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Sökning: WFRF:(Kautsky Nils)

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1.
  • Hedberg, Nils, et al. (författare)
  • Antibiotic use in Vietnamese fish and lobster sea cage farms; implications for coral reefs and human health
  • 2018
  • Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 495, s. 366-375
  • Tidskriftsartikel (refereegranskat)abstract
    • Several papers have reported on the development of antibiotic resistance and implications for human medicine but fewer deal with environmental impacts of antibiotic use. Marine sea cage aquaculture in SE Asia is often established close to coral reef ecosystems. Large amounts of antibiotics are used in the cultivation of fish and lobster and hence released directly into the environment. This study investigates the antibiotic practices in sea cage farms producing fish and spiny lobster in Vietnam, mainly for the domestic market. There are approximately 3500 sea cage farms in Vietnam and we performed semi-structured interviews with 109 sea cage farmers asking them if they use antibiotics and if so; what sort/when/how often/how much. We found that the Vietnamese cage farmers are using antibiotics in an unstructured way, which seems to have little or no effect on the survival of the stock, or profit of the farm. The fact that the farmers live at their farm and use the sea next to the cages both for fishing and collecting filter-feeding bivalves for direct consumption, as well as a toilet, poses an additional risk for the spreading of human antibiotic resistant pathogens. Thirteen different antibiotics were found in the study. Eighty-two percentage of the lobster farmers and 28% of the fishfarmers used antibiotics. The average amounts used were over 5 kg per produced ton of lobster and about 0.6 kg per ton of fish, which is much higher than in other studies. Several antibiotic substances listed as critical and highly important for human medicine by WHO were used prophylactically and routinely with little control and enforcement of regulations. We tested and detected antibiotic resistance to Tetracycline, Vancomycin and Rifampicin in the coral associated bacteria Bacillus niabensis as far as 660m from fish farms with resistance decreasing with distance from the cage farms. The antibiotics are likely to have negative effects on the coral-symbiont relationship adding further risks to an already stressed environment.
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4.
  • Hedberg, Nils, et al. (författare)
  • Causes and consequences of spatial links between sea cage aquaculture and coral reefs in Vietnam
  • 2017
  • Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 481, s. 245-254
  • Tidskriftsartikel (refereegranskat)abstract
    • A majority of the sea cage farms in South East Asia are located close to coral reefs. This causes a conflict between conservation and food production since sea cage aquaculture has a number of negative impacts on coral reefs. The aim of this investigation was to assess the drivers causing the sea cage farmers to place their farms close to reefs and to examine some potential farming effects in detail i.e. usage of coral reef fish for grow out farming and feed. For some 3500 Vietnamese fish and lobster farms, we measured; the distance to the closest coastal city (proxy for infrastructure access), satellite derived Chl a (proxy for water quality), wind fetch, and the adjacent coastal slope and elevation. We also performed 159 semi-structured interviews with fish and lobster cage farmers from three regions in Vietnam. The interviews revealed that the choice of farming site is mainly determined by access to infrastructure, wind and wave shelter, and water quality. Although the farmers used coral reef services, e.g. coral reef derived seedlings, they were in general not aware of coral reef presence or did not find it important for selection of site. Both coral reefs and sea cage farms were found close to steep rocky coasts, which are favorable for corals, and provide sufficient depth for sea cages. Sea cages were always found on the leeward side of the coast where the wind fetch is low enough for the floating farms and their inhabitants. Most of the farms were located within 20 km from a coastal city confirming the importance of access to infrastructure. With few exceptions, sea cage farms were located in areas with good water quality, where also coral reefs are present. The study showed that several of the coral associated species groups farmed were dependent on wild caught seedlings and that 22% of the feed used at farms was trashfish of coral reef associated species. We consider the spatial correlation between sea cage farms and coral reefs as circumstantial and suggest that shared environmental preferences explain the farm distribution pattern, rather than access to ecosystem services provided by the nearby reef itself. We found no evidence that it is necessary for sea cage farms to be located near coral reefs and strongly recommend that sea cages are moved further away from coral reefs, but to areas still providing clear water, shelter and access to infrastructure.
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5.
  • Hedberg, Nils, 1981- (författare)
  • Sea cages, seaweeds and seascapes : Causes and consequences of spatial links between aquaculture and ecosystems
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Aquaculture is of growing importance in the global seafood production. The environmental impact of aquaculture will largely depend on the type of environment in which the aquaculture system is placed. Sometimes, due to the abiotic or biotic conditions of the seascape, certain aquaculture systems tend to be placed within or near specific ecosystems, a phenomenon that in this thesis is referred to as aquaculture system - ecosystem links. The exposed ecosystems can be more or less sensitive to the system specific impacts. Some links are known to be widespread and especially hazardous for the subjected ecosystem such as the one between the shrimp aquaculture and the mangrove forest ecosystem. The aim of this thesis was to identify and investigate causes and consequences of other spatial links between aquaculture and ecosystems in the tropical seascape.Two different aquaculture system - ecosystem links were identified by using high resolution satellite maps and coastal habitat maps; the link between sea cage aquaculture and coral reefs, and the one between seaweed farms and seagrass beds. This was followed by interviews with the sea cage- and seaweed farmers to find the drivers behind the farm site selection. Many seaweed farmers actively choose to establish their farms on sea grass beds but sea cage farmers did not consider coral reefs when choosing location for their farms. The investigated environmental consequences of the spatial link between sea cage aquaculture and coral reefs were considerable both on the local coral reef structure, and coral associated bacterial community. Furthermore, coral reef associated fish are used as seedlings and feed on the farms, which likely alter the coral food web and lower the ecosystem resilience. Unregulated use of last resort antibiotics in both fish- and lobster farms were also found to be a wide spread practice within the sea cage aquaculture system, suggesting a high risk for development of antibiotic resistant bacteria. The effects of seaweed farms on seagrass beds were not studied in this thesis but have earlier been shown to be rather substantial within the borders of the farm but less so outside the farm.Further, a nomenclature is presented to facilitate the discussion about production system - ecosystem links, which may also be used to be able to incorporate the landscape level within eco-certifying schemes or environmental risk assessments. Finally - increased awareness of the mechanisms that link specific aquaculture to specific habitats, would improve management practices and increase sustainability of an important and still growing food producing sector - the marine aquaculture.
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7.
