DMSP, DMS and DMSO Concentrations and Temporal Trends in Marine Surface Waters at Leigh, New Zealand

Abstract

Marine waters at the Leigh Marine Laboratory (36° 17’ S, 174° 48’ E), situated on the north-east coast of the North Island of New Zealand, were investigated on four occasions during 1993. Surface sampling was conducted at 1 or 2 h intervals for 24 or 48 h. Dissolved DMSO was determined in all cases. During the later two field trips, dissolved DMS, total DMSP (DMSP(t)) and chlorophyll a concentrations were also measured. DMS and DMSP(t) exhibited no apparent diurnal trends with respect to concentration. The DMS content was positively correlated to that of DMSP(t), but with differing slopes (3 in late August and 1 in mid November). The results for DMSO are tantalising rather than conclusive. Concentrations show a marked seasonal change, with lowest values observed during winter. The DMSO content also exhibited obvious diurnal variations, with a maximum usually in the afternoon and minimum values just before sunrise. Night-time loss processes for DMSO have no profound influence on the ambient DMS levels. Positive correlations are apparent for DMSO with respect to DMS and with respect to sunlight intensity. Given that DMSO concentrations generally exceed those of DMS by an order of magnitude, the photo-oxidation of DMS seems unlikely to be the sole source of DMSO. The direct biosynthesis of DMSO may account in part for its abundance in the marine environment.