According to Liu and Dickut (1997) the sea surface microlayer (SML) is perhaps one of the most important but also most poorly characterised regions of the marine environment. The AIRWIN project consisted in a multidisciplinary approach to characterize processes occurring in the sea surface microlayer (SML) and their relevance to global change and effect on the marine environment and its living resources. This project brought together chemists, biologists and engineers
(i) To define the role of the SML in the entry and loss of organic and inorganic pollutants in the marine environment,
(ii) To identify those pollutants which are preferentially transfered to humans through marine food webs,
(iii) To identify and to isolate microorganisms that could be used for bioremediation and as cosmetic products to improve human's health,
(iv) To provide potential bioindicators of atmospheric pollution.
The biology and chemistry of the SML are sufficiently different from the subsurface waters as to be regarded as an important and distinct ecological compartment of the marine environment. The SML is generally enriched in metals, organic matter and pollutants, hydrocarbons, pesticides and PCBs. The SML is also exposed to strong UV radiation which photochemically alters the dissolved organic matter leading to the formation of photooxidants. Therefore because biological activity at the SML is generally high, organisms living in this layer may have developed resistance mechanisms to overcome oxidative stress and more generally to grow in the presence of toxic compounds. Oxidants may also lead to a more rapid oxidative turnover of materials at the SML and, potentially, to reactions and processes not observed in the bulk waters. Despite this, little is known on the structure of biological communities inhabiting the SML, on biological processes occurring at this layer, and on interactions between chemical and biological compartments. In this respect, there is an urgent need to investigate the structure of biological communities living and growing in the SML, and their role in the transport and cycling of natural organic matter and xenobiotics, including lipids, metals and persistent organic pollutants (POPs). It is also urgent to determine the role of the SML in the transfer of pollutants to the underlying waters and food webs and/or to the atmosphere, as well as the synergistic or antagonistic effects of metals and UV radiation on these processes.
The AIRWIN project proposes a multidisciplinary approach to characterize processes occurring in the SML and their relevance to global change and effect on the marine environment and its living resources. This project brings together chemists, biologists and engineers who will help (i) to define the role of the SML in the entry and loss of organic and inorganic pollutants in the marine environment, (ii) to identify those pollutants which are preferentially transferred to humans through marine food webs, (iii) to identify and to isolate microorganisms that could be used for bioremediation and as cosmetic products to improve human health and lastly, (iv) to provide bioindicators of atmospheric pollution.
Appropriate sets of three different sampling and analytical techniques will be used to investigate the chemical and biological components of the SML in both oligotrophic and highly industrialized coastal areas. Cell sorting techniques will be used to isolate and to identify organisms able to live in the presence of toxic compounds and UV radiation. The role of resistant organisms in the accumulation and/or transformation of toxic compounds and metals, in modifying the air-seawater exchanges, and in the transfer of contaminants to underlying waters will be investigated. Special attention will be given to compounds responsible for accumulation, aggregation and polymerisation processes mediated by UV radiation and microbial activity. Petrogenic and pyrolytic hydrocarbons (PAHs), chlorinated pesticides, PCBs, surfactants and trace metals will be analyzed in marine samples (SML, underlying waters, surface particulate matter, neuston and sinking particles) to model the cycle of pollutants in the SML.
The following objectives will be addressed by field studies and laboratory experiments using water and organisms from the study sites.
Objectives of field studies:
Ø Assessment of the abundance, production, and taxonomic structure of bacterial and phytoplanktonic communities, the abundance and diversity of heterotrophic and mixotrophic protists and the density of viruses at both the SML and underlying waters (1-50 cm).
Ø Identification and isolation of the largest possible number of bacterio- and phyto-plankton species living and growing in the SML, to build-up a collection of organisms of potential biotechnological importance.
Ø Quantification of non-toxic chemical compounds including lipids, polysaccharides, amino-acids, pigments in the SML and in underlying waters.
Ø Quantification of toxic contaminants including hydrogen peroxide, metals and semi-volatile organic compounds, including PAHs, halogenated compounds and surfactants in the SML and in underlying waters.
Ø Identification of different toxic contaminants and metabolites potentially present in the different types of organisms (e.g. dead and inactive bacteria, active bacteria, picophytoplankton, nanophytoplankton) and determine which type of organisms may metabolize toxic compounds or accumulate and transfer them into the underlying food webs.
Ø Evaluation of the risks of the contamination of SML by chemical and biological species with regard to human health.
Ø Quantitative estimation of how the SML alters the air-sea transfer process of persistent pollutants compared with models which do not include the microlayer.
Ø Assessment of the UV dose received above and below the SML and thus, the attenuation of selected wavelengths in the UVR range to determine the UV dose received by dissolved organic matter (DOM) and organisms, and the formation of photoproducts.
Ø Development of models able to predict the mutual influence of marine and atmospheric pollution in coastal areas depending on meteorological conditions, chemical compounds and biogeochemical parameters.
Ø Development of science-based criteria and methodological procedures for the identification of new persistent pollutants as candidates for future international action.
Objectives of laboratory experiments:
Ø Characterisation of the physiological properties and growth requirements of isolated species and identification of organic compounds produced by these species (polysaccharides, lipids, amino-acids, pigments).
Ø Assessment of the effect of UV radiation on the growth of these species and analysis of organic compounds produced by resistant species, in tandem with research on antioxidant molecules and analysis of DNA repair mechanisms.
Ø Assessment of the resistance of isolated species to different concentrations of a wide variety of xenobiotics and heavy metals and their potential use for bioremediation purposes.
Ø Assessment of the sensitivity of specific neuston organisms (those which spend all their life cycle in the SML) to different categories and concentrations of toxic compounds to determine if they are suitable bioindicators of atmospheric pollution.
Ø Degradation and/or transformation of toxic contaminants in the presence of the isolated neuston organisms.
Ø Effect of UV radiation on the abiotic transformation of specific toxic contaminants.
The research programme was organized into five work-packages and into 18 Deliverables
Workpackage 1 : Neuston identification and isolation
Workpackage 2 : Biological activity
Workpackage 3 : Natural chemical compounds
Workpackage 4 : Toxic compounds and modelling
Workpackage 5 : Screening of microorganisms