The Australian Antarctic Division is coordinating a field-based ocean acidification experiment in Antarctic waters near Casey Station, Windmill Islands, East Antarctica ( 66°17′ S 110°31′ E) this austral summer 2014-15. This antFOCE (antarctic Free Ocean Carbon Dioxide Enrichment) experiment will expose a range of benthic marine animals and algae to a constant supply of CO2-enriched water within large transparent chambers. After several months incubation, various measurements of marine animals, algae and sediment collected from between CO2-enriched and unenriched chambers will be compared.
The Aquation Respirometer System will play an important role in measuring short-term physiological responses of marine organisms and assemblages to elevated CO2. Representative organisms or communities will be placed within enclosures, and continuous measurements made of oxygen concentration that will enable us to calculate rates of respiration and photosynthesis. Additional measurements include temperature, photosynthetically active radiation (PAR), and modulated chlorophyll fluorescence and electron transport rate (ETR). Variability in ETR over the course of a day will provide a good estimate of photosynthetic activity, and laboratory-based relationships determined between ETR and oxygen consumption/production can then be used to interpret fluorescence/PAR measurements made in the field in terms of in situ productivity. So far our intent is to measure photosynthesis and respiration of microphytobenthos (MPB, diatom assemblages on the sediment surface) and calcifying algae, and respiration of one or more species of macrofauna, possibly the burrowing urchin Abatus. Measurements will be complemented with samples for pigment determinations and species composition.
Diving in Antarctica presents unique problems, yet can offer the advantages of a stable sea-ice platform from which to work, invariant water temperatures (-1.8C), and often very still and clear waters. With the use of drysuits, thermal clothing and full-face AGA masks with communications, diving in Antarctica can be a (relatively) comfortable experience.
Australian Antarctic Program antFOCE experiment: