Organochlorine compounds in common dolphins (Delphinus delphis) from the Atlantic and Mediterranean waters of Spain

Blubber of free-ranging common dolphins (Delphinus delphis) from the northw estern coast of Spain (Atlantic), sampled in 1984 and 1996, and of common d olphins entangled in fishing nets in the southwestern Mediterranean, sample d during 1992-1994, was analysed for organochlorine pollutants. In the Atla ntic, concentration of all pollutants was significantly higher in males tha n in females. The overall tPCB/tDDT ratio in this area was 3.35, which indi cates a predominance of industrial inputs over those associated with agricu lture. Individuals sampled in 1996 showed significantly lower DDT concentra tions but a higher ppDDE/tDDT ratio than those sampled in 1984, which refle cts the aging of the environmental load. In the same period, tPCB concentra tion remained constant and, as a consequence, the tPCB/tDDT ratio more than doubled. In the Mediterranean, the reduced sample size of adult individual s precluded proper statistical investigation of sex-related variation. The overall tPCB/tDDT ratio was 1.12, suggesting a higher contribution of pollu tants of agricultural origin. individuals had significantly higher levels o f all DDT forms and a higher ppDDE/tDDT ratio than their counterparts from the Atlantic, but similar PCB concentrations. However, the relative frequen cy of the different congeners in relation to the total PCB load was differe nt in the two areas. This indicates that the two populations do not mix, at least in the short- or medium-term. Organochlorine levels in both areas ar e at the mid to low end of the range of concentrations detected in other co mmon dolphin populations and in that of other Delphinidae species from the same region. Although the impact of the organochlorine concentrations on th e common dolphin populations surveyed cannot be assessed, it is considered unlikely that they have played a significant role in the decline that the s pecies has suffered in recent decades in the western Mediterranean. (C) 200 1 Elsevier Science Ltd. All rights reserved.