MORPHOMETRIC ANALYSIS OF THE SHELLS OF AMMONIA SPP. FROM A POLLUTED ESTUARY, TORRECILLA LAGOON, PUERTO RICO

Torrecilla Lagoon is an important component of the San Juan Estuary system in Puerto Rico. This lagoon has a long history of impact by human activities including sewage and other waste disposal. Dredge and fill activities have altered tidal circulation, resulting in localized areas of anoxia. Bulk-sediment concentrations were determined for selected metals (Cu, Hg, As, Pb) in samples from Torrecilla Lagoon. Fifty randomly picked specimens of Ammonia spp. were analyzed morphometrically from the same sediment samples. Parameters measured were maximum, intermediate and minimum shell diameters. Regressions of minimum to maximum diameter and intermediate to maximum diameters demonstrated linear relationships. The r² values ranged from 0.17 to 0.79, with a negative relationship between metal concentrations and r². The increased variability in shell morphologies is consistent with increasing environmental stress, though whether the metal concentrations are causal or positively covary with unidentified stressors is unknown. Currently more surface and core samples are being analyzed. In addition, the hypothesis that selected metals increase morphological variability in Ammonia is being tested in culture experiments.