An unexpected champion has emerged in the increasingly tough battle to save Florida’s endangered coral reefs: spiny lobsters that urinate in the water and deter predatory worms and snails that want to feast on the vulnerable organisms.
The finding is one of the more bizarre conclusions of a three-year study by scientists from the Florida Fish and Wildlife Conservation Commission (FWC), who also warn that it may already be too late for some coral species to survive without significant human help. .
Last summer’s record ocean warmth further accelerated the decline of healthy coral in the Florida Keys by 90% since the 1970s. The National Oceanic and Atmospheric Administration (Noaa) confirmed last month that persistently high temperatures were causing the world to experience its fourth global bleaching event in history, and the second in a decade.
The reef-dwelling lobsters, the researchers say, could act as “knights in spiky armor” as the battle continues to prevent reefs in various states of degradation from completely collapsing. Not only does the smell of their urine seem to deter coral-eating snails and fireworms that like to nibble on live coral, but the langoustines themselves also like to eat the smaller creatures that are unaffected by the smell.
“Lobsters urinate quite often, it’s part of the way they communicate with each other, and they are social animals, so they seek out the scent of other lobsters and gather shelters together. Prey can smell that odor and avoid it,” said Casey Butler, associate professor and head of the lobster research program at FWC.
In places where greenhouse-grown coral was planted as part of restoration programs, Butler said, the lobsters played an equally important role in devouring the creatures that harmed it.
“Those little clumps of coral that are planted out are tasty and as soon as you put them down the snails and worms go straight to them,” she said.
“But lobsters themselves are also great universal predators, especially the spotted spiny lobster which lives and forages right on the reef their entire lives. It’s like eating from a buffet.”
The study, funded by a grant from the Fish & Wildlife Foundation of Florida, combined field and laboratory research. It also looked at how the ‘food web’ around vulnerable coral reefs was changing by studying the gut contents of two species: the spotted spiny lobster, and its close relative, the Caribbean spiny lobster, which leaves the reef at night to feed .
“We were interested in trying to understand whether lobsters could act as a kind of biological control against these coral predators when the corals are having so much trouble surviving, and the other part of the question was: how do food webs change? ” said Butler.
“In the better quality reefs or less degraded reefs, the lobsters ate things higher up in the food web, benthic [bottom dwelling] fish, molluscs, fireworms and even lionfish.
“With more degraded reefs you see a more diversified gut content, they eat whatever is available, things with lower trophic profiles, so lower in the food web, like worms, brittle stars, detritivores and things like that. So the entire food web of the coral reef really changes due to this degradation.”
The study comes, as Butler acknowledges, at a particularly depressing time for coral reefs worldwide, amid a worsening climate crisis. A succession of storm surges, cyclones and floods have turned Australia’s Great Barrier Reef into a “coral graveyard”; And about 54% of coral reef ocean waters worldwide have experienced heat stress high enough to cause bleaching, Noaa’s Reef Watch said last month.
In Florida, pillar coral has all but disappeared, and other species will struggle to recover without robust and diverse replanting programs from land-based nurseries, among other protective measures, she said. And lobsters, she says, can play at least a small role.
“Unfortunately, it doesn’t seem like a panacea. But if it’s applied in a thoughtful way, you could potentially use them alongside coral restoration because they eat things that are corallivores and things like that on the higher quality reefs,” she said.
“We don’t have pristine reefs in the Florida Keys, all of our reefs are degraded to some degree, so outplanting is taking place to increase the coverage of live coral of different species on the reefs. If the outplanting takes place on higher quality reefs, those spotted crawfish might be useful in keeping corallivores down.
Ultimately, Butler said, it will take an all-round effort to save the reefs.
“There’s a lot of smart people working on this, like looking at genetics and what types of genes result in greater resilience to things like bleaching and disease,” she said.
“So it takes some of that stuff, but also just a lot of willpower and hope. Some species will be more difficult to rehabilitate without the help of people. Corals can survive to some extent, but it has been a downward trend for a while.”