Spatial-temporal influence of integrated multi-trophic aquaculture-derived organic effluent on adjacent marine communities

Date

2011-10-17

Authors

Weldrick, Christine Kim

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Abstract

Aquaculture facilities have been demonstrated to emit massive quantities of waste that incorporates in to the surrounding water column, effectively altering patterns and processes of nearby marine communities. Given that products from aquaculture is heavily relied upon to meet global fisheries demands, understanding its effects is essential to inventing less harmful practices. This research examines one such facility located in Kyuquot, British Columbia. The purpose of this thesis is to spatially and temporally measure the degree and magnitude of integrated multi-trophic aquaculture (IMTA)-derived organic waste as a potential subsidy to adjacent marine communities. Stable carbon and nitrogen isotopes analysis was applied to intended extractive organisms (sablefish Anoplopoma fimbria, Pacific scallops Patinopectin caurinus, blue mussels Mytilus edulis, sea urchin Strongylocentrotus franciscanus, sea cucumber Parastichopus californicus, kelp Saccharina latissima), epibiont biofouling species (brooding transparent tunicates Corella inflata, hairy tunicate Boltenia villosa, broadbase tunicates Cnemidocarpa finmarkiensis) as well as fish feed and sablefish faeces. Stable isotopes of blue mussels and brooding transparent tunicates sampled from both the IMTA and a reference site were compared in order to examine spatial influence of IMTA-derived waste. IMTA site sampled mussels exhibited the most enriched and least variable values among all four sample groups. Brooding transparent tunicates exhibited the most isotopic variability which demonstrates that IMTA-derived waste is not among the most important food source available. This is corroborated by the three-source mixing model results. Only sablefish isotopic signatures were measured to be more enriched than those of fish feed and fish faeces. Isotopic mixing models were employed to all IMTA samples and found that IMTA effluent signatures were proportionately higher in their diets than averaged marine particulate organic matter (POM) signatures taken from the literature. Mixing model results also showed IMTA effluent to be proportionately less than marine POM. Circular statistical results did not demonstrate particular directional change for all IMTA sampled isotopic signatures which could be due to the consistent nature of available fish feed throughout the year and/or perhaps feeding choice changes constantly. Further examination into the monthly physical properties of this region (eg. rainfall, irradiance) as well as measurements of marine POM signatures would greatly compliment these results and are recommended for future study.

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Keywords

aquaculture, Kyuquot, B.C., organic waste

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