Effect of Sewage Pollution on Macroalgal Diversity and HeavyMetal Accumulation along Al-Hanyaa Coastline, Libya

Background: Some aquatic organisms can tolerate anthropogenic pollution but others are vulnerable to disappearance. Objective: To study the effect of sewage pollution on macroalgal diversity and heavy metal accumulationalong Al-Hanyaa coastline, Libya during winter 2014.The seawater content of Cu, Zn, Mn, Pb and Cd as well as algal diversity were investigated at three nearby sitesdiffering in the nature of substratum and load of pollutants. Results: The concentrations of these heavy metals in seawater were in general low, with Zn being the most abundant (5.4-7.4 μg l^-1) and Cd the least abundant metal (0.02-0.07 μg l^-1). Despite of the limited spatial variation in metal concentrations of water the variation in floristic composition was radical. Most of the encountered species were brown and red algae. The preference of heavy metal accumulation differed according to the degree of water pollution and the macroalgal species; with a particular preference of Cu, Zn and Pb by Corallina elongata, of Mn by Jania adhaerens and of Cd by Cystoseira corniculata and Dictyota dichotoma.In absolute terms Cd was the least accumulated metal irrespective of site and species but due to its low levels in sea water Cd exhibited a fairly high bioaccumulation factor. Jania adhaerens showed unique ability to accumulate heavy metals (having the highest metal pollution index)  followed  by C. elongate  and  D.  dichotoma.  Conclusion:  The  substratum  nature  and  the  pollution  status  of   water substantially affect diversity of macroalgae.