UNIVERSITY PARK, Pa. -- An invasive species of symbiotic micro-alga has spread across the Caribbean Sea, according to an international team of researchers. These single-cell algae, which live within the cells of coral animals, are improving the resilience of coral communities to heat stress caused by global warming, but also are diminishing the abilities of corals to build reefs.
"The results raise a potentially contentious issue about whether this invasion is relatively good or bad for the long-term productivity of reef corals in the Atlantic Ocean and the ecosystems they support," said Todd LaJeunesse, associate professor of biology, Penn State.
The team's findings appear in today's (JUNE 1) issue of the Proceedings of the National Academy of Sciences.
According to LaJeunesse, relationships between corals and photosynthetic algae evolved over millions of years and are generally mutually beneficial. Corals derive energy and nutrients from algae, and in turn algae obtain nutrients and protection by living in the tissues of corals.
"Coral reefs are highly important to the biosphere, and they also have enormous economic and societal value in the form of tourism, recreation and coastal protection, and as a source of food and pharmaceuticals," said LaJeunesse. "Currently, these ecosystems are threatened by synergistic effects of diminished water quality, increased temperature and reduced ocean alkalinity."
LaJeunesse and his team, which includes researchers from the University of Delaware and the Universidad Nacional Autonoma de Mexico (UNAM), used DNA sequencing techniques to document this possible new threat to coral reefs -- the spread of non-native, Symbiodinium trenchii, which comes from the Indo-Pacific.
To determine that S. trenchii's presence in the Caribbean likely came from a limited introduction and then began to spread, the team used population genetic markers to analyze the genetic diversity among populations of S. trenchii in the Indo-Pacific and compared this diversity with that in the Caribbean Sea.