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CoastLine: Sponges Proliferate Across Ocean Floor As Corals Die

Coral reefs are among the clearest harbingers of climate change.  That’s because they live at the upper end of their thermal spectrum – which means they’re sensitive to slight changes.  

When water is too warm, according to the National Oceanic and Atmospheric Administration, corals expel the algae that lives in their tissues.  That causes them to turn white – which doesn’t always mean that they’re dead.  Coral bleaching can also happen if water gets too cold – as it did in the Florida Keys in 2010, when the ocean temperature dropped by twelve degrees. 

But there is a worldwide die-off of corals underway.  Scientists are looking for causes – some of which are clear.  Some are not. 

A new study, reported on by National Geographic, shows that some corals are feeding on microplastics in favor of their natural food.  When given the option, coral polyps are choosing tiny plastic beads, which have no nutritional value, over shrimp eggs. 

On this edition, we explore some of the causes are of coral deaths.  We find out what role sponges play in the ecosystem, whose populations grow more robust as corals die.  And we learn about new techniques scientists are experimenting with to save coral populations.


Joe Pawlik is the Frank Hawkins Kenan Distinguished Professor of Marine Biology at the University of North Carolina Wilmington in the Department of Biology and Marine Biology.  

Nikki Fogarty is a Professor in UNCW’s Department of Biology and Marine Biology where she studies Coral Reef Ecology. 

Rachel hosts and produces CoastLine, an award-winning hourlong conversation featuring artists, humanitarians, scholars, and innovators in North Carolina. The show airs Wednesdays at noon and Sundays at 2 pm on 91.3 FM WHQR Public Media. It's also available as a podcast; just search CoastLine WHQR. You can reach her at rachellh@whqr.org.