Scientists at NOAA’s Atlantic Oceanographic & Meteorological Laboratory (AOML) and the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) have successfully overseen the first-ever crossbreeding between grooved brain corals (Diploria labyrinthiformis) collected from a highly urbanized site in PortMiami and a nearby reef – a breakthrough that could revolutionize efforts to restore local coral reefs.
On Wednesday, April 23rd, an hour and half before sunset, Coral Program scientists from AOML and the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) donned wetsuits for the third night in a row. They were hoping that this would be the night that they had been awaiting for three years—the night they witnessed corals in PortMiami spawn.
With snorkeling gear on and cameras at the ready, researchers swam between colonies of grooved brain coral (Diploria labyrinthiformis), alert for signs of spawning, like small egg bundles rising from corals and forming an oily-slick across the surface.
These corals are not just any corals, but a specific population of corals coined “urban corals”, which scientists are studying for their remarkable resilience in spite of extreme fluctuations in the port’s water chemistry.
Forty-five minutes in and the grooved brain corals begin releasing gametes—not in the field where researchers had carefully placed their spawning tents, but inside tanks at the University of Miami Hatchery (UM Hatchery) where urban coral fragments had been kept since February. In a rush of excitement, the team dismantled their field setup and returned to shore, eager to collect the prized gametes of these urban corals.
“To our knowledge, it is the first time in the U.S. that an urban coral has spawned – and we collected the gametes,” says Ashley Rossin, Ph.D., a postdoctoral researcher working on AOML’s Urban Coral Project.
Urban corals exist in highly variable coastal environments in South Florida, where they experience drastic shifts and extremes in temperature, salinity, and water quality. In this port environment, the corals often settle on artificial seawalls and rip-rap, where they are also exposed to frequent disturbances from commercial shipping, dredging activities, and coastal development; yet, they exhibit an impressive survivorship and resilience in the face of these stressors. For Michael Studivan, Ph.D.—the principal investigator of AOML’s Urban Coral Project—this inherent genetic advantage makes urban coral gametes highly sought after.
Since corals spawn in coordination with moonlight cycles, usually in the summer just after the full moon, most spawning events are predictable. Yet, in Studivan’s experience, spawning in urban corals has proven challenging to pin down, in part because proximity to light pollution may be altering their natural cues. The team even utilized Kilocams, an open-source, low-cost time-lapse camera platform built in-house by Coral Program scientists, Ben Chomitz and Taylor Gill, to increase efficiency and extend monitoring windows. Even though Studivan and Rossin could confirm through histology samples that the urban corals were releasing their gametes during the overall spawning season, they hadn’t observed spawning or been able to collect gametes from urban corals until now. This allows Studivan and Rossin to move forward with the next phases of their research— lab experiments with juveniles from different parental crosses.
“One of the best parts about urban corals is how resilient they are to all the stressors they are dealing with… they have advantages inherent to their genes that could help Florida’s reefs, and we want to run experiments to see if that’s true in reef-urban crosses,” says Rossin. In particular, Studivan and Rossin are keen to see how the reef-urban juveniles respond when exposed to thermal stress or acidic conditions, and whether they exhibit levels of resilience similar to that of urban corals.
The larvae start their lives free-swimming, but soon settle on a substrate, growing anchored to the same place for the rest of their lives. As the coral babies grow to a size large enough for experiments, Rossin and Studivan are in close collaboration with project partners including the University of Miami’s Coral Reef Futures Lab, The Reef Institute, and NOAA’s Southeast Fisheries Science Center, where the nearly 1,500 recruits are being cared for. Rossin says that at one year old, the recruits could be big enough to outplant on Florida’s reefs–an upcoming milestone in the project.
The bigger picture is that restoring Florida’s reefs is a challenge that can only be met through broad collaboration. Studivan and Rossin’s efforts have been supported by programs like the Coral Reef Conservation Program, the Florida Department of Environmental Protection, and AOML’s ‘Omics Program. Achievements like Studivan and Rossin’s urban-reef crosses are the result of a dedicated community of scientists, reef practitioners, non-profits, universities, and federal and state departments—all deeply committed to researching and restoring Florida’s reefs. Together, their work is helping pave the way for a more resilient future for Florida’s reefs.
