The future of some of Florida's smallest and most seldom seen inhabitants is under threat from climate change, and that could spell big trouble further up the food chain, scientists say. South Florida's coral and algae populations are declining as ocean temperatures rise and there's an economic factor to consider, according to researchers who study the coastal underwater ecosystems.
"Millions of people visit our coral reefs and offshore oceanic systems to scuba, snorkel and fish. It's a big source of income for Florida, from the Keys to Martin County," said Kate Peach, a PhD candidate in integrative and marine biology at Florida Atlantic University. Her work is part of the FAU Climate Change Initiative, and her lab conducts research at the FAU Marine Lab at Gumbo Limbo Nature Center in Boca Raton.
Recreational saltwater fishing alone has long been a boon to Florida's economy. A recently released National Oceanic and Atmospheric Administration (NOAA) economic report shows that in 2011, saltwater fishing on the east coast of Florida generated 29,000 jobs and $3.3 billion in sales. But the sustainability of those sought-after fish is dependent upon the plants and animals at the base of the food chain, and at that level, things are looking a bit grim.
Peach currently is investigating how climate change impacts the marine algal communities that support a healthy coral reef ecosystem. As the oceans warm and higher levels of carbon dioxide dissolve in the water, these critical organisms could likely die off in greater numbers.
Many algae already are living at their "thermal limit" and a rise of "even just a few degrees" could be devastating, Peach said. The NOAA reports the global sea surface temperature has risen about one and a half degrees Fahrenheit in the last century, according to a PBS story last year on endangered coral reefs in the Florida Keys.
But warmer water is only part of the problem, scientists say. The rise in carbon dioxide levels also causes ocean acidification, which can diminish certain organism's ability to "produce and maintain their shells" according to the NOAA. The organization reports:
Since the beginning of the Industrial Revolution, the pH of surface ocean waters has fallen by 0.1 pH units. Since the pH scale, like the Richter scale, is logarithmic, this change represents approximately a 30 percent increase in acidity. Future predictions indicate that the oceans will continue to absorb carbon dioxide and become even more acidic.
Part of Peach's work is to study how the algae that maintains a symbiotic relationship with coral will react or adapt to acidification.
"We're already finding that coral could be affected," Peach said. She said while there are no "clear-cut answers" as to what can or will happen with any one species, the potential loss of algae would have a ripple effect on the entire ecosystem.
"They are the base of the food chain," Peach said. "When you take out the base, it will cause the rest of the food web to collapse."
Eric Buck, a scientist with the Nature Conservancy's Coral Restoration project in the Virgin Islands, is well acquainted with the effects that ocean acidification and water temperature have on coral reefs. He said as temperatures rise and speed up algae's metabolism, they put additional stress on the coral host. This in turn causes the coral to "kick out" the algae leading to coral "bleaching." Bleaching leaves the coral with an exposed skeleton and "makes it susceptible to disease."
Buck, who worked and studied oceanic systems in the Miami area for several years, now lives in St. Thomas where he helps to construct refuges for endangered corals. His primary targets are two threatened species, the elkhorn coral and staghorn coral, which the NOAA has proposed listing under the Endangered Species Act. (The NOAA is accepting public comment on the potential reclassification through April 6. Click here to learn more.)
The decline of the coral reefs isn't as visible to newcomers in the area, but Buck said he hears from long-time residents who say the change is evident.
"If you talk to people who've been down here for 40 years, it's nowhere near what it was," Buck said. "There used to be huge strands of stackhorn and elkhorn branching coral that are just rubble now."
If coral reefs decline or disappear, not only would the crustaceans, tropical and game fish vanish, but human residents could expect to see major changes in the South Florida coastline. Right now, coral reefs help to "block" some of the water from getting to shore and buffer some of the effects of hurricanes; both are necessary features, given that many Florida beaches lack the substantial sand dunes needed to prevent breach erosion.
"If the reefs weren't there, it may be better for surfing, but it would change the style of the beach," Buck said.
Even the basis for the beach itself could suffer in the wake of changing ocean climates and diminishing coral reefs, both Buck and Peach said. Turns out, the algae that lives on coral reefs also has a role in sand production. Parrotfish nosh on chunks of algae, ingesting bits of coral and later expelling the coral as sand.
"That nice white sand on the beaches, some of it comes through a fish," Buck said.
As scientists continue to study how climate change will impact oceanic life, South Florida will remain an important research site.
"South Florida is an ideal location to do some of these studies," Peach said. "It's the only state with a shallow, near-shore coral reef system."
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