Primary production, physiological state and composition of phytoplankton in the Atlantic Sector of the Southern Ocean

• Published in: Marine ecology. Progress series (Halstenbek) 1999-12, Vol.190, p.1-16
• Main Authors: Bracher, A. U., Kroon, B. M. A., Lucas, M. I.
• Format: Article
• Language: English
• Subjects: Algae; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomass; Chaetoceros; Diatoms; Fundamental and applied biological sciences. Psychology; Irradiance; Marine; Oceans; Phaeocystis; Photons; Phytoplankton; Pigments; Primary productivity; Productivity; Pseudonitzschia lineola; Sea water ecosystems; Seas; Southern Ocean; Synecology; Thalassiothrix
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps190001

Phytoplankton species composition and primary production were studied in the Atlantic Sector of the Southern Ocean in early austral summer 1995/1996. Results from photosynthesis-irradiance experiments (P vs E curves) were used to examine photosynthetic adaptation in this part of the ocean. The study area comprised 3 different provinces: the Antarctic Polar Front (APF), the Antarctic Circumpolar Current (ACC) beyond the influence of frontal systems, and the marginal ice zone (MIZ). Phytoplankton composition derived from HPLC data, P*m (maximum biomass-specific photosynthetic production rate) values and areal daily primary production (ADP) rates showed different features for these zones. The central core of the APF was dominated (60%) by a bloom of large (>20 μm) diatoms (Thalassiothrix spp., Pseudonitzschia cf. lineola and Chaetoceros spp.), equal values for P*m at the surface and 1% light depths and ADP rates exceeding 900 mg C m–2 d–1. At the fringes of the APF core, phytoplankton were smaller, diatom abundance decreased and dinoflagellates, prymnesiophytes and chrysophytes became more important within the community. Chlorophyll a concentrations and ADP rates were low and comparable to values for the ACC outside the front: