Effects of environmental changes, tissue types and reproduction on the emissions of dimethyl sulfide from seaweeds that form green tides

Abstract

Environmental context Dimethyl sulfide (DMS) is released by marine algae and is important to sulfur transfer between the oceans and the atmosphere. We measured DMS emissions from algae that form large blooms, and found that the hydration of the plants, seawater temperatures and salinity affect DMS release, but their effects were species-specific. Thus, the effect of algal blooms on sulfur transfer will depend on the bloom’s species composition and the environmental conditions experienced by the algae. Abstract Bloom-forming ulvoid macroalgae produce dimethylsulfoniopropionate (DMSP), which when cleaved in response to biotic and abiotic stresses results in the emission of dimethyl sulfide (DMS) into the atmosphere. We quantified DMS emission rates from three intertidal seaweeds (Ulva intestinalis, Ulva lactuca and Ulvaria obscura) that form green tide blooms in the Salish Sea. The algae were subjected to different salinities (freshwater to seawater), temperatures (15 to 35°C) and desiccation levels, and DMS emission rates were measured. We also quantified tissue DMSP concentrations and DMS emissions by different life history stages of U. intestinalis. All three species had significantly higher emission rates if the plants were dry, relative to damp or submerged plants, with highest emissions in the high intertidal species and lowest emissions in the low intertidal species. Seawater temperature did not affect emission rates by U. intestinalis or U. lactuca, but emission rates by U. obscura were significantly higher at 35°C. Hyposaline conditions also increased emission rates by U. obscura and U. lactuca but had no effect on emission by U. intestinalis. DMSP concentrations did not differ in sporophytes and gametophytes, but were twice as high in the tips as the bases of sporophytes. Most spores were released from the tips of the blades. Spores had average DMSP concentrations of 258±114 fmol spore–1. Our results demonstrate that the amounts of DMS emitted by green tides will depend on the bloom’s species composition and the environmental conditions experienced by the algae.