New algae threaten the conservation of Caribbean coral reefs

Human activity is making conservation of Caribbean coral reefs difficult, but a new algal threat is adding pressure to an already precarious situation

Corals are marine invertebrates that build large exoskeletons from which coral reefs are built. They are, unfortunately, so beautiful that humans regularly want to see them whenever they can. This leads to physical disruption and stress on the coral itself, which can kill these fragile but essential elements of the ecosystem.

How does algae affect the reef?

In order for new reef structures to grow, small floating corals must first successfully attach to a stable surface. They prefer to settle on the crunchy surface created by a specific type of friendly algae that grow on local rocks. These crusted coral algae, or CCAs, act as guides for coral larvae, producing biochemical signals along with their associated microbial community, which entice baby coral to attach to it.

“These PAC crusts have biochemical and structural defenses that they deploy to discourage grazing by fish and other marine creatures,” explained Chen-Ming Fan, at the Carnegie Institution for Science.

“It is possible that these same mechanisms, which make them successful in invading marine bio-space, also discourage corals.”

The Caribbean experiment

For the past four years, Bryan Wilson of Oxford University, Chen-Ming Fan of Carnegie, and Peter Edmunds of California State University Northridge have studied the biology and ecology of peyssonnelid algal crusts, or PACs, in the U.S. Virgin Islands, which are out – compete with coral larvae for a limited area and then grow on existing reef architecture, greatly damaging the ocean’s fragile ecosystems.

What does this mean for Caribbean coral reefs?

The team wanted to find out how the golden brown PAC affects coral reefs in the Caribbean. What they found is that PAC creates a different microbial community than others that attract corals.

“There is a new genomic and evolutionary frontier to explore to help us understand the complexity of the interactions of organisms on the reef, both mutualistic and antagonistic,” Fan added.

“This alga appears to be a kind of ecological winner in our evolving world,” described lead author Wilson, noting that various other threats to coral communities make them more susceptible to algal scabs.

The research team believes algae could be a fatal thing for the reef, perhaps. They will do more work to find out if the Caribbean reef will survive this new challenge.

Peter Edmunds further commented: “Coral and their ecosystem are as fragile as they are. They are attacked by environmental pollution and global warming. We have made their lives so fragile, yet they are in there.

“And now this is thrown into the fray. We don’t know if this is the straw that breaks the camel’s back, but we have to find out. “

Read their results here.