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- Hagberg, Jacob, et al.
(författare)
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Uncertain biotic and abiotic interactions in benthic communities
- 2003
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 100:2, s. 353-361
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Tidskriftsartikel (refereegranskat)abstract
- We analyze marine benthic communities at different sites in Skagerrak with the purpose of understanding the role of exogenous and endogenous factors in explaining the species' temporal dynamics. The previous finding that the dynamics of these species communities are mainly driven and synchronized by environmental (temperature) forcing was only weakly supported when analyzing single-species dynamics at five sites where four of the species were present every year. There was no consistent pattern in how the temperature affected the realized per capita growth rate, either across species at a given site, or among sites for a given species. Furthermore, there was no net-interaction from the community on a given species strong enough to give rise to second-order dynamics. However, when implementing a Multi Dimensional Scaling (MDS) analysis and incorporating all sampling sites and species -we found that the different communities clustered in relation to depth, hence, communities at the same depth were more "similar" than communities at different depth. Revealing the underlying interactions shaping these marine benthic communities is a challenge that calls for an array of various and complementary approaches.
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| 2. |
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| 3. |
- Johnsson, Jörgen I, 1959, et al.
(författare)
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Compensatory growth for free? A field experiment on brown trout, Salmo trutta
- 2005
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 111:1, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory studies suggest that animals may be capable of compensatory growth after periods of food shortage. There is, however, a lack of field experiments investigating the incidence and consequences of compensatory growth in the wild, and the relevance of compensatory responses in natural populations has recently been questioned. Here we addressed the hypotheses that (1) food restriction during critical growth periods can induce compensatory growth, and (2) that compensatory growth is associated with delayed costs in natural populations. These hypotheses were addressed by (1) manipulating the food intake of brown trout in spring, (2) measuring growth rate responses over the first month following release, and (3) measuring growth and mortality (i.e. recapture rate) over the subsequent fall and winter. We found that brown trout restored lost body weight and condition within a month, providing the first experimental demonstration of compensatory growth in the wild. However, no delayed costs of the compensatory response could be detected within the timespan of the experiment. We suggest that wild brown trout have an adapted "buffer capacity" to withstand fluctuations in food supply, allowing restoration of lost lipid reserves when feeding conditions improve. However, when prolonged food deprivation affect structural components, compensation may not be possible without compromising long-term performance.
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| 4. |
- Moksnes, Per-Olav, 1965, et al.
(författare)
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Trophic cascades in a temperate seagrass community
- 2008
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 117:5, s. 763-777
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Tidskriftsartikel (refereegranskat)abstract
- We assessed the relative importance of bottom-up and top-down processes in structuring an eelgrass community in Sweden, a system impacted both by eutrophication and overfishing. Using artificial seagrass as substrate, we manipulated nutrient levels and predator abundance in a full-factorial cage-experiment. The results revealed a seagrass community dominated by strong top-down processes controlling the aggregate biomass of mesograzers and macroalgae. In the absence of predators the large amphipod Gammarus locusta became very abundant resulting in a leaf community with low biomass of algae and smaller mobile fauna. One enclosed gobid fish predator reduced the abundance of adult G. locusta by > 90%, causing a three to six times increase in the biomass of algae, smaller mesograzers and meiofauna. Numerous small predators in uncaged habitats reduced the biomass of G. locusta and other mesograzers by > 95% in comparison to the fish treatment, further increasing the biomass of epiphytic algae and meiofauna. Although water column nutrient enrichment caused a temporal bloom of the filamentous macroalgae Ulva spp., no significant nutrient-effects were found on the algal community at the end of the experiment. The only lasting nutrient-effect was a significant increase in the biomass of G. locusta, but only in the absence of ambient predators. These results demonstrate that mesograzers can respond to enhanced food supply, increase their biomass and control the algal growth when predation rates are low. However, in the assessed system, high predation rates appear to make mesograzers functionally extinct, causing a community-wide trophic cascade that promotes the growth of ephemeral algae. This top-down effect could penetrate down, despite a complex food-web because the interaction strength in the community was strongly skewed towards two functionally dominant algal and grazer species that were vulnerable to consumption. These results indicate that overexploitation of gadoid fish may be linked to increased macroalgal blooms and loss of eelgrass in the area through a trophic cascade affecting the abundance of mesograzers.
