Annual cycle of tintinnids in Admiralty Bay with an emphasis on seasonal variability in <i>Cymatocylis affinis/convallaria</i> lorica morphology

Abstract

In water samples collected from the middle of Admiralty Bay (King George Island 62°08'S 58°25'W) between February 1990 and January 1991, 17 Tintinnina species were noted. Total Tintinnina numbers in summer were very high (up to 5000 cells m −3 ), but species diversity was low, consisting mainly of Cymatocylis affnislconvallaria , forma convallaria . During austral winter, cell numbers were very low, but species composition was diverse. Cymatocylis affnislconvallaria , forma affinis, and C.affmis/convallaria , forma convallaria , the polymorphic forms of one species C.affinis/convallaria , appear to be interchangeable during the year. The transition from one form to the other occurs in the spring and autumn. The typical Tintinnina polymorphism can be attributed to the prevailing environmental conditions.