DDT RESIDUES IN SEA WATER AND PARTICULATE MATTER IN 

 THE CALIFORNIA CURRENT SYSTEM 



James L. Cox 

 ABSTRACT 



Continuous samples of seawater and organic particulate material collected along linear transects in 

 the California current system were analyzed for DDT residues. DDT residue concentrations in whole 

 seawater, as determined by continuous-flow, liquid-liquid extraction, ranged from 2.3 X W~^^ g/ml off 

 Oregon and Washington, to 5.6 X 10"'^ g/ml off southern California. Geographical patterns in these 

 concentration values are discussed in relation to mechanisms of land-sea DDT residue transfer. DDT 

 residue concentrations in particulate material collected by continuous-flow centrifugation and filtration 

 of the centrifugal pellet onto GFC-glass-fiber filters, ranged from 1.2 to 5.7 X 10^^ g/g carbon (with 

 one exception). These values were related to the density of the standing crops. DDT residues in this 

 particulate fraction accounted for less than 10% of the DDT residues in the whole seawater samples. 

 Residues which are fixed to particles of less than 1-2 ^ in diameter may account for the balance of the 

 DDT residues in the whole water samples. Experimental results are described which implicate adsorp- 

 tion as the uptake mechanism for algal cells; these experiments also support the idea that <l-2 u, di- 

 ameter particles carry most of the DDT residues in whole seawater. 



DDT and its metabolites have dispersed into the 

 ocean and are found in high concentrations in 

 the predators of oceanic food chains. Theoret- 

 ical considerations predict a net transfer of 

 extant DDT residues to the oceans, via atmos- 

 pheric and river currents (Smith, 1970). In 

 view of the well-known chemical stability of the 

 principal constituents of the DDT complex, j),p'- 

 DDT, DDD, and especially DDE, it is not sur- 

 prising that levels of DDT residues in marine 

 plankton samples have risen during the past de- 

 cade (Cox, 1970a) . No published data are avail- 

 able, however, on concentrations of DDT residues 

 in seawater and in oceanic particulate matter. 

 Chlorinated pesticides have been found in con- 

 centrations up to 13 X 10"" g/ml in surface 

 slicks in Biscayne Bay, Fla., and at concentra- 

 tions of about "'- g/ml in the surrounding waters 

 (Seba and Corcoran, 1969). Measurements of 

 DDT concentration in the open ocean are needed 

 to construct a systematic account of DDT residue 

 transport to the pelagic environment of the 

 ocean, and to estimate the ultimate transport 

 of DDT residues to the sediments. 



' Formerly at Stanford University, Hopkins Marine 

 Station, Pacific Grove, Calif. 93950; present address: 

 Department of Biology, Southeastern Massachusetts 

 University, North Dartmouth, Mass. 02747. 



Manuscript received January 1971. 



FISHERY BULLETIN; VOL. 59, NO. 2. 1971. 



METHODS AND MATERIALS 



Samples of water and particulate material 

 were collected during cruises of the RV Proteus 

 in May 1970 from Monterey Bay, Calif., to San 

 Diego, Calif., passing outside the islands off the 

 southern California coast and returning closer 

 to shore through the Santa Barbara Channel. 

 A second cruise was made in September 1970 

 from Vancouver, British Columbia, to just off 

 the mouth of San Francisco Bay, Calif. Fig- 

 ures 1 and 2 show the cruise tracks and the sta- 

 tion enumeration for these cruises. 



Sampling was continuous and was done while 

 the ship was underway. Water was obtained 

 from the shipboard seawater system (PVC and 

 Teflon) which pumped water from about 1-2 m 

 below the surface. The stream was first fil- 

 tered through a 0.176-mm mesh net to remove 

 larger zooplankton from the sampled water. 

 The stream was then split; part of the water 

 was directed into a peristaltic pump which me- 

 tered the flow of particle-bearing water into a 

 continuous-flow, internal recycle and recovery, 

 liquid-liquid extracter of the type described by 

 Kahn and Wayman ( 1964) . Flow rates through 

 the liquid-liquid extracter averaged 480 ml/hr. 



443 



