17.
  • Chirico, Angelica A. D., et al. (författare)
  • Effects of marine protected areas on inter- and intraspecific trait variability in tropical seagrass assemblages
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Marine ecosystems are under increasing human pressure and therefore in need of effective management. Marine protected areas (MPAs) can reduce the effects of local disturbances on habitat-forming benthic organisms like corals and seagrasses and are well-known to affect species composition. However, we know considerably less about their effects on organisms’ traits (physiological, morphological, and/or behavioural characteristics), which in turn dictate how organisms respond to stressors and influence ecosystem processes and services. We conducted a field survey along the Kenyan coast to assess the effects of MPAs on species and trait composition of seagrass assemblages; an important group of habitat-forming plants in shallow coastal areas that form the basis for multiple ecosystem services. We measured five morphological traits (shoot density, leaf length and width, number of leaves per shoot, and above:below-ground biomass ratio) on multispecies seagrass assemblages within government MPAs, community MPAs, and fished areas in three habitat zones (shallow, mid-lagoon and, reef). Using causal modelling (path analysis) of multivariate data, we found that MPAs influence seagrass species composition and, indirectly, trait composition in mid-lagoon areas. Meanwhile, there were no MPA effects in the shallow intertidal (potentially because of impacts from MPA-related tourism), and weak effects in the reef zone, presumably due to competition from corals. Finally, most of the MPA effects on overall seagrass trait composition were explained by species turnover, rather than phenotypic plasticity. In conclusion, MPAs appear to be an effective conservation tool for seagrass assemblages by reducing local disturbances and favouring seagrass species with certain traits, primarily in mid-lagoon areas. However, the lack of MPA effect in intertidal areas highlights the need for management approaches that regulate human impacts across the whole tropical coastal zone.
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18.
  • Chirico, Angelica, et al. (författare)
  • A marine protected area speeds up seagrass recovery and decreases sediment erosion following experimental disturbance
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Marine ecosystems subjected to human impacts are increasingly managed using marine protected areas (MPAs). MPAs have been suggested to not only benefit harvested species but also to increase ecosystem resilience (resistance to and/or recovery from disturbances), but this hypothesis has to our knowledge never been tested experimentally. Theory suggests that MPA effects on recovery from disturbance should be particularly important for recovery from large (vs. small) disturbances, because large disturbances generally increase the likelihood that local assemblages are pushed into alternative trajectories and do not recover. In this study we experimentally tested the effects of a no-take MPA on the recovery of seagrasses from experimental small-scale disturbance (clearings of two sizes; 0.25 and 1m2) in coastal Kenya. There was a faster seagrass recovery and less sediment erosion within the MPA than in three reference sites. Moreover, small clearings recovered faster than large clearings in terms of sediment erosion, but there was no such size effect on seagrass cover. These MPA effects were relatively weak, dissipated over time and were not detectable after 2 years. In summary, this study supports the hypothesis that MPAs can increase recovery from disturbance, and hence ecosystem resilience, but the relatively weak and dissipating effects emphasize the need for more and large-scale studies critically assessing the relationship between MPAs and ecosystem resilience.
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19.
  • Chirico, Angelica, 1982- (författare)
  • Effects of community- and government-managed marine protected areas on tropical seagrass and coral communities
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Tropical seagrass beds and coral reefs are among the most productive and diverse ecosystems on Earth and provide ecosystem services, such as fish production and coastal protection, and support livelihoods of millions of people. At the same time, these ecosystems are threatened globally by anthropogenic disturbances, such as overfishing, pollution and global warming. Implementation of marine protected areas (MPAs) is one of the main strategy to achieve conservation goals and has proven to restore biodiversity and fish stocks, at least on coral reefs. However, studies assessing protection effects on seagrass communities are scarce. Moreover, many MPAs are government-managed and increasingly criticized for excluding and marginalizing local communities. Therefore, MPAs that are managed by the communities themselves, i.e. community-managed MPAs, constitute a promising yet poorly studied alternative.The aim of this thesis was to investigate ecological effects of government- and community-managed MPAs on seagrasses, corals, and their associated benthic and fish communities in the tropical seascape. We used a space-for-time replacement approach and surveyed coral and seagrass communities in fished areas, recently established community MPAs (1-6 years of protection) and old government MPAs (20-44 years) in coastal Kenya, East Africa. Results suggest that only a few years of protection in community MPAs can increase diversity of benthic communities (Paper I), and also protect economically valuable fish stocks (Paper II). Protection also appeared to induce a community shift, from dominance of pioneering and stress-tolerant coral and seagrass species in fished areas, to structurally complex climax species in old government MPAs (Paper I). Additionally, effects of protection on seagrass communities seems to be most apparent in the mid-lagoon by favoring seagrass species with high shoot density; an effect that was mostly caused by species turnover but also phenotypic plasticity. Meanwhile, effects in the shallow intertidal and reef zones were weak or non-existing (Paper III). Finally, a two-year field experiment suggests that a community MPA speeds up seagrass recovery and decrease sediment erosion following experimental disturbance, most likely by reducing additional disturbances (e.g. fishing practices) on recovering plants and sediments (Paper IV).Based on these results I make three conclusions. First, MPAs seem to protect seagrasses in a similar way as they protect corals, suggesting that MPAs can aid local seagrass conservation. Seagrass beds should therefore be actively incorporated in marine spatial planning. Second, even though recently established community MPAs were not as effective as the old government MPAs, they appear to benefit both seagrass and coral communities (Paper I, II, IV). Given that previous studies show that they can also fulfill socio-economic community level-values (e.g. involvement in MPA design and enforcement), our findings emphasize their potential as a complement to government MPAs. Third, MPAs are an effective tool to protect seagrass and coral communities from local disturbances, particularly in mid-lagoon and reef areas, but they do not appear to protect the shallow intertidal seagrass beds (Paper III), possibly because of MPA-related tourism activities. This highlights the need for more detailed MPA evaluations, but also the need for more holistic conservation approaches, like integrated coastal zone management.
  •  
20.
