| 1. |
- Hedberg, Nils, et al.
(author)
-
Antibiotic use in Vietnamese fish and lobster sea cage farms; implications for coral reefs and human health
- 2018
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In: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 495, s. 366-375
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Journal article (peer-reviewed)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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| 2. |
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| 3. |
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| 4. |
- Hedberg, Nils, et al.
(author)
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Causes and consequences of spatial links between sea cage aquaculture and coral reefs in Vietnam
- 2017
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In: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 481, s. 245-254
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Journal article (peer-reviewed)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-
(author)
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Sea cages, seaweeds and seascapes : Causes and consequences of spatial links between aquaculture and ecosystems
- 2017
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Doctoral thesis (other academic/artistic)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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| 6. |
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| 7. |
- Hedberg, Nils, et al.
(author)
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Spatial correlation and potential conflicts between sea cage farms and coral reefs in South East Asia
- 2015
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In: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 448, s. 418-426
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Journal article (peer-reviewed)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-
(author)
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Radionuclides in the Baltic Sea : Ecosystem models and experiments on transport and fate
- 2004
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Doctoral thesis (other academic/artistic)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-
(author)
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Macroalgae in tropical seascapes : regulating factors and functions in the coastal ecosystem
- 2010
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Doctoral thesis (other academic/artistic)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-
(author)
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Human Abuses of Coral Reefs- Adaptive Responses and Regime Transitions
- 2004
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Doctoral thesis (other academic/artistic)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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| 11. |
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| 12. |
- Barrett, Scott, et al.
(author)
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Social dimensions of fertility behavior and consumption patterns in the Anthropocene
- 2020
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In: 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
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Journal article (peer-reviewed)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-
(author)
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Ecological connectivity in East African seascapes
- 2012
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Doctoral thesis (other academic/artistic)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.
(author)
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Exploring 'knowns' and 'unknowns' in tropical seascape connectivity with insights from East African coral reefs
- 2012
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In: Estuarine Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 107, s. 1-21
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Journal article (peer-reviewed)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.
(author)
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In situ determination of PCB biodeposition by Mytilus edulis in a Baltic coastal ecosystem
- 2000
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In: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 194, s. 193-201
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Journal article (peer-reviewed)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.
(author)
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General resilience to cope with extreme events
- 2012
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In: Sustainability. - : MDPI AG. - 2071-1050. ; 4:12, s. 3248-3259
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Journal article (peer-reviewed)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.
(author)
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Earth stewardship : Shaping a sustainable future through interacting policy and norm shifts
- 2022
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In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 51:9, s. 1907-1920
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Journal article (peer-reviewed)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-
(author)
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Effects of community- and government-managed marine protected areas on tropical seagrass and coral communities
- 2020
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Doctoral thesis (other academic/artistic)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.
(author)
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Social-ecological systems as complex adaptive systems : modeling and policy implications
- 2013
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In: Environment and Development Economics. - 1355-770X .- 1469-4395. ; 18:2, s. 111-132
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Journal article (peer-reviewed)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-
(author)
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Of Mangroves and Middlemen : A study of social and ecological linkages in a coastal community
- 2006
-
Doctoral thesis (other academic/artistic)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-
(author)
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Humans and Seagrasses in East Africa : A social-ecological systems approach
- 2006
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Doctoral thesis (other academic/artistic)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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- Eggertsen, Linda, 1981-
(author)
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Identification and implications of fish nurseries in tropical and subtropical seascapes
- 2019
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Doctoral thesis (other academic/artistic)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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- Eggertsen, Linda, et al.
(author)
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Seaweed beds support more juvenile reef fish than seagrass beds in a south-western Atlantic tropical seascape
- 2017
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In: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 196:5, s. 97-108
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Journal article (peer-reviewed)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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