  • Hedberg, Nils, et al. (författare)
  • Spatial correlation and potential conflicts between sea cage farms and coral reefs in South East Asia
  • 2015
  • Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 448, s. 418-426
  • Tidskriftsartikel (refereegranskat)abstract
    • In the South China and Java Seas, cage farming is a recent regional activity, which since the year 2000 has experienced an annual growth of 29%. The region holds the highest diversity of marine life, which is partly or completely dependent on coral reefs. The increasingly growing coastal human population in the area relies on ecosystem goods and services provided by the reefs that are threatened by anthropogenic activities. Sea cage farming is one of the stressors negatively impacting coral reefs by being point sources of nutrients and other effluents. To date no systematic information is available on the physical location of marine farms in relation to the coral reefs. Little is known about the distance where impact from the farms can be detected on nearby coral reefs. The present survey aimed to fill this gap by assessing to what extent marine cage farms in South East Asia are placed in the vicinity of the reefs and at which distance stress indicators from the farms are observed. We used Google Earth satellite images to investigate the extension and spatial distribution of sea cage aquaculture in relation to the presence of coral reefs. The stress indicators were locally assessed in Central Vietnam by recording turf algal overgrowth, coral mortality, live coral and branching coral cover at increasing distances from the farms. We found that 90% of sea cage farms throughout the region clustered closer than 5 km from coral reefs and 50% of them closer than 1 km from reefs. In Taiwan, 71% of the cages were located within 100m from a reef. This pattern is nonrandom and could not be explained by the natural distribution of coral reefs; only 5% of the Vietnamese coast harbors coral reefs, and sea cage farms are present in these areas only. This indicates that the farms require similar conditions as the reefs including clear and shallow waters and protection against storms and wave action. We found that turf algal overgrowth decreased at 287 m +/- 54 m, dead coral at 1446m +/- 154 m, live coral cover increased at 566 +/- 221 m and branching corals increased at 867 m +/- 140 m from the cage farms. We conclude that proximity to coral reefs should be considered when planning future developments of sea cage aquaculture, and recommend that distances of at least 1.5 km should be kept. Statement of relevance: Consider coral reefs when planning sea cage aquaculture site.
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8.
  • Kumblad, Linda, 1974- (författare)
  • Radionuclides in the Baltic Sea : Ecosystem models and experiments on transport and fate
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Manmade radionuclides have been introduced to the environment for almost a century. The main source has been the nuclear weapons testing programmes, but accidental releases from the nuclear power production industries have also contributed. The risk to humans from potential releases from nuclear facilities is evaluated in safety assessments. Essential components of these assessments are exposure models, which estimate the transport of radionuclides in the environment, the uptake in biota, and transfer to humans. Recently, there has been a growing concern for radiological protection of the whole environment, not only humans, and a first attempt has been to employ model approaches based on stylised environments and transfer functions to biota based exclusively on bioconcentration factors. They are generally of a non-mechanistic nature and involve no knowledge of the actual processes involved, which is a severe limitation when assessing real ecosystems. The research presented in this thesis attempts to introduce a methodology for modelling exposure of biota that is based on systems ecological theories and concepts. All presented papers concern bioaccumulation and circulation of radionuclides in coastal areas of the Baltic Sea, which is a sea surrounded by several nuclear power plants, waste repositories and reprocessing facilities. Paper I illustrates how an ecosystem model can be used to predict the fate of C-14 in a bay, and to explore the influence of uptake route and water exchange on the concentrations in biota. Due to the longevity of many radionuclides, time spans of thousands of years need to be considered in assessments of nuclear waste facilities. In Paper II, the methodological problems associated with these long timescales are discussed and a new modelling approach is proposed. An extension and generalisation of the C-14 flow model into a generic model for other radionuclides is described and tested in Paper III. This paper also explores the importance of three radionuclide specific mechanisms (plant uptake, excretion and adsorption to organic surfaces) for the concentrations in biota. In Paper IV, the bioaccumulation kinetics of three radionuclides in three key benthic species of the Baltic Sea is studied experimentally. Paper V considers remobilisation and redistribution of sediment-associated radionuclides due to biological mixing, in a microcosm study. The findings in this thesis show both that it was possible to use an ecosystem approach to assess the exposure to biota, and that this approach can handle many of the problems identified in the use of traditional exposure models for radionuclides. To conclude, frameworks for the protection of the environment from ionising radiation would benefit from implementing methodologies based on ecologically sound principles and modelling techniques.
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9.
  • Lilliesköld Sjöö, Gustaf, 1981- (författare)
  • Macroalgae in tropical seascapes : regulating factors and functions in the coastal ecosystem
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Although macroalgae usually are inconspicuous on pristine coral reefs, they often thrive on reefs that are subjected to various types of anthropogenic disturbance. This thesis consists of five papers and investigates how biomass and composition of macroalgal communities on coral reefs are affected by regulating factors, such as nutrient availability, herbivory, substrate availability and hydrodynamic forces. In addition, ecological functions and potential impacts of both wild and farmed macroalgal communities are evaluated. Paper I describes a method for using macroalgal tissue nutrient concentrations as bioindicator for nutrient availability, with the possibility to map nutrient loading from larger coastal cities. Papers II and III are manipulative studies comparing top-down and bottom-up regulation of macroalgal communities, where herbivore consumption seems to be the main regulator of biomass whereas nutrient availability mainly influences community composition. Exclosure of large-bodied herbivores had a positive influence on algal biomass in both studies, and during different climatic periods. Paper III also includes the influence of hydrodynamic forces on algal community biomass and structure by comparing a reef crest and a back reef-habitat. Alterations of top-down and bottom-up regulation generally had a stronger effect within the protected back reef-habitat, suggesting that such environments may be more sensitive to anthropogenic influence. Paper IV confirms the general conclusions from papers II and III by studying macroalgal biomass and composition on reef sites with different environmental prerequisites. This study also supports the notion that herbivorous fish can suppress accumulation of macroalgal biomass if substrate availability is low, but not where coral cover is reduced and plenty of substrate is open to macroalgal colonization. The study also found a large temporal variation of macroalgal standing stock and associated nutrients at sites with low top-down regulation. Paper V evaluates potential impacts of seaweed farming on coral reefs and nutrients in the seascape by experimentally studying growth, survival and nutrient binding capacity of Eucheuma denticulatum. This study showed that seaweed farms counteract eutrophication through nutrient extraction and that the risk of farmed algae colonizing local reefs seems to be small as they were rapidly consumed. In conclusion, the studies in this thesis contribute to the understanding of macroalgal regulation and function in tropical seascapes, thereby adding to the knowledge base for coastal management.
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10.
  • Nordemar, Ingrid, 1968- (författare)
  • Human Abuses of Coral Reefs- Adaptive Responses and Regime Transitions
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • During the last few decades, coral reefs have become a disappearing feature of tropical marine environments, and those reefs that do remain are severely threatened. It is understood that humans have greately altered the environment under which these ecosystems previously have thrived and evoloved. Overharvesting of fish stocks, global warming and pollution are some of the most prominent threats, acting on coral reefs at several spatial and temporal scales. Presently, it is common that coral reefs have been degraded into alternative ecosystem regimes, such as macroalgae-dominated or sea urchin-barren. Although these ecosystems could potentially return to coral dominance in a long-term perspective, when considdering current conditions, it seems likely that they will persist in their degraded states. Thus, recovery of coral reefs cannot be taken for granted on a human timescale. Multiple stressors and disturbances, which are increasingly characteristic of coral reef environments today, are believed to act synergistically and produce ecological surprises. However, current knowledge of effects of compounded disturbances and stress is limited. Based on five papers, this thesis investigates the sublethal response of multiple stressors on coral physiology, as well as the effects of compounded stress and disturbance on coral reef structure and function. Adaptive responses to stress and disturbance in relation to prior experience are highlighted. The thesis further explores how inherent characteristics (traits) of corals and macroalgae may influence regime expression when faced with altered disturbance regimes, in particular overfishing, eutrophication, elevated temperature, and enhanced substrate availability. Finally, possibilities of affecting the resilience of macroalgae-dominaed reefs and shifting the community composition towards a coral-dominated regime are explored.
