Caribbean coral have been invaded by algae that slow their growth and may have been introduced by humans.

Credit: Dustin Kemp/Univ. Georgia

Tye Pettay and Todd LaJeunesse at Pennsylvania State University in University Park and their colleagues sampled various coral species (Orbicella faveolata; pictured) from around the world and analysed the genetics of their symbiotic algae. They found that one alga in the Caribbean, Symbiodinium trenchii, comprised just a few lineages that were closely related to those in the Indian and Pacific oceans. Corals living with this symbiont tolerated high temperatures better than those without it, but incorporated calcium into their skeletons at around half the rate.

The findings indicate that this alga invaded the Caribbean thanks to human activities, and could have negative long-term ecological impacts in this region.

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1502283112 (2015)