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- Nguyen, Thanh Tam, 1981-
(författare)
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Pesticide use in rice farming and its impacts on climbing perch (Anabas testudineus) in the Mekong Delta of Vietnam
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The intensification of agricultural production in the Mekong Delta has faced serious challenges with respect to increased use of agrochemicals and especially pesticides. The indiscriminate use of pesticide could potentially impact on the long-term food production, environmental and human health in the delta. The aim of this thesis was to investigate the negative side effects of the current use of pesticides on climbing perch (Anabas testudineus) in rice fields using brain acetylcholinesterase (hereafter referred to as AChE) activity as a biomarker. The empirical work, on which this thesis is based, includes structured questionnaires, laboratory and field experiments. First, a field survey using questionnaires was carried out to gain a better understanding of the current state of rice farming systems, the use of pesticides and attitude to pest management strategies among rice and rice-fish farmers, as well as to provide basic information for the set-up of the laboratory and field experiments. Secondly, laboratory studies were conducted to clarify if the selected insecticides applied alone and in mixtures caused negative side effects on climbing perch fingerlings. Thirdly, further toxicity studies were carried out, under rice field conditions, to further investigate the toxicity effects of the insecticides, applied alone, in mixtures and under sequential applications, on climbing perch fingerlings.The results showed that although there were a more selective use of pesticides and an increased awareness among farmers of the negative side effects of pesticides in 2007 as compared to 1999, the current use of pesticide in the Mekong Delta still cause many problems to the environment and human health. Chlorpyrifos ethyl (hereafter referred to as CPF) was found to cause a significant and more prolonged inhibition on the brain AChE activity in climbing perch than fenobucarb (hereafter referred to as F). The inhibition by the mixture of CPF and F were significantly higher than the inhibition by only F, but less prolonged and significant lower than the inhibition by only CPF. The results suggest that the combined effect from a mixture of F and CPF can create both additive effects initially and later antagonistic effects.CPF and F applied at concentrations used by farmers, either as separate doses, in a mixture or in sequential doses, decreased the brain AChE activity, growth and survival rates in climbing perch. The results demonstrate that brain AChE activity in climbing perch is a relevant biomarker for monitoring of exposure to, and sub-lethal impacts from organophosphates and carbamates under tropical conditions. The result also shows that 2-PAM re-activate the brain AChE activity, and can be used as an alternative method to assess the AChE inhibition level in organisms recently exposed to OP’s, in situation where it may be difficult to find unexposed individuals as controls.In conclusion, this thesis shows that the current use of pesticides in the Mekong Delta has a negative effect on climbing perch living in rice fields. It indicates that a sustained long-term food production in the Mekong Delta must be based on ecological principles, taking advantages of ecosystem biodiversity and productivity, and not through intensified use of pesticides.
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| 3. |
- Hedberg, Nils, 1981-
(författare)
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Sea cages, seaweeds and seascapes : Causes and consequences of spatial links between aquaculture and ecosystems
- 2017
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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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| 4. |
- Jörgensen, Tove Lund, 1975-
(författare)
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Coral Reef Habitats and Fish Connectivity : Implications for coastal management and fishery
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Coral reefs have one of the highest levels of biodiversity of all ecosystems in the world and are important for both human livelihood and food security throughout many tropical countries. However, due to increased anthropogenic pressure on marine ecosystems, especially during the last couple of decades, coral reefs have become critically over-fished, and many reefs are now in a degraded state and are facing additional future threats due to further over-exploitation, chemical pollution, sedimentation, and effects of climate change.The main aim of this PhD thesis was to understand effects of anthropogenic disturbances on tropical coastal ecosystems and fish connectivity for coastal management purposes. Therefore, linkages between anthropogenic disturbance and corals were investigated (Paper I), as well as interactions between coral reef habitat and associated fish assemblage (Paper II). Furthermore, connectivity between coral reefs and other tropical coastal ecosystems was explored (Paper III), as well as fish migration to reproduction sites (Paper IV), and evaluations of spatial ecology methods (Paper V).The result showed that coral reefs that are already exposed to disturbances, such as freshwater and nutrient run-offs, may be more sensitive to climate change, in terms of increased sea surface temperatures (Paper I). In addition, there were also clear linkages between coral reef quality, in terms of coral coverage, and fish assemblages, which displayed high spatial variability and suggesting patchy recovery after the 1997/1998 bleaching and subsequent coral mass mortality event (Paper II). This highlights the importance of understanding effects of disturbances on corals, especially in terms of synergistic effects between increased water temperatures and other coastal stressors such as decreased salinity and increased nutrients; and the indirect effects of habitat degradation on the fish community.Linkages between fish and different coastal habitats were further explored. The results showed that coral reefs were strongly connected with mangrove and seagrass beds, through ontogenetic migration of fish (Paper III). Migrations to spawning sites of groupers were related to lunar activities when thousands of fish gather for reproduction purposes during new moon, which increases the risk of over-exploitation (Paper IV). The results emphasises the importance of protecting key areas such as nursing grounds and reproduction sites. Furthermore, acoustic telemetry has become an increasingly common method in studies of fish movement, and the results showed that efficiency of acoustic arrays may increase depending on deployment strategies and habitat characteristics (Paper V).In conclusion, the results from this PhD thesis emphasises the importance of protecting coral reef habitats, as well as identifying related susceptible tropical coastal areas, such as nursing grounds and reproduction sites. Indeed, a better scientific understanding of coral reef ecology and indirect and direct effects on fish assemblages are needed for efficient and accurate coastal management decisions.