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12.
  • Barrett, Scott, et al. (författare)
  • Social dimensions of fertility behavior and consumption patterns in the Anthropocene
  • 2020
  • 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. ; 117:12, s. 6300-6307
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider two aspects of the human enterprise that profoundly affect the global environment: population and consumption. We show that fertility and consumption behavior harbor a class of externalities that have not been much noted in the literature. Both are driven in part by attitudes and preferences that are not egoistic but socially embedded; that is, each household's decisions are influenced by the decisions made by others. In a famous paper, Garrett Hardin [G. Hardin, Science 162, 1243-1248 (1968)] drew attention to overpopulation and concluded that the solution lay in people abandoning the freedom to breed. That human attitudes and practices are socially embedded suggests that it is possible for people to reduce their fertility rates and consumption demands without experiencing a loss in wellbeing. We focus on fertility in sub-Saharan Africa and consumption in the rich world and argue that bottom-up social mechanisms rather than top-down government interventions are better placed to bring about those ecologically desirable changes.
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13.
  • Berkström, Charlotte, 1978- (författare)
  • Ecological connectivity in East African seascapes
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Coral reefs, seagrass beds and mangroves constitute a complex mosaic of habitats referred to as the tropical seascape. Great gaps exist in the knowledge of how these systems are interconnected. This thesis sets out to examine ecological connectivity, i.e. the connectedness of ecological processes across multiple scales, in Zanzibar and Mafia Island, Tanzania. Paper I examined the current knowledge of interlinkages and their effect on seascape functioning, revealing that there are surprisingly few studies on the influences of cross-habitat interactions and food-web ecology. Furthermore, 50% of all fish species use more than one habitat and 18% of all coral reef fish species use mangrove or seagrass beds as juvenile habitat in Zanzibar. Paper II examined the seascape of Menai Bay, Zanzibar using a landscape ecology approach and studied the relationship between fish and landscape variables. The amount of seagrass within 750m of a coral reef site was correlated with increased invertebrate feeder/piscivore fish abundance, especially Lethrinidae and Lutjanidae, which are known to perform ontogenetic and feeding migrations. Within patch seagrass cover was correlated with nursery species abundance. Paper III focused on a seagrass-dominated seascape in Chwaka Bay, Zanzibar and showed that small-scale habitat complexity (shoot height and density) as well as large-scale variables such as distance to coral reefs affected abundance and distribution of a common seagrass parrotfish Leptoscarus vaigiensis. Paper IV studied the connectivity and functional role of two snappers (Lutjanus fulviflamma and L. ehrenbergii) using stable isotopes (δ15N and δ13C) and found that connectivity between habitats was maintained by ontogenetic and foraging migrations by these species. The thesis concludes that ecological connectivity and multi-habitat usage by fish is a general and important characteristic in the Western Indian Ocean and should be considered in management planning.
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14.
  • Berkström, Charlotte, 1978-, et al. (författare)
  • Exploring 'knowns' and 'unknowns' in tropical seascape connectivity with insights from East African coral reefs
  • 2012
  • Ingår i: Estuarine Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 107, s. 1-21
  • Tidskriftsartikel (refereegranskat)abstract
    • Applying a broader landscape perspective to understand spatio-temporal changes in local populations and communities has been increasingly used in terrestrial systems to study effects of human impact and land use change. With today's major declines in fishery stocks and rapid degradation of natural coastal habitats, the understanding of habitat configuration and connectivity over relevant temporal and spatial scales is critical for conservation and fisheries management of the seascape. Coral reefs, seagrass beds and mangroves are key-components of the tropical seascape. The spatial distribution of these habitat types may have strong influences on cross-habitat migration and connectivity patterns among organisms. However, the consequences of seascape fragmentation and ecological connectivity are largely unknown. Here, we review the literature to provide an overview of current knowledge with regards to connectivity and food-web interactions within the tropical seascape. We show that information on fish acting as mobile links and being part of nutrient transfer and trophic interactions is scarce. We continue by making an in-depth analysis of the seascape around Zanzibar (Eastern Africa) to fill some of the knowledge gaps identified by the literature survey. Our analysis shows that (i) fifty percent of all fish species found within the Zanzibar seascape use two or multiple habitat types, (ii) eighteen percent of all coral reef-associated fish species use mangrove and seagrass beds as juvenile habitat, and (iii) macrocarnivores and herbivores are highly represented among those coral reef fish species that use mangrove and seagrass beds as juvenile habitat. We argue that understanding the inter-linkages within and between habitat types is essential for successful management of the tropical seascape. (c) 2012 Elsevier Ltd. All rights reserved
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15.
  • Björk, Mikael, et al. (författare)
  • In situ determination of PCB biodeposition by Mytilus edulis in a Baltic coastal ecosystem
  • 2000
  • Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 194, s. 193-201
  • Tidskriftsartikel (refereegranskat)abstract
    • Biodeposits of the blue mussel Mytilus edulis and pelagic and near-bed settling particulate matter were collected in situ over a 1 yr period in a coastal area of the Northern Baltic proper. The amounts of carbon and PCBs (polychlorinated biphenyls) in the collected biodeposits were compared to those in pelagic and near-bed settling material and rates of carbon and PCB biodeposition by mussels were estimated. The filter-feeding activity and subsequent release of faecal matter by the mussels increased gross sedimentation of carbon to benthos by 45 % if compared to areas with no mussels. By selectively feeding on particles rich in organic carbon the mussels also concentrated associated contaminants and thereby increased gross sedimentation of PCBs by 50 %. This suggests that mussel biodeposition will enhance the availability of PCBs to benthic deposit feeders living in or in the vicinity of mussel beds. Extrapolation of the experimental results to the total Swedish coastal zone of the Baltic proper indicates that mussel biodeposition is responsible for a significant part of PCB net sedimentation, i.e. 17 % or 96 kg yr(-1). Consequently, even when seen from a large geographical scale, mussels are important modifiers of PCB cycling by directing considerable amounts of PCBs towards the benthic food web and thereby influencing the retention time of these and probably many other contaminants in the coastal zone. It is also Likely that changes in mussel biomass, for example owing to shifts in primary production or salinity, will markedly affect the transport and fate of contaminants in the Baltic Sea.
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16.
  • Carpenter, S. R., et al. (författare)
  • General resilience to cope with extreme events
  • 2012
  • Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 4:12, s. 3248-3259
  • Tidskriftsartikel (refereegranskat)abstract
    • Resilience to specified kinds of disasters is an active area of research and practice. However, rare or unprecedented disturbances that are unusually intense or extensive require a more broad-spectrum type of resilience. General resilience is the capacity of social-ecological systems to adapt or transform in response to unfamiliar, unexpected and extreme shocks. Conditions that enable general resilience include diversity, modularity, openness, reserves, feedbacks, nestedness, monitoring, leadership, and trust. Processes for building general resilience are an emerging and crucially important area of research.
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17.
