Coral reef fishes exposed to acid oceans lose their sense of smell – and their sense of caution – and are more likely to fall prey to natural enemies, according to new research in Nature Climate Change.
The finding is based on observations of the behaviour of four species at a reef off the coasts of Papua New Guinea where natural carbon dioxide seeps out of the rock, and confirms a series of other such studies in the last year.
A cool volcanic discharge in the reef has served as a natural laboratory for years: water in the region reaches an average pH of 7.8. This standard measure of acidity is co-incidentally the level predicted for all the world’s oceans by 2100, as atmospheric carbon dioxide levels continue to rise, according to the Intergovernmental Panel on Climate Change.
Australian and US scientists observed the fishy behaviour from a boat moored above the reef, and also tested the fish on board the vessel. What they observed was that, away from the volcanic bubbles of carbon dioxide, in conditions of more normal ocean chemistry, damsel fish and cardinal fish seemed able to smell predators and stayed in sheltered places in the reef to avoid becoming prey.
Fish from the waters richer in carbonic acid seemed not to sense the presence of predators, and were more likely to venture into dangerous waters.
After a sudden scare that sent all the fish racing for cover, the fish from the bubble reef ventured forth much sooner. In normal circumstances, such fish spend 80% of their time under cover.
The bubble reef fish spent at most only 12% of their time in hiding. Mortality accordingly was five times higher.
“Their sense of smell was acutely affected in CO2-rich waters in ways that gravely threaten their survival,” said Alistair Cheal of the Australian Institute of Marine Science.
“We were able to test long-term realistic effects in this environment,” said another author, Danielle Dixson of the Georgia Institute of Technology in the US. “One problem with ocean acidification research is that it’s all laboratory-based, or you’re testing something that’s going to happen in 100 years’ time with fish that are from the present day, which is not actually accurate.”
The reasoning is that the change in pH levels disrupts a neuroreceptor in the fishes’ brains and affects faculties or alters behaviour. Similar experiments with Californian rockfish have demonstrated much the same effect.
But increased acidification of the oceans is also likely to affect shellfish and corals in other ways, and research in the Great Barrier Reef region of Australia has documented a dramatic behaviour change in a jumping snail that suggested impaired decision-making capability as pH levels alter.
Sea water is already 30% more acidic that it was at the start of the Industrial Revolution 200 years ago. The rate of change is at least 100 times faster than at any time in the last 650,000 years.
The bubbling waters of the reef under test are not unique – such localized carbonic acid seeps occur in many places all over the world – and the fact that predators might find easy pickings in such places makes no real difference to population levels in the vastness of the rest of the ocean. But such experiments raise the question: can ecosystems adapt to changing water chemistry?
“Continuous exposure does not reduce the effect of high CO2 on behaviour in natural reef habitat and this could be a serious problem for fish communities in the future when ocean acidification becomes widespread as a result of continued uptake of anthropogenic CO2 emissions,” the authors conclude.
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Diving with Frogfish in Costa Rica: A Hidden Gem Underwater
In the vast and vibrant underwater world of Costa Rica, there’s a peculiar creature that often goes unnoticed but holds a special place in the hearts of divers: the frogfish. This enigmatic and somewhat odd-looking species is a master of camouflage and a marvel of marine life. Diving with frogfish in Costa Rica is not just a dive; it’s an adventurous treasure hunt that rewards the patient and observant with unforgettable encounters. Let’s dive into the world of frogfish and discover what makes these creatures so fascinating and where you can find them in Costa Rica.
The Mystique of Frogfish
Frogfish belong to the family Antennariidae, a group of marine fish known for their incredible ability to blend into their surroundings. They can be found in a variety of colors, including yellow, pink, red, green, black, and white, and they often have unique spots and textures that mimic the coral and sponges around them. This camouflage isn’t just for show; it’s a critical survival tactic that helps them ambush prey and avoid predators.
One of the most remarkable features of the frogfish is its modified dorsal fin, which has evolved into a luring appendage called an esca. The frogfish uses this esca to mimic prey, such as small fish or crustaceans, enticing unsuspecting victims close enough to be engulfed by its surprisingly large mouth in a fraction of a second. This method of hunting is a fascinating spectacle that few divers forget once witnessed.
Where to Find Frogfish in Costa Rica
Costa Rica’s Pacific coast is dotted with dive sites that offer the chance to encounter these intriguing creatures. Bat Islands (Islas Murciélagos), Catalina Islands (Islas Catalinas), and the area around the Gulf of Papagayo are renowned for their rich marine life, including frogfish. These sites vary in depth and conditions, catering to both novice and experienced divers.
The key to spotting frogfish is to dive with a knowledgeable guide who can point out these master camouflagers hiding in plain sight. They’re often found perched on rocky outcroppings, nestled within coral, or even hiding among debris, perfectly mimicking their surroundings.
Diving Tips for Spotting Frogfish
Go Slow: The secret to spotting frogfish is to move slowly and scan carefully. Their camouflage is so effective that they can be right in front of you without being noticed.
Look for Details: Pay attention to the small details. A slightly different texture or an out-of-place color can be the clue you need.
Dive with Local Experts: Local dive guides have an eagle eye for spotting wildlife, including frogfish. Their expertise can significantly increase your chances of an encounter.
Practice Buoyancy Control: Good buoyancy control is essential not just for safety and coral preservation but also for getting a closer look without disturbing these delicate creatures.
Be Patient: Patience is key. Frogfish aren’t known for their speed, and sometimes staying in one spot and observing can yield the best sightings.
Conservation and Respect
While the excitement of spotting a frogfish can be thrilling, it’s crucial to approach all marine life with respect and care. Maintain a safe distance, resist the urge to touch or provoke, and take only photos, leaving behind nothing but bubbles. Remember, the health of the reef and its inhabitants ensures future divers can enjoy these incredible encounters as much as you do.
Join the Adventure
Diving with frogfish in Costa Rica is just one of the many underwater adventures that await in this biodiverse paradise. Whether you’re a seasoned diver or taking your first plunge, the waters here offer an unparalleled experience filled with wonders at every turn. Beyond the thrill of the hunt for frogfish, you’ll be treated to a world teeming with incredible marine life, majestic rays, playful dolphins, and so much more.
So, gear up, dive in, and let the mysteries of Costa Rica’s underwater realm unfold before your eyes. With every dive, you’re not just exploring the ocean; you’re embarking on an adventure that highlights the beauty, complexity, and fragility of our marine ecosystems. And who knows? Your next dive might just be the one where you come face-to-face with the elusive and captivating frogfish. Join us at Rocket Frog Divers for the dive of a lifetime, where the marvels of the ocean are waiting to be discovered.
About the Author: Jonathan Rowe
Are you looking to make a splash online? As a seasoned diver and digital marketer, I specialize in crafting bespoke websites and innovative marketing strategies for dive shops worldwide. With my expertise, your business will not only be seen but also remembered.
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