Nutrient limitation of the bottom‐ice microalgal biomass (southeastern Hudson Bay, Canadian Arctic)1

Abstract

In April 1983, differential-enrichment bioassays were conducted on natural sea-ice microalgae from Hudson Bay, Canadian Arctic. Incubations were done both in the laboratory (at about 4"-5°C) and in situ at the ice-water interface (-1.5"C). Actual growth of the cultures was nutrient limited. On the basis of our observations and using recalculated data from the literature, we tentatively set the mean generation time of Arctic-ice microalgae between 8 and 17 days. Nitrogen was demonstrated to govern the algal yield when illumination and grazing allowed the algae to grow. The low (NO,-+ NO,-+ NH,+):P0,3-mean ratio (5.9) in the water at the ice interface leads to the same conclusion. In situ dissolved inorganic nitrogen and phosphorus progressively decreased during the course of sampling, but were never exhausted. We hypothesize that the K, of epontic as well as of other benthic microalgae is higher than that of phytoplankton, so that they cannot deplete the natural nutrient reservoir. We conclude that the bottom-ice dynamics is controlled not only from above, by the seasonal (climatic) changes in light intensity as generally assumed, but also from below, by the shorter term (hydrodynamic) events of vertical mixing that replenish the ice-water interface with nutrients.

Changes in photosynthetic carbon allocation in algal assemblages of Arctic sea ice with decreasing nutrient concentrations and irradiance

“…The growth rates of the algal communities and the genus-specific growth rates were generally similar to observations in other Arctic and Antarctic ice-algae studies (Maestrini et al 1986, Grossi et al 1987, Cota & Sullivan 1990, Gilstad & Sakshaug 1990, Johnson & Hegseth 1991, Hegseth 1992, Kirst & Wiencke 1995, and agree exceptionally well with growth rates recorded during field studies in the Barents Sea (Hegseth 1992). Nonetheless, different growth rates of the diatom genera lead to a species succession with time.…”

“…This is the case for steady state growth, which possibly does not exist under the unstable conditions typical in nature (Smetacek 1996). Photosynthate allocation to lipids and carbohydrates in phytoplankton as well as ice algae varies directly with the availability of light (Smith & Morris 1980, Li & Platt 1982, Smith et al 1989, 1997, Smith & Herman 1992 and nutrients (e.g., , Maestrini et al 1986, Smith et al 1987, 1997, Smith & Herman 1992, this is also evident in temperate phytoplankton (Iwamoto et al 1955, Fogg 1959, Opute 1974, Li et al 1980, Shifrin & Chisholm 1981, Tadros & Johansen 1988. Low-light conditions, for example stimulate the dominance of glycolipids, which are important structural components of chloroplast membranes as a consequence of shade acclimation (Pohl & Zurheide 1979, Harwood & Jones 1989, Klyachko-Gurvich et al 1999.…”

“…Palmisano & Sullivan 1982, Kottmeier & Sullivan 1988, salinity (Bates & Cota 1986, Bartsch 1989, Fiala & Oriol 1990, Kirst & Wiencke 1995 and essential nutrients (Maestrini et al 1986, Demers et al 1989, Syvertsen & Kristensen 1993.…”

In situ net primary productivity of an Antarctic fast ice bottom algal community

“…There is now also evidence that nutrients (Maestrini et al 1986, Palmisano et al 1988, Lizotte & Sullivan 1992, McMinn et al 1999a) and even ultraviolet-B radiation (Ryan & Beaglehole 1994, McMinn et al 1999b) might reduce, and perhaps even limit, production in some circumstances.…”

Physical control of arctic ice algal production

“…Several independent lines of evidence have led to recent suggestions that inorganic nutrients may limit ice algal production (Grainger 1977, Gosselin et al 1985, McConville et al 1985, Palmisano & Sullivan 1985, Maestrini et al 1986. Cota e t al.…”