Summer phytoplankton community variability in nearshore waters of the Western Antarctic Peninsula

MASCIONI, MARTINA; ALMANDOZ, GASTÓN O.; CUSICK, ALLISON; VERNET, MARIA

Congreso; SCAR 2020 ONLINE; 2020

SCAR

The western Antarctic Peninsula (WAP) is one of the most productive regions in Antarctica. The nearshore waters, within fjords between 62-67 ºS harbor large Antarctic krill stocks that represent the main food source for higher trophic levels and, consequently overlap with breeding and feeding locations for penguin, seal and whale populations. This food web is supported by high primary productivity, however, phytoplankton studies in these waters are scarce. For this study, samples were collected during austral summers 2016-2019 from November to March, through a citizen science project ? FjordPhyto ? in collaboration with the International Association of Antarctica Tour Operators vessels (IAATO). Microscopy counts from six areas between 64 and 65ºS were analyzed (Cierva Cove, Wilhelmina Bay, Cuverville Island, Danco Island, Neko Harbor and Paradise Bay). Species identification and enumeration were performed by light and scanning electron microscopy and carbon biomass was estimated by cell-volume conversion. Phytoplankton abundance and carbon biomass varied up to 10 orders of magnitude. In general, phytoplankton was scarce during November, peaked during December and January (up to 9.5 × 106 cells L−1 and 1,597 μgC L−1) and decreased during February through March. Preliminary results suggest that diatoms were not predominant, while blooms of cryptophytes and prasinophytes were recurrently observed. Moreover, an intense dinoflagellate bloom was first recorded in the WAP. Most of these bloom-forming nanoflagellates do not coincide with Antarctic species. This study highlights the nearshore waters of the Danco/Graham coast as areas of high accumulation of phytoplankton biomass during austral summer.