Gulf of Alaska | Ecosystem Perspectives MASTER’S ORAL PRESENTATION Trophic pathways and their relationship to growth in nearshore consumers across the northern Gulf of Alaska Presenter: Katherine Corliss , kcorliss@alaska.edu, University of Alaska Fairbanks
Katrin Iken , kbiken@alaska.edu, University of Alaska - Fairbanks Vanessa von Biela , vvonbiela@usgs.gov, USGS Alaska Science Center Heather Coletti , Heather_Coletti@nps.gov, National Park Service Daniel Esler , desler@usgs.gov, USGS Daniel Monson , dmonson@usgs.gov, USGS Brian Robinson , brobinson@usgs.gov, US Geological Survey James Bodkin , jldbodkin@gmail.com, USGS
Nearshore ecosystems provide essential habitat for marine organisms including many that are important for subsistence, commercial fisheries, and recreation. In the Gulf of Alaska (GOA), macroalgae and phytoplankton form the base of nearshore food webs. Availability of these basal producers likely varies with environmental factors, suggesting nearshore food webs within the GOA may be susceptible to effects of climate change like warming waters, marine heatwaves, and rapidly melting glaciers. Our goal is to understand how changes in the proportional contributions of carbon from these two primary producer sources may affect performance of nearshore consumer species. As part of the Nearshore Component of the Gulf Watch Alaska program, we are using carbon and nitrogen stable isotope analysis to investigate trophic dependencies of filter-feeding mussels ( Mytilus trossulus ), pelagic feeding Black Rockfish ( Sebastes melanops ), and benthic feeding Kelp Greenling ( Hexagrammos decagrammus ) in four different GOA regions: Western Prince William Sound, Kenai Fjords National Park, Kachemak Bay, and Katmai National Park & Preserve. All three focal species consume a mix of phytoplankton- and macroalgal-based diets in each region but macroalgae are the major source of carbon in the diet of all three species. There was a significant increase of macroalgal-based contribution to mussels in 2017 compared to previous years, possibly reflecting the large pulse of detritus from the 2016 macroalgae die-off during the Pacific Marine Heatwave. We used annual growth increments in each of these consumers as a measure of performance across the four regions to better understand the effect of variation in primary production sources to secondary production. Initial results for mussels suggest that the relationship between growth and carbon sources varies by region, possibly related to regional differences in environmental variables, such as temperature. Clarifying relationships among climate, trophic pathways, and growth will help better predict the future state of nearshore ecosystems.
Alaska Marine Science Symposium 2023 33
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