  • Chirico, Angelica, et al. (författare)
  • Effects of marine protected areas on inter- and intraspecific trait variability in tropical seagrass assemblages
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Marine ecosystems are under increasing human pressure and therefore in need of effective management. Marine protected areas (MPAs) can reduce the effects of local disturbances on habitat-forming benthic organisms like corals and seagrasses and are well-known to affect species composition. However, we know considerably less about their effects on organisms’ traits (physiological, morphological, and/or behavioural characteristics), which in turn dictate how organisms respond to stressors and influence ecosystem processes and services. We conducted a field survey along the Kenyan coast to assess the effects of MPAs on species and trait composition of seagrass assemblages; an important group of habitat-forming plants in shallow coastal areas that form the basis for multiple ecosystem services. We measured five morphological traits (shoot density, leaf length and width, number of leaves per shoot, and above:below-ground biomass ratio) on multispecies seagrass assemblages within government MPAs, community MPAs, and fished areas in three habitat zones (shallow, mid-lagoon and, reef). Using causal modelling (path analysis) of multivariate data, we found that MPAs influence seagrass species composition and, indirectly, trait composition in mid-lagoon areas. Meanwhile, there were no MPA effects in the shallow intertidal (potentially because of impacts from MPA-related tourism), and weak effects in the reef zone, presumably due to competition from corals. Finally, most of the MPA effects on overall seagrass trait composition were explained by species turnover, rather than phenotypic plasticity. In conclusion, MPAs appear to be an effective conservation tool for seagrass assemblages by reducing local disturbances and favouring seagrass species with certain traits, primarily in mid-lagoon areas. However, the lack of MPA effect in intertidal areas highlights the need for management approaches that regulate human impacts across the whole tropical coastal zone.
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21.
  • Chirico, Angelica, et al. (författare)
  • Marine protected areas increase diversity and alter composition of benthic communities across a tropical seascape gradient
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The tropical seascape consists of a complex mosaic of interconnected systems like coral reefs, seagrass beds and mangrove forests that support biodiversity and ecosystem services. Over the last decades, human-induced habitat destruction and declines in biodiversity have contributed to an increasing implementation of marine protected areas (MPAs). However, as MPAs primarily focus on excluding impacts of fisheries on target species, particularly in coral reef, we know less of how MPAs affect habitat-forming, benthic species across the whole seascape. Here, we investigated how community- and government-managed MPAs affect the species composition, diversity and cover of benthic sessile organisms along a seascape gradient, from the intertidal to the subtidal reef zone, in 12 sites along the Kenyan coast. Community-managed MPAs with only a few years (≤6 years) of protection had a higher diversity of coral- and seagrass assemblages than fished areas, most likely by facilitating the presence of both early and late successional species. Moreover, MPAs appear to increase total seagrass cover in intertidal and mid lagoon zones, as well as topographic complexity in the reef zone, but have no effects on total coral cover (which was very low in all sites). Finally, using a space-for-time substitution approach, our results suggest that protection may in the long term (>20 years) facilitate a gradual shift in assemblage composition, from dominance of structurally simple and stress-tolerant foundation species in fished areas, to structurally complex and stress-sensitive species. To our knowledge, this study is the first indicating that MPAs can increase biodiversity and cause a shift from structurally simple to complex species in soft-bottom seagrass-dominated systems. In summary, our findings suggest that community-managed MPAs protected for <10 years increase the diversity of benthic communities across the tropical seascape, whereas dominance by structurally complex species with disproportional importance for ecosystem functioning is restricted to government-managed MPAs protected for several decades.
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22.
  • Christiansson, Elisabeth, 1965-, et al. (författare)
  • Se människan! : En bok om Ersta diakoni
  • 2017. - 1
  • Bok (populärvet., debatt m.m.)abstract
    • Ersta diakoni har en fantastisk historia som sträcker sig över tre sekler. Med den här boken vill vi försöka ge en inblick i den verksamhet som bedrivits genom åren, och de människor som passerat revy, såväl medarbetare som patienter, boende och andra. Ersta har ofta gått före och visat vägen i det sociala och omvårdande arbetet, och funnits med i situationer där andra backat undan. Vad som alltid varit utmärkande för Ersta diakoni är långsiktigheten. Vårt diakonala uppdrag är detsamma nu som för över 160 år sedan: att se människan, att tjäna, lindra, bota, stötta och vara ett synligt tecken på Guds barmhärtighet. Även i en sekulariserad värld.
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23.
  • de Fouw, Jimmy, et al. (författare)
  • A facultative mutualism facilitates European seagrass meadows
  • 2023
  • Ingår i: Ecography. - 0906-7590 .- 1600-0587. ; 2023:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal ecosystem functioning often hinges on habitat-forming foundation species that engage in positive interactions (e.g. facilitation and mutualism) to reduce environmental stress. Seagrasses are important foundation species in coastal zones but are rapidly declining with losses typically linked to intensifying global change-related environmental stress. There is growing evidence that loss or disruption of positive interactions can amplify coastal ecosystem degradation as it compromises its stress mitigating capacity. Multiple recent studies highlight that seagrass can engage in a facultative mutualistic relationship with lucinid bivalves that alleviate sulphide toxicity. So far, however, the generality of this mutualism, and how its strength and relative importance depend on environmental conditions, remains to be investigated. Here we study the importance of the seagrass-lucinid mutualistic interaction on a continental-scale using a field survey across Europe. We found that the lucinid bivalve Loripes orbiculatus is associated with the seagrasses Zostera noltii and Zostera marina across a large latitudinal range. At locations where the average minimum temperature was above 1 °C, L. orbiculatus was present in 79% of the Zostera meadows; whereas, it was absent below this temperature. At locations above this minimum temperature threshold, mud content was the second most important determinant explaining the presence or absence of L. orbiculatus. Further analyses suggest that the presence of the lucinids have a positive effect on seagrass biomass by mitigating sulphide stress. Finally, results of a structural equation model (SEM) support the existence of a mutualistic feedback between L. orbiculatus and Z. noltii. We argue that this seagrass-lucinid mutualism should be more solidly integrated into management practices to improve seagrass ecosystem resilience to global change as well as the success of restoration efforts.
