Relationship Between Heavy Metal Concentrations in Certain Macroalge and Two Allied Mollusc Species Collected From Costal Waters of Tobruk City, Libya

Abstract

The relationship between heavy metals bioaccumulation ability of two algal species; Polysiphonia opaca (Rhodophyta) and Ectocarpus siliculosus (Phaeophyta), and two species of their allied gastropoda; Monodonta turbinata and Patella caerulea were studied. The samples were collected from two sites, clean (S1) and polluted (S2) during winter 2017from Tubrok coastline, Libya. Various degrees of Cu, Zn, Pb, Cd and Mn accumulation weredemonstrated depending on the investigated species. Epizoic Poly.opaca and E. siliculosus affected negatively the bioaccumulation ability of P. caerulea in both sites. The most tolerant M. turbinata, being have longevity than macroalgae, has better bioaccumulative properties towards most of the investigated metals. Poly.opaca was restricted to clean seawater, referring to its sensitivity to pollution, while E. siliculosus was restricted to polluted seawater, exhibiting its tolerance to pollution. The present results indicated that the presence or absence of macroalgal species was shown to be a good indicator for the quality of seawater. Based on the bioaccumulation factors (BAFs), the five heavy metals arranged in the descending order as Cd >Mn>Pb> Cu > Zn in clean site compared to Mn>Cd > Cu >Pb> Zn in polluted site. Whereas, the descending order of metal pollution index (MPI) was M. turbinata > healthy P. caerulea> infected P. caerulea>poly. opaca >E. siliculosus. Statistical analysis showed a significant correlation between species and the investigated Cu, Pb, Mn and Cd. Poly. opaca, E. siliculosus, cosmopolitan M. turbinata and P. caerulea are considered to be good environmentally friendly bioindicators for heavy metal pollution in the Mediterranean Sea.