As summer heat warms waters around the Florida Keys, scientists again on alert for more coral bleaching across the beleaguered reef will begin studying a feeding program in nurseries if conditions worsen.
If the project works, it could eventually be used on the reef as a way to deal with high stress heating events.
“The idea is if you can give the corals a little bit of supplemental food when it gets too hot, or prior to getting too hot, that they may be able to withstand the heat stress and then ultimately, once it cools down, to recover,” said Andy Bruckner, research coordinator for the Florida Keys National Marine Sanctuary.
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The National Oceanic and Atmospheric Administration held a briefing with Bruckner and other scientists Monday to talk about conditions and explain strategies for protecting coral as the summer bleaching season approaches.
This year, coral got a bit of a reprieve. The spring started out hotter than last year, when a late spring heat wave spiked temperatures and caused prolonged stress. That bleached coral across the Florida Keys and in some shallow waters off the mainland in one of the worst events to hit the reefs in a decade. By June, about 12 weeks of higher than usual temperatures caused some mild bleaching, when stressed coral become too warm and spit out the tiny algae they need to survive.
Scientists say climate change driving up ocean temperatures are hitting reefs hard. In just 10 years, the planet has now experienced four global bleaching events.
Rain helped cool waters and bring temperatures down by the end of June. This month, however, bright, hot days have caused water temperatures to again begin climbing, Burckner said, about a month earlier than such high temperatures normally arrive.
“There are still predictions that if this continues this way, we could get up to an alert level two potentially right now by August,” he said, or a risk of reef-wide bleaching with some corals dying.
In the meantime, Sanctuary officials have started preparing. Sanctuary superintendent Sarah Fangman announced last month that plans had already been put in place to close three areas to recreational use to create deepwater refuges for coral if needed. Some coral have also been moved to land-based nurseries to preserve genetics, said Ken Nedimyer, technical director of Reef Renewal, the nonprofit working with NOAA.
But unlike last year, when the sudden heat wave triggered a rush to save coral, scientists this year are taking a more long-term strategic approach.
“The deep nursery is really just an emergency,” Nedimyer said. “We shouldn't be trying to grow and outplant coral that can't make the summers like this. It's not easy to watch them die. But I want to invest my time in coral that is going to make it. Not a coral that has to be coddled every year.”
Understanding coral reefs’ food supply
The feeding project itself is a strategy to better understand what happens to food supplies during high temperatures. Coral normally feed at night on plankton. Adding lights would attract more plankton to boost food supplies. But it’s not clear what kind or plankton and how much. Or, if too much plankton upsets the reef food chain by attracting other marine life that comes to rely on it for food.
“There's some theory that the plankton that these corals feed on may actually be different during a hot water event,” Bruckner added. “What we don't know is if it's too hot, these plankton that are coming from deep water where it's cooler may not even migrate up to the surface, or are different types of plankton.”
At two nurseries this year, Bruckner said scientists plan to use lights invented at the University of Alabama that can be manipulated to turn on either with a setting sun or timers that pulse the light to attract more food. They’re testing the projects in nurseries, where the coral have been studied and identified, to better understand the effectiveness.
“We can compare the same species of corals, the same genetic strain, with and without feeding,” he explained. “It's basically to understand whether this is even a piece of a little approach for the future.”
It’s part of a new approach to restoration as climate change makes the work more complicated and urgent.
“Restoration isn't just about dumping a bunch of corals out there,” Bruckner said. “It's what Ken and his team have been doing for a long time, and what a lot of the other practitioners are all trying to do, is do this in a science-based way so we understand how do we cope with changing conditions that we didn't have when we started restoration.”
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