Respiratory electron transport system (ETS) activities in zooplankton and micronekton of the Indo-Pacific region

Abstract

ABSTRACT: ETS activities of natural zooplankton assemblages and some micronekton species from the eastern Banda Sea and western Arafura Sea (Indonesia) were measured during the SE and NW monsoons, when respectively rich upwehng and poor downwelling condtlons occur. Weight-specific ETS activities of the zooplankton community decreased with depth; 13 to 20 % of this decrease was related to temperature, and another 5 to 10 % to hlgher water contents of the deeper samples. Large geographical dfferences, but no seasonal differences, were detected within the area studled. About 65 % of the total zooplankton ETS activity in the upper 500 m was confined to the upper 100 m. Day/ night differences in ETS profiles were observed during the less fertile NW monsoon period, attributed to diel vertical migration of the zooplankton, and resulting in a 9 to 36 90 lower activity in the water column during daytime. Since no diel migration by the zooplankton was seen in the fertlle SE monsoon season, the abundance of food, or the necessity to conserve energy, seems a major factor in determining del vertical migration. Of the micronekton examined, shallow-living species and those performing del vertical migration showed higher weight-specific ETS activities than deeper living and non-migrating species. Myctophid fishes and carid crustaceans showed very high weight-specific activities; chauliodontids, gonostomatids, euphausids and sergestids moderate activities; and leptocephali, chdeiognains, saips, siphonophores and medusas low activities. None of the micronekton species investigated showed seasonal differences in ETS activity.