Phytoplankton Production and Distribution in Howe Sound, British Columbia: A Coastal Marine Embayment–Fjord Under Stress

Abstract

Phytoplankton production and distribution were examined over a 2-yr period in relation to man-induced and natural factors that stress the system by mainly affecting the light regime in surface layer(s) of Howe Sound, British Columbia. Production rate and biomass values were greatest at the seaward boundary of the Sound where surface waters mix with the Strait of Georgia. Production decreases linearly in an up-inlet direction, reaching minimum values at the head of the Sound where the influence of the turbid Squamish River discharge is greatest. Annual production in the boundary waters of the Sound for 1973 and 1974 was 300 and 516 g C∙m−2, compared to an average of 118 and 163 for remaining stations. Strong light attenuation by the turbid Squamish River and flushing by the seaward moving surface layer were considered the most important factors controlling phytoplankton production and distribution in Howe Sound. Colored effluent from two pulp mills and turbid mine tailings and gravel washing water were minor perturbants to the system as a whole, but in affected bays and subregions of the Sound their effects on phytoplankton production were considerable. Annual production in Howe Sound was slightly higher than values for the Strait of Georgia and considerably greater than estimates from the North Pacific. Key words: phytoplankton, production, fjord–embayment, coastal marine, phytoplankton distribution, succession