US EPA

2199932 

Technical Report 

Oceans as alphabet soup: focus on DDT and PCB's 

Gilluly, RH 

1972 

HAPAB/72/01164 

News 

2 

HAPAB Recent studies on the occurrence of DDT and PCBs (polychlorinated biphenyls) in marine organisms have provided a wealth of facts, but the significance of the findings is difficult to determine. Results of studies performed by investigators from the Woods Hole Oceanographic Institution and presented at the Nobel Symposium in August of 1971 indicate that ingestion of DDT and PCBs by multicelled organisms which feed near the sea surface at night but migrate to considerable depths during the day may accelerate transport of organochlorine compounds from the biologically active upper ocean layers to the ''abyssal sink''. This removal process may explain why large-scale extinctions of life forms have not occurred, although environmental DDT concentrations are theoretically high enough to have caused them. The absence of the anticipated organochlorine concentration gradients in relation to land sources suggests that the atmospheric mode of organochlorine distribution is more important and the water-borne route less so, on a worldwide scale, than previously assumed. An unexpectedly broad range of variability in DDT and PCB concentration up food chains was also encountered, possibly due to the significance of non-food/drink ingestion pathways in aquatic organisms. Sediment cores collected on the 1970 expedition will be analyzed to investigate organochlorine removal from the water column. 1972