Dissolved organic carbon concentration and distribution at Potter Cove (South Shetland Is., Antactica).

FERREYRA, G., SCHLOSS, I., MERCURI, G., GONZÁLEZ, O., RICHTER, K. U., KATTNER, G., FERREYRA, L.

Buenos Aires, Argentina

Simposio; V° Simposio Argentino y I° Latinoamericano sobre Investigaciones Antárticas; 2004

DNA

It was suggested that dissolved organic carbon (DOC) is a main sink of organic carbon in the ocean. 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. Up to now, few studies were carried out on these key compounds in coastal areas of Antarctica. The aim of this study was to know their concentration and distribution in the water column at Potter Cove. A field sampling was conducted during January-March 2000 at two stations, one located in the inner part of the cove (S1) and the second one in the outer part of the cove (S2). Vertical profiles of temperature and salinity were obtained with a CTD instrument. Discrete water samples were taken at 0, 5, 10, 20 and 30 m depth with Niskin bottles for chlorophyll a (Chla), suspended particulate matter (SPM), and dissolved organic carbon (DOC) analyses. Chla, SPM and DOC were measured by spectrophotometry, gravimetry, and high-temperature catalytic oxidation, respectively. CTD vertical profiles evidenced the presence of a shallow pycnocline, located between 5-10 m depth. Such density gradient was stronger in S1 than S2, due to glacier and creeks freshwater inputs. Chla presented low concentrations (average 1 µg L-1), with maximum values above the pycnocline. In contrast, SPM maxima were found in the whole upper layer of the water column (average 13 mg L-1), with minimum concentrations at higher depths (average 5.5 mg L-1). DOC concentration ranged from 51-52 mM in surface waters to 55 mM at 30 m depth. Vertical distribution showed an opposite pattern when compared with the vertical distribution of SPM, with surface minima and bottom maxima. DOC values in the inner cove (S1) were lower than those measured in the outer cove (S2), whereas SPM surface concentration was higher in S1 than in S2, due to terrigenous inputs. Our results suggest that terrigenous inputs of DOC via freshwater runoff in the studied environment are low, and that bio-optical properties of the water column in Antarctic coastal environments with strong land inputs are mainly influenced by the presence of high concentrations of suspended particles.