  • Chapin III, F. Stuart, et al. (författare)
  • Earth stewardship : Shaping a sustainable future through interacting policy and norm shifts
  • 2022
  • Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 51:9, s. 1907-1920
  • Tidskriftsartikel (refereegranskat)abstract
    • Transformation toward a sustainable future requires an earth stewardship approach to shift society from its current goal of increasing material wealth to a vision of sustaining built, natural, human, and social capital—equitably distributed across society, within and among nations. Widespread concern about earth’s current trajectory and support for actions that would foster more sustainable pathways suggests potential social tipping points in public demand for an earth stewardship vision. Here, we draw on empirical studies and theory to show that movement toward a stewardship vision can be facilitated by changes in either policy incentives or social norms. Our novel contribution is to point out that both norms and incentives must change and can do so interactively. This can be facilitated through leverage points and complementarities across policy areas, based on values, system design, and agency. Potential catalysts include novel democratic institutions and engagement of non-governmental actors, such as businesses, civic leaders, and social movements as agents for redistribution of power. Because no single intervention will transform the world, a key challenge is to align actions to be synergistic, persistent, and scalable.
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18.
  • 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.
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19.
  • Crépin, Anne-Sophie, et al. (författare)
  • Social-ecological systems as complex adaptive systems : modeling and policy implications
  • 2013
  • Ingår i: Environment and Development Economics. - 1355-770X .- 1469-4395. ; 18:2, s. 111-132
  • Tidskriftsartikel (refereegranskat)abstract
    • Systems linking people and nature, known as social-ecological systems, are increasingly understood as complex adaptive systems. Essential features of these complex adaptive systems – such as nonlinear feedbacks, strategic interactions, individual and spatial heterogeneity, and varying time scales – pose substantial challenges for modeling. However, ignoring these characteristics can distort our picture of how these systems work, causing policies to be less effective or even counterproductive. In this paper we present recent developments in modeling social-ecological systems, illustrate some of these challenges with examples related to coral reefs and grasslands, and identify the implications for economic and policy analysis.
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20.
  • Crona, Beatrice, 1974- (författare)
  • Of Mangroves and Middlemen : A study of social and ecological linkages in a coastal community
  • 2006
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis studies some of the links between the social and ecological components in a coastal Social-Ecological System (SES) of East Africa to gain insight into factors affecting natural resource management at a community level. It does so by assessing the return of ecosystem goods and services in restored mangroves through both ecological and socio-economic measurements, and by empirically studying variations and diversity in content of local ecological knowledge among resource users, its relation to valuation of ecosystem goods and services and its distribution across a social network.Taking its starting point in a study of the return of ecological functions in restored mangroves (Paper I) the main results of the thesis are presented in three sections. The ecological perspective, showing restored mangroves as nursery grounds for juvenile shrimp communities, is complemented by findings from interviews with local user groups revealing a range of ecosystem goods and services associated with natural and replanted forests (Paper II). The thesis moves on to show heterogeneity in local ecological knowledge held by groups of resource users (Paper III) and how this can be correlated with structure of the social network for transferring such information and knowledge (Paper IV). This network structure is elaborated upon in the third and final section to look at the role it might play for community social capital and for structurally well positioned individuals to access such capital and initiate collective action for natural resource management (Paper V). The role played by social capital in shaping the informal institution represented by middlemen in the study area is also touched upon as is the function of middlemen in linking social and ecological dynamics of the coupled Social Ecological System (Paper VI). Finally, the implications of these findings are discussed in the context of natural resource management with focus on co-management and community involvement.
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21.
  • de la Torre-Castro, Maricela, 1965- (författare)
  • Humans and Seagrasses in East Africa : A social-ecological systems approach
  • 2006
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The present study is one of the first attempts to analyze the societal importance of seagrasses (marine flowering plants) from a Natural Resource Management perspective, using a social-ecological systems (SES) approach. The interdisciplinary study takes place in East Africa (Western Indian Ocean, WIO) and includes in-depth studies in Chwaka Bay, Zanzibar, Tanzania. Natural and social sciences methods were used. The results are presented in six articles, showing that seagrass ecosystems are rich in seagrass species (13) and form an important part of the SES within the tropical seascape of the WIO. Seagrasses provide livelihoods opportunities and basic animal protein, in from of seagrass associated fish e.g. Siganidae and Scaridae. Research, management and education initiatives are, however, nearly non-existent. In Chwaka Bay, the goods and ecosystem services associated with the meadows and also appreciated by locals were fishing and collection grounds as well as substrate for seaweed cultivation. Seagrasses are used as medicines and fertilizers and associated with different beliefs and values. Dema (basket trap) fishery showed clear links to seagrass beds and provided the highest gross income per capita of all economic activities. All showing that the meadows provide social-ecological resilience. Drag-net fishery seems to damage the meadows. Two ecological studies show that artisanal seaweed farming of red algae, mainly done by women and pictured as sustainable in the WIO, has a thinning effect on seagrass beds, reduces associated macrofauna, affects sediments, changes fish catch composition and reduces diversity. Furthermore, it has a negative effect on i.a. women’s health. The two last papers are institutional analyses of the human-seagrass relationship. A broad approach was used to analyze regulative, normative and cultural-cognitive institutions. Cooperation and conflict take place between different institutions, interacting with their slow or fast moving characteristics, and are thus fundamental in directing the system into sustainable/unsustainable paths. Ecological knowledge was heterogeneous and situated. Due to the abundance of resources and high internal control, the SES seems to be entangled in a rigidity trap with the risk of falling into a poverty trap. Regulations were found insufficient to understand SES dynamics. “Well” designed organizational structures for management were found insufficient for “good” institutional performance. The dynamics between individuals embedded in different social and cultural structures showed to be crucial. Bwana Dikos, monitoring officials, placed in villages or landing sites in Zanzibar experienced four dilemmas – kinship, loyalty, poverty and control – which decrease efficiency and affect resilience. Mismatches between institutions themselves, and between institutions and cognitive capacities were identified. Some important practical implications are the need to include seagrass meadows in management and educational plans, addressing a seascape perspective, livelihood diversification, subsistence value, impacts, social-ecological resilience, and a broad institutional approach.
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22.
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23.
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24.
  • 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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25.
  • Eggertsen, Linda, et al. (författare)
  • Seaweed beds support more juvenile reef fish than seagrass beds in a south-western Atlantic tropical seascape
  • 2017
  • Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 196:5, s. 97-108
  • Tidskriftsartikel (refereegranskat)abstract
    • Seascape connectivity is regarded essential for healthy reef fish communities in tropical shallow systems. A number of reef fish species use separate adult and nursery habitats, and hence contribute to nutrient and energy transfer between habitats. Seagrass beds and mangroves often constitute important nursery habitats, with high structural complexity and protection from predation. Here, we investigated if reef fish assemblages in the tropical south-western Atlantic demonstrate ontogenetic habitat connectivity and identify possible nurseries on three reef systems along the eastern Brazilian coast. Fish were surveyed in fore reef, back reef, Halodule wrightii seagrass beds and seaweed beds. Seagrass beds contained lower abundances and species richness of fish than expected, while Sargassum-dominated seaweed beds contained significantly more juveniles than all other habitats (average juvenile fish densities: 32.6 per 40 m2 in Sargassum beds, 11.2 per 40 m2 in back reef, 10.1 per 40 m2 in fore reef, and 5.04 per 40 m2 in seagrass beds), including several species that are found in the reef habitats as adults. Species that in other regions worldwide (e.g. the Caribbean) utilise seagrass beds as nursery habitats were here instead observed in Sargassum beds or back reef habitats. Coral cover was not correlated to adult fish distribution patterns; instead, type of turf was an important variable. Connectivity, and thus pathways of nutrient transfer, seems to function differently in east Brazil compared to many tropical regions. Sargassum-dominated beds might be more important as nurseries for a larger number of fish species than seagrass beds. Due to the low abundance of structurally complex seagrass beds we suggest that seaweed beds might influence adult reef fish abundances, being essential for several keystone species of reef fish in the tropical south-western Atlantic.
