In 2010, environmental studies highlighted a severe ecological crisis in Guánica Bay, Puerto Rico. Decades of industrial discharge, agricultural runoff, and improper waste disposal turned the bay into a hotspot for polychlorinated biphenyls (PCBs)—synthetic organic chemical compounds known for their persistence and toxicity. Although PCBs were banned in the United States in 1979, these legacy contaminants linger in marine and coastal sediments for decades without breaking down.
This chemical buildup posed an immediate existential threat to one of the island's most vulnerable inhabitants: the critically endangered Puerto Rican Crested Toad (Peltophryne lemur). As the only toad native to Puerto Rico, these amphibians rely on delicate coastal ecosystem habitats, including ephemeral breeding ponds near the bay. Bioaccumulation occurs when organisms absorb toxic substances at a rate faster than they can metabolize or excrete them.
Because amphibians possess highly permeable skin and undergo complex lifecycles spanning both aquatic and terrestrial environments, they are uniquely susceptible to toxin uptake. In Guánica Bay, PCBs infiltrated the local food web, starting with benthic invertebrates and bioaccumulating up into terrestrial predators. For the crested toad, exposure to these lipophilic compounds led to severe biomagnification within their body fat.
Research indicated that PCB toxicity disrupted the endocrine systems of the toads, impairing their reproductive success, immune responses, and developmental metamorphosis. Tadpoles raised in contaminated waters exhibited higher mortality rates and morphological abnormalities. The 2010 findings spurred intense conservation interventions, combining EPA cleanup efforts with zoo-led captive breeding programs aimed at reintroducing healthy toad populations to safer, unpolluted microhabitats across Puerto Rico.