Revisiting the imposex queen conch Aliger gigas near Port Everglades, Florida: demographics, histopathology, and sediment contamination

Port Everglades is an industrial seaport in South Florida that requires periodic maintenance dredging, suspending potentially contaminated sediments laden with metals and organotins. Directly south of the entrance to Port Everglades is an aggregation of queen conch Aliger gigas, where we have previously documented the presence of masculinized females (i.e. imposex). The species is listed as threatened under the US Endangered Species Act, making it essential to establish pre-dredging baselines to fulfill federal requirements. We conducted 2 demographic surveys, assessed ovarian and cerebral ganglion histology, and analyzed sediments from within the aggregation for the presence of organotin compounds and metals. Imposex females continued to be observed in the aggregation; prevalence was 11.4%. These individuals exhibited a significantly lower percentage of developed ovarian tissue and a significantly lower density of ganglion cells compared to normal females. However, the presence of imposex did not affect the demographics of the aggregation. Adult density, density of egg-laying females, and sex ratio (counting imposex as females) were all similar to areas where no imposex is observed. Although imposex females are indicative of prior organotin exposure, the concentrations of organotin compounds were below detection limits. However, 13 other potentially toxic metals/metalloids were detected. As substantial infrastructure upgrades are planned for Port Everglades, these demographic and contaminant data provide a useful baseline for subsequent monitoring of this vulnerable queen conch aggregation.