Relative Contributions of Ice Algae, Phytoplankton, and Benthic Microalgae to Primary Production in Nearshore Regions of the Beaufort Sea

Abstract

Phytoplankton, ice algae, and benthic microalgae are the three sources of primary production in the western Beaufort Sea in winter and spring. Phytoplankton levels in winter are low with chlorophyll a levels near the limit of detection. Microflagellates are the most abundant organisms present in the water column along with a few diatoms. Low chlorophyll a, standing stock, and primary productivity continue into June when the ice breaks up. Cells are present in sea ice from the time it forms in the fall and are generally scattered throughout the ice thickness. Microflagellates are the most abundant organisms, but some diatoms, mostly pennate species, are also present. Cells concentrate in the bottom few cm of ice during March-April in response to increasing light levels. Growth continues until late May-early June when maximum production and standing stock occur. Benthic microalgal production was barely detectable in spring although chlorophyll a levels were high, perhaps left from the previous production season. Light is apparently the major factor controlling production in the spring, with the ice algae being able to take advantage of increasing light levels early in spring. This community shades both the water column and benthos so that production in those habitats does not increase until after the ice algae disappear in early June, but the ice community may be inhibited by layers of sediment in the ice. During this study, the ice algae provided about two-thirds and the phytoplankton one-third of the spring primary production; the benthic community contribution was negligible.

Key words: western Beaufort Sea, phytoplankton, ice algae, benthic microalgae, primary productivity, chlorophyll a, standing stock, species present, environmental factors