Photosynthetic performance and productivity of phytoplankton in the Southern Ocean

• Main Author: Cheah, W
• Format: Thesis
• Language: English
• Published: 2012
• Subjects: phytoplankton; physiology; productivity; fast repetition rate; flurometry; southern ocean; Antarctic; Southern Ocean; Antarc*
• Online Access: https://eprints.utas.edu.au/15902/; https://eprints.utas.edu.au/15902/1/front-cheah-2012.pdf; https://eprints.utas.edu.au/15902/2/whole-cheah-2012-ex_pub_mat.pdf; https://eprints.utas.edu.au/15902/3/original-cheah-2012.pdf

Marine phytoplankton account for approximately half of global primary production, an amount equivalent to their terrestrial counterpart. These short-lived organisms, with turnover rates between one and three weeks, support nearly all life in the ocean and have a profound effect on global biogeochemical cycles and climate. The connection between marine phytoplankton and climate is intimate and changes to either will profoundly affect the other. Over the years, due to high operational costs and distance from major human settlements, the Southern Ocean has been the least studied ocean, despite its signicance in the distribution of nutrients to the world oceans, especially the lower latitudes, and controlling global climate. In order to capture the response of the phytoplankton to environmental change across the vast Southern Ocean, a method with high spatio-temporal resolution is desirable. By focusing on the Australian sector of the Southern Ocean, this dissertation examines the productivity and physiology of natural phytoplankton communities in situ using the fast repetition rate (FRR) uorometry technique. The FRR uorometry technique was used to derive direct estimation of in situ primary productivity in the Southern Ocean during the SAZ-Sense (Sub-Antarctic Zone Sensitivity to Environmental Change) voyage in Jan-Feb 2007. A statistically significant correlation between FRR- and 14C-derived primary production was observed (r2 = 0.85, slope = 1.230.05, p < 0.01, n = 85) but the relationship between the methods differed vertically and spatially, mainly due to the effect of non-photochemical quenching under high irradiance. This indicates the FRR uorometry technique can be used to determine in situ primary productivity in the Southern Ocean but care should be taken in the interpretation of the data. In addition to the primary production measurements, the photosynthetic performance of phytoplankton was investigated to provide a better understanding of how natural phytoplankton communities acclimate to different ...