  •  
24.
  • De La Torre-Castro, Maricela, et al. (författare)
  • Seagrass importance in food provisioning services: fish stomach content as a link between seagrass meadows and local fisheries
  • 2008
  • Ingår i: Western Indian Ocean Journal of Marine Science. - 0856-860X .- 2683-6416. ; 7:1, s. 95-110
  • Tidskriftsartikel (refereegranskat)abstract
    • The links between ecosystem processes and functions and ecosystem services (i.e. the humanbenefits from those) are elusive. In this paper, the food provisioning service of seagrass meadows isoperationalized through the study of the stomach contents of 13 important commercial fish species inChwaka Bay, Zanzibar. Using local fishers’ knowledge on bait, scientific knowledge about the structureof the meadows (associated flora and fauna), stomach content analysis and multivariate statistics, the foodprovisioning service associated with seagrasses and its importance for fish (as important diet component)and for humans (in small-scale artisanal fisheries) are described. The study presents the food items for 13commercial fish species identified at the lowest possible taxonomical level and compares with previousliterature findings. In addition, differences in stomach contents of Siganus sutor and Leptoscarus vaigiensiscaught with both drag-nets and dema basket traps are investigated in order to explore bait presence andindirectly evaluate fishers’ knowledge on bait preference. The results show that most of the items consumedby commercial fishes are associated with seagrass beds and that there are clear indicators that the baittraditionally used seems to be effective. The paper elaborates on the consideration of seagrass ecosystemsin a holistic perspective, the difficulties in valuation of ecosystem services and finally the crucial importanceof these aspects for human well-being and sustainability in coastal communities of the Western IndianOcean.
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25.
  • Donadi, Serena, et al. (författare)
  • A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems
  • 2017
  • Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 284:1859
  • Tidskriftsartikel (refereegranskat)abstract
    • Trophic cascades occur in many ecosystems, but the factors regulating them are still elusive. We suggest that an overlooked factor is that trophic interactions (TIs) are often scale-dependent and possibly interact across spatial scales. To explore the role of spatial scale for trophic cascades, and particularly the occurrence of cross-scale interactions (CSIs), we collected and analysed food-web data from 139 stations across 32 bays in the Baltic Sea. We found evidence of a four-level trophic cascade linking TIs across two spatial scales: at bay scale, piscivores (perch and pike) controlled mesopredators (three-spined stickleback), which in turn negatively affected epifaunal grazers. At station scale (within bays), grazers on average suppressed epiphytic algae, and indirectly benefitted habitat-forming vegetation. Moreover, the direction and strength of the grazer-algae relationship at station scale depended on the piscivore biomass at bay scale, indicating a cross-scale interaction effect, potentially caused by a shift in grazer assemblage composition. In summary, the trophic cascade from piscivores to algae appears to involve TIs that occur at, but also interact across, different spatial scales. Considering scale-dependence in general, and CSIs in particular, could therefore enhance our understanding of trophic cascades.
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26.
  • Donadi, S., et al. (författare)
  • Cross-habitat interactions among bivalve species control community structure on intertidal flats
  • 2013
  • Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 94:2, s. 489-498
  • Tidskriftsartikel (refereegranskat)abstract
    • Increasing evidence shows that spatial interactions between sedentary organisms can structure communities and promote landscape complexity in many ecosystems. Here we tested the hypothesis that reef-forming mussels (Mytilus edulis L.), a dominant intertidal ecosystem engineer in the Wadden Sea, promote abundances of the burrowing bivalve Cerastoderma edule L. (cockle) in neighboring habitats at relatively long distances coastward from mussel beds. Field surveys within and around three mussel beds showed a peak in cockle densities at 50–100 m toward the coast from the mussel bed, while cockle abundances elsewhere in the study area were very low. Field transplantation of cockles showed higher survival of young cockles (2–3 years old) and increased spat fall coastward of the mussel bed compared to within the bed and to areas without mussels, whereas growth decreased within and coastward of the mussel bed. Our measurements suggest that the observed spatial patterns in cockle numbers resulted from (1) inhibition effects by the mussels close to the beds due to preemptive algal depletion and deteriorated sediment conditions and (2) facilitation effects by the mussels farther away from the beds due to reduction of wave energy. Our results imply that these spatial, scale-dependent interactions between reef-forming ecosystem engineers and surrounding communities of sedentary benthic organisms can be an important determinant of the large-scale community structure in intertidal ecosystems. Understanding this interplay between neighboring communities of sedentary species is therefore essential for effective conservation and restoration of soft-bottom intertidal communities.
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27.
  • Donadi, Serena, et al. (författare)
  • Density-dependent positive feedbacks buffer aquatic plants from interactive effects of eutrophication and predator loss
  • 2018
  • Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 99:11, s. 2515-2524
  • Tidskriftsartikel (refereegranskat)abstract
    • Self-facilitation allows populations to persist under disturbance by ameliorating experienced stress. In coastal ecosystems, eutrophication and declines of large predatory fish are two common disturbances that can synergistically impact habitat-forming plants by benefitting ephemeral algae. In theory, density-dependent intraspecific plant facilitation could weaken such effects by ameliorating the amount of experienced stress. Here, we tested whether and how shoot density of a common aquatic plant (Myriophyllum spicatum) alters the response of individual plants to eutrophication and exclusion of large predatory fish, using a 12-week cage experiment in the field. Results showed that high plant density benefitted individual plant performance, but only when the two stressors were combined. Epiphytic algal biomass per plant more than doubled in cages that excluded large predatory fish, indicative of a trophic cascade. Moreover, in this treatment, individual shoot biomass, as well as number of branches, increased with density when nutrients were added, but decreased with density at ambient nutrient levels. In contrast, in open cages that large predatory fish could access, epiphytic algal biomass was low and individual plant biomass and number of branches were unaffected by plant density and eutrophication. Plant performance generally decreased under fertilization, suggesting stressful conditions. Together, these results suggest that intraspecific plant facilitation occurred only when large fish exclusion (causing high epiphyte load) was accompanied by fertilization, and that intraspecific competition instead prevailed when no nutrients were added. As coastal ecosystems are increasingly exposed to multiple and often interacting stressors such as eutrophication and declines of large predatory fish, maintaining high plant density is important for ecosystem-based management.
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28.
  • Dorn, Michael, et al. (författare)
  • Logistik 2015-2020 : En framtidsstudie om logistiksimulering: FoT 19 logistik
  • 2006
  • Rapport (populärvet., debatt m.m.)abstract
    • In this study an attempt is made to put forward ideas about how logistic support to the Armed Forces of the future will be dealt with, based on a sur­vey of current social, military and economic trends. The aim is to identify those logistic matters, which it would be relevant to simulate within a 10 to 15-year period. The study has been carried out with the aid of NATO logis­tic doctrine and a qualitative method, which is closely comparable to idea analysis.One of the findings of the study is that the Swedish Armed Forces could be one module, amongst many (e.g. police, rescue services and aid organisa­tions), tailor-made for a particular peace support operation, led by a national HQ. It can also be taken that civilian actors, to a much greater extent than today, will be part of the logistics system and that this system could resem­ble the “IKEA model”, i.e. small stores of equipment that can quickly be put together to meet different needs. All this will require a greater degree of specialisation and coordination, both in Sweden and in other countries.Those logistic matters identified as being relevant for simulation within a 10 to15-year period have been brought together in a summary. The main con­clusion of the study indicates that it is of the utmost importance to simulate a model of the complete logistic chain. In the meantime, in order to carry out the simulation, the collection of experiences and lessons learned must be systemised and recorded. If this does not happen, it is doubtful that the simulation can be used as a system to support decision-making.
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29.
  • Duffy, J. Emmett, et al. (författare)
  • A Pleistocene legacy structures variation in modern seagrass ecosystems
  • 2022
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:32
  • Tidskriftsartikel (refereegranskat)abstract
    • Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems. 
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30.
  • Duffy, J. E., et al. (författare)
  • Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach
  • 2015
  • Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 18:7, s. 696-705
  • Tidskriftsartikel (refereegranskat)abstract
    • Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.
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31.
  • Edstam, Monika M., et al. (författare)
  • Coexpression patterns indicate that GPI-anchored non-specific lipid transfer proteins are involved in accumulation of cuticular wax, suberin and sporopollenin
  • 2013
  • Ingår i: Plant Molecular Biology. - : Springer Netherlands. - 0167-4412 .- 1573-5028. ; 83:6, s. 625-649
  • Tidskriftsartikel (refereegranskat)abstract
    • The non-specific lipid transfer proteins (nsLTP) are unique to land plants. The nsLTPs are characterized by a compact structure with a central hydrophobic cavity and can be classified to different types based on sequence similarity, intron position or spacing between the cysteine residues. The type G nsLTPs (LTPGs) have a GPI-anchor in the C-terminal region which attaches the protein to the exterior side of the plasma membrane. The function of these proteins, which are encoded by large gene families, has not been systematically investigated so far. In this study we have explored microarray data to investigate the expression pattern of the LTPGs in Arabidopsis and rice. We identified that the LTPG genes in each plant can be arranged in three expression modules with significant coexpression within the modules. According to expression patterns and module sizes, the Arabidopsis module AtI is functionally equivalent to the rice module OsI, AtII corresponds to OsII and AtIII is functionally comparable to OsIII. Starting from modules AtI, AtII and AtIII we generated extended networks with Arabidopsis genes coexpressed with the modules. Gene ontology analyses of the obtained networks suggest roles for LTPGs in the synthesis or deposition of cuticular waxes, suberin and sporopollenin. The AtI-module is primarily involved with cuticular wax, the AtII-module with suberin and the AtIII-module with sporopollenin. Further transcript analysis revealed that several transcript forms exist for several of the LTPG genes in both Arabidopsis and rice. The data suggests that the GPI-anchor attachment and localization of LTPGs may be controlled to some extent by alternative splicing.
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32.
  • Eggertsen, Linda, 1981- (författare)
  • Identification and implications of fish nurseries in tropical and subtropical seascapes
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Many species of reef fish reside in specific nursery habitats as juveniles. Seagrass meadows, and mangroves are examples of well-recognized nursery habitats, but only recently canopy-forming seaweeds have been found to provide important habitats for some fish species in the tropics. Availability of nurseries can have effects on the abundance and spatial distribution of adult fish, which is why it is important to recognize key nursery habitats for proper management. Information on reef fish nurseries is largely lacking in the South Western Atlantic (SWA), while information in the Western Indian Ocean (WIO) and elsewhere is more extensive. However, more information on the  consequences of nursery availability on adult fish populations is needed. This thesis studies nursery habitat use of reef fish on tropical and subtropical reefs in the SWA and in seagrass and reef systems in the WIO. The hypothesis that seagrass and canopy-forming macroalgae meadows function as a nursery habitat for reef fish is tested in the SWA. The aim of this thesis is also to understand distribution patterns of fish arising from the arrangement of the seascape, using a seascape ecology approach, linking patterns to non-reef nursery habitat use (mangroves and seagrass systems). Results showed that spatial and temporal patterns of juvenile reef fish abundance were weak on rocky, subtropical reefs in the SWA (Paper I), while there was a stronger preference for certain habitats on SWA tropical biogenic reefs, especially seaweed beds dominated by Sargassum (Paper II). The widely accepted paradigm that seagrass meadows function as nursery habitats for reef fish was not supported by the results from the study site in the tropical SWA (Paper II). This may be related to habitat availability in the seascape. In the SWA, seagrass meadows are spatially small, fragmented and less complex, compared to in the WIO, where they display high structural complexity and cover large areas. At the WIO study site (Bazaruto Archipelago), the juvenile fish assemblage in the seagrass meadows encompassed a number of reef fish species from a range of trophic groups and families, as well as resident seagrass species (Paper III). Key variables and extent of spatial scales that structure ontogenetic migrations were identified in both seagrass and reef habitats. Fish distribution patterns in the seagrass seascape was strongly influenced by seascape configuration and distance to adjacent habitats, highlighting that not all seagrass meadows are equally productive as nursery habitats. Variables important for distribution patterns of fish were identified, which in most cases were species-specific, and related to life history and functional traits of species. Effects of two small protected areas on the fish assemblage was also linked to geographical placement of reserves in the seascape. Likewise, the adult fish community composition on the reefs was found to be structured by the spatial arrangement of nursery habitats in the seascape, and presence of stretches of sand acting as isolating barriers (Paper IV). Nursery fish species were less abundant on reefs far from nurseries, resulting in differences in community and functional group composition along distance gradients in the seascape. Depending on functional traits of the nursery fish assemblage, seagrass and mangroves can enhance certain ecological functions on reefs. Both community structure and ecosystem functioning may therefore change depending on nursery habitat availability, highlighting the need to adopt a holistic seascape approach in management.
