Organochlorine dynamics between zooplankton and their environment, a reassessment

• Published in: Marine ecology. Progress series (Halstenbek) 1986-10, Vol.33 (2), p.167-191
• Main Author: Harding, Gareth C.
• Format: Article
• Language: English
• Subjects: Chlorinated hydrocarbons; Coastal water; Lipids; Marine; Oceans; Plankton; Polychlorinated biphenyls; REVIEW; Sea water; Seas; Surface water; Zooplankton
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps033167

The level of organochlorine contamination in estuarine, coastal or oceanic waters and various depth strata, including surface films, is important in predicting bioaccumulation in zooplankton. Present and past levels of contamination in seawater are briefly reviewed and summarized. Most of the evidence indicates that little organochlorine is truly dissolved in seawater: most molecules are sorbed onto particulate material or sequestered into micellar structures. A first-order kinetic model is adequate to describe the accumulation of organochlorines by zooplankton from seawater because current laboratory techniques are not refined enough to distinguish pathways within the organism. The chemical nature of the compounds, such as chlorine content, influences the time taken to reach an equilibrium level in an organism and the bioaccumulation at equilibrium. Size of organism, and temperature and salinity of the environment affect organochlorine uptake rates; this is believed to be related to the weight-specific surface area of the zooplankter exposed per unit time. The lipid content influences the carrying capacity of the zooplankter or its bioconcentration factor from seawater. The same kinetic model can be expanded to include organochlorines assimilated through feeding on contaminated food. Experimental studies have shown that 'field' levels of contamination in zooplankton can be reached in the lab within days by accumulation from food. The transfer of organochlorines from generation to generation in the lipid-rich eggs of zooplankters is discussed and explored with the kinetic model. Juvenile stages are predicted to contain the highest organochlorine levels after yolk absorption and therefore should experience the greatest mortality. Finally, it is concluded, from consideration of present levels of contamination, that the water column is the present and probably ultimate repository of most organochlorine compounds in the marine environment and that zooplankton play a major role in distributing organochlorines from atmospheric 'fallout' throughout the ocean depths.