Lipid dynamics in the southern hemisphere: a 30-year meta-analysis of marine consumers

Abstract

Assessing the total lipid content (TLC, expressed as % wet weight, WW) and constituent fatty acid (FA) composition (expressed as % of total FA) in marine organisms provides vital knowledge about the transfer of energy and essential nutrients from primary producers to higher-order consumers, including humans. To obtain a broad understanding of marine lipid dynamics, we used information from more than 470 species of Australian and Southern Ocean marine consumers spanning across the food web, from secondary to apex predators, sampled over a 30 yr period (1989 to 2019). Taxa group, trophic guild, and collection period were found to be the most influential drivers of variability in 4 key variables (TLC, docosahexaenoic acid [DHA, 22:6n-3], eicosapentaenoic acid [EPA, 20:5n-3] and arachidonic acid [ARA, 20:4n-6]). Highest TLC was observed in marine mammals and mid-trophic consumers, highest DHA occurred in fish and apex predators, highest EPA occurred in krill and other lower-level consumers, and highest ARA was present in rays and other apex predators. Horizontal habitat type was also an important driver with significantly higher TLC, EPA, and DHA found in samples from oceanic and pelagic habitat types, whilst coastal habitat samples had significantly higher ARA. Generalised additive mixed models determined that there were regional spatial patterns and interannual trends for all variables over the 30 yr period across all taxa groups. This study provides new understanding of the spatial distribution, temporal trends, and drivers of lipid and essential fatty acids (EFA) in marine ecosystems in the southern hemisphere.