Abstract:
The levels of persistent organochlorine (OC) contaminants, including polychlorinated biphenyls (PCBs) and OC pesticides, were determined in a New Zealand marine foodchain. Samples analysed include Crustacea (Nyctiphanes australis), small mesopelagic fish (Hygophum, Myctophum and Electrona species), hoki (Macruronus novaezelandiae), jack mackerel (Trachurus sp.), fur seal (Arctocephalus forsteri) blubber and sediment. Samples were collected from Cook Strait, the east coast New Zealand and the Chatham Rise. Concentrations of OCs, patterns of bioaccumulation and biomagnification were examined and compared with those of other studies. Likely sources of contamination were also considered.
Concentrations of total PCB ranged from 138 pg g-1 in Crustacea, to 1.07 µg g-1 in fur seals. Levels of OC pesticides ranged from 3.05 pg g-1 for dieldrin in sediment, to 8.65 µg g-1 for total DDT in fur seals. OC concentrations were predominantly lower than those reported in studies overseas and lower than those previously reported in New Zealand. Accumulation patterns suggest that equilibrium partitioning and bioconcentration are the major factors affecting accumulation in the lower trophic levels. While those in higher trophic levels suggest foodchain biomagnification and metabolism are the principal factors affecting contaminant accumulation.
Biomagnification factors (BMFs) were calculated for the major contaminant groups for each trophic step. They ranged, on a wet weight basis, from 496 for ΣDDT (for the trophic transfer from hoki and jack mackerel to fur seals) to 0.66 for ΣHCH (for small fish to hoki and jack mackerel). On a lipid weight basis, BMFs ranged from 46.4 for ΣDDT (for hoki and jack mackerel to fur seals), to 0.10 for HCB (for hoki and jack mackerel to fur seals). Biomagnification was exhibited by ΣDDT and ΣPCB, but not by dieldrin, HCH, chlordane and HCB (BMFs < 1.00). According to their respective BMFs, OC compounds were ranked from the most to least biomagnified in the following order: ΣDDT>ΣPCB> >dieldrin>ΣHCH>Σchlordane>HCB.
