TY - BOOK

T1 - Effects of Harmful Algae on the Physiology of Fishes

AU - Svendsen, Morten Bo Søndergaard

PY - 2016

Y1 - 2016

N2 - Blooms of harmful planktonic algae causing adverse effects in aquatic environments are a global problem,causing both human morbidity and killing aquatic lifeforms worldwide. Focusing on fish kills, it is largelyunknown what mechanisms of the fish’s physiology are affected during exposure to harmful algae.It is demonstrated that for an alga with a known mode of action, Prymnesium parvum affecting the gills,conventional readily available methods in fish physiology can be used to establish an adverse outcomepathway. More specifically, intermittent flow respirometry and observing ventilatory movements and gillclearing frequency can be used to determine the action of Prymnesium parvum as a gill irritant, causingmortality of fish via reduced oxygen uptake capability, a pathway likely initiated by the alleged toxinPrymnesin. The hypothesis that fish can recover after Prymnesium parvum exposure is deemed unlikely onbasis of rainbow trout (Onchorhyncus mykiss) not recovering.The specific toxicity of Pseudochattonella spp. is unknown, but by studying the effects of Pseudochattonellaspp. on fish during a natural bloom occurring at a trout farm an adverse outcome could be created. Theadverse outcome pathway indicate that fish mortality arise as a result of winter stress syndrome; thesyndrome being an interaction of low temperature and an environmental stressor. This is concluded on thebasis of sorting affected fish on according to their reflex impairment score combined with an anatomicalhealth assessment index, in turn forming similar anatomical appearance as fish affected by the winterstress syndrome. The conclusion is supported by modelling the aerobic scope of the fish during the bloombased on previously reported data for salmonids, and available environmental data.Even though Alexandrium monilatum has been studied intensively the effects of Alexandrium monilatum onfish is largely unknown. In the Chesapeake Bay, Eastern U.S.A., fishes are further challenged in late summerby an oxygen squeeze from deep part of the water column, limiting their utilizable habitat to mid-watershaving enough oxygen to sustain life, but not too warm like the surface water layer. The proposed adversepathway, being gill destruction, for fish exposed to Alexandrium monilatum suggests that co-occurringevents of Alexandrium monilatum and oxygen squeeze events will tighten the oxygen limitation squeeze onstriped bass (Morone saxatilis).In order to ensure continuous progress in research in physiology and toxicology of fishes, analyticalapproaches to environmental stressors are needed. One such approach is the Dynamic Energy Budgetmodels; however, a recent paper called for solution to a problem of a weird theoretical animal challengingthe assumptions of the model. It is argued based on literature review, that the maintenance assumptions ofthe weird animal are similar to those of fishes, where challenges to homoeostasis are related to gill area. Itis further emphasized that the assumptions of a model should correspond to what one can observe on liveanimals. It is emphasized that homoeostasis and challenges to it are continuously changing, and thuscannot be assumed constant.The last study of the thesis demonstrates that for Prymnesium parvum as well as for Alexandriummonilatum the oxygen tolerance of fish decrease when exposed for a short time. Based on the analyticalderivation, two thresholds for oxygen limitation are proposed. It is further concluded that a measure withconcentration units, KB, can be used for describing changes of hypoxia tolerance in fishes.Work surrounding the core subject of the thesis primarily concerned intermittent flow respirometry.Intermittent flow respirometry is a common used method, and a key method of this thesis. A review onhow to design and setup an experiment using intermittent flow respirometry was conducted in thebeginning of the thesis. Likewise, the development of a free open-source software, AquaResp 2 (and now3), for use in automating intermittent flow respirometry experiments. By using the open source software, itwas also established prior to harmful algae experimentation that the observed variation in respirometryexperiments is largely caused by the fish and to a lesser extent the experimental setup.Before this thesis, systematic studies of fish physiology under the influence of harmful algae consisted ofone algae species, Chattonella marina. Now there are a total of 4 species studied. Lastly, during the PhDprojectparticipation in three EU Cost Action conferences resulted in the creation of two physiologicaldatabases; one on acute thermal tolerance of aquatic ectotherms, and one on the aerobic scope of fishes.Likewise work carried out concerning maximum swimming speeds of fishes was presented at the Society ofExperimental Biology annual

