The potential ecological significance of dissolved and particulate matter in the water column of Potter Cove, King George Island (Isla 25 de Mayo), South Shetland Islands

GUSTAVO FERREYRA, IRENE SCHLOSS, GUILLERMO MERCURI, LUCAS FERREYRA & KLAUS-UWE RICHTER3

Berichte zur Polar und Meeresforschung - Reports on Polar and Marine Research

Año: 2008 p. 47 - 57

1618-3193

Several studies with regards to primary production and particulate matter have been performed in the Potter Cove area, a shallow coastal environment characterized by low pelagic primary production and phytoplankton biomass during the whole year, and by a high load of suspended particles originated from terrigenous inputs and resuspension by winds (Klöser et al. 1994; Schloss and Ferreyra 2002; Schloss et al. 1999). The allochtonous inputs of particles mainly come from a glacier surrounding the cove, and from two freshwater streams (Matias and Potter). These freshwater inputs, together with the dominant wind stress conditions, define the typical structure of the water column in the zone, characterized by a shallow pycnocline (< 20 m, Schloss 1997). A conceptual model was developed by Schloss et al. (2002) aiming to explain the low phytoplankton biomass in the site, which show the characteristics of a typical HNLC (High Nutrients – Low Chlorophyll) system. Such a model hypothesized that the combination of the time scale of the physical factors (winds, freshwater runoff and ice cover) affecting both the radiation penetrating the water column and the depth of vertical turbulent mixing limit algal biomass accumulation. It has been shown that freshwater streams in Antarctica may be a significant source of dissolved organic carbon (DOC) from terrestrial origin (Downes et al. 1986). However, very few data are available for Potter Cove (DOC) (Abele et al. 1999). It was suggested that DOC is a main sink of organic carbon in the ocean (Farrington, 1992). Part of the DOC reservoir is the primary source of energy for bacterioplankton respiration, therefore representing a significant component of the carbon cycle in marine environments. Moreover, photochemical reactions with ultraviolet-B radiation result in both, hydrogen peroxide formation as a photoproduct and low molecular weight compounds from the breakdown of the original molecules (Abele et al. 1999). This may enhance bacterial activity, thus modifying the dynamics of the carbon cycle. The aim of this research was to assess the concentration and variability of DOC and suspended particles in the water column at Potter Cove, a small fjord-like environment (50 m maximum depth) located in King George Is. (25 de Mayo Is., 62 14´S, 58 40´W).14´S, 58 40´W).