HIGH OCCURANCE AND BIOMASS OF SARGASSUM FILIPENDULA IN BEACH WRACK ALONG CAPE COD, MA

Pelagic blooms of macroalgae of the genus Sargassum spp. have been increasing across the Atlantic and into the Caribbean and other coastal areas. Along the Northwest Atlantic coastline in Cape Cod, MA, we observed an increase in occurrence of Sargassum filipendula, an attached-benthic form of Sargassum, washing up on beaches. In a survey, S. filipendula was found in the beach wrack of 77% of sites visited, with a maximum wet weight biomass of up to 6.6 kg m^-2. Comparing nitrogen and carbon isotopic signatures from historic samples to present day samples, we found an increase in δ¹⁵N from 4.7 to 7.5 ‰ and a decrease in δ¹³C from -18.0 to -21.1 ‰, suggesting a shift in N and C sources. Heavier δ¹⁵N signature reflect an increase in wastewater as a source of N, which may be driving an increase in bloom occurrences. Lighter δ¹³C signatures reflect possible changes in metabolism and uptake of DIC in the region. An experimental study of desiccation exposure of S. filipendula showed signs of short-term desiccation tolerance with less than 3 hours of exposure compared to another bloom forming macroalga of the genus Gracilaria. These results imply that Sargassum has the potential to survive and expand to new areas even after detachment if desiccation exposure remains short-term between low and high tides. However, with more than 6 hours of desiccation exposure over repetitive days, a decrease in photosynthetic yield (Fv/Fm) and tissue loss was observed, indicating that these species are not able to cope or recover under longer-term desiccation conditions.

Presentation Preference: Oral

Primary Presenter: Mirta Teichberg, Marine Biological Laboratory (mteichberg@mbl.edu)

Authors:

Agustin Moreira-Saporiti, Marine Biological Laboratory  (amoreirasaporiti@mbl.edu)

Sarah Merolla, Marine Biological Laboratory  (smerolla@mbl.edu)

Kristen Beach, Dickinson College  (beachkr@dickinson.edu)

Vincent Difilippo, Bridgewater State University  (vdifilippo@student.bridgew.edu)

Elena Lopez Peredo, Rochester Institute of Technology  (elpsbi@rit.edu)

Mirta Teichberg, Marine Biological Laboratory  (mteichberg@mbl.edu)