AB - Blooms of harmful planktonic algae causing adverse effects in aquatic environments are a global problem,causing both human morbidity and killing aquatic lifeforms worldwide. Focusing on fish kills, it is largelyunknown what mechanisms of the fish’s physiology are affected during exposure to harmful algae.It is demonstrated that for an alga with a known mode of action, Prymnesium parvum affecting the gills,conventional readily available methods in fish physiology can be used to establish an adverse outcomepathway. More specifically, intermittent flow respirometry and observing ventilatory movements and gillclearing frequency can be used to determine the action of Prymnesium parvum as a gill irritant, causingmortality of fish via reduced oxygen uptake capability, a pathway likely initiated by the alleged toxinPrymnesin. The hypothesis that fish can recover after Prymnesium parvum exposure is deemed unlikely onbasis of rainbow trout (Onchorhyncus mykiss) not recovering.The specific toxicity of Pseudochattonella spp. is unknown, but by studying the effects of Pseudochattonellaspp. on fish during a natural bloom occurring at a trout farm an adverse outcome could be created. Theadverse outcome pathway indicate that fish mortality arise as a result of winter stress syndrome; thesyndrome being an interaction of low temperature and an environmental stressor. This is concluded on thebasis of sorting affected fish on according to their reflex impairment score combined with an anatomicalhealth assessment index, in turn forming similar anatomical appearance as fish affected by the winterstress syndrome. The conclusion is supported by modelling the aerobic scope of the fish during the bloombased on previously reported data for salmonids, and available environmental data.Even though Alexandrium monilatum has been studied intensively the effects of Alexandrium monilatum onfish is largely unknown. In the Chesapeake Bay, Eastern U.S.A., fishes are further challenged in late summerby an oxygen squeeze from deep part of the water column, limiting their utilizable habitat to mid-watershaving enough oxygen to sustain life, but not too warm like the surface water layer. The proposed adversepathway, being gill destruction, for fish exposed to Alexandrium monilatum suggests that co-occurringevents of Alexandrium monilatum and oxygen squeeze events will tighten the oxygen limitation squeeze onstriped bass (Morone saxatilis).In order to ensure continuous progress in research in physiology and toxicology of fishes, analyticalapproaches to environmental stressors are needed. One such approach is the Dynamic Energy Budgetmodels; however, a recent paper called for solution to a problem of a weird theoretical animal challengingthe assumptions of the model. It is argued based on literature review, that the maintenance assumptions ofthe weird animal are similar to those of fishes, where challenges to homoeostasis are related to gill area. Itis further emphasized that the assumptions of a model should correspond to what one can observe on liveanimals. It is emphasized that homoeostasis and challenges to it are continuously changing, and thuscannot be assumed constant.The last study of the thesis demonstrates that for Prymnesium parvum as well as for Alexandriummonilatum the oxygen tolerance of fish decrease when exposed for a short time. Based on the analyticalderivation, two thresholds for oxygen limitation are proposed. It is further concluded that a measure withconcentration units, KB, can be used for describing changes of hypoxia tolerance in fishes.Work surrounding the core subject of the thesis primarily concerned intermittent flow respirometry.Intermittent flow respirometry is a common used method, and a key method of this thesis. A review onhow to design and setup an experiment using intermittent flow respirometry was conducted in thebeginning of the thesis. Likewise, the development of a free open-source software, AquaResp 2 (and now3), for use in automating intermittent flow respirometry experiments. By using the open source software, itwas also established prior to harmful algae experimentation that the observed variation in respirometryexperiments is largely caused by the fish and to a lesser extent the experimental setup.Before this thesis, systematic studies of fish physiology under the influence of harmful algae consisted ofone algae species, Chattonella marina. Now there are a total of 4 species studied. Lastly, during the PhDprojectparticipation in three EU Cost Action conferences resulted in the creation of two physiologicaldatabases; one on acute thermal tolerance of aquatic ectotherms, and one on the aerobic scope of fishes.Likewise work carried out concerning maximum swimming speeds of fishes was presented at the Society ofExperimental Biology annual

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122792619705763

M3 - Ph.D. thesis

BT - Effects of Harmful Algae on the Physiology of Fishes

PB - Department of Biology, Faculty of Science, University of Copenhagen

ER -