MEPS 394:111-124 (2009)  -  DOI:

Phytoplankton taxa, irradiance and nutrient availability determine the seasonal cycle of DMSP in temperate shelf seas

Stephen D. Archer*, Denise G. Cummings, Carole A. Llewellyn, James R. Fishwick

Plymouth Marine Laboratory, Prospect Place, Plymouth, Devon PL1 3DH, UK

ABSTRACT: The influences of physico-chemical and biological variables on the concentrations of dimethyl sulphide (DMS) and its precursor β-dimethylsulphoniopropionate (DMSP) were investigated through an annual cycle in the temperate shelf seas of the western English Channel. Total DMSP to chlorophyll a ratios (DMSPt/chl a) varied seasonally by 40-fold, and DMS and DMSP concentrations became temporally uncoupled, with elevated relative DMS concentrations during spring and mid-summer. Taxonomic succession of high DMSP-producing phytoplankton, including Phaeocystis pouchetii, Scrippsiella trochoidea and Prorocentrum minimum, is apparent in the seasonal pattern of DMSPt concentrations. Peridinin and DMSPt concentrations showed similar seasonal trends (p < 0.0001), illustrating the substantial contribution by dinoflagellate taxa to DMSP production. Summer-time stratification of the water column coincided with increased mixed layer doses of photosynthetically active radiation (PAR), increased surface ultraviolet-B (UVB) irradiance relative to PAR and a decrease in nitrate and phosphate availability. PAR dose explained 68% of the variability in DMSP/chl a during the seasonal study; whilst nitrate concentrations were inversely related to DMSP/chl a and explained 64% of the variability in log-transformed DMSP/chl a. PAR dose explained only 25% of the variation in DMS concentration, whilst nitrate concentration was inversely related to DMS and explained 49% of the variation in log-transformed DMS concentration. The highly significant relationship between DMSP/chl a and PAR dose was similar to those observed for the chlorophyll-specific accumulation of the photoprotective xanthophyll compounds diadinoxanthin and diatoxanthin and the chlorophyll-specific concentrations of UV-absorbing mycosporine-like amino acids. These results lend further, indirect evidence for a photoprotective role of DMSP, possibly associated with physiological stress caused by high PAR and UV radiation and intensified by nutrient limitation.

KEY WORDS: DMSP · DMS · Seasonal cycle · Xanthophyll pigments · MAAs · Nutrients

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Cite this article as: Archer SD, Cummings DG, Llewellyn CA, Fishwick JR (2009) Phytoplankton taxa, irradiance and nutrient availability determine the seasonal cycle of DMSP in temperate shelf seas. Mar Ecol Prog Ser 394:111-124.

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