ZOOPLANKTON COMMUNITY STRUCTURE OF PRYDZ BAY, ANTARCTICA, JANUARY-FEBRUARY 1993 (18th Symposium on Polar Biology)

概要

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Previous large scale surveys around Prydz Bay have identified the continental shelf edge as an area of rapid transition between three major zooplankton communities. One of these is dominated by the Antarctic krill Euphausia superba. This community was located mainly along the continental shelf edge, usually between the offshore main oceanic community dominated by copepods and chaetognaths, and the neritic community dominated by E. crystallorophias. A survey in January-March 1991 found similar community compositions but the krill community was restricted to the western part of the area. This study reports on the results of a repeat survey in January-February 1993 which extended the survey area to the west. Using the same multivariate analyses, the characteristic shelf and oceanic assemblages were again similar to previous surveys, but the krill community was restricted to three scattered sites. A number of hypotheses are presented to explain the apparent absence of krill: 1) there has been a genuine decline in krill numbers since the earlier surveys; 2) the overall distribution pattern of krill has changed and they were outside the survey area; and 3) the krill biomass had not declined or moved geographically but remained in the survey area but dispersed, thus not forming a distinctive community.
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