The diatoms and dinoflagellates of Hudson Bay

Abstract

Phytoplankton samples from 130 stations in Hudson Bay taken during summer 1975 were examined. Diatoms formed the largest group of phytoplankton comprising 27 genera and 59 species, 24 of which are not previously recorded from Hudson Bay. Twelve genera and 45 species of dinoflagellates were identified of which 33 have not been previously reported from the Bay.Various patterns of distribution were observed; some species were only found inshore, while others were distributed throughout the Bay with the exception of the low salinity waters of the southwest coast. Highest cell counts were found inshore; diatoms reached 200 000 cells per litre around the Belcher Islands. Dinoflagellates reached 125 000 cells per litre south of Mansel Island, and exceeded 60 000 cells per litre in the Chesterfield Plume and along the southwest coast. Thus certain areas of Hudson Bay have much higher phytoplankton standing crops than previously believed, often greatly exceeding counts from Foxe Channel and Hudson Strait. The lowest diversity indices of diatoms, dinoflagellates, and diatoms and dinoflagellates combined, were observed at lower salinities along the southwest coast. The diversity index of diatoms and dinoflagellates combined was otherwise high throughout the Bay (> 3) and was highest in the Coats and Mansel islands area.