Abstract
Chromophoric dissolved organic matter (CDOM) is highly enriched in bottom sea ice in the Arctic during ice algal blooms, giving rise to multifaceted ecological implications in both the sea ice and the underlying seawater. We conducted laboratory culture incubations to assess the potential role of ice algae in the accumulation of CDOM in Arctic sea ice. Non-axenic monocultures of Attheya septentrionalis and Nitzschia frigida and a natural ice algal assemblage (NIAA) were grown at 4 °C in an f/2 medium under cool white fluorescent light. Culture samples were collected several days apart throughout the exponential, stationary, and senescent phases, and analyzed for CDOM absorbance, chlorophyll a, and bacterial cell abundance. The cultures displayed apparent specific growth rates of algal and bacterial cells comparable to those in the field. Accumulations of CDOM were observed in all cultures during the time-course incubations, with the senescent phase showing the largest accumulations and the highest production rates. The senescent-phase production rate for NIAA was ~40% higher than that for A. septentrionalis. The chlorophyll a-normalized CDOM production rates in the cultures are comparable to those reported for Arctic first-year sea ice. The absorption spectra of CDOM in the cultures exhibited characteristic short-ultraviolet shoulders similar to those previously identified in sea ice. This study demonstrates that ice algal-derived CDOM can account for the springtime accumulation of CDOM in Arctic sea ice.
Highlights
Chromophoric dissolved organic matter (CDOM) is highly enriched in bottom sea ice in the Arctic during the spring season [1,2,3,4,5,6,7]
Cell autolysis is a possible mechanism for CDOM production by ice algae, as the fastest generation of CDOM in the cultures occurred during the senescent phase
The three ice algal cultures tested in this study displayed apparent specific growth rates of algal and bacterial cells comparable to those in the field
Summary
Chromophoric dissolved organic matter (CDOM) is highly enriched in bottom sea ice in the Arctic during the spring season [1,2,3,4,5,6,7]. The presence of this dense CDOM pool plays an important role in regulating in-ice and under-ice optics and biogeochemistry [1,8,9,10]. After sea-ice CDOM is released into seawater during the melting season, it becomes a potentially significant player in water-column optics, heat budget, and biogeochemical cycling [1,2,9]. The main cause for the enrichment of CDOM in sea ice has been attributed to in situ biological activity of sympagic organisms including ice algae, bacteria, and protozoan and/or metazoan grazers [12,15,16]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
