Effect of sinking spring phytoplankton blooms on lipid content and composition in suprabenthic and benthic invertebrates in a cold ocean coastal environment

Abstract

Lipids were measured in 19 suprabenthic and benthic invertebrate taxa from 5 phyla to determine their responses to a sinking spring diatom bloom. In Conception Bay, as in many areas of coastal Newfoundland, Canada, benthic organisms experience sub-zero temperatures year round. Among specimens collected at depths between 210 and 220 m, the small mysid Erythrops erythrophtalma had, on average, the highest lipid concentration (6% of wet weight), while a holothurian (Order Apodida) had the lowest (0.3%). In E. erythrophtalma, 73% of the lipids were found in the neutral fraction, while in the sea cucumber 68% were polar lipids. The euphausiid Thysanoessa raschii had the highest proportion of essential ω3 fatty acids (41% total fatty acids) while the holothurian had the lowest (21%). Pseudocalanus spp. showed the highest mean value for the C16 polyunsaturated fatty acid (PUFA) ratio indicative of lipids from nutrient-replete diatoms. The amphipods Acanthostepheia malmgreni and Anonyx spp. responded immediately to each spring bloom with increased total and neutral lipid contents. The mysid Pseudomma truncatum also showed a transient increase in total lipid content, but this occurred much later in the summer. However, P. truncatum, together with the decapod Pandalus borealis, the mysid Mysis mixta, and the polar bivalve Yoldia hyperborea, did respond immediately based on increased proportions of ω3 fatty acids, while the asteroid Ctenodiscus crispatus showed increased ω3 fatty acid proportions in its gonads much later. The chaetognath Parasagitta elegans differed from most other species in that it maintained very similar total lipid and C16 PUFA proportions throughout the sampling period, suggesting little direct response to the bloom. Thus, we found a variable response to the bloom with respect to phenology, even within orders, which depended upon feeding behaviour and gonadogenesis.