Abstract

The upper metre of the ocean is a transition zone between the atmosphere and deeper water and can be subdivided into strata (nanolayer, microlayer, millilayer and centilayer) with different chemical and biological characteristics. A variety of techniques has been used to collect samples from different depths for chemical and biological analysis. Autotrophic and heterotrophic neuston (surface dwelling biota) range in size from less than 2 μm (piconeuston) to a metre or more (macroneuston) and are represented by, perhaps, several thousand species worldwide. They occur in much greater densities than their sub-surface counterparts, the plankton and nekton.

Anthropogenic organic compounds and metals frequently occur in greater concentrations in the microlayer (upper 10-6 m) than in deeper layers. These surface enrichments originate from a variety of sources, but in offshore and in some coastal areas atmospheric deposition is particularly important. Enrichment factors (microlayer concentration/bulk-water concentration) for Pb, Cd, Cu, Zn, some radionuclides and aromatic hydrocarbons are typically 10 to 102 and for chlorinated organics may be 103 or more.

Increases in global sea-surface contamination and/or ultraviolet radiation could threaten important sea-surface biological communities and processes. Contaminated films deposited on intertidal beaches during receding tides could negatively impact shellfish and infauna. The majority of marine fish has floating eggs or larvae which could be adversely affected.