Abundance and production of ice algae n Resolute Passage, Canadian Arctic

Abstract

Abundance and photosynthetic activity of ice algae in Resolute Passage in the Canadian high Arctic were measured in relation to in situ irradiance throughout the main growth season in 1985 and 1986. A simple model was used to calculate in situ production rates and the theoretical maximum (light limited) size of crops and production rates. Both the observed and the maximum possible crop sizes and production rates varied directly with irradiance over the natural range of snow cover, and crops attained the theoretical maximum imposed by self-shading (77 to 225 mg m-' chlorophyll a under thin snow cover) in both years. Calculated in situ production of ice algae under thin snow cover (S to 23 gC m-2 yr-l) could equal or exceed typical values for Arctic plankton. Comparison against observed biomass accumulation in the ice indicated that as much as 65 % of the production could be exported from the ice during the growth season. Where light was artificially increased by maintaining snow-free areas, observed crops were much less than the theoretical maximum despite the abscence of photosynthetic photoinhibition. Crops reported from some other arctic sites were also much less than their corresponding theoretical maxima. Low irradiance often limits ice algal growth, but our results suggest that losses associated with excessive irradiance and with grazing by amphipods at near-shore sites are additional factors determining algal abundance and production.

Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation

“…where P 0 is the maximum primary production rate in the photosynthesis to irradiance (P /I ) curve for sea-ice algae, I is irradiance and I k is the photoadaptation parameter or the irradiance level at which photosynthesizing organisms begin to become saturated with light (Platt et al, 1980;Smith et al, 1988;Suzuki et al, 1997). represents conditions where density stratification in the water column appeared to be persistently present while the lightly shaded region (1-2 cm s −1 ) represents conditions where stratification was occasionally observed.…”

Physical control of arctic ice algal production

“…There is little doubt that light availability has a major influence on ice algal biomass and production in the Arctic, Subarctic and Antarctic (Apollonio 1961, 1965, Clasby et al 1976, Horner & Schrader 1982, Gosselin et al 1985, Horner 1985, Grossi et al 1987, Smith et al 1987, 1988, SooHoo et al 1987, especially during the winter-spring transition when incident irradiance increases dramatically. Growth irradiance (in situ light level) can also be manipulated and maintained fairly easily by stabilizing surface snow cover with a low profile snow fence (Cota 1985).…”

“…Under conditions of low light (ca 2 to 25 pE m-2 S-') and temperature (-1.8"C) in the high Canadian Arctic ice algae, predominantly pennate diatoms, form dense populations (up to ca 100 to 300 mg chl m-2) in a thin layer (ca 1 cm) on the bottom of 1 to 2 m of annual sea ice (Apollonio 1961, 1965, Cota 1985, Smith et al 1987, 1988. In addition to augmenting total marine productivity, ice algae extend the brief summer open water season of phytoplankton production by about 2 mo in spring.…”

“…In addition to augmenting total marine productivity, ice algae extend the brief summer open water season of phytoplankton production by about 2 mo in spring. Seasonal fluctuations of sea ice cover are ca 7 X 10"m2 in the Arctic (Walsh & Johnson 1979), and on annual sea ice, algal abundance normally reaches levels of 10 to 50 mg chl m-2 or more depending upon snow and ice conditions (Horner & Schrader 1982, Horner 1985, Smith et al 1988. These ice algae form one of the most intense chlorophyll maxima in any marine environment and presumably represent the most concentrated food resource that grazers ever encounter in this ecosystem (Bradstreet & Cross 1982, Horner & Schrader 1982, Carey 1985, Grainger et al 1985, Conover et al 1986).…”

“…The temporal development of algal populations in Present address: Graduate Program in Ecology, University of Tennessee, Knoxville, Tennessee 37996-1610, USA bottom ice can be followed with comparative ease, because they are fixed spatially in a relatively predictable and nearly planar environment and can be revisited repeatedly to document changes in biomass and physiology , Smith et al 1987, 1988. There is little doubt that light availability has a major influence on ice algal biomass and production in the Arctic, Subarctic and Antarctic (Apollonio 1961, 1965, Clasby et al 1976, Horner & Schrader 1982, Gosselin et al 1985, Horner 1985, Grossi et al 1987, Smith et al 1987, 1988, SooHoo et al 1987, especially during the winter-spring transition when incident irradiance increases dramatically.…”