Bacterial Standing Stock, Activity, and Carbon Production during Formation and Growth of Sea Ice in the Weddell Sea, Antarctica

Abstract

Bacterial response to formation and growth of sea ice was investigated during autumn in the northeastern Weddell Sea. Changes in standing stock, activity, and carbon production of bacteria were determined in successive stages of ice development. During initial ice formation, concentrations of bacterial cells, in the order of 1 x 108 to 3 x 108 liter-, were not enhanced within the ice matrix. This suggests that physical enrichment of bacteria by ice crystals is not effective. Due to low concentrations of phytoplankton in the water column during freezing, incorporation of bacteria into newly formed ice via attachment to algal cells or aggregates was not recorded in this study. As soon as the ice had formed, the general metabolic activity of bacterial populations was strongly suppressed. Furthermore, the ratio of [3H]leucine incorporation into proteins to [3H]thymidine incorporation into DNA changed during ice growth. In thick pack ice, bacterial activity recovered and growth rates up to 0.6 day-' indicated actively dividing populations. However, biomass-specific utilization of organic compounds remained lower than in open water. Bacterial concentrations of up to 2.8 x 109 cells liter-' along with considerably enlarged cell volumes accumulated within thick pack ice, suggesting reduced mortality rates of bacteria within the small brine pores. In the course of ice development, bacterial carbon production increased from about 0.01 to 0.4 ,ug of C liter-' h-1. In thick ice, bacterial secondary production exceeded primary production of microalgae.

Linkages among the bioreactivity, chemical composition, and diagenetic state of marine dissolved organic matter

“…Ϫ1 during the lag phase to maximal values of 4.2 nM leucine h Ϫ1 . High bacterial production rates in sea ice have been reported by several investigators(Bunch and Harland 1990;Grossmann and Dieckmann 1994). These peak values during sea-ice DOM decomposition are as high as values usually measured in productive coastal waters (Chin-Leo and Benner 1992;Amon and Benner 1998).…”

Bacterial communities in Arctic first‐year drift ice during the winter/spring transition

“…The main drivers in sea-ice bacterial community succession are believed to be substrate supply, together with availability of sites of bacterial attachment, such as extracellular polymeric substances (EPSs), particles, brine channel walls and protists (Kottmeier et al, 1987;Helmke and Weyland, 1995;Bowman et al, 1997b;Junge et al, 2002;2004;Eronen-Rasimus et al, 2014;2015). In the initial phases of sea-ice formation, the parent water determines the bacterial community composition (Barber et al, 2014;Eronen-Rasimus et al, 2014;2015), and bacterial activity is close to the detection limit (Grossmann and Dieckmann, 1994;Eronen-Rasimus et al, 2015). During the low-productive, cold and dark winter period, the Arctic sea-ice bacterial community composition, dominated by oligotrophic Alphaproteobacteria (SAR11 clade), remains nearly unchanged in the upper ice column despite the loss of bacterial cells (Collins et al, 2008;2010).…”

Bacterial community dynamics and activity in relation to dissolved organic matter availability during sea‐ice formation in a mesocosm experiment

“…Bacterial growth in sea ice is governed by the interaction of salinity, temperature, and nutrients (Pomeroy and Wiebe 2001;Kuosa and Kaartokallio 2006) as well as biotic factors such as grazing (Kaartokallio 2004;Riedel et al 2007a). Bacteria seem to become entrained in sea ice along with phytoplankton (Grossmann and Gleitz 1993;Grossmann 1994;Grossmann and Dieckmann 1994;Helmke and Weyland 1995;Weissenberger and Grossmann 1998;Riedel et al 2007b), whereas physical enrichment alone seems to be ineffective (Grossmann and Dieckmann 1994;Weissenberger and Grossmann 1998). Other possible explanations for bacterial entrainment in sea ice are gas vacuoles (Staley and Gosink 1999) and interaction with microgels in the EPS continuum (Ewert and Deming 2011).…”

“…Other possible explanations for bacterial entrainment in sea ice are gas vacuoles (Staley and Gosink 1999) and interaction with microgels in the EPS continuum (Ewert and Deming 2011). In newly formed sea ice, bacterial activity can be suppressed, but as the ice consolidates, bacterial activity has been shown to increase (Grossmann and Gleitz 1993;Grossmann 1994;Grossmann and Dieckmann 1994;Helmke and Weyland 1995;Kaartokallio 2004;Kaartokallio et al 2008) and psychrophilic bacteria become more abundant (Helmke and Weyland 1995). There is evidence that the subsequent development of the bacterial communities is more dependent on the availability and lability of organic matter than on temperature (Helmke and Weyland 1995).…”