Master's Thesis Seminar

Within the Arctic Alaskan Beaufort Sea, food webs are comprised of many phyla representing multiple consumer feeding modes across a continuum of trophic levels and potentially utilizing multiple food sources. Amidst this complexity, a notable incongruity exists between the stable carbon isotopic signatures of consumers and those of known food sources across the Arctic. Phytoplankton, ice algae, sediment particulate organic matter, or macroalgae cannot explain the carbon isotope (δ¹³C) values of some coastal deposit and filter feeders. Given this, other food sources must be available within the coastal ecosystem to account for consumer δ¹³C values. Within other coastal food web studies outside of the Arctic, benthic microalgae (MPB) are typically ¹³C-enriched compared to phytoplankton, and they can be an important component of benthic consumer diets. Despite this, MPB have never been directly isolated from coastal Arctic sediments and measured for stable isotope ratios. Therefore, the primary purpose of this study was to validate MPB as a food source to the benthic food web by direct collection from the field and measure the likelihood of consumer assimilation by stable isotope analysis. This study presents stable carbon and nitrogen isotope values for MPB across five estuarine ecosystems along the Alaskan Beaufort Sea coast applied to mixing models assessing the relative contributions of MPB to benthic invertebrate consumers.