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26.
  • Eggertsen, Maria, 1981-, et al. (författare)
  • Coral-macroalgae interactions : herbivory and substrate type influence growth of the macroalgae Eucheuma denticulatum on a tropical reef
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Invasive macroalgae can alter coral reef habitats by causing phase shifts from coral to macroalgal domination with negative ecological effects and dramatic reductions in coral cover. In Tanzania, South East Asian haplotypes of the macroalgae Eucheuma denticulatum, documented to overgrow reef corals in other locations, have been introduced through seaweed farming practices. In this study we examine growth and holdfast development of introduced and native E. denticulatum on live and dead branches of Acropora sp. in the presence and absence of herbivores in Unguja Island, Zanzibar. Coral and macroalgae health were also estimated. Macroalgae did not attach to any live coral. Coral health was not impacted by the presence of E. denticulatum regardless of origin and gene expression analyses did not indicate any additional stress in corals. Necrotic tissue on the macroalgae in areas of direct contact indicated damage inflicted by the coral. The biomass of E. denticulatum did not differ between live or dead corals but was strongly influenced by herbivory.  The study indicates that E. denticulatum may not pose a strong immediate threat to healthy acroporids in the WIO region but stresses the importance to keep corals healthy and maintaining viable populations of macroalgae feeding species.
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27.
  • Eggertsen, Maria, et al. (författare)
  • Coral-macroalgal interactions : Herbivory and substrate type influence growth of the macroalgae Eucheuma denticulatum (N.L. Burman) Collins & Hervey, 1917 on a tropical coral reef
  • 2021
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 542
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduced macroalgae becoming invasive may alter ecological functions and habitats in recipient ecosystems. In the Western Indian Ocean (WIO), non-native strains of the native macroalgae Eucheuma denticulatum were introduced for farming practices and consequently spread into the surrounding seascape. We investigated potential effects of non-native and native strains of this macroalgae on a branching coral. We conducted a four-factor field experiment where we examined growth and holdfast development of introduced and native E. denticulatum on live and dead branches of Acropora sp. in the presence and absence of herbivores in Unguja Island, Zanzibar. Moreover, we estimated coral and macroalgae condition by visual examinations, gene expression analyses, and photosynthetic measurements. Macroalgae did not attach to any live coral and coral condition was not impacted by the presence of E. denticulatum, regardless of geographical origin. Instead, necrotic tissue on the macroalgae in areas of direct contact with corals indicated damage inflicted by the coral. The biomass of E. denticulatum did not differ between the replicates attached to live or dead corals in the experiment, yet biomass was strongly influenced by herbivory and replicates without protection from herbivores had a significantly lower biomass. In the absence of herbivory, introduced E. denticulatum had significantly higher growth rates than native algae based on wet weight measurements. These results contribute to an increased understanding of environmental effects by the farming of a non-native strain of algae on corals and stresses the importance to maintain viable populations of macroalgal feeding fishes in such areas.
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28.
  • 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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29.
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30.
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31.
  • Folke, Carl, et al. (författare)
  • Aquaculture and ocean stewardship
  • 2022
  • Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 51:1, s. 13-16
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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32.
  • Folke, Carl, et al. (författare)
  • Transnational corporations and the challenge of biosphere stewardship
  • 2019
  • Ingår i: Nature Ecology & Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 3:10, s. 1396-1403
  • Tidskriftsartikel (refereegranskat)abstract
    • Sustainability within planetary boundaries requires concerted action by individuals, governments, civil society and private actors. For the private sector, there is concern that the power exercised by transnational corporations generates, and is even central to, global environmental change. Here, we ask under which conditions transnational corporations could either hinder or promote a global shift towards sustainability. We show that a handful of transnational corporations have become a major force shaping the global intertwined system of people and planet. Transnational corporations in agriculture, forestry, seafood, cement, minerals and fossil energy cause environmental impacts and possess the ability to influence critical functions of the biosphere. We review evidence of current practices and identify six observed features of change towards 'corporate biosphere stewardship', with significant potential for upscaling. Actions by transnational corporations, if combined with effective public policies and improved governmental regulations, could substantially accelerate sustainability efforts.
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33.
  • Fröcklin, Sara, 1981- (författare)
  • Women in the Seascape : Gender, Livelihoods and Management of Coastal and Marine Resources in Zanzibar, East Africa
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • All over the world, coastal populations depend on, and influence, the environment in pursue of their livelihoods. Managing the environment, while meeting the growing demand for marine resources, is a challenge. It further requires knowledge about all actors. Women's contribution is often overlooked in research, policy and management of marine and coastal resources. This thesis aims to reduce this gap; a gender analysis is applied to differentiate women and men's access and use of the seascape and to address key gender issues in coastal livelihoods in Zanzibar, Tanzania. Paper I shows that men are typically engaged in fisheries and have access to the whole seascape, whereas women engage in less economically viable activities, such as seaweed farming and invertebrate harvesting, in near-shore areas. A limitation for women to reach the whole seascape is a general lack of boat transport, swimming skills and fishing gear. Paper II analyzes occupational health within seaweed farming and shows that women seaweed farmers suffer from a variety of problems, such as eye infections, musculoskeletal pains, respiratory problems and fatigue, because of poor working conditions. Paper III addresses social and ecological aspects of invertebrate harvesting. This activity lacks proper management and over a five-year period (2005 to 2010), invertebrate abundance and species richness have decreased. It also reveals gender disparities in access to invertebrate collecting grounds and species of higher economic value. Paper IV examines gender within fish trade; women traders have less access to markets, high-value fish, a diverse customer-base, cold-storing facilities and fish trade associations. Income data shows that women's income is always lower. The management system is found to be androcentric and this thesis thus argues for the need to look at the "bigger picture"; the whole seascape, both men and women, and their interests should be considered in coastal and marine management.
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34.
  • Gilek, Michael, et al. (författare)
  • Physiological performance and general histology of the blue mussle, Mytilus Edulis L, from the Baltic and North seas
  • 1992
  • Ingår i: Netherlands Journal of Sea Research. - 0077-7579. ; 30, s. 11-21
  • Tidskriftsartikel (refereegranskat)abstract
    • A physiological approach has been proposed for studying the ecological consequences of diseases and parasitism in bivalve molluscs. We investigated effects of some naturally occurring non-lethal parasites and histological changes in the blue mussel, Mytilus edulis L., on some commonly used bivalve condition indices, viz the oxygen:nitrogen ratio, the scope for growth and the body condition index. We found no correlation between these physiological condition indices, which implies that an individual can be classified as in 'good condition' according to e.g. the O:N ratio and the body condition index, while at the same time this mussel may have a low scope for growth indicating a stressed status. This is probably because the O:N ratio, the scope for growth and the body condition index integrate metabolic processes over different periods of time. No general deleterious effects on these condition indices could be detected either due to parasitic infestation or general histological changes. Hence, it was not possible to translate detrimental effects of histological conditions directly into energy equivalents.
