UPTAKE FROM SEAWATER AND CLEARANCE OF PARA,PARA'-DDT BY MARINE PLANKTONIC CRUSTACEA

A simple expontential model is used to interpret the simultaneous uptake and clearance of p,p'-DDT by euphausiids and copepods to and from seawater. The clearance rate constant for euphausiids, 0.043/d, is not significantly different from that observed for copepods, 0.048/d. No trend in kt values is detected over the range of p,p'-DDT concentrations in seawater used, 27.8-1388 ngL. Furthermore, there is a great deal of overlap in the uptake rate constant values between organisms. Uptake rate constants range from 0.76 to 1.21 x 104/d for euphausiids and from 1.04 to 2.51 x 104/d for copepods. There appears to be no need to use a surface-area term if the concentration of p,p'-DDT in the organism is expressed per unit dry weight even though the euphausiids are 2 orders of magnitude larger than copepods. Knowing levels of ΣDDT present in planktonic crustaceans in nature, back calculations suggest that there must be <0.1 ng ΣDDT/L in seawater. A considerable amount of the ΣDDT reported in seawater must therefore be unavailable to plankters because it is 'bound' to particles.