MEPS 357:33-49 (2008)  -  DOI: https://doi.org/10.3354/meps07277

ABSTRACT: To test the hypothesis that low temperature inhibits utilization of sinking spring bloom material, we studied the formation and fate of the bloom in Conception Bay, Newfoundland, Canada, where the entire water column is <0°C during the spring bloom and the benthos is <–1°C year round. The bloom formed in April and sank from the upper mixed layer in May, following nutrient depletion in the upper 50 m. Using sediment traps (40, 80, 150, and 240 m depth), we determined time-averaged fluxes of total particulate matter, particulate organic carbon, particulate organic nitrogen, and chlorophyll a as the material sank to the bottom. The sinking material was dominated by zooplankton fecal pellets before and after the sinking event, but by diatom vegetative cells and spores during it. Over half (56%) of the primary production during the spring bloom was exported from the upper mixed layer. The principal fate of sinking phytodetritus was aerobic utilization by benthic microorganisms (42%), followed by consumption by water column zooplankton (18%). Although rates of primary production and sinking in Conception Bay were not exceptional in a global context, the quality of the sinking material was extremely high in terms of properties such as percent organic matter, percent carbon, and percent nitrogen. We found little evidence for low temperature regulation of the utilization of organic carbon from the spring bloom in Conception Bay, but we propose a role of low temperature in maintaining high nutritional quality of sinking phytodetritus.

KEY WORDS: Vertical flux · Sediment trap · Spring bloom · Pigments · Temperature · Benthos