S. D. Archer

PHYSICAL EXCHANGES AT THE AIR-SEA INTERFACE UK-SOLAS Field Measurements

As part of the U.K. contribution to the international Surface Ocean–Lower Atmosphere Study, a series of three related projects—DOGEE, SEASAW, and HiWASE—undertook experimental studies of the processes controlling the physical exchange of gases and sea spray aerosol at the sea surface. The studies share a common goal: to reduce the high degree of uncertainty in current parameterization schemes. The wide variety of measurements made during the studies, which incorporated tracer and surfactant release experiments, included direct eddy correlation fluxes, detailed wave spectra, wind history, photographic retrievals of whitecap fraction, aerosol-size spectra and composition, surfactant concentration, and bubble populations in the ocean mixed layer. Measurements were made during three cruises in the northeast Atlantic on the RRS Discovery during 2006 and 2007; a fourth campaign has been making continuous measurements on the Norwegian weather ship Polarfront since September 2006. This paper provides an overview of the three projects and some of the highlights of the measurement campaigns.

Grazing-induced production of DMS can stabilize food-web dynamics and promote the formation of phytoplankton blooms in a multitrophic plankton model

Volatile infochemicals including climatically relevant dimethylsulphide (DMS) have been suggested to play important roles in the structuring and functioning of marine food webs. Experimenting with complex natural plankton communities or several trophic levels in laboratory microcosms is challenging and, as a result, empirical data confirming the role of DMS in trophic interactions is lacking. Models are a suitable tool to provide insight into such complex interactions. Here we consider a model of the interactions between three trophic levels of plankton: phytoplankton, grazing microzooplankton and predatory mesozooplankton. We show that the inclusion of a grazing-induced DMS production term has a stabilizing effect on the system dynamics under the assumption that DMS acts as an info-chemical and increases the rate of mesozooplankton predation on grazing microzooplankton. We further demonstrate how this feedback between trophic levels can potentially lead to the formation of a phytoplankton bloom. The model provides a suitable framework for further study into the possible role of DMS in the ecology of marine food webs beyond its recognised role as a climate-cooling gas.