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33.
  • Eggertsen, Maria, 1981-, et al. (författare)
  • Different environmental variables predict distribution and cover of the introduced red seaweed Eucheuma denticulatum in two geographical locations
  • 2021
  • Ingår i: Biological Invasions. - : Springer. - 1387-3547 .- 1573-1464. ; 23, s. 1049-1067
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we examined abiotic and biotic factors that could potentially influence the presence of a non-indigenous seaweed, Eucheuma denticulatum, in two locations, one outside (Kane’ohe Bay, Hawai’i, USA) and one within (Mafia Island, Tanzania) its natural geographical range. We hypothesized that the availability of hard substrate and the amount of wave exposure would explain distribution patterns, and that higher abundance of herbivorous fishes in Tanzania would exert stronger top–down control than in Hawai’i. To address these hypotheses, we surveyed E. denticulatum in sites subjected to different environmental conditions and used generalized linear mixed models (GLMM) to identify predictors of E. denticulatum presence. We also estimated grazing intensity on E. denticulatum by surveying the type and the amount of grazing scars. Finally, we used molecular tools to distinguish between indigenous and non-indigenous strains of E. denticulatum on Mafia Island. In Kane’ohe Bay, the likelihood of finding E. denticulatum increased with wave exposure, whereas on Mafia Island, the likelihood increased with cover of coral rubble, and decreased with distance from areas of introduction (AOI), but this decrease was less pronounced in the presence of coral rubble. Grazing intensity was higher in Kane’ohe Bay than on Mafia Island. However, we still suggest that efforts to reduce non-indigenous E. denticulatum should include protection of important herbivores in both sites because of the high levels of grazing close to AOI. Moreover, we recommend that areas with hard substrate and high structural complexity should be avoided when farming non-indigenous strains of E. denticulatum.
  •  
34.
  • Eggertsen, Maria, 1981-, et al. (författare)
  • Different environmental variables predict distribution of the introduced red seaweed Eucheuma denticulatum in two geographical locations
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • In this study we examined abiotic and biotic factors that could potentially influence the presence of a non-indigenous seaweed, Eucheuma denticulatum, in two locations, one outside (Kane’ohe Bay, Hawai’i, USA) and one within (Mafia Island, Tanzania) its natural geographical range. We hypothesized that the availability of hard substrate and the amount of wave exposure would explain distribution patterns, and that higher abundance of herbivorous fishes in Tanzania would exert stronger top-down control than in Hawai’i. To address these hypotheses, we surveyed E. denticulatum in sites subjected to different environmental conditions and used generalized linear mixed models (GLMM) to identify predictors of E. denticulatum presence. We also estimated grazing intensity on E. denticulatum by surveying the type and the amount of grazing scars. Finally, we used molecular tools to distinguish between indigenous and non-indigenous strains of E. denticulatum on Mafia Island. In Kane’ohe Bay, the likelihood of finding E. denticulatum increased with wave exposure, whereas on Mafia Island, the likelihood increased with cover of coral rubble, and decreased with distance from areas of introduction (AOI), but this decrease was less pronounced in the presence of coral rubble. Grazing intensity was higher in Kane’ohe Bay than on Mafia Island. However, we still suggest that efforts to reduce non-indigenous E. denticulatum should include protection of important herbivores in both sites,    because of the high amount of grazing damages close to AOI. Moreover, we recommend that areas with hard substrate and high structural complexity should be avoided when farming non-indigenous strains of E. denticulatum.
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35.
  • Eggertsen, Maria, 1981- (författare)
  • Introduced and indigenous macroalgae : Ecological effects, functions and regulating factors in tropical seascapes
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Tropical marine shallow-water areas are highly productive systems that promote important ecological functions and biodiversity. Stressors on these systems are intensifying due to increasing anthropogenic disturbances on multiple scales. The need to increase understanding of ongoing patterns and processes within the near-shore seascape is therefore imperative.In Tanzania in the Western Indian Ocean (WIO), introductions of South East Asian (SEA) strains of the red macroalgae Eucheuma denticulatum are made through seaweed farming, with unknown environmental consequences. Because this species occurs naturally in East Africa (EA), an ongoing introduction is difficult to assess. Also, there is limited knowledge about the extent of a possible spread and environmental factors that regulate this. Hence, ecological consequences are difficult to predict. The aims of this thesis are therefore to 1) identify and address important knowledge gaps concerning environmental effects of introduced E. denticulatum on the surrounding tropical seascape, and 2) study ecological processes and factors that influence spread, distribution and interactions with indigenous species. In doing so, the thesis also includes herbivorous fishes associated with macroalgal habitats and environmental variables influencing these fish assemblages.Paper I reviews the current scientific knowledge on introductions of SEA E. denticulatum in the WIO, and identifies knowledge gaps such as potential competition with native benthic taxa and environmental factors impacting spread. Paper II investigates environmental factors that affect the distribution and presence of SEA E. denticulatum in two geographical locations; one where E. denticulatum has turned into a nuisance and one where this is still unknown. We found that hard substrate and distance to areas of introduction best predicted SEA algal presence. Paper III examines the potential effects of E. denticulatum on corals. A field experiment showed that E. denticulatum did not induce any stress responses in corals, nor could it attach to live corals. Fish herbivory was the strongest factor controlling biomass of algae. In Paper IV and V, we focus on how seascape configuration and environmental factors influence the distribution and herbivory of reef fishes. In Paper IV, we show that macroalgal consumption was density dependent (inversely related to macroalgal cover) and that different habitats held distinct herbivorous fish communities. Moreover, Paper IV and V showed that presence and traits of macroalgae had a positive influence on the abundance of juvenile parrotfish, suggesting the potential of macroalgae to provide important nursery functions.In conclusion, this thesis indicates that negative effects by farming of  SEA E. denticulatum in the WIO are minor, and might be problematic only in areas already subjected to environmental disturbances. In marine systems with high cover of live coral and healthy populations of herbivorous fishes, competition with indigenous benthic taxa is limited. Furthermore, the thesis highlights that the abundance and ontogeny of herbivorous fishes can be affected by the presence of macroalgal habitats and plant traits, suggesting macroalgal beds are key habitats with important ecological functions to be included in marine spatial planning and conservation efforts.
