Phytoplankton biomass and photosynthetic competency in the summertime Mertz Glacier Region of East Antarctica

Abstract

Abstract Vertical profiles of water temperature, salinity, beam transmission, density, pressure, wind speed, wind direction, phytoplankton biomass (chlorophyll a (Chl a) plus phaeophytin a), and photosynthetic competency (by fast repetition-rate fluorometry) are presented for the Mertz Glacier region, East Antarctica, for a 3-week period during the austral summer 2000–2001. Injection of low-salinity water from the melting of the ice pack formed a shallow (ca. 25 m) mixed layer offshore. Two distinct deep mixing features were observed associated to varying degrees with high chlorophyll levels and high photosynthetic competency. Along the Adelie Land coast, a deep mixing layer (1400 m) with Chl a concentrations of 386 mg m−2 and elevated Fv/Fm (>0.5) was observed. At the eastern end of the study area, along a seaward extension of fast-ice, a bloom of Phaeocystis antarctica bloom formed within a shallow (24 m) mixed layer, with surface Chl a concentrations of ca. 8 mg m−3 and elevated Fv/Fm (0.5). This feature also had high surface salinity (>34) and was contiguous with a deep-mixing feature (236 m). FRRF parameters Fv/Fm and σPSII were strongly suppressed in surface waters (