Dr Aaron Galloway1, Dr. Julie Schram2, Dr. Chuck Amsler3, Mr. Ross Whippo1
1Oregon Institute of Marine Biology, University of Oregon, Charleston, USA, 2University of Alaska Southeast, Juneau, USA, 3University of Alabama Birmingham, Birmingham, USA
The shallow and rocky littoral zone of the northern portion of the western Antarctic peninsula (60-64⁰S) is often dominated (>80% cover) by diverse macroalgal assemblages. Little is known about the algal composition in the southern peninsula (65-70⁰S), but increased ice cover and turbidity is expected to suppress algal cover. Ice cover duration and extent is changing rapidly along the Peninsula, which may lead to changes in the algal composition and benthic food webs in this system. In April-May 2019, we did comprehensive diving surveys and organism collections at 14 sites which comprised a wide ice cover and latitudinal gradient, between Anvers Island in the north and Marguerite Bay in the south. Replicate vertical video transects and collections were performed using scuba between 40-5m depths at each site. These surveys quantified large variation across this gradient in algal assemblage and cover. We used fatty acids as trophic biomarkers to investigate whether macroalgae and benthic macroinvertebrates that were found at nearly all study sites also differed across this gradient. We found clear differences in fatty acids of macroalgae and invertebrates depending on species identity. The multivariate fatty acid signatures of a seastar (Odontaster validus), a tunicate (Cnemidocarpa sp.), a sea urchin (Sterechinus neumayeri), and one gastropod (Nacella concinna) generally differed across the sites, but these patterns were nuanced and not clearly connected to the algal cover or ice cover across the gradient. These initial results suggest that the trophic ecology of these consumers is not tightly coupled to local macroalgal production.
Biography:
Aaron Galloway is an Associate Professor at the Oregon Institute of Marine Biology, the marine lab of the University of Oregon. Dr. Galloway leads the Coastal Trophic Ecology Lab (CTELab), which is generally focused on trophic inferences in marine benthic food webs, with an emphasis on algae-invertebrate interactions. To do this work, the group often uses fatty acids as trophic biomarkers, paired with underwater natural history, scuba diving, lab and field experimentation, and modeling.
