Long-term consequences of coastal development as bad as an oil spill on coral reefs.

Habitats near the coast of Bahía Las Minas on the central Caribbean coast of Panama became contaminated long after a refinery accident in 1986. Over the next five years, there was a significant decrease in the number and diversity of corals. Thirty years later, researchers from the Smithsonian Tropical Research Institute (STRI) and collaborating institutions report on the long-term changes in the oil spill in coral communities. Their findings were published in the journal. Marine biodiversity.

Oil pollution is known to cause lethal and sub-lethal responses in coral communities in the short term, but its long-term effects have not been widely studied. The oil spill at Bahía Las Minas, which contaminated some 40 square kilometers (about 15 square miles) near the Smithsonian’s Galeta Point Marine Laboratory in Colón and became the largest coastal habitat on record in Panama, served as an opportunity to understand how coral reefs in tropical areas Ecosystems recover from acute pollution over time.

“Monitoring these coral reefs was complex, exhausting and intense due to the large spatial scale of the project,” said Héctor M. Guzmán, STRI marine ecologist. “Originally, we compared the contaminated refinery area with uncontaminated reef systems some 50 kilometers to the east between Portobelo and Isla Grande.”

After the first five years, the team discovered that the abundance and diversity of most hard corals (Scleractinia), some branched and massive corals, and fire corals (Millepora) had decreased in the affected area. Other organisms, such as crustaceous coralline algae, a type of fouling stony algae that grow in the spaces between coral reefs, and Agaricia tenuifolia, a type of hard coral lettuce, had increased.

“Oil residues from the spill on the sediment surface were rapidly degraded through natural weathering processes,” said Stefanie Kaiser, a marine biologist at the University of Lodz. “However, a large amount of oil has been trapped in deeper layers where weathering processes are severely hampered. The chronic effects of this recurring oil leakage from the sediments could have been much worse for the affected coral communities than the acute effects of the spill. “

A similar phenomenon occurred after the Deepwater Horizon oil spill in the Gulf of Mexico in April 2010, the largest in the history of the United States. Ten years later, high levels of oil contamination continue to be found in organisms that inhabit the seabed. However, as ocean currents stir these contaminated sediments, they also contaminate species that live in shallow water.

Thirty years after the Bahía Las Minas spill, there were no longer significant differences between the area near the oil refinery and the area that the original equipment used for the comparison. Since the mid-1990s, this area has been affected by coastal development and deforestation. In both areas, the number and diversity of species had decreased and the number of juvenile colonies was low. That is, the younger corals and associated organisms were not sufficient to regenerate healthy coral communities.

The similarities between the two areas had more to do with the sustained deterioration of the Portobelo-Isla Grande coastal zone than with an improvement in the conditions of Bahía Las Minas after the oil spill. These effects were related to coastal development and other human-related impacts on reefs, such as rising sea temperatures, coral diseases, overfishing, and aquatic contamination and sedimentation.

“The initial impact on the reef community was clear and somewhat predictable, a gradual recovery and an increase in the most resistant coral species,” said Guzmán. “However, we did not expect to see a similar response in our ‘control’ reefs where the long-term impact of coastal development was equal to or greater than the initial oil spill.”

Although the long-term consequences of oil pollution in reef communities could not be determined, scientists are concerned with how these external factors are contributing to the deterioration of marine ecosystems in previously healthy areas and preventing recovery in areas affected by oil pollution.

“Coral reefs along the central Caribbean coast of Panama are practically doomed for coastal development,” said Guzmán. “If unplanned development continues to increase, they can continue to survive, but without substantial recovery.”

The members of the research team are affiliated with the Smithsonian Tropical Research Institute, the University of Hamburg, the University of Łódź and the University of Puerto Rico. The researchers involved were funded by the Smithsonian Tropical Research Institute, the Smithsonian Institution’s Environmental Science Program, the US Mineral Management Service. USA And the National Secretariat of Science, Technology and Innovation of Panama (SENACYT).