| Summary: | Progress Code: completed Purpose Materials and Methods The experimental population of krill was collected from the Indian Ocean sector of the Southern Ocean at 64 degrees 09'S, 100 degrees 46'E during the 2010/11 field season. The krill were maintained in the Australian Antarctic Division's marine research aquarium, where they matured and spawned naturally. Experimental set-up Experimental sea water was supplied from a 70 l header tank and equilibrated with air (control) or CO2-enriched air before being delivered to experimental jars (250 ml clear polycarbonate) containing krill eggs. CO2-enriched air was prepared with a mass flow controller (Horiba STEC SEC-E-40) and by an air valve, to regulate flow rates of pure CO2 and atmospheric air, respectively. The pCO2 levels of the CO2-enriched air and sea water were monitored by a CO2 monitor (Telaire 7001) and indirectly from pH measurement (Mettler Toledo Seven Go Duo pro), respectively. Experimental temperature was set at 0.5 degrees C. Experiments were conducted in a refrigerator system maintained at 0.5 degrees C, equipped with 6 shelves. Each shelf was randomly assigned to a CO2 level treatment, and experimental jars were randomly distributed within each shelf. Effluent from each jar was drained into a 70 l sump, and recirculated through a degassing unit before returning back to the header tank via a filtration and cooling system. Total alkalinity was measured using an alkalinity titrator (Model Kimoto ATT-5). Hatching experiment Fertilized eggs were obtained in January 2012 from females that spawned in the laboratory. A total of eleven egg batches, each originating from different females, were used. Each batch was randomly distributed into experimental jars, with approximately 20-30 eggs per jar. Two types of experiments were conducted. Detailed response of hatch rates against increasing CO2 (experiment 1) For eight batches of eggs, the embryos were incubated at: 380 micro atm (control), 1000, 1250, 1500, 1750, and 2000 micro-atm pCO2. Approximately 20-30 ...
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