Grazing and sedimentation of ice algae during and immediately after a bloom at the ice-water interface

Abstract

Sinking of pigmented particulate matter during and immediately after an ice algal bloom was studied in southeastern Hudson Bay at a 45 m deep station, using consecutive short-term deployments of sediment traps 30 m below the undersurface of the ice. Cell sinking and grazing by herbivores were assessed by measuring the vertical fluxes of chlorophyll a and phaeopigments. There were 2 peaks of cell sedimentation, a minor one during the first half of the bloom (mid-April) and a major one at the end of the bloom (mid-May); both were related to atmospheric warming events. The fluxes of both phaeopigments and fecal pellets (mainly from large herbivores) increased at the end of the bloom as ice algae were released from the ice environment. The total export of ice algae to the benthos (sinking cells + fecal pellets) was estimated to be ca 20 % of the ice algal production during the measurement period. A large proportion of ice algal production (ca 30 %) was still suspended in the upper water column at the end of the sampling season. The fate of the remaining 50 '10 is not known, but it is hypothesized that a significant fraction was retained in the pelagic environment.

Contribution of algal sinking and zooplankton grazing to downward flux in the Lazarev Sea (Southern Ocean) during the onset of phytoplankton bloom: a lagrangian study

“…Higher loss rates of chl a could be found in regions where the bulk of plant pigments was either found in FPC of large metazoans (Schnack 1985, Thibault et al 1999 or represented by sinking of phytoplankton in the ice zone (Sasaki & Hoshiai 1986, Tremblay et al 1989, Handa et al 1992). …”

“…Sasaki & Hoshiai 1986, Matsuda et al 1987, Tremblay et al 1989, massive sinking of ice-edge blooms (e.g. , Wilson et al 1986, Bathmann et al 1991, and sedimentation of algae from the spring-summer phytoplankton bloom (e.g.…”

Seasonal changes in the sinking export of particulate material under first-year sea ice on the Mackenzie Shelf (western Canadian Arctic)

“…Werner 2000, Fortier et al 2002 and, to a lesser extent, by sympagic fauna (Nozais et al 2001. The bulk of the ice algal biomass is mainly released into the water column at the time of spring ice melt (Tremblay et al 1989, Michel et al 1996, Fortier et al 2002. However, Melnikov (1998) suggested an export of material from the sea ice during ice growth, as a result of episodic brine drainage.…”

“…Several studies looking at temporal changes in under-ice sinking fluxes of organic material have shown increasing sinking fluxes in response to the release of material from the sea ice during spring melt (Carey 1987, Tremblay et al 1989, Michel et al 1996, Fortier et al 2002. Melnikov (1998) suggested that ice algae in the western Weddell Sea are released from the ice during winter through brine drainage during ice growth.…”

Grazing of Arctic under-ice amphipods on sea-ice algae

“…The total mean grazing impacts are in the same range as those imposed on melted-ice algae by pelagic sub-ice species (mainly Pseudocalanus spp. and Calanus glacialis) in spring (0.5 to 2.3%; Tremblay et al 1989). In the Antarctic, the daily grazing impact of ice krill Euphausia crystallorophias has been estimated to range between < l and 5% of the phytoplankton standing stock (Pakhomov & Periss~notto 1996).…”