Assessment Of Trace Metals Pollution Along The Central Namibian Marine Coastline: Using Choromytilus Meridionalis (Black Mussel) As Indicator Organisms

ABSTRACT

This study was carried out at four stations along the Central Namibian marine coastline towns (Walvis Bay, Swakopmund, Henties Bay and Cape Cross) to assess trace metals pollution using Choromytilus meridionalis as indicator organism. Samples were collected using randomized sampling techniques during winter and summer months of 2012. EPA 3050B and ICP-OES protocols were used to digest and assimilate the samples. Data were analysed using a 4x2x3 factorial model of a completely randomised design and results showed there was a significant interaction (p < 0.05) of only Pb and Fe levels between stations, seasons and substrates studied. However, there was no significant interaction (p > 0.05) between Cu and Zn levels between stations, substrates and seasons respectively. Metal levels in mussels and sediments ranked in the order: Fe > Zn > Cu > Pb. Walvis Bay recorded increased metal levels (P < 0.05) than other stations probably due to factors like port activities e.g. ship repairs, urban and residential settlements, tourism and recreation as well as run-off water from catchment areas. Sediments exhibited significantly higher mean trace metals than mussels and water (P < 0.05). In addition, clear-cut significant correlation (p < 0.05) of metals was observed between some stations and substrates. Maximum Fe, Zn, Cu, and Pb mean values in mussels were 483.7, 79.3, 6.50, and 2.30 ppm of sample dry weight respectively while maximum Fe, Zn, Pb; and Cu values in sediments were 44, 749.90, 100.0, 79.30 and 50.50 ppm of sample dry weight respectively. All metal values recorded in this study were lower or within those reported elsewhere. Overall, mussels grown in this part of the coastline could be regarded safe for human consumption; however, levels observed in samples from Walvis Bay are of health concerns. Findings from this study have stressed the need for continued monitoring of these metals along the Namibian marine shoreline for regulatory purposes.