Mimicking Annual Cycles to Successfully Propagate Corals in a Land-based Nursery

Coral reefs have been in decline worldwide due to increasing frequency and intensity of heat events, exacerbated by the run-off of nutrients and sediments from land. Nowhere in the world has this loss been more drastic than in Florida; Florida’s Coral Reefs have lost over 90% in coral cover since the 1970s. The loss of coral reefs is very troubling because they serve as nurseries for many fish species and protect the coastline from wave action during storm events that lead to erosion, flooding and ultimately the loss of property. Scientists are attempting to minimize this loss by breeding corals in the lab to then place them on the reef to restore some its function.

At the National Coral Reef Institute, Joana Figueiredo, PhD, the Interim Executive Director and also an Associate Professor in the Department of Marine and Environmental Sciences of the Nova Southeastern University Halmos College of Arts & Sciences, and her graduate students have been sexually propagating corals of several local species at their land-based nursery for the past 5 years.

The great star coral Montastraea cavernosa is one of their research focuses. This reef building coral is responsible for about 50% of the coral cover off Fort Lauderdale, Broward County, Florida, but its local population has been severely depleted in the past decade, leaving colonies so far apart from each other that the eggs of a female have very few chances of ever meeting the sperm of a male colony, making impossible for them to create babies that could replenish their population. Dr. Figueiredo and her team have been sexually reproducing this species in the lab for the past 5 years. This year, on July 30 and 31, the corals held in the lab since 2019 have once again spawned in a highly synchronized fashion 8 and 9 days after the full moon of July shortly after sunset, just like they do on the reef.

 

Female M. cavernosa Releasing Eggs

Male M. cavernosa Releasing Sperm

 

The NSU team achieves this my mimicking annual cycles of temperature, sun and moon light in the lab’s aquaria, using artificial lighting. The eggs released by five females were successfully fertilized by the sperm released by nine males, producing over 500,000 embryos (babies) which will be reared in the lab until they reach the size of a quarter and can be outplanted on the reef. Scientists are working to improve the aquaculture of corals so one day enough corals can be produced to accelerate the rate of recovery on the reefs. However, it is important to emphasize that these efforts will only be truly successful if action to curtail greenhouse gases emissions is undertaken, starting now.

 

 

This work is supported by funding from the Florida’s Department of Environmental Protection.