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35.
  • Gräslund, Sara, 1971- (författare)
  • Chemical use in shrimp farming and environmental implications of antibiotic pollution
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Shrimp farming is a highly important industry in southeast Asia. A major threat to profitable shrimp farming is disease outbreaks, which has lead to a situation where a large number of chemicals are used to prevent and treat infections. The aim of this thesis was to assess the environmental risk of chemical use in shrimp farming, with emphasis on the use of certain antibiotics.A review of earlier studies on chemical use in shrimp farming in southeast Asia identified a serious lack of information regarding the types and amounts of products used. Thus, an interview survey was conducted in Thailand, gathering information from shrimp farmers on the use of chemicals and biological products. The farmers used on average 13 different products, mainly soil and water treatment compounds, disinfectants and pesticides, probiotics, vitamins, antibiotics, fertilisers and different feed additives. Seventy-four percent of the shrimp farmers used antibiotics of at least 13 different types, most commonly the fluoroquinolone norfloxacin. Many farmers were not well informed about safe and effective application practices, e.g., many farmers used antibiotics prophylactically, and several used them to treat viral infections. A study of the occurrence of antibiotic resistant bacteria and pollution of antibiotic substances in shrimp farming areas revealed a high proportion of antibiotic resistance among the bacteria isolated from shrimp farms, in particular to fluoroquinolones, non-fluorinated quinolones, sulphonamides and trimethoprim. Furthermore, the study showed widespread pollution by the fluoroquinolone norfloxacin in mussel samples from the investigated areas. To investigate the potential effects of antibiotics on microorganisms in marine benthic communities, a microcosm test method was developed and used to investigate the effects of three different antibiotics (norfloxacin, sulphamethoxazole and tetracycline) on microorganisms in a Swedish marine benthic system. The results indicated that high doses of the investigated antibiotics caused a decrease in microorganism activity in the systems.In conclusion, several of the antibiotics used in shrimp farming are a potential threat to the environment, and in addition to human health and to the shrimp production itself. Increased level of inspections of chemical residues in shrimp in importing countries appeared to be an important incentive for a more restrictive use of antibiotics in shrimp farming. There were indications that promotional activities by the companies marketing chemicals for use in shrimp farming increased the level of usage, which was often unnecessary or even counterproductive from a shrimp farming perspective. Hence, there is a potential to decrease usage through raising awareness among farmers about safe and efficient use of chemicals.
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36.
  • Gustafsson, Kerstin, 1973- (författare)
  • Uptake and toxicity of brominated flame retardants and pesticides : Studies on littoral organisms and model communities
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, brackish and freshwater littoral model communities (microcosms) of varying size and complexity were used to study the effects of brominated flame retardants (BFRs) and pesticides. The brackish water microcosms consisted of natural water, sediment and associated organisms, while the larger freshwater microcosms also contained submersed macrophytes (Elodea canadensis). Both the BFR hexabromocyclododecane (HBCDD) (Paper II) and the strobilurin fungicide azoxystrobin (Paper III) were found to dramatically reduce the abundance of the dominating crustacean zooplankton, calanoid copepods, in brackish water microcosms. For the fungicide, these effects were observed at concentrations more than an order of magnitude lower than reported no-effect concentrations for crustaceans in standard toxicity tests. The direct toxic effects on the copepods reduced their grazing pressure on phytoplankton. Indirect effects on the phytoplankton community were observed as increased abundance and biomass and altered community structure. Heterotrophic flagellates (Paper II) and rotifers (Paper III) increased in exposed microcosms, apparently also an indirect response to the reduced copepod grazing. In Papers IV-V, indoor freshwater microcosms dominated by the vascular macrophyte Elodea canadensis, were monitored following exposure to the sulfonylurea herbicide metsulfuron-methyl. The macrophytes were directly susceptible to the substance, and growth and biomass declined. The reduced competition from the macrophytes induced secondary indirect effects on the algal community, for example an increased phytoplankton primary production and altered community structure. The zooplankton community was also indirectly affected by the herbicide treatment. The community structure was altered and the total zooplankton biomass increased in exposed microcosms towards the end of the study. The need for increased knowledge on the uptake and bioaccumulation potential of chemical compounds in biota is often stressed. In one of the studies (Paper I) we investigated the uptake and bioaccumulation of BFR polybrominated diphenyl ethers (PBDE) in blue mussels. High bioaccumulation but also high depuration rates were found, especially for the tetra- and penta-BDE congeners. These results indicate that blue mussel may provide a source of PBDEs for other organisms in the Baltic Sea. It can be concluded from the effect studies that apart from direct toxic effects on sensitive organisms, the tested substances induced secondary, indirect effects on organisms not themselves susceptible to the toxicants. These indirect effects resulted from changes in interactions between organisms, and would not have been detected in single species test systems where no inter-specific interactions take place. Unanticipated community level responses can occur at considerably lower concentrations than the direct toxicity suggested from existing single species toxicity data, and in natural shallow aquatic ecosystems, the ecological consequences might be severe.
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37.
  • Halling, Christina, 1970- (författare)
  • Seaweed Integrated Mariculture : Prospects and Constraints Towards Increased Sustainability
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Increased global demand for seafood and stagnating catches from capture fisheries contributed to the doubling of aquaculture production taking place the last decade. Expansion within the aquaculture sector is expected to persist, and by many seen as the only mean to meet future demand for seafood. Aquaculture development has however, been associated with different types of adverse environmental impacts. One such impact, originating from the flow-through behavior of modern aquaculture, and with potential negative consequence for coastal waters, is the release of nutrients. The present thesis investigates the possibilities to use seaweeds as biofilters if being integrated with fish farming. Focus is mainly on open-water fish cage cultures (e.g. salmon) and the general objective is to analyze seaweed integration in respect from its ecological and large-scale perspective. From reviewing existing literature on seaweed integration in aquaculture an imbalance between land-based and open-water culture systems becomes apparent. In land-based aquaculture several studies acknowledged the potential of using integrated seaweed as biofilters for dissolved fish waste. Such aquaculture system has also proved successful on a large-scale, both from a technical and economical perspective. However, for open water systems even basic biological, hydrological and technical understandings are lacking. This is unfortunate, as integration may presently be the only viable treatment solution for open water-cage cultures. The red seaweed Gracilaria chilensis, mainly used for agar extraction, showed high biofiltering capacity when being integrated with a salmon cage farm, with increased growth rates and nutrient content. Integrated Gracilaria growth was up to 40% (SGR 7% day-1) higher compared to monocultures and even if agar content decreased, this was more than compensated for by the higher yield and enhanced agar quality. Analysis of stable isotopes (15N/14N and 14C/13C) in seaweed thalli cultivated at different distances (e.g. 10, 30, 60, 300 m) from cages, verifies that the nutrients being incorporated by the integrated seaweed originates from the fish farm effluent. However, the continuous nutrient supply near the cages has limited effect on seaweed growth during seasons when water temperature and light overrides nutreints as limiting factors. Even if the epiphytic abundance were moderate (2-50%) compared to common bottom cultivations, epiphytes and fouling organisms may also constrain the success of open-water integration especially high infestation of bryozoa that hamper thalli growth and mussels causing the thalli to detach due to weight. The development of suitable methods for suspended seaweed cultivation is crucial for possible commercial implementation of integrated systems. Such methods must be easy manageable with respect to stocking, operation and harvesting and also be durable for open-water conditions. Spore-inoculated Gracialria ropes were found to be unsuitable for Chilean open water conditions and trials with seaweed thalli on twisted ropes showed better performance. Limited effects from integration on seaweed growth, due to seasonal variability and its spatial needs, imply that economic incentives for commercial impementation may be weak. However this could be changed if seaweeds with higher market values were cultured or if costs for nutrient abatement were internalized in the production. Seaweed integration may be one option for developing more environmentally friendly culture techniques, but this will only be confirmed from more scientific studies that include large-scale experiments.
