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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. C10, 3316, doi:10.1029/2001JC001138, 2003

Physical control of chlorophyll a, POC, and TPN distributions in the pack ice of the Ross Sea, Antarctica

Kevin R. Arrigo

Department of Geophysics, Stanford University, Stanford, California, USA

Dale H. Robinson

Romberg Tiburon Center, San Francisco State University, Tiburon, California, USA

Robert B. Dunbar

Geological and Environmental Sciences, Stanford University, Stanford, California, USA

Amy R. Leventer

Department of Geology, Colgate University, Hamilton, New York, USA

Michael P. Lizotte

Department of Biology and Microbiology, University of Wisconsin Oshkosh, Oshkosh, Wisconsin, USA

Abstract

The pack ice ecosystem of the Ross Sea was investigated along a 1470-km north-south transect during the spring 1998 oceanographic program Research on Ocean-Atmosphere Variability and Ecosystem Response in the Ross Sea (ROAVERRS). Snow and sea ice thickness along the transect varied latitudinally, with thinner snow and ice at the northern ice edge and thin new ice in the vicinity of the Ross Sea polynya. Relative to springtime observations in other sea ice regions, algal chlorophyll a (Chl a) concentrations were low. In contrast, particulate organic carbon (POC), total particulate nitrogen (TPN), and POC:Chl a were all high, indicating either that the ice contained substantial amounts of detritus or nonphotosynthetic organisms, or that the algae had a high POC:Chl a ratio. The abundance of Chl a, POC, and TPN in the sea ice was related to ice age and thickness, as well as to snow depth: older ice had thinner snow cover and contained higher algal biomass while new ice in the polynya had lower biomass. Older pack ice was dominated by diatoms (particularly Fragilariopsis cylindrus) and had vertical distributions of Chl a, POC, and TPN that were related to salinity, with higher biomass at the ice-water interface. Fluorescence-based measurements of photosynthetic competence (Fv/Fm) were higher at ice-water interfaces, and photosynthesis-irradiance characteristics measured for bottom ice algae were comparable to those measured in pack ice communities of other regions. Nutrient concentrations in extracted sea ice brines showed depletion of silicate and nitrate, depletion or regeneration of phosphate and nitrite, and production of ammonium when normalized to seawater salinity; however, concentrations of dissolved inorganic nitrogen, phosphorous, and silica were typically above levels likely to limit algal growth. In areas where pack ice and snow cover were thickest, light levels could be limiting to algal photosynthesis. Enrichment of δ¹³C-POC in the sea ice was correlated with the accumulation of POC, suggesting that carbon sources for photosynthesis might shift in response to decreasing CO₂ supply. Comparisons between new ice and underlying waters showed similar algal species dominance (Phaeocystis antarctica) implying incorporation of phytoplankton, with substantially higher POC and TPN concentrations in the ice.

Received 7 September 2001; accepted 29 April 2003; published 10 October 2003.

Index Terms: 4207 Oceanography: General: Arctic and Antarctic oceanography; 4540 Oceanography: Physical: Ice mechanics and air/sea/ice exchange processes; 4805 Oceanography: Biological and Chemical: Biogeochemical cycles (1615); 4815 Oceanography: Biological and Chemical: Ecosystems, structure and dynamics.

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Citation: Arrigo, K. R., D. H. Robinson, R. B. Dunbar, A. R. Leventer, and M. P. Lizotte (2003), Physical control of chlorophyll a, POC, and TPN distributions in the pack ice of the Ross Sea, Antarctica, J. Geophys. Res., 108(C10), 3316, doi:10.1029/2001JC001138.

Copyright 2003 by the American Geophysical Union.