Choose of Heavy Metals Pollution Biomonitors: A Critic of the Method that uses Sediments total Metals Concentration as the Benchmark

The study aimed to come up with a list of specific macroalgae species, which could be used to biomonitor specific metal elements in the coastal waters of East Africa. Water extraction, EDTA, aqua regia extraction and optimized BCR 3-step sequential extracts were used to mimic bioavailable metals under various environmental conditions. The results indicated that Ulva lactuca could be used as a biomonitor to predict BCR 3-step sequential bioavailable Al, Cd, Co, Fe, Mn, Zn and Ni whereas Sargassum species could be used as a biomonitor for BCR 3-step sequential bioavailable Co, Cu, Fe, Mn and Zn. In Sargassum spp. only Co showed significant correlation with concentration in sediment’s aqua regia extracted metals whereas in Ulva lactuca only Al, Co, Cu and Fe showed significant correlation with total metals extracted through aqua regia procedure. This study therefore recommends the use of Ulva lactuca and Sargassum for biomonitoring of Al, Cd, Co, Fe, Mn, Zn, Ni and Co, Cu, Fe, Mn, Zn respectively. The study recommends the use of labile fraction of BCR sequential extraction for screening of macroalgae to be used for heavy metal pollution monitoring in East Africa region.