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38.
  • Hedman, Jenny E, 1972- (författare)
  • Fate of contaminants in Baltic Sea sediment ecosystems : the role of bioturbation
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Aquatic sediments are of major importance for the cycling of environmental pollutants, acting as both sinks and secondary sources of contaminants to the ecosystem. Sediment-living organisms can affect the fate and transport of contaminants through activities like feeding and burrowing, collectively called bioturbation. Apart from high contaminant levels, the Baltic benthic ecosystem is affected by stressors such as eutrophication-induced anoxic conditions and invading alien species. The main objectives of this thesis were to determine the effects of bioturbation on contaminant fluxes in Baltic Sea sediments and to increase the understanding of how these other stressors act together upon contaminant fate in the benthic ecosystem. Bioturbation affected contaminants in a species-specific way. The native species Monoporeia affinis and Macoma balthica increased the incorporation of BDE-99 and Cd deposited on the sediment surface, enhancing their retention in the sediment. The invasive polychaete Marenzelleria sp. did not contribute to the incorporation of surface-deposited contaminants, however, significantly increased the release of contaminants back to the water column. Reoxygenation of anoxic laminated sediments and bioturbation by Marenzelleria increased the sediment-to-water flux of dissolved organic contaminants. When the bioturbation-driven release of PCB was compared to the release caused by physical sediment resuspension, results indicated that the continuous activities of benthic infauna can be just as, or even more, important than physical disturbance for the remobilization of sediment-bound contaminants. Bioaccumulation was significantly higher when contaminants were deposited associated to phytoplankton compared to lignin or sediment, suggesting that there are likely seasonal differences in the mobilization of contaminants in the benthic ecosystem. In summary, bioturbation is an important process influencing contaminant fate in Baltic Sea sediments, and the risk of remobilization of historically buried contaminants may increase with improved benthic redox conditions and the invasion of new deeper-digging species, such as Marenzelleria.
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39.
  • Huitric, Miriam, et al. (författare)
  • Development and government policies of the shrimp farming industry in Thailand in relation to mangrove ecosystems
  • 2002
  • Ingår i: Ecological Economics. - : Elsevier. - 0921-8009. ; 40:3, s. 441-455
  • Tidskriftsartikel (refereegranskat)abstract
    • Intensive shrimp farming arrived in Thailand during the 1980s and developed virtually unregulated until 1987. Subsidised by the government, it quickly became an important export industry and Thailand has been the world's largest producer of tiger shrimp since 1991. However, the development of the shrimp farming industry in Thailand over the last 20 years in relation to its use of mangrove ecosystems is an example of sequential exploitation of natural resources witnessed through the shift in farm development from one region to another. This sequential exploitation has caused widespread degradation of mangrove ecosystems, and the benefits of the industry may be less than perceived as a result of subsidies and environmental and social impacts. This study follows the development of shrimp farming in Thailand from the 1940s to 1997 and studies national legislation and associated government policy as examples of driving forces behind this development. From our findings it appears that the development of legislation has not followed the same pace as the development of the industry, neither temporally, nor in content nor implementation, and contradictory policies have arisen.
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40.
  • Huitric, Miriam, 1974- (författare)
  • Masking environmental feedback : Misfits between institutions and ecosystems in Belize and Thailand
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The thesis analyses relationships between ecological and social systems in the context of coastal ecosystems. It examines human impacts from resource extraction and addresses management and governance behind resource exploitation. The main premises are that a lack of ecological knowledge leads to poor ecosystem management and that the dichotomy between social and natural systems is an artificial one. The thesis illustrates the importance of basing resource management on the ecological conditions of the resource and its ecosystem. It also demonstrates the necessity of accounting for the human dimension in ecosystem management and the challenges of organising human actions for sustainable use of ecosystem services in the face of economic incentives that push users towards short-term extraction.Many Caribbean coral reefs have undergone a shift from coral to macroalgal domination. An experiment on Glovers Reef Atoll in Belize manually cleared patch reefs in a no-take zone and a fished zone (Papers I and II). The study hypothesised that overfishing has reduced herbivorous fish populations that control macroalgae growth. Overall, management had no significant effect on fish abundance and the impacts of the algal reduction were short-lived. This illustrated that the benefits of setting aside marine reserves in impacted environments should not be taken for granted. Papers III and IV studied the development of the lobster and conch fisheries in Belize, and the shrimp farming industry in Thailand respectively. These studies found that environmental feedback can be masked to give the impression of resource abundance through sequential exploitation. In both cases inadequate property rights contributed to this unsustainable resource use. The final paper (V) compared the responses to changes in the resource by the lobster fisheries in Belize and Maine in terms of institutions, organisations and their role in management. In contrast to Maine’s, the Belize system seems to lack social mechanisms for responding effectively to environmental feedback. The results illustrate the importance of organisational and institutional diversity that incorporate ecological knowledge, respond to ecosystem feedback and provide a social context for learning from and adapting to change.
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41.
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42.
  • Kautsky, Nils, et al. (författare)
  • Aquaculture
  • 2000. - 1
  • Ingår i: Encyclopedia of Biodiversity. - San Diego : Academic Press. - 0122268652 ; , s. 185-198
  • Bokkapitel (refereegranskat)
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43.
  • Kautsky, Nils, et al. (författare)
  • Ecosystem perspectives on management of disease in shrimp pond farming
  • 2000
  • Ingår i: Aquaculture. - Amsterdam : Elsevier. - 0044-8486 .- 1873-5622. ; 191:1-3, s. 145-161
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper reviews and discusses, from an ecological perspective, the causes behind the development and spreading of pathogens in shrimp aquaculture. The risk of disease in shrimp farming often increases with culture intensity and high stocking densities, and when polyculture is replaced by monoculture. High pond densities will facilitate the spread of pathogens between ponds. Shortage of clean water supply and insufficient waste removal lead to overloading of metabolites, environmental degradation, and to the shrimp becoming stressed by bad water quality, and thus more prone to becoming affected by disease. Excessive fluctuations in abiotic factors like oxygen, salinity, and temperature may also increase stress and susceptibility to disease. The location of farms in mangrove environments can lead to acidification that may directly, or indirectly, through release of heavy metals from the sediments, lower disease resistance. The use of hatchery-reared larvae will increase genetic uniformity and thus disease risk in comparison to the collection of wild larvae where selection has already favored the most viable individuals. Global and regional transportation of seed larvae and broodstock will facilitate the spread of pathogens. Apart from the above factors, which are all dependant on the farming itself, contamination by pesticides and pollutants from agriculture and industrial activities may lower disease resistance of the shrimp, especially if combined with other environmental factors.We show that shrimp farming is, to a large extent, dependent on ecological services supplied by nature, and discuss the carrying capacity of shrimp pond farming from an ecosystem perspective, including aspects like culture intensity, pond density and sustainability. Since aquaculture is basically a natural ecological process, although in intensive shrimp farming it reaches industrial proportions, it is essential that we do not forget the underlying ecological principles, as this may help us to understand and contribute to the solution of some of the disease problems faced by shrimp farming.
