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

Abstract

The structure of sea-ice bacterial communities is frequently different from that in seawater. Bacterial entrainment in sea ice has been studied with traditional microbiological, bacterial abundance, and bacterial production methods. However, the dynamics of the changes in bacterial communities during the transition from open water to frozen sea ice is largely unknown. Given previous evidence that the nutritional status of the parent water may affect bacterial communities during ice formation, bacterial succession was studied in under ice water and sea ice in two series of mesocosms: the first containing seawater from the North Sea and the second containing seawater enriched with algal-derived dissolved organic matter (DOM). The composition and dynamics of bacterial communities were investigated with terminal restriction fragment length polymorphism (T-RFLP), and cloning alongside bacterial production (thymidine and leucine uptake) and abundance measurements (measured by flow cytometry). Enriched and active sea-ice bacterial communities developed in ice formed in both unenriched and DOM-enriched seawater (0–6 days). γ-Proteobacteria dominated in the DOM-enriched samples, indicative of their capability for opportunistic growth in sea ice. The bacterial communities in the unenriched waters and ice consisted of the classes Flavobacteria, α-and γ-Proteobacteria, which are frequently found in natural sea ice in polar regions. Furthermore, the results indicate that seawater bacterial communities are able to adapt rapidly to sudden environmental changes when facing considerable physicochemical stress such as the changes in temperature, salinity, nutrient status, and organic matter supply during ice formation.

Physical and bacterial controls on inorganic nutrients and dissolved organic carbon during a sea ice growth and decay experiment

“…Leu and TdR and bacterial abundance. At the beginning of the experiment, the majority of bacteria in ice were probably not wellacclimated to the sea ice environment and possibly undergoing a community shift (Eronen-Rasimus et al, 2014), resulting in a decrease in abundance throughout the ice before day 7. After day 7, cell-specific Leu and TdR were generally stable, but bacterial abundance increased in the bottom ice sections and decreased in the ice interior, pointing to active bacterial growth in the lower ice layers being also subject to brine convection before day 15.…”

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).…”

Autochthonous Dissolved Organic Matter Drives Bacterial Community Composition during a Bloom of Filamentous Cyanobacteria

“…Many Gammaproteobacteria are known to be copiotrophic opportunists (e.g., Lauro et al, 2009;Spring et al, 2015), and capable of high growth rates (Teira et al, 2009). Some of them benefit from algae-derived organic matter (e.g., Teeling et al, 2012;Eronen-Rasimus et al, 2014) and can contribute to the decomposition of algal-derived organic matter during phytoplankton blooms (Teeling et al, 2012). Most of the Gammaproteobacteria in this study affiliated to Pseudomonas, which can occasionally be abundant in the Baltic Sea (Hagström et al, 2000;Koskinen et al, 2011).…”