Estimating primary productivity of marine macroalgae in East Antarctica using in situ fluorometry
Aquation Director Dr John Runcie and colleague Dr Martin Riddle from the Australian Antarctic Division on the 05Nov2012 published a paper “Runcie, J.W., Riddle, M.J. (2012) “Estimating primary productivity of marine macroalgae in East Antarctica using in situ fluorometry ”. European Journal of Phycology 47(4): 449-460, DOI:10.1080/09670262.2012.736535
Productivity in marine systems has been typically conducted by measuring the flux of oxygen and/or CO2 within enclosed chambers underwater for 24 hour intervals. This can be time consuming and expensive. Simpler modulated chlorophyll fluorescence measurements have long been suggested as a more convenient proxy for productivity, but differences between estimates of carbon fixed per photon derived from gas exchange and chlorophyll fluorescence tend to differ widely in high light conditions. In this paper, the relation between the two is determined over a wide range of light intensities. The derived empirical relation is then applied to in situ chlorophyll fluorescence data (effective quantum yield ( 
)) and irradiance as PAR. Estimates of photosynthesis in the day and respiration in the night are calculated for samples examined only for chlorophyll fluorescence and ambient irradiance. The results show the technique is effective in gathering productivity data in environments were only the deployment of a fluorometer and PAR sensor is required. While the data for the paper was collected at Casey, one of Australia’s continental Antarctic Research Stations, the approach is applicable to most aquatic and terrestrial algae and plants. The Aquation submersible fluorometers are well suited to regularly taking these fluorescence and irradiance measurements.
Abstract
Photosynthetic activity of marine macroalgae in the Windmill Islands, East Antarctica, was measured in situ using submersible modulated fluorometers. An empirical relation incorporating terms for respiration and non-linear electron transport was derived from simultaneous in vivo measurements of effective quantum yield ( ) and oxygen evolution. This relation was used with in situ measurements of 
and photosynthetic photon flux density acquired over 24-h periods to estimate oxygen evolution rates of algae over the course of the measurement period. Productivity ranged from −8 to 19 µmol O2 g−1 FW h−1 (FW = fresh weight), with daily carbon gain ranging from −1.5 to 3.6 mg C g−1 FW d−1 for midnight ice-covered algae and midday ice-free algae, respectively. These values were similar to published values of productivity of Antarctic species derived from oxygen- and carbon-based techniques. The technique described here provides a simple and rapid means of estimating primary productivity in marine systems.
A PDF of the paper is available from the author on request: john.runcie “at” aquation.com.au