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| 5. |
- Eklöf, Johan, 1978, et al.
(författare)
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Community-level effects of rapid experiment warming and consumer loss outweigh effects of rapid ocean acidification.
- 2015
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 124:8, s. 1040-1049
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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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| 7. |
- Gamfeldt, Lars, 1975, et al.
(författare)
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Marine biodiversity and ecosystem functioning: What's known and what's next?
- 2015
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 124:3, s. 252-265
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Tidskriftsartikel (refereegranskat)abstract
- Marine ecosystems are experiencing rapid and pervasive changes in biodiversity and species composition. Understanding the ecosystem consequences of these changes is critical to effectively managing these systems. Over the last several years, numerous experimental manipulations of species richness have been performed, yet existing quantitative syntheses have focused on a just a subset of processes measured in experiments and, as such, have not summarized the full data available from marine systems. Here, we present the results of a meta-analysis of 110 marine experiments from 42 studies that manipulated the species richness of organisms across a range of taxa and trophic levels and analysed the consequences for various ecosystem processes (categorised as production, consumption or biogeochemical fluxes). Our results show that, generally, mixtures of species tend to enhance levels of ecosystem function relative to the average component species in monoculture, but have no effect or a negative effect on functioning relative to the 'highest- performing' species. These results are largely consistent with those from other syntheses, and extend conclusions to ecological functions that are commonly measured in the marine realm (e.g. nutrient release from sediment bioturbation). For experiments that manipulated three or more levels of richness, we attempted to discern the functional form of the biodiversity-ecosystem functioning relationship. We found that, for response variables related to consumption, a power-function best described the relationship, which is also consistent with previous findings. However, we identified a linear relationship between richness and production. Combined, our results suggest that changes in the number of species will, on average, tend to alter the functioning of marine ecosystems. We outline several research frontiers that will allow us to more fully understand how, why, and when diversity may drive the functioning of marine ecosystems. Synthesis The oceans host an incredible number and variety of species. However, human activities are driving rapid changes in the marine environment. It is imperative we understand ecosystem consequences of any associated loss of species. We summarized data from 110 experiments that manipulated species diversity and evaluated resulting changes to a range of ecosystem responses. We show that losing species, on average, decreases productivity, growth, and a myriad of other processes related to how marine organisms capture and utilize resources. Finally, we suggest that the loss of species may have stronger consequences for some processes than others.
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| 8. |
- Gamfeldt, Lars, 1975, et al.
(författare)
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Scaling-up the biodiversity-ecosystem functioning relationship: the effect of environmental heterogeneity on transgressive overyielding
- 2023
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 2023:3
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of how biodiversity sustains ecosystem function comes predominantly from studies focused on small spatial scales. Thus, we know relatively little about the role of biodiversity at larger scales of space and time where habitats become increasingly heterogeneous. Efforts to upscale the relationship between biodiversity and function have yielded inconclusive results. Given that increasing habitat heterogeneity is a ubiquitous consequence of increasing spatial scale, we asked: as habitat heterogeneity increases, can single species continue to maintain ecosystem function? Or, does transgressive overyielding (functioning of species mixture divided by the functioning of the highest functioning single species) change with habitat heterogeneity? We addressed this using a combination of computer simulations, an experiment and a meta-analysis. The three parts followed the same rationale: habitat heterogeneity was increased by aggregating local habitats with different conditions into larger and more heterogeneous landscapes. The computer simulations showed that, on average, transgressive overyielding increased with habitat heterogeneity because monoculture functioning decreased with habitat heterogeneity. We tested this expectation experimentally by varying the strain richness from one to five species across 10800 bacterial communities in five different habitats defined by sub-inhibitory concentrations of antibiotics. On average, the experimental results concurred with the simulations. We tested the generality of this result using a meta-analysis of 26 published experiments that manipulated habitat conditions and species richness. This confirmed that transgressive overyielding tended to increase with habitat heterogeneity but only when species were specialised to different habitats and were not inhibited in mixtures by negative species interactions. This was not the case in several experiments used in our meta-analysis where one species maximised functioning across all habitats, contrary to the assumptions of many ecological models. Our results illustrate the importance of biodiversity at larger spatial scales with more heterogeneity but also highlights contingencies that this pattern depends on.
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