Abstract:
The fluorescence quantum yield (FQY. of marine phytoplankton refers to the ratio of photons emitted as fluorescence to those absorbed by individual cells, which serves as a first order estimate of photosynthetic efficiency. Dedicated instrumentation to measure this optical indicator is currently limited. In this study, a JFE Advantech Multi-Exciter Fluorometer (MFL., originally designed to discriminate phytoplankton species in a population based on accessory pigment composition, was selected as a low-cost option to derive FQY. Two different approaches were employed to optically characterise the fluorometer, providing a robust calibration that has yielded quantitative in situ measurements. The nine different excitation wavelengths of the MFL allows for both a spectral and total FQY derivation. This has both in situ and remote sensing application, allowing for the determination of the potential species composition influence on FQY variability, alongside comparable measurements to investigate current remote sensing limitations. The MFL was deployed in the Atlantic sector of the Southern Ocean during the austral winter of 2012 and summer of 2013/2014, where the FQY was determined at various stations. Fluorescence quantum yield in the Southern Ocean is influenced by light history, taxonomy and micronutrient availability. Our initial results indicate the fine scale resolution of community structure into smaller phytoplankton groups contains a wealth of physiological information. This new insight may be used to expand current remote sensing algorithms of the region. Improving our understanding of the physical and biological drivers of photosynthetic variability, particularly in the ecologically important Southern Ocean, is imperative to improving our predictive capabilities of a changing climate. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.