Sponges as simple biomonitoring tools for trace element pollution in marine environments: insights from a Kenyan study focused on the leaf sponge Phyllospongia foliascens

The potential of the marine leaf sponge Phyllospongia foliascens as a simple biomonitor of trace element pollution was assessed. The concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn) and zinc (Zn) in sediments and in P. foliascens from four sites of varying anthropogenic impacts along the Kenyan coast were determined. The concentrations of all elements, other than Mn, were higher in P. foliascens relative to the sediment at Mkomani Beach, the most polluted site, and the concentrations of As and Cd were higher in P. foliascens than in sediments at all sites. The concentration ratio C P. foliascens /Csed, representing the extent of accumulation of the elements in the sponge relative to the sediment, ranged between 1.25 and 9.43 for all the elements except for Mn at Mkomani Beach, and between 1.26 and 13.30 for As and Cd at all the sites. The results suggest that P. foliascens could be a suitable biomonitor of As and Cd. Further studies are recommended to identify suitable biomonitors of a variety of pollutant elements that could inform policy decisions geared towards novel and efficient options for managing trace element pollution in Kenya’s coastal and marine environment.