Contamination levels in and cellular responses of intertidal invertebrates as biomarkers of toxic stress caused by heavy metal contamination in False Bay

[摘要] ENGLISH ABSTRACT:Heavy metals are persistent environmental contaminants whose sources of inputs intothe environment are both natural and anthropogenic. The levels of heavy metals(cadmium, copper, nickel, lead and zinc) in the False Bay intertidal zone weremeasured in the water, sediments and invertebrate species between August 2000 andAugust 2001. The results of the water and sediment analyses revealed that mostpollution was associated with the northern shore of the bay between Strand andMuizenberg, where the most populated and industrial catchments occur. Significantspatial variations occurred, indicating the presence of localised contamination, whileseasonal variations may be related to changes in precipitation and runoff at differenttimes of the year. The concentrations of cadmium, nickel and lead were occasionallyhigher than the levels recommended by the South African Water Quality Standards.The possible sources of pollution at the different sites are also discussed. Theconcentrations of the five metals in the different invertebrate species (Oxysteletigrina, 0. sinensis, Choromytilus meridionalis, Patella oculus, Patiriella exigua andTetraclita serrata) also revealed significant seasonal and spatial variations, with boththe soft tissues and shells accumulating heavy metals. The barnacle T serrata fromRooiels had the highest cadmium concentration (70.67 J.lg/g dry weight), which maybe related to historic pollution inputs from the military activities which took place at aweapons testing site at this site between 1987 and 1994, although no evidence wasfound to confirm this. The periwinkle 0. tigrina from Strand had the highest copperconcentration (70.25 J.lg/g) while the limpet P. oculus from the same site had thehighest nickel concentration (35.75 J.lg/g). The shells of the mussel C. meridionalisfrom Muizenberg had the highest concentration of lead (25.75 J.lg/g). Since cadmiumoccurs as a constituent of phosphate fertilisers used widely in the False Baycatchments, the effects of cadmium exposure on the different species wereinvestigated during 14-day laboratory exposures to 200 and 400 J.lg/LCdCh. Theresults revealed a general pattern of tissue metal increase in the exposed organisms,followed by slight reductions after decontamination in clean seawater. The visceraand kidneys of C. meridionalis accumulated most of the dissolved cadmium. Theshells of the mussels also accumulated cadmium, indicating the possible use of shellsas a detoxification matrix.

[发布机构] Stellenbosch University