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36.
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37.
  • Eklöf, Hanna, 1974-, et al. (författare)
  • Stress och påverkan på de nationella provresultaten för åk 3
  • 2014
  • Konferensbidrag (refereegranskat)abstract
    • Hur upplever 9-10 åringar de nationella proven i åk 3? Påverkar upplevelsen prestationen? Påverkas något matematikdelområde mer eller mindre av upplevelsen? Skiljer sig olika uppgifter åt beroende på om de har mer eller mindre text respektive bilder? Vad kan man som lärare tänka på och göra i allmänhet och i synnerhet vid prov/förhörssituationer?Läsåret 2012/13 genomfördes en studie med 624 st elever i åk 3 för att bringa klarhet i ovan frågor. Eleverna fick göra olika arbetsminnesövningar och svara på frågor om stress, motivation och attityder, etc. Teoretiskt tror man nämligen att allt för hög nivå av t ex stress (prestationsångest) sänker ens prestation på ett prov/förhör. Resultaten på de olika nationella delproven i matematik kördes därför statistiskt mot nivå av självrapporterad stress/ångest och uppskattad eller egentlig prestationsförmåga hos eleverna.Uppskattad eller egentlig förmåga att prestera i matematik för elever kan mätas genom t ex deras arbetsminneskapacitet. Arbetsminne är en kognitiv förmåga som är väl klarlagd för att väsentligen påverka prestation och utveckling inom t ex matematik- och läsförståelse hos både vuxna och barn (Menon, 2010). Det finns dessutom starka kopplingar mellan arbetsminneskapacitet och skolprestation i teoretiska ämnen. Majoriteten av de elever som har inlärningssvårigheter i skolan verkar även ha svag arbetsminnesförmåga (Gathercole et al., 2006).Arbetsminnet kan förenklat beskrivas som bestå av tre olika specialiserade komponenter. En huvudcentral som t ex kontrollerar, fördelar, uppmärksammar och processerar information, och hämtar/lagrar information från/i långtidsminnet. Till sin hjälp har denna huvudcentral en visuell-spatial del för hantering av bilder, former och dimension, samt en auditiv del för behandling av lingvistik (Baddeley, 1986). Matematik innefattar olika områden som beror av olika kognitiva förmågor (t ex huvudräkning, problemlösning), vilka i sin tur är relaterade till visuell-spatial och/eller auditiv fakta (Rasmussen & Bisanz, 2005).”Provstress” eller ”provängslan” är en etablerad term för att beskriva elevers påverkan och upplevelse av prov. Termen innefattar ofta för barn observerbara beteenden (t ex gå på toan, vicka på stolen, titta sig omkring), tankar/oro (t ex jag kommer aldrig att klara det här, mina föräldrar kommer att bli arga om jag misslyckas), autonoma/somatiska reaktioner (t ex svettas, ont i magen, varm om kinderna) (Zeidner, 2007). Man tror att provängslan är ett inlärt beteende som väcks tidigt i skolåren (Pekrun, 2000). Det är ett väldigt inskränkande tillstånd (Rothman, 2004) som starkt kan begränsa elevers prestation i alla åldrar (Birenbaum & Gutvirtz, 1993). Även om ett visst mått av provängslan är nödvändigt för att öka fokus, motivation och förberedelse (Gregor, 2005), kan det i allt för höga nivåer negativt påverka en elevs prestation och resultat på ett prov (Zeidner, 2007), särskilt i matematik (e.g. Putwain, 2008). Om och hur stark den kognitiva störningen är av provängslan används alltså i vår studie som ett mått eller symptom på elevers ev. underprestation. Vi undersöker också om eleverna uppvisar mer eller mindre av beteenden, autonoma reaktioner eller tankar relaterat till provängslan. Slutligen summerar vi våra resultat mot undervisning och prov/förhörssituationer. En jämförelse kommer även att göras med Finländska och Kinesiska åk-3 elever.
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38.
  • Eklöf, Johan, et al. (författare)
  • Attitudes towards Bats in Swedish History
  • 2021
  • Ingår i: Journal of Ethnobiology. - : Society of Ethnobiology. - 0278-0771. ; 41:1, s. 35-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Bats have always fascinated people by their unusual appearance, but fear towards them is also common, particularly in Western societies. Making headlines worldwide during the recent COVID-19 pandemic, bats were all too often accused of carrying and transmitting a disproportionate share of dangerous viruses. We enquired about the origin and persistence of this thinking in Sweden by searching old literature and original museum records where bats are mentioned. In the Bible, the bat is an explicitly unclean animal. At least since the Middle Ages, it has been used as a symbol of the Devil, with the dark skin wings in deliberate contrast to the white wings of angels. However, according to our folklore records, the bat was usually seen in a different and generally positive context by the people, and was treated with respect. Its magic properties, particularly contained in the blood, eyes, and wings, could bring fortune and prevent bad luck in various everyday contexts. A minority of records refer to bats being used in witchcraft, black magic, or, following the religious dogma, claiming that they are ugly or unclean and cannot be the work of God. We found no indication that bats were considered aggressive, dangerous, or to carry disease. Hence, we surmise there was little fear of bats in Swedish (Nordic) history, despite the religious message. Hence, the general attitude towards bats in the past seems to have been opposite to the view currently met in Western societies.
