Crustacean Zooplankton of Southwestern Lake Ontario in Spring 1973 and at the Niagara and Genesee River Mouth Areas in 1972 and Spring 1973

Abstract

In southwestern Lake Ontario during three cruises in spring 1973, the common zooplankters were nauplii (78%), immature cyclopoid copepodids, Cyclops bicuspidatus thomasi CVI, and immature calanoid copepodids. Zooplankton was most abundant in late April-early May (second cruise) and least abundant at the end of May. There was more zooplankton than at the same stations a year earlier probably because of earlier copepod reproduction. In the river mouth areas during four cruises in 1972 and one cruise in May 1973, the common zooplaankters were nauplii, immature cyclopoid and calanoid copepodids, bosminids with mucro, Cyclops bicuspidatus thomasi CVI, Eubosmina coregoni, Ceriodaphnia lacustris, Daphnia retrocurva (Genesee River only), D. galeata mendotae (Niagara River only), Tropocyclops prasinus mexicanus CVI (Genesee River only), Diaptomus oregonensis CVI (Niagara River only). At the Genesee River the common zooplankters were most abundant in late August or November; at the Niagara River mouth copepods were most numerous in the spring and cladocerans in August and December. When compared to its nearest nonriver mouth IFYGL station in Lake Ontario, the Genesee River area supported less zooplankton and the Niagara River mouth area more. Several species of harpacticoid copepods were encountered which have not been reported previously from Lake Ontario. They were Bryocamptus zschokkei CVI, Epactophanes richardi CVI, Nitocra hibernica CVI, Nitocra spinepes CVI.