Dr. Chris Parrish - December 5
Nutritional and Biomarker Lipids in Marine Food Webs
We have been investigating trophic connections in marine ecosystems, nutrition in aquaculture and where these two themes interact in terms of impacts of aquaculture on the environment and their mitigation. In marine ecosystems lipids provide the densest form of energy which is transferred from algae to vertebrates via zooplankton. These carbon-rich compounds are also a solvent and absorption carrier for organic contaminants and thus can be drivers of pollutant bioaccumulation in marine ecosystems. Among the lipids, certain essential fatty acids and sterols are considered to be important for ecosystem health and stability. The physical characteristics of biological membranes are a key determinant of membrane structure and function which can be defended from the influence of changing temperature, pressure or lipid peroxidation by altering the fatty acid and sterol composition of the lipid bilayer. We have been investigating lipids in fish in the context of changing diets and changing temperature.
Lipids in marine ecosystems are also a valuable tool to measure inputs, cycling and loss of material. Their heterogeneous nature means that they are versatile biomarkers that can be used in trophic studies in marine food webs, often with the help of multivariate statistics, to delineate carbon cycling and transfer of material. We have developed a rapid, direct transmethylation method that can facilitate the acquisition of large quantities of fatty acid data from wide ranging generalist predators such as tuna. Multidimensional scaling, analysis of similarities and similarity of percentages analysis of fatty acids in tuna muscle collected in the southwest Pacific showed clear spatial differences and the importance of DHA proportions in Coral Sea tuna. Integrating stable isotope data with lipid data can facilitate the interpretation of both data sets and can provide a quantitative estimate of transfer across trophic levels. We have also used stable isotopes in our work on environmental interactions with aquaculture. We have been studying the particle field associated with fish farms and how benthic organisms interact with it near cage sites and in land-based facilities. We have shown that mussels ingest wastes being generated from aquaculture sites, and that the fraction that is removed is that which has the greatest potential to spread.