Benthic Foraminiferal Assemblages as Bio-Indicators of Potentially Toxic Elements in Puerto Rico

Benthic foraminiferal assemblages in Jobos Bay show a concordant relationship with potentially toxic element (PTE) concentrations found in bulk sediment samples (analyses performed by ACTLABS Canada). Relatively higher PTE concentrations are associated with lower foraminiferal density and diversity even though preliminary analyses reveal PTE concentrations below toxic levels. Copper, however, seems to have an effect on the ecosystem due to its concentration being greater than ERL (Effect Range Low). High organic matter content (>20%) coupled with framboidal pyrite suggests low oxygen regimes. This scenario may limit the amount of bioavailable PTE's that will affect the foraminiferal assemblage distribution. Ammonia spp. – Elphidium spp. is a stress-tolerant assemblage found in areas of relatively higher PTE concentrations coupled with finer grain size (mud) and high (>20%) organic matter content. The Quinqueloculina spp. – Triloculina spp. assemblage is found more predominantly in areas of lower PTE concentration and is found associated with coarser grain size (fine-medium sand). Both assemblages commonly follow the spatial distribution of PTE's. Foraminiferal shell deformities (i.e., double aperture, aberrant tests, twin tests) are common (>2%) and generally found within the rotaliids (Ammonia spp.+ Elphidium spp.) and miliolids (Quinqueloculina spp.+ Triloculina spp.).