DIETARY PLASTICITY DIFFERENTIATIES TROPHIC NICHES OF DOLIOLIDS AND SALPS

Filter feeding by pelagic tunicates links them to both the grazing and microbial food webs, thus influencing the quantity and form of particulate organic matter (POM) in the water column. On the South Atlantic Bight (SAB) continental shelf, the doliolid Dolioletta gegenbauri populations persist year-round and occasionally form dense blooms in response to favorable conditions. SAB primary productivity fluctuates seasonally and interannually, and we hypothesize that trophic niche breadth in doliolids, but not co-occurring salps, varies following these fluctuations in food availability and quality. In August of 2021, 2022, and 2023, we sampled several parameters to quantify the microbial and phytoplankton communities on the SAB shelf, including bacterial production rates, POC:Chl-a ratios, and Chl-a:Phaeopigment ratios. We also measured the δ¹³C and δ¹⁵N composition of POM and representative zooplankton samples, including doliolids and salps. Doliolid trophic niche breadth differed appreciably from year to year, whereas the niche breadth of salps was less variable. Understanding the factors that modulate trophic strategy among pelagic tunicates and other gelatinous organisms is key for resolving different trophic pathways for carbon in shelf systems.

Presentation Preference: Either

Primary Presenter: Emily Gipson, University of Georgia (emily.gipson@uga.edu)

Authors:

Anita Minniefield, University of Georgia - Skidaway Institute of Oceanography  (anita.minniefield@uga.edu)

Patrick Duffy, University of Georgia - Skidaway Institute of Oceanography  (patrick.duffy@skio.uga.edu)

Laura Treible, Savannah State University  (treiblel@savannahstate.edu)

Adam Greer, University of Georgia - Skidaway Institute of Oceanography  (atgreer@uga.edu)

Jay Brandes, University of Georgia - Skidaway Institute of Oceanography  (jay.brandes@skio.uga.edu)

Marc Frischer, University of Georgia - Skidaway Institute of Oceanography  (marc.frischer@skio.uga.edu)