Spatial variability of thermohaline parameters and phytoplankton of West Antarctica during austral summer

Abstract

Thermohaline parameters and phytoplankton spatial variability were studied during RAE65 austral summer cruise of the IBRV Akademik Tryoshnikov. The study area in Pacific sector of Southern Ocean (February – March 2020) included eastern boundary of the Ross Sea at Cape Colbeck along the 156°W (transect 1, T1), area near Antarctic station Russkaya (transect 2, T2) along the 138°W, Bransfield Strait (transect 3, T3) and episodic CTD station in the Bay of Whales, Ross Sea. Low salinity of surface waters was revealed in T1, T2. The temperature of 50-meter surface layer of T1 and T2 was 0 and –1.5 °C respectively, meanwhile at most T3’s stations 200 m upper layer temperatures varied from 0 to +2 °C. In terms of oxygen content and salinity the data collected at T3 corresponds to earlier studies. 49 algae taxa were identified. Diatoms dominated in all studied areas. The majority of diatom species were attributed to Fragilariopsis genus. Phaeocystis antarctica was identified both above shelf break area or behind it at depths more than 50 m for T1 and T2. In T3 P. antarctica presented in surface waters and at depth. Rice in number to the maximum at depths about 50 m was revealed for the vertical distribution of phytoplankton at some CTD stations both in the shelf area and at shelf break. For T2 the correlation between phytoplankton abundance and water temperature and salt concentration was detected. Between three transects the greatest similarity in species composition had shelf stations, deep–water ones had the least. Most homogeneous in species composition among stations was T2, and the least was T3.

Keywords: spatial variability, thermohaline parameters, West Antarctica, Bransfield Strait, shelf, phytoplankton