| 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.
|
|
| 2. |
|
|
| 3. |
|
|
| 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.
|
|
| 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.
|
|
| 6. |
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
| 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.
|
|
