Effect of metals on zooplankton abundance and distribution in the coast of southwestern Taiwan

Abstract

Three transects were established along the southwestern coast of Taiwan; transects from north to south were respectively extended from the Kaohsiung Harbor, Kaoping River estuary, and Fangshan River estuary. Six metals including Pb, Cd, Cr, Cu, Zn, and Ni were analyzed in the zooplankton and seawater samples. A total of 24 groups of zooplankton were identified. Calanoid was the frequently collected group and accounted for greater than 40% of the relative abundance of zooplankton. Results showed that metal concentrations in seawater close to coast were higher than those in the outside of transect. The mean of metal concentrations in zooplankton followed the hierarchy: Zn > Cu > Pb > Ni > Cr > Cd. On the whole, metal concentrations in zooplankton from sampling sites in the coastal region were observed to be higher than those in the offshore region. The bioconcentration factor of zooplankton ranged within 10³–10⁵ for all studied metals and indicated that zooplankton in the seawater of southwestern Taiwan can accumulate metal even at background concentrations of metals. The value of diversity indices exhibited an increase in the distance to the coast, whereas the abundance showed no significant correlation with that. Consequently, the lowest mean abundance of zooplankton and the highest average metal bioaccumulation were found in transect outside Kaohsiung Harbor, representing that Kaohsiung Harbor has the contamination of anthropogenic metals that results in the impact on zooplankton.