Researchers from the University of the Virgin Islands and University of Miami’s Rosenstiel School of Marine and Atmospheric Science have discovered that a threatened coral species (mountainous star coral) that lives in deeper waters off the U.S. Virgin Islands produce more eggs than its shallow-water counterparts. See excerpts below:
From a joint study titled “Fertile Fathoms: Deep Reproductive Refugia for Threatened Shallow Corals,” the findings have important implications for the future of coral reefs worldwide, according to UVI.
The new study showed that mountainous star corals (Orbicella faveolata) located at nearly 140 feet deep may produce one trillion more eggs per square kilometer than those on shallow reefs. Caribbean coral reefs have declined by 50 percent in the past 50 years, according to the 2014 “Status and Trends of Caribbean Coral Reefs” report. In 2005, coral reefs in the U.S. Virgin Islands were severely impacted by high temperatures and disease.
“Coastal pollution, storms and warm water can stress a coral out, which is why we’re looking at what’s going on in deeper offshore habitats,” UVI post-doctorate researcher Daniel Holstein said in a UVI statement. “These deeper habitats tend to be cooler and less strenuous for corals – and thus, coral spawning may be more spectacular,” said Holstein, who is also a UM Rosenstiel School alumnus.
Mountainous star corals reproduce by broadcast spawning, where corals release their eggs and sperm in the water during a highly synchronized event. The researchers used remote cameras at a field site off St. Thomas and laboratory observations during broadcast spawning events to show that the mesophotic corals, which live in deeper reef waters typically between 100 and 500 feet, released their eggs in near synchrony with shallow-water corals.
“The reefs that produce more larvae are more likely to be successful in seeding the reefs with their offspring,” said Claire Paris, associate professor of ocean sciences at the UM Rosenstiel School and coauthor of the study. “Protecting these potent reproductive deep refuges could represent the key to the survival of coral reefs for future generations,” she said.
Mesophotic coral ecosystems are buffered from environmental disturbances due to their depth and distance from shore. These deeper coral reef ecosystems may offer reproductive refuge to neighboring shallow-water coral reefs that are in decline, according to the research team.
“These deep reefs offer a glimmer of hope,” said Tyler Smith, a UVI associate professor of marine science. “They may be an incredible resource for the U.S. Virgin Islands, and for the entire Caribbean, if they can supply consistent sources of coral larvae,” he said. [. . .]
[First photo above from https://en.wikipedia.org/wiki/Orbicella_faveolata; second photo from http://phys.org/news/2015-07-fertile-corals-deeper-virgin-islands.html: St. Thomas, US Virgin Islands; the dominant corals are boulder star corals (Orbicella franksi). The two groupers are yellowfin groupers (Mycteroperca venenosa). Credit: Tyler B Smith – April 22, 2012.]
See Nature’s Scientific Report at http://www.nature.com/srep/2015/150721/srep12407/full/srep12407.html
Also see http://www.rsmas.miami.edu/