Habitats | Ecosystem Disturbance

May 25, 2023

Giant Clam (by Silke Baron CC BY 2.0 via Flickr)

Bleaching, It’s Not Just for Corals – Hakai Magazine

Giant clams suffer similar struggles with warming water, though the consequences don’t seem quite as dire.

Bleaching occurs when a stressed marine creature, most commonly a coral, expels its symbiotic algae and turns a ghostly white, often in response to a warming sea. But bleaching affects more than just corals. Giant clams—massive mollusks that can grow more than 1.2 meters in diameter and weigh as much as 225 kilograms—can bleach, too. And in recent research, scientists have learned more about how bleaching disrupts these sessile giants, affecting everything from their nutrition to their reproduction.

Giant clams live on coral reefs and are the largest bivalves on Earth. Like corals, giant clams bleach when they’re stressed, often as a response to excessively warm water. As with a coral, a bleached giant clam expels the algae, called zooxanthellae, that live inside it. These algae dwell in the soft tissue of the clam’s mantle and provide energy for the animal through photosynthesis, leaving a bleached clam with less energy and nutrients. At worst, bleaching can kill giant clams through food deficiency.

Scientists have been studying bleaching in giant clams for decades. In 1997 and 1998, during a brief period that saw extensive coral bleaching worldwide with corals succumbing in at least 32 disparate countries, bleached giant clams were observed from Australia’s Great Barrier Reef to French Polynesia after water temperatures in the South Pacific rose significantly. In 2010, similar temperatures in the water off Thailand’s Ko Man Nai Island also led to scores of deaths.

Of the 12 species of giant clams, some are more resistant to heat stress than others. But as scientists are finding, even when a giant clam survives bleaching, other physiological functions can still be severely impaired.

A recent study in the Philippines of wild clams, for example, found that bleaching can hamper their reproduction. Bleaching reduces the number of eggs giant clams produce, and the more severe the bleaching, the fewer eggs they make. Reproducing “takes a lot of energy. So instead of using that energy for reproduction, they just use it for their survival,” says Sherry Lyn Sayco, the lead author of the study and a graduate student at the University of the Ryukyus in Japan…


More on Habitat | Ecosystem Disturbance

Blooming Cyanobacteria! (by Charos Pix CC BY-NC-ND 2.0 via Flickr).

The Foul Chartreuse Sea – Yale Climate Connections

Researchers in Kotzebue, Alaska, are investigating why their town is increasingly playing host to harmful cyanobacteria.

Dead fish were everywhere, speckling the beach near town and extending onto the surrounding coastline. The sheer magnitude of the October 2021 die-off, when hundreds, possibly thousands, of herring washed up, is what sticks in the minds of the residents of Kotzebue, Alaska. Fish were “literally all over the beaches,” says Bob Schaeffer, a fisherman and elder from the Qikiqtaġruŋmiut tribe…

Sargassum Seaweed, Sunny Isles, Florida (by Jimmy Baikovicius CC BY-SA 2.0 via Flickr).

Giant blobs of seaweed are hitting Florida. That’s when the real problem begins – NPR

It used to be that the conversation around subtropical marine life centered on declines: the death of coral beds, the diminishing variety of seagrasses, the disappearance of fish. But for now, it’s an overabundance that’s hard to miss. From Montego to Miami, an influx of algae called sargassum is leaving stinky brown carpets over what was once prime tourist sand. It’s the most sargassum researchers have tracked this early in the year. Deciding what to do with it is proving more challenging the more we learn about it — and inspiring some entrepreneurs to rethink removing sargassum altogether…

Polyethylene heat welded sculpture made to demonstrate the great Oceanic Gyres created by waste. This artwork is part of a collection titled "The creation of Plastikos" (by Simon MAX Bannister, CC BY 3.0 via Wikimedia).

Surprising Creatures Lurk in the Great Pacific Garbage Patch – Scientific American

Scientists have long known that critters such as worms, crustaceans and mollusks could make their home on plastic debris. Animals have even crossed the Pacific Ocean on these makeshift rafts after a devastating tsunami struck Japan in 2011. But new research published on April 17 in the journal Nature Ecology & Evolution adds two details that could be concerning for existing ecosystems. First, it finds that plastic is providing a home for coastal species to thrive in the open ocean thousands of miles from shore. Second, some of these species are reproducing despite the alien environment…

A flat fan at Elphinstone Reef, Red Sea, Egypt (by Derek Keats CC BY 2.0 via Flickr).

The Red Sea Could be a Climate Refuge for Coral Reefs – Inside Climate News

When Lina Challita dives along Egypt’s coast, she doesn’t just see a colorful array of corals and fish. She sees hope. Against the grim backdrop of climate models that project most coral reefs dying by the end of this century in overheating oceans, the northern end of the Red Sea may end up being one of the last places on Earth where those critical ocean ecosystems can survive, at least at least for a while, and perhaps longer if countries of the world manage to cap global warming and stabilize the climate…

Southern sea otter pup learns how to eat shellfish by mimicking mother's actions, first by manipulating an empty shell (Photo © Kim Steinhardt).

The Edge of Extinction: Can sea otters survive the human threat? – Kim Steinhardt

I was hooked the first time I saw a southern sea otter bobbing in the surf off the coast of California’s Big Sur. I didn’t know then that I would be as spellbound by these rare creatures decades later as I was at that very first sighting. And little did I know that I was witnessing the latest act in a continuing saga of survival against all odds and an all too real human threat…

Clam Shells (by Lindsey B. CC BY-SA 2.0 via Flickr).

Clamshells Face the Acid Test – Hakai Magazine

As acidification threatens shellfish along North America’s Pacific Coast, Indigenous sea gardens offer solutions.   

It’s low tide in Bodega Bay, north of San Francisco, California, and Hannah Hensel is squishing through thick mud, on the hunt for clams. The hinged mollusks are everywhere, burrowