Biogenic Particle Sources and Vertical Flux Patterns in the Seasonally Ice-Covered Greenland Sea Rolf Peinert 1 , Eduard Bauerfeind 1 , Rolf Gradinger, Olaf Hauptl, Marita Krumbholz\ Ilka Peeken 1 , Iris Werner and Bernt Zeitzschel 1 , Institute for Marine Research, Kiel University, Diisternbrooker Weg 20, 24105 Kiel, Germany 2 Institute for Polar Ecology, Kiel University, Wischhofstrasse 1-3, 24148 Kiel, Germany Abstract: Pelagic and ice-associated particle sources have been investigated to determine their contribution to vertical fluxes from upper ocean layers. Process studies were conducted from 1988 to 1997 during various seasons between 72° Nand 82° N in the Marginal Ice Zone (MIZ) and open waters ofthe Greenland Sea. Ice-bound (in-ice and under-ice) particle production begins as early as April, prior to pelagic production, and provides material which may be set free in the course of melting or originate from food-web processes in the under-ice habitat (namely grazing by sym- pagic amphipods). These particles may be deposited from surface waters, degraded within pelagic food webs or, in the case of autotrophic components, may serve as a seeding population for pe- lagic production. Findings on transects from the open water into the pack ice stress the overall im- portance of the MIZ for particle export. The MIZ is characterized by highly variable physical and biological conditions which foster local phytoplankton blooms. Particle exports from the MIZ are very variable but generally high, with prominent autotrophic diatom contributions (up to 60 mg poe m- 2 d-', 30 mg Opal-Si m- 2 d-' and 10 7 diatoms m- 2 d-'). Analyses of algal pigments and their degradation products, combined with microscopical inventories, permit the differentiation of sources of particle export. Freshly produced material from the MIZ can rapidly sediment to great depths, feeding the benthos and affecting sediment geochemistry. Introduction Surface circulation, deep winter convection, eddy fields (Hopkins 1991; Johannessen et al.1987, 1994; Schafer et al. this volume; Schott et al. 1994) and, in a promi- nent manner, sea-ice dynamics (Ramseier et al. 1999, this volume; Johannessen et al.1994) are physical con- straints of particle production and export in the Green- land Sea. The control of particle flux in this seasonally ice-covered oceanic region is thus much more complex than in waters which are ice-free all year. In addition to pelagic particle sources, attention must be paid to ice- related sources and to the manner in which sea ice modifies pelagic export conditions. Furthermore, the spatial distribution of physical and biological variables is notoriously heterogeneous on a scale of meters for processes in and under the ice (Werner and Lindemann 1997), and pelagic processes in the marginal ice zone vary at the scale of nautical miles in relation to ice and melt-water distribution. Peinert et al. (this volume) compare seasonal and annual fluxes and interannual variability in this Polar Province with those in the Atlantic Province of the Norwegian-Greenland Sea. Here, focus is placed on smaller temporal and spatial scales as well as on the sources contributing to fluxes. Ice-related and pelagic particle sources are presented schematically in Figure 1 for the pack ice zone, the marginal ice zone in which ha- line stratification prevails, and adjacent open waters which are not affected by melt water. Ice-associated sources (i.e. in-ice and under-ice habitats as well as melt water ponds) are unique in the sense that they are con- fined to a substratum in which primary production can begin early in the season. Very high concentrations of ice algae can accumulate in a thin layer in the lowermost centimeters of the ice, where interaction with the un- derlying pelagial takes place. Sympagic habitats vanish once the ice has completely melted. Haline stratification in the marginal ice zone (MIZ) permits pelagic autotro- phic growth to commence earlier than it does in adjacent From The Northern NorthAtlantic: A Changing Environment, edited by P. Schafer, W. Ritzrau, M. SchlUter, and J. Thiede, pp. 69-79, Springer, Berlin, 2001