Observations of marine diversity during a coral spawning event in the Flower Gardens Bank National Marine Sanctuary
Mass coral spawning events are one of nature’s most spectacular phenomena. Spawning happens every year in the Flower Garden Banks National Marine Sanctuary (FGBNMS) like clockwork, one week after the last full moon, just before the end of summer. MBON researchers from the College of Marine Science at the University of South Florida joined an expedition coordinated by the Sanctuary research staff to the East and West Flower Garden Banks on August 24-26 2016 to study the diversity of marine life during a massive coral spawning event.
The team sailed on the Sanctuary vessel, the R/V Manta, and collected samples while diving. The MBON objective was to measure the diversity of genetic material swirling in the water above the coral using a new test method called “environmental DNA” (eDNA). By measuring trace amounts of DNA left behind, the test detect which types of organisms are, or were in the area. The MBON team sought to determine whether eDNA could detect the diversity of spawning corals, sponges, and brittle stars as they released their sperm and eggs into the water during this annual massive reproduction event.
Due to massive rain in the previous month, the researchers were uncertain whether the spawning event was going to happen on time due to an unprecedented die-off of corals, sponges, brittle stars, sea urchins, fish, and many other organisms in the eastern FGBNMS. Researchers suspect that the die-off was the result of a massive and very quick offshore movement of coastal brackish water in late June and early July, after weeks of heavy rainfall in Texas.
“We studied this episode using NASA and NOAA satellites and looking at imagery, ship data, and numerical models going back to 1979 to see how often these events happen” said Frank Muller-Karger, Sanctuaries MBON PI and director of USF’s Institute for Marine Remote Sensing.
Fortunately, the coral reef organisms began their spawning ritual as scheduled by nature. The FGBNMS diving team was led by Michelle Johnston, John Embesi, Ryan Eckert, Kelly Drinnen, and Dustin Picard. They went overboard right after the sunset to collect seawater bathing the corals before, during, and after the spawning event. They collected the samples in 1-liter sterile bags.
The samples were processed on the deck of the R/V Manta. The water was filtered through sterile filters, which were then stored frozen in liquid nitrogen to be transported to the USF in ST. Petersburg, FL for DNA analyses. Anni Djurhuus, a postdoctoral researcher at USF, extracted and sequenced the DNA in November and December 2016.
If proven successful, the eDNA technique could be applied by NOAA operationally in a wide range of marine ecosystems to see how life in the ocean is changing. New technology, such as automated Environmental Sample Processors being developed by the Monterey Bay Aquarium Research Institute (MBARI), would allow unattended collection in remote areas, process the samples, and communicating eDNA data via satellites back to scientists around the world.
MBON update by Enrique Montes.