Mean respiration and excretion rates for micronekton Southern Ocean GLOBEC

Collection of specimens. Crustaceans were collected using either mouth-closing Tucker trawls (9.0 m² or 2.25 m² mouth area) or downward-looking, vertically deployed plummet nets (1 m² mouth area). Tucker trawls were equipped with either blind or thermal-turbulence-protecting cod-ends (Childress et al. 1978); plummet nets terminated in bind cod-ends only. Specimens were taken in the upper 1000m of the water column in the vicinity of the marginal ice zone during spring (November-December) 1983, fall (March) 1986, and winter (June-August) 1988 as part of the AMERIEZ (Antarctic Marine Ecosystem Research at the Ice Edge Zone) program to study ice edge biology. Sampling locations were all in the Scotia-Weddell Sea region but moved with seasonal movement of the pack ice edge. Thus, spring and winter collections were in the Scotia Sea in the vicinity of 60deg S, 40deg W; fall sampling took place further south, 65deg S, 46deg W. Collections were made on a continuum from deep in the pack ice out to 300 km seaward of the ice edge in fall and winter. In spring, collections were made in the open water only. Station locations are given in Donnelly et al. (1990).

Oxygen consumption rates were determined by allowing individuals to deplete the oxygen in a sealed container filled with filtered (0.45 um pore size) seawater. Temperature was maintained at 0.5 C (+/- 0.1 C) using a refrigerated water bath. Oxygen partial pressure (PO₂) was continuously monitored using a Clark polarographic oxygen electrode (Clark 1956) as an individual reduced oxygen levels to low (10 to 20 mm Hg) partial pressures. Electrodes were calibrated using air- and nitrogen-saturated seawater at the experimental temperature. The time required for consumption of oxygen to low levels varied from 12 to 18 h. Streptomycin and Neomycin (each 25 mg 1^-1) were added to the seawater to minimize microbial growth. To control for possible oxygen consumption by microorganishs, an individual was removed after selected runs, its volume was replaced with fresh seawater, and oxygen consumption was again measured for 2 to 4 h. In all cases microbial oxygen consumption was negligibly low.

References:
Torres, Joseph J., et al., 2007; The physiology of autumn and winter krill (Euphausia superba) in the waters of the Western Antarctic Peninsula Shelf. GLOBEC International Newsletter, 13:1, 60-62.

Contact:
Jose Torres
College of Marine Science
University of South Florida
140 Seventh Avenue, South
St. Petersburg, FL 33701
jtorres@marine.usf.edu