Overall objectives To assess the effect of hydrothermalism on the chemistry, production and biodiversity of the oligotrophic Sea of Crete. Specific objectives
1. To determine the extent of submarine venting, measure
bacterial production and export, quantify geochemical fluxe and their modification by bacterial growth. Establish periodicity of venting, the role of episodic events due to storms and seismicity.
2. Measure the effects of naturally occurring excess nutrients anc CO2 on the photosynthetic rate of phytoplankton, benthic diatoms and cyanobacteria and on chemosynthesis by sulphur-oxidising bacteria.
3. Compare the diversity of bacteria and epifauna in venting and nonventing areas, estimate the importance of chemosynthesis compared wit photosynthesis in the food web.
4. To isolate, identify and characterise hyperthomophiles and halophiles with bioproduct potential.
State of the Art Hydrothermal areas around Milos were examined as' part of previous MAST projects on production in areas of high sulphide, and methane concentrations. These studies showed that 35 km of seabed around this one island were hydrothermally active. Free CO2 flux was 1-4% of the global mid-ocean ridge flux. Areas of seabed were influenced by hydrothermal brine, of similar composition to that in the reservoir 1 km below. Mats of sulphur-oxidising bacteria, >lOOm across, overlay the seeps. Bacterial H2S oxidation lowered the pH to 2 and released high concentrations of phosphate. Additional phosphate, ammonia, silicate, and other nutrients were released by the venting of hydrothermal fluids and gases. Episodic events were noted, including earthquakes, white smoker activity and release of brines resulting in a bottom-hugging, submarine 'fog'. We propose to study the processess controlling fluxes at accessible shallow sites and relate these to parameters which can be measured on wider-scale surveys, such as bubble plume intensity, area of mid-water plumes and chemical tracers of hydrothermalism, e.g. Mn and CH4. Rates due to diffusion and to advection will be determined using bottom landers with micro-electrodes and recording fluid-flow meters. Studies at instrumented sites will be supplemented by spot measurements at a wider range of sites. Chemical fluxes will be related to heat flux. The role of periodic events will be studied using a seismometer network, tide and current meters and temperature loggers at a range of sites. Changes at instrumented sites will be observed by time lapse photography. The CO2 flux off Milos makes a natural laboratory for studying effects of CO2 on photosynthetic and chemosynthetic production. Microbial biodiversity will be determined by molecular taxonomy and halophytic and thermophilic species of bioproduct potential will be cultured. Epifaunal diversity will be examlned and related to chemcal and physical parameters.
Funding SchemeCSC - Cost-sharing contracts
19100 La Spezia
19100 La Spezia
15784 Zographos, Athens
8000 Aarhus C