At sea, animals were captured for physiological experiments using a 1 m diameter, 150 µm (in 2011) or 335 µm (in 2012) mesh Reeve net trawl, or a 1 m2 MOCNESS tow with 150 µm mesh nets. Pteropods were placed in filtered seawater at densities of < 30 individuals liter-1 and acclimated for at least 8 hours at 20° C, 15°C or 10°C in temperature controlled waterbaths. After acclimation, individuals that were in good condition were put into glass syringe respiration chambers with a known volume of 0.2 micron filtered seawater for at least four hours.
In 2012 on cruise NH1208, an experiment was conducted to determine whether antibiotics changed the metabolic rate of the pteropods. In this experiment water was treated with 25mg each of Streptomycin and Ampicillin liter-1 or without antibiotics.
Unless otherwise explicitly stated, the water contained 25mg each of Streptomycin and Ampicillin liter-1, to prevent bacterial growth, and was bubbled with certified gas mixes to achieve normal air saturated (21% O2, 380 ppm CO2), high CO2 (21% O2, 800 ppm CO2), low O2 (10% O2, 380 ppm CO2) or low O2 high CO2 (10% O2, 800 ppm CO2) conditions. Bubbling of 10% O2 achieved a mean initial O2 concentration of 10-13% in low O2 treatments.
During all experiments, we simultaneously ran a control syringe (without an animal) to monitor background respiration of microbes. At the conclusion of the experiments, we measured the O2 level by withdrawing a sample of water from the chamber using a 500 µL airtight Hamilton syringe and injected past a Clarke-type O2 electrode (#1302) and meter (#782) in a water-jacketed injection port (#MC100, Strathkelvin Instruments, North Lanarkshire, United Kingdom; Marsh and Manahan, 1999). Our resulting O2consumption rates are reported in µmoles g-1 h-1 (wet mass). Notes on carbonate chemistry and net profiles are in the cruise report.
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