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46.
  • Levin, Simon A., et al. (författare)
  • Governance in the Face of Extreme Events : Lessons from Evolutionary Processes for Structuring Interventions, and the Need to Go Beyond
  • 2022
  • Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 25:3, s. 697-711
  • Tidskriftsartikel (refereegranskat)abstract
    • The increasing frequency of extreme events, exogenous and endogenous, poses challenges for our societies. The current pandemic is a case in point; but once-in-a-century weather events are also becoming more common, leading to erosion, wildfire and even volcanic events that change ecosystems and disturbance regimes, threaten the sustainability of our life-support systems, and challenge the robustness and resilience of societies. Dealing with extremes will require new approaches and large-scale collective action. Preemptive measures can increase general resilience, a first line of protection, while more specific reactive responses are developed. Preemptive measures also can minimize the negative effects of events that cannot be avoided. In this paper, we first explore approaches to prevention, mitigation and adaptation, drawing inspiration from how evolutionary challenges have made biological systems robust and resilient, and from the general theory of complex adaptive systems. We argue further that proactive steps that go beyond will be necessary to reduce unacceptable consequences.
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47.
  • Mörk, Erik, 1978- (författare)
  • Macroalgal community dynamics on coral reefs : Implications for management
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Although rather inconspicuous on healthy coral reefs, macroalgae form the basis of coral food webs. Today, macroalgae are generally increasing and many reefs undergo transitions from coral to macroalgal dominance resulting from e.g. enhanced nutrient loading or increased fishing.This thesis aims to investigate the relative importance of top-down and bottom-up regulation, and different herbivore types, on macroalgal distribution, fecundity and community composition on coral reefs. Papers I and II indicate that macroalgal abundance in a coral reef system is largely governed by top-down regulation through grazing by herbivores, while bottom-up regulation through enhanced nutrient availability rather influence algal species composition. Paper II also shows that these regulating effects are not as evident in an area with relatively strong water motion, suggesting that impacts of anthropogenic disturbance may be site-specific. Paper III shows that herbivory is an important factor influencing macroalgal growth and subsequent reproduction. Furthermore, Paper IV and V conclude that efficiency in removing macroalgal biomass is dependent on the type of dominant herbivore, where sea urchins seem to be more effective than fish. Paper IV indicates a seasonal variation in macroalgal biomass and distribution in a small geographic scale but with relatively high temporal resolution. Paper V on the other hand shows these same effects, but with a focus on geographic variation, including a large part of the East African region, as well as between year temporal variations in Kenya. Together, results from the two latter studies indicate that herbivory by fish may not be able to prevent a macroalgal bloom in a degraded system where substrate availability for algal colonization is high, but that it may still facilitate coral recovery over time. Thus, a large algal biomass may not necessarily indicate a reef beyond the possibility of recovery.
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48.
  • Mörk, Erik, 1978-, et al. (författare)
  • Top–down and bottom–up regulation of macroalgal community structure on a Kenyan reef
  • 2009
  • Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 84:3, s. 331-336
  • Tidskriftsartikel (refereegranskat)abstract
    • Top–down and bottom–up regulation in the form of grazing by herbivores and nutrient availability areimportant factors governing macroalgal communities in the coral reef ecosystem. Today, anthropogenicactivities, such as over-harvesting of herbivorous fish and sea urchins and increased nutrient loading, arealtering the interaction of these two structuring forces. The present study was conducted in Kenya andinvestigates the relative importance of herbivory and nutrient loading on macroalgal communitydynamics, by looking at alterations in macroalgal functional groups, species diversity (H0) and biomasswithin experimental quadrats. The experiment was conducted in situ for 42 days during the dry season.Cages excluding large herbivorous fish and sea urchins were used in the study and nutrient addition wasconducted using coated, slow-release fertilizer (nitrogen and phosphorous) at a site where herbivory isgenerally low and nutrient levels are relatively high for the region. Nutrient addition increased tissuenutrient content in the algae, and fertilized quadrats had 24% higher species diversity. Herbivoreexclusion resulted in a 77% increase in algal biomass, mainly attributable to a >1000% increase in corticatedforms. These results are in accordance with similar studies in other regions, but are unique in thatthey indicate that, even when prevailing nutrient levels are relatively high and herbivore pressure isrelatively low, continued anthropogenic disturbance results in further ecological responses and increasedreef degradation.
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49.
  • Norling, Pia, 1974- (författare)
  • Importance of blue mussels for biodiversity and ecosystem functioning in subtidal habitats
  • 2009
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Blue mussels, Mytilus spp., occur on rocky and sedimentary shores worldwide where they often form dense aggregates. These assemblages change the local environment and create unique habitats. By extensive filter-feeding, the mussels regulate availability and flow of resources such as nutrients and organic material, and are thereby important in benthic-pelagic coupling. This thesis investigates the role of Mytilus spp. for the diversity of associated species, ecosystem functioning and services that the mussels provides. My results show that Mytilus habitats support highly diverse associated communities, especially in subtidal sediment habitats in the Skagerrak and Baltic Sea. The macrofauna species richness was shown to correlate with mussel patch size and biomass. Structural properties of Mytilus spp. provide substrate for attachment, shelter and increase habitat complexity in the system, which was found to enhance species diversity. Biological activities of the mussels, e.g. filter-feeding, biodeposition and nutrient regeneration, seemed to determine the abundance, biomass and functioning of the associated plant and animal communities. The communities are dependent on import of energy resources through the mussels filter-feeding from the pelagic system, which increase contents of organic carbon and nitrogen in sediments by biodeposition even in very small patches. At larger scale, the role of Mytilus spp. as a habitat-modifying species varied between substrate types. On soft substrate, where physical structure is scarce, Mytilus spp. had strong positive effects on the associated algal community, while on hard substrate much less influence was found. In Flensborg fjord, when coexisting with eelgrass, Zostera marina, presence of Mytilus edulis influenced the grain size and biogeochemistry of the sediment, which in turn, seemed to induce sulphide stress in the plants and change plant performance. Due to its biomass dominance and substantial water-filtering capacity, Mytilus sp. tends to counteract eutrophication and maintain water quality maintenance services in the Baltic Sea. The mussels' filtration of plankton and particulate organic material from the pelagic system improves the light climate for benthic algae and increase production of other benthic organisms. This promotes a shift from a turbid plankton dominated system to a highly diverse and productive benthic system. I conclude that Mytilus spp. is important for sustaining biodiversity and ecosystem functioning of subtidal habitats, especially in the Baltic coastal zone.
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