SHIFTS IN PHYTOPLANKTON DIVERSITY WITH RELATION TO GLACIAL MELTWATER ALONG THE WESTERN ANTARCTIC PENINSULA

PINPOKINTR, ANESSE; CUSICK, ALLISON; MASCIONI, MARTINA; RICK REYNOLDS; VERNET, MARIA

Congreso; Ocean Sciences Meeting 2022; 2022

ASLO

Antarctica is one of the fastest warming regions in the world, and a highly productive area where phytoplankton play a critical role in biogeochemical cycles. These organisms are responsible for sequestering about 40% of the carbon in the Southern Ocean, yet little is known about their composition in the nearshore waters of the Western Antarctic Peninsula (WAP). Input from glacial meltwater changes this composition each year, which in turn can affect higher trophic levels, including organisms such as krill, a keystone species. In a previous study, larger phytoplankton, with more carbon biomass were found to be switching to smaller, lower biomass phytoplankton, which provide less energy to the food web. Variability in sea surface temperature and freshwater input is expected to favor different phytoplankton assemblages and shift bloom timing. This study examines the effects that glacial meltwater has on phytoplankton diversity in the WAP and hypothesizes that there will be a shift from large to small phytoplankton with more abundance in cryptophytes over diatoms. Sampling was conducted through the citizen science project – Fjord Phyto – during austral summer from 2017 to 2020. The data collected at each location includes euphotic depth, CTD data, and 18S amplicon sequencing data which was analyzed for phytoplankton composition and diversity. The 18S amplicon sequencing and CTD data showed that cryptophytes bloomed when temperature was lower and salinity was higher which contradicts previous studies, however, cryptophytes prefer the region with fresher water compared to diatoms. This indicates a switch from cryptophytes to diatoms in the future if higher glacial melt persists. This new knowledge will provide us with a better understanding of how climate change and glacial meltwater affect phytoplankton diversity and phenology, as well as give us more insight into how the upper trophic levels may respond to these changes.