RELATIONSHIP BETWEEN DIMETHYLSULFIDE AND PHYTOPLANKTON PIGMENT CONCENTRATIONS IN THE ROSS SEA, ANTARCTICA

Dimethylsulfide (DMS), particulate dimethylsulfoniopropionate (DMSP(p) ) and phyto-plankton pigments were measured on three transects in the Ross Sea, Antarctica during February 1992. Although relatively low chi a levels (mean of 0.7 mu g l(-1)) were encountered, the DMS inventory in the photic zone ranged from 81 to 3484 mu mol m(-2). In comparison , the DMSO(p) standing stock was very low (range of 13-298 mu mol m(-2 )) and accounted for only 11% of the average integrated DMS concentrat ion. DMS:chl a ratios (58-78 nmol mu g(-1)) were significantly higher in waters dominated by Phaeocystis antarctica compared to diatom-domin ated waters (2-12 nmol mu g(-1)). A strong DMS gradient was observed f rom south to north with the highest DMS concentrations (123 nM) measur ed in the southern Ross Sea and the lowest (<1 nM) observed in the nor thern Ross Sea. In general, this gradient was similar to that observed for the Ph. antarctica pigment, 19'-hexanoyloxyfucoxanthin (HEX), nor malized to chi a. Areas with high fucoxanthin:chl a ratios were associ ated with relatively low DMS concentrations as conpared to areas with high HEX:chl a ratios. There was no significant linear relationship, h owever, observed between DMS and HEX, chi a, or primary productivity i n waters where Ph. antarctica dominated. In contrast, we observed a si gnificant correlation between DMS and chi a in the northern Ross Sea w here diatoms dominated and where the DMSP(p):DMS ratio was the highest (0.43). We hypothesize that short-term DMS accumulation and the prese nce of a large pool of dissolved DMSP were responsible for such high D MS concentrations during post-bloom conditions in the southern and cen tral Ross Sea.