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39.
  • Eklöf, Johan, 1978, et al. (författare)
  • Community-level effects of rapid experiment warming and consumer loss outweigh effects of rapid ocean acidification.
  • 2015
  • Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 124:8, s. 1040-1049
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change and consumer loss simultaneously affect marine ecosystems, but we have limited understanding of the relative importance of these factors and the interactions between them. Moreover, effects of environmental change are mediated by organism traits or life histories, which determine their sensitivity. Yet, trait-based analyses have rarely been used to understand the effects of climate change, especially in the marine environment. Here we used a five-week mesocosm experiment to assess the single and interactive effects of 1) rapid ocean warming, 2) rapid ocean acidification, and 3) simulated consumer loss, on the diversity and composition of macrofauna communities in eelgrass Zostera marina beds. Experimental warming (ambient versus + 3.2°C) and loss of a key consumer (the omnivorous crustacean, Gammarus locusta) both increased macrofauna richness and abundance, and altered overall species trait distributions and life history composition. Warming and consumer-loss favored poorly defended epifaunal crustaceans (tube-building amphipods), and species that brood their offspring. We suggest these organisms were favored because warming and consumer-loss caused increased metabolism, food supply and, potentially, settling substrate, and lowered predation pressure from the omnivorous G. locusta. Importantly, we found no single, or interactive, effects of the rapid ocean acidification (ambient versus −0.35 pH units). We suggest this result reflects natural variability in the native habitat and, potentially, the short duration of the experiment: organisms in these communities routinely experience rapid diurnal pH fluctuations that exceed the mean ocean acidification predicted for the coming century (and used in our experiments). In summary, our study indicates that macrofauna in shallow vegetated ecosystems will be significantly more affected by rapid warming and consumer diversity loss than by rapid ocean acidification.
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40.
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41.
  • Eklöf, Johan, 1978, et al. (författare)
  • Experimental climate change weakens the insurance effect of biodiversity
  • 2012
  • Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 15:8, s. 864-872
  • Tidskriftsartikel (refereegranskat)abstract
    • Ecosystems are simultaneously affected by biodiversity loss and climate change, but we know little about how these factors interact. We predicted that climate warming and CO 2-enrichment should strengthen trophic cascades by reducing the relative efficiency of predation-resistant herbivores, if herbivore consumption rate trades off with predation resistance. This weakens the insurance effect of herbivore diversity. We tested this prediction using experimental ocean warming and acidification in seagrass mesocosms. Meta-analyses of published experiments first indicated that consumption rate trades off with predation resistance. The experiment then showed that three common herbivores together controlled macroalgae and facilitated seagrass dominance, regardless of climate change. When the predation-vulnerable herbivore was excluded in normal conditions, the two resistant herbivores maintained top-down control. Under warming, however, increased algal growth outstripped control by herbivores and the system became algal-dominated. Consequently, climate change can reduce the relative efficiency of resistant herbivores and weaken the insurance effect of biodiversity.
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42.
  • Eklöf, Johan, 1978-, et al. (författare)
  • Habitat-Mediated Facilitation and Counteracting Ecosystem Engineering Interactively Influence Ecosystem Responses to Disturbance
  • 2011
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203.
  • Tidskriftsartikel (refereegranskat)abstract
    • Recovery of an ecosystem following disturbance can be severely hampered or even shift altogether when a point disturbance exceeds a certain spatial threshold. Such scale-dependent dynamics may be caused by preemptive competition, but may also result from diminished self-facilitation due to weakened ecosystem engineering. Moreover, disturbance can facilitate colonization by engineering species that alter abiotic conditions in ways that exacerbate stress on the original species. Consequently, establishment of such counteracting engineers might reduce the spatial threshold for the disturbance, by effectively slowing recovery and increasing the risk for ecosystem shifts to alternative states. We tested these predictions in an intertidal mudflat characterized by a two-state mosaic of hummocks (humps exposed during low tide) dominated by the sediment-stabilizing seagrass Zostera noltii) and hollows (low-tide waterlogged depressions dominated by the bioturbating lugworm Arenicola marina). In contrast to expectations, seagrass recolonized both natural and experimental clearings via lateral expansion and seemed unaffected by both clearing size and lugworm addition. Near the end of the growth season, however, an additional disturbance (most likely waterfowl grazing and/or strong hydrodynamics) selectively impacted recolonizing seagrass in the largest (1 m2) clearings (regardless of lugworm addition), and in those medium (0.25 m2) clearings where lugworms had been added nearly five months earlier. Further analyses showed that the risk for the disturbance increased with hollow size, with a threshold of 0.24 m2. Hollows of that size were caused by seagrass removal alone in the largest clearings, and by a weaker seagrass removal effect exacerbated by lugworm bioturbation in the medium clearings. Consequently, a sufficiently large disturbance increased the vulnerability of recolonizing seagrass to additional disturbance by weakening seagrass engineering effects (sediment stabilization). Meanwhile, the counteracting ecosystem engineering (lugworm bioturbation) reduced that threshold size. Therefore, scale-dependent interactions between habitat-mediated facilitation, competition and disturbance seem to maintain the spatial two-state mosaic in this ecosystem.
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43.
