Biological Productivity of the Southern Beaufort Sea: phytoplankton and seaweed studies

Standing stock and in situ primary productivity of the southern Beaufort Sea phytoplankton were determined during the summers of 1973, 1974, and 1975. Average cell numbers were 10 times greater at inshore stations than at offshore stations at corresponding depths while the rate of primary productivity was 2 to 8 times greater at inshore stations. Cell numbers ranged from 2.0 to 4802.0 x 10³ cells/1, while integrated productivity values averaged 47.45 mg C/m²/h for inshore stations and 8.82 mg C/m²/h for offshore stations. Possible reasons for a greater standing stock and primary productivity at inshore stations are discussed. 

The largest group represented was the Bacillariophyta with 64 species, followed by the Pyrrophyta with 5 species, the Chrysophyta with 3 species, the Chlorophyta with 2 species and the Euglenophyta and Cyanophyta with 1 species each. There were at least 87 species identified.

The phytoplankton community consisted mainly of diatoms and flagellates. Diatoms dominated the inshore stations and flagellates were more abundant at offshore stations. Possible reasons for this unique distribution are discussed.

Diatoms were more sensitive than flagellates when they were exposed to crude oils, Corexit and crude oil-Corexit mixtures. The toxicity of crude oil-Corexit mixtures on algal photosynthesis and growth was greater than crude oil or Corexit alone. Possible long-term ecological consequences of such differential sensitivity and selective toxicity are discussed.

Primary production of seaweed was severely inhibited by all types of crude oil at relatively low concentrations.