Graduation Year

2004

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Marine Science

Major Professor

Daly, Kendra L.

Keywords

Southern Ocean, gelatinous zooplankton, respiration, ROV, digestion

Abstract

The distribution, abundance, chemical composition, metabolism, and feeding ecology of the tentaculate ctenophore, Callianira antarctica (Chun 1897), were investigated during austral winter 2001and autumn & winter 2002, in the vicinity of Marguerite Bay west of the Antarctic Peninsula. Callianira antarctica had a widespread distribution during autumn and winter, and variable abundance (0.02 to 2.6 ind. m-2) during winter 2001 associated with specific circulation features. Size frequency distributions for autumn and winter suggest that more than half of the C. antarctica population may have experienced 'degrowth' during winter due to low food availability. Callianira antarctica is a fairly robust ctenophore with geometric mean (geomean) carbon (C) and nitrogen (N) values of 8.41 and 1.83% dry weight (DW), respectively.

Winter oxygen consumption and ammonium excretion rates ranged from 0.059 to 0.410 micro l O2 [mg DW]-1 h 1 and 0.60 to 31.1 ig-at N [g DW]-1 h-1, respectively, at 0oC. Daily minimum maintenance rations based on respiration experiments were 2.7% to 3.6% of the total body carbon (TBC) for small ctenophores, and 1.4% to 1.9% TBC for larger ctenophores. Calanoid copepods and larval and juvenile Antarctic krill were offered to ctenophores in incubation experiments. Digestion times were variable, lasting 8 to 20 h, and were independent of ctenophore size and dependent on number and type of prey. Gut content analysis from one autumn and two winter seasons indicated C. antarctica preyed on both copepods and krill in situ, with an increased dependence on larval krill during winter. Lipid biomarker analysis on C. antarctica and their potential prey confirmed these results. Divers observed aggregations of C. antarctica

passively drifting with tentacles extended near dense concentrations of larval Euphausia superba during winter. These observations along with gut content and lipid biomarker analysis suggest that larval krill is an important prey item for C. antarctica during winter.

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