New Study Finds Corals Genetically Distinct at Varied Depths in Belize

Given the multitude of threats to coral reefs and steady declines of shallow coral cover observed over the past several decades, deeper reefs are proposed to be potential refuges for at-risk, shallow reefs, but new research shows that may not be the case for all coral colonies.

A newly released study finds corals in Belize are genetically distinct at different depths. Ryan Eckert, a graduate student at FAU’s Harbor Branch Oceanographic Institute, led the study under the direction of Joshua Voss, Ph.D., an associate research professor and executive director of NOAA’s Cooperative Institute for Ocean Exploration, Research and Technology (CIOERT).

Results, recently published in Frontiers in Microbiology, reinforce that corals at different depths in Belize are distinct and are not one large, well-connected population. “For this work, we were interested in how the communities of algal symbionts within one coral species varied across depth on the Belize Barrier Reef,” Eckert said. “We looked at DNA sequences from the algal symbionts and found that deeper coral populations harbor different communities of algal symbionts than shallower coral populations. We found the depth differentiation for the algal symbionts matches the genetic differences we had previously found for the coral populations.”

Researchers genotyped M. cavernosa colonies from four depth zones at four study sites within Belizean marine management zones using nine polymorphic microsatellite loci. They observed strong contemporary genetic differentiation between relatively shallow M. cavernosa populations (10 m, 16 m) and relatively deep (25 m, 35 m) populations, coinciding with a transition from reef crest to reef slope.

“These findings indicate coral reef management strategies in Belize should target protections for both the well-studied shallow reefs and lesser-known mesophotic coral reefs,” Voss said. The research was funded in part by CIOERT and donations from the Banbury Fund in memory of John and Andreija Robertson and the River Branch Foundation.