Bioaccumulation of trace metals in the ocypodid burrowing crab, Paratylodiplax blephariskios, in Richards Bay Harbour, South Africa

Abstract

Bioaccumulation of metals in an endemic ocypodid burrowing mud crab, Paratylodiplax blephariskios, was investigated in contaminated mudflats of the subtropical Richards Bay Harbour (RBH), South Africa. Following sampling of water, sediment and mud crabs from three sites (Bhizolo, Mzingazi and Richards Bay Coal Terminal) in RBH during 2016/2017, tissue and sediment samples were oven dried for 48 hours, weighed and digested in an advanced microwave digester. Samples were then analyzed in triplicate for Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES). Highest tissue concentrations of Co, Cu, Mn, Ni, Pb and Zn were recorded at Bhizolo. High Biota Sediment Accumulation Factor (BSAF) values for Cd, Cu, Mn, Ni and Zn at all sites confirmed that crabs bioaccumulated these metals. The high Cr concentration in sediment (Bhizolo: 104 ± 18.2 µg g⁻¹; Richards Bay Coal Terminal (RBCT): 104 ± 29.2 µg g⁻¹; Mzingazi: 94.1 ± 38.7 µg g⁻¹) was not reflected in the biota-sediment accumulation factor (BSAF) value, suggesting low bioavailability of Cr. High BSAF values for Cd, Cu, Mn, Ni and Zn suggest that the threshold of regulation in P. blephariskios was exceeded, resulting in net bioaccumulation.