  • Eklöf, Johan (författare)
  • Inventering av fladdermöss i gotländska kyrkor
  • 2023
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Det finns brunlångöra i drygt 60 procent av de gotländska kyrkorna men tittar man enbart på kyrkor utan fasadbelysning är siffran högre (75%) och i kyrkor med fasadbelysning från flera sidor är siffran endast 32 procent. Ljuset från en strålkastare mot en kyrkvägg överstiger den ljusmängd som brunlångöra tolererar med ungefär tio gånger. Det är alltså tydligt att belysning och mängden belysning påverkar fladdermössen, precis som har konstaterats i tidigare studier i Västergötland. Även artantalet vid kyrkorna verkar minska med antal strålkastare, något som också har konstaterats i andra delar av landet. Problemet verkar dock vara något mindre på Gotland, så till vida att det fortfarande finns ett stort antal kolonier kvar, även i belysta kyrkor. En anledning är att flera pastorat reglerar belysningen genom att framför allt släcka efter en viss tid på kvällen. Detta ger fladdermössen fortsatt möjlighet att flyga ut. Belysningen överlag på Gotland är också förhållandevis sparsam med avsaknad av gatljus längs många vägar. Vi vet dock inte om populationen är stabil eller på väg ner. Flera av de funna kolonierna var små och det finns undersökningar som tyder på att långvarig belysning sakta gör kolonierna mindre. Detta utgör dock ett bra underlag för fortsatt övervakning så att populationen av brunlångöra och i viss mån övriga fladdermöss kan följas över en längre tid. Med kunskap om ljusets påverkan kan vi också planera för bättre, det vill säga mer faunaanpassad belysning. I bilaga 3 finns en sammanställning över åtgärder för att minska ljusföroreningar.
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44.
  • Eklöf, Johan S., et al. (författare)
  • A spatial regime shift from predator to prey dominance in a large coastal ecosystem
  • 2020
  • Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Regime shifts in ecosystem structure and processes are typically studied from a temporal perspective. Yet, theory predicts that in large ecosystems with environmental gradients, shifts should start locally and gradually spread through space. Here we empirically document a spatially propagating shift in the trophic structure of a large aquatic ecosystem, from dominance of large predatory fish (perch, pike) to the small prey fish, the three-spined stickleback. Fish surveys in 486 shallow bays along the 1200 km western Baltic Sea coast during 1979–2017 show that the shift started in wave-exposed archipelago areas near the open sea, but gradually spread towards the wave-sheltered mainland coast. Ecosystem surveys in 32 bays in 2014 show that stickleback predation on juvenile predators (predator–prey reversal) generates a feedback mechanism that appears to reinforce the shift. In summary, managers must account for spatial heterogeneity and dispersal to better predict, detect and confront regime shifts within large ecosystems.
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45.
  • Eklöf, Johan S., 1978- (författare)
  • Anthropogenic Disturbances and Shifts in Tropical Seagrass Ecosystems
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Seagrasses constitute the basis for diverse and productive ecosystems worldwide. In East Africa, they provide important ecosystem services (e.g. fisheries) but are potentially threatened by increasing resource use and lack of enforced management regulations. The major aim of this PhD thesis was to investigate effects of anthropogenic distur-bances, primarily seaweed farming and coastal fishery, in East African seagrass beds. Seaweed farming, often depicted as a sustainable form of aquaculture, had short- and long-term effects on seagrass growth and abundance that cascaded up through the food web to the level of fishery catches. The coastal fishery, a major subsistence activity in the region, can by removing urchin predators indirectly increase densities of the sea urchin Tripneustes gratilla, which has overgrazed seagrasses in several areas. A study using simulated grazing showed that high magnitude leaf removal – typical of grazing urchins – affected seagrasses more than low magnitude removal, typical of fish grazing. Different responses in two co-occurring seagrass species furthermore indicate that high seagrass diversity in tropical seagrass beds could buffer overgrazing effects in the long run. Finally, a literature synthesis suggests that anthropogenic disturbances could drive shifts in seagrass ecosystems to an array of alternative regimes dominated by other or-ganisms (macroalgae, bivalves, burrowing shrimp, polychaetes, etc.). The formation of novel feedback mechanisms makes these regimes resilient to disturbances like seagrass recovery and transplantation projects. Overall, this suggests that resource use activities linked to seagrasses can have large-scale implications if the scale exceeds critical levels. This emphasizes the need for holistic and adaptive management at the seascape level, specifically involving improved techniques for seaweed farming and fisheries, protection of keystone species, and ecosystem-based management approaches.
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46.
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47.
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48.
  • Eklöf, Johan S., 1978-, et al. (författare)
  • Effects of seasonal spawning closures on pike (Esox lucius L.) and perch (Perca fluviatilis L.) catches and coastal food webs in the western Baltic Sea
  • 2023
  • Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 263
  • Tidskriftsartikel (refereegranskat)abstract
    • Marine protected areas have become one of the main tools in the battle to curb marine biodiversity loss and habitat degradation. Yet, implementation of permanent fishery closures has often generated resource user conflicts that ultimately undermine conservation goals. Here we assessed the influence of an alternative and often more accepted measure – seasonal fish spawning closures – on large predatory fish and coastal food webs in the western Baltic Sea (Sweden). In spring 2017, we conducted a multivariable field survey in 11 seasonal closures and 11 paired references areas open to fishing. In each area, pike was sampled through angling, and perch and mesopredators through gillnet surveys. To assess trophic cascades, we measured zooplankton abundance and loss of tethered gammarids from predation. Catches per unit effort of northern pike (Esox lucius) – the main target species in recreational fisheries – were ca. 2.5 times higher per unit effort in closures than reference areas; an effect that may be caused by higher abundance and/or higher catchability of pike in the absence of fishing. Catch and weight per unit effort of the more common predator European perch (Perca fluviatilus), and the mesopredators roach (Rutilus rutilus) and three-spined stickleback (Gasterosteus aculeatus) in survey nets were, however, unaffected by closures. Moreover, a previously hypothesized trophic cascade from perch to zooplankton via three-spined stickleback was supported by the analyses, but appeared independent of closures. Yet, predation risk for tethered gammarid amphipods (a prey of stickleback and an important grazer on macroalgae) was three times higher in fished areas than in closures; a cascading closure effect that may potentially be caused by small predatory fish being less active in protected areas to avoid pike predation. Overall, our results suggest that spawning closures impact pike abundance and/or behavior and could help limit the effects of fishing, but that more research is needed to disentangle i) what mechanism(s) that underlie the protection effect on pike catches, ii) the apparently weaker closure impacts on other fish species, as well as iii) the potential for cascading effects on lower trophic levels. Therefore, new seasonal spawning closures should be implemented in addition to (and not instead of) much-needed permanent closures, which have well-known effects on the wider ecosystem.
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