San Nicolas Bay is located on Aruba’s southeastern coast. Adjacent to the bay is the town of San Nicolas and the island’s large oil refinery. The San Nicolas Bay Reef Islands – five small, low-lying, boulder-coral reef islets – are separated from the mainland by a shallow lagoon that is just a few metres deep. These islets are owned by the government and not formally protected by Aruban law, however they receive some informal protection from the coastguard and the staff of the adjacent oil refinery.
Three of the five islands that make up the San Nicolas Bay Reef Islands provide habitat for important communities of Buttonwood (Conocarpus erectus) and other salt-resistant plants including Sea Purslane (Sesuvium portulacastrum) and Bay Cedar (Suriana maritima). The endemic Aruban Whiptail Lizard (Cnemidophorus arubensis) has been recorded on the islets. Globally threatened sea turtles and Queen Conch (Lobatus gigas) occur in the waters of San Nicolas Bay.
San Nicolas Bay is an important bird habitat and home to one of the largest and most diverse breeding populations of terns in the entire Caribbean. The seabirds breed on the reef islands, which have been designated as an Important Bird Area (IBA) by Birdlife International because of their globally and regionally important population of nesting gulls and terns. In a study in 2009, it was estimated that San Nicolas Bay contained approximately 25% of the world’s population of Cayenne Terns, over 90% of the Caribbean population of Common Terns and 25% of the Caribbean’s Black Noddy.
The island’s oil refinery, which is built on the edge of San Nicolas Bay, has unfortunately been the source of significant oil pollution. Hundreds of oil tankers navigate through the bay each year to and from Venezuela’s oil fields and Aruba’s refinery, and oil slicks are frequently reported around the bay. The coral reefs in the San Nicolas Bay area are constantly under pressure from a mixture of high nutrients, metals, oil and other toxic chemicals that are released into the water. As a result, coral abundance, cover, and species diversity has declined precipitously in the area. The impact of this facility on nearby coral reef communities was studied from January 1987 to August 1989, after the refinery was closed down in 1985 (it re-opened in 1991). The study found that reef structure, coral cover, and numbers of juvenile corals varied significantly in relation to the location of the refinery and local current direction. While upstream and downstream control sites were found to be in good health and exhibited high diversity, reefs adjacent to the refinery exhibited low coral density and diversity of live corals and abundant dead coral rubble.