Standing crops and species composition of diatoms in sea ice From Robeson Channel to the Gulf of St. Lawrence

Abstract

Standing crops of diatoms, measured in terms of chlorophyll la concentration, and measurements of phosphate, silicate and salinity in sea ice are presented from Robeson Channel, West Barrow Strait, West Hudson Bay and the Gulf of St. Lawrence. Salinity profiles in the Gulf of St. Lawrence showing highest salinities in the lowest segment of the ice differed from those at the three northern stations, in which higher salinities were found at the top and the bottom of the ice, lowest at midlevels. Nutrient concentrations were similar in all four areas. Chlorophyll a concentrations in the lowest segment of the ice, and chlorophyll la concentrations expressed as weight per square meter, were from one to two orders of numbers higher in the northern stations than in the Gulf of St. Lawrence. Between 96 % and 99 % of the diatoms at the northern stations were pennate species, mainly benthic forms, whereas only 57 % were pennates in the Gulf of St. Lawrence, the remainder being planktonic centric species.