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- Nyberg, Oskar, 1985-
(författare)
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Protecting food with poison : Exploring ecotoxicity of agrochemicals and pharmaceuticals
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chemicals are being emitted into the environment through human activities, such as agriculture or animal husbandry. Emissions can either occur intentionally, as pesticide application of crops, or inadvertently, such as pharmaceutical residues in wastewater effluents. Chicken manure (CM) is occasionally used as a cheap fertilizer in aquaculture pond farms to increase the productivity and the profitability. Depending on local regulation and production strategy, animal manures can contain substantial amounts of antibiotics (AB) and other pharmaceuticals used for raising animals. The benefits of this practice, however, have not been clearly established in relation to the potential adverse consequences. By analysing production data from Egyptian fish farms in Study I, I show that CM fertilization promotes eutrophication, without corresponding to increased fish yields or clear benefits for the producers. Study I support arguments to cease CM fertilization in Egyptian aquaculture if the goal is to increase fish yields or profitability. Additionally, I employ a qPCR assay to show that CM fertilization correlates with increased abundance of antibiotic resistance genes (ARGs) in pond sediment. AB emitted to the environment can induce resistance development in bacteria and promote selection of resistant genotypes. Study II aim to capture the effects of AB emitted throughout the value chain of agri-food products, and life cycle assessment (LCA) is investigated for this purpose. LCA is a framework developed to assess environmental impacts throughout the value chain of products. In Study II, I present an approach to quantify potential AB resistance enrichment in the environment within LCA. I also discuss a mass-balance approach to capture the relationship between regional AB use and regional human health impacts, in order to capture the full range of potential impacts caused by emissions of AB. Characterizations of potential toxic effects of chemicals in LCA are generally drawn from species sensitivity distribution models that aim to describe an ecosystem-wide response to chemical emission. While this provides insights into the toxicity of a chemical, predictions of the “true” ecosystem wide effects will always be shrouded by uncertainty, depending on the availability and quality of data. Detailed knowledge on adverse effects and potential hazard chemicals impose are required for stakeholders at both global and local scales to make informed decisions on how to regulate the use and emissions of chemicals. Study IV identify LCA studies where toxicological impacts are evaluated and chemicals in the inventory are classified towards ecotoxicological impact, but ecotoxicological characterizations are missing, which leads to underestimating the ecotoxicological impact. To enhance the precision of ecotoxicological effect assessments for chemicals, Study III gathers an extensive toxicological dataset and present a method to assess the uncertainty associated with ecotoxicological effect calculations. The proposed method opens up for exploring uncertainty in ecotoxicological effect calculations, but data availability is limiting the number of chemicals that can be assessed for ecotoxicological effect and uncertainty. To gap-fill information on toxic effect of chemicals, Study IV explores quantitative structure-activity relationship (QSAR) models to predict ecotoxicological effect of chemicals. However, mechanistic understanding of toxic mode of action is not provided by these models. Thus, the accuracy and validity of predicted toxicological effect data are not yet established. Since current LCA software lacks functionality to aggregate uncertainties throughout assessments, the use of predicted toxicological data is discouraged.This thesis presents some of the many challenges we face when assessing toxicological impacts from chemicals emitted to the environment, and provides methods and recommendations how to better evaluate impacts and uncertainties in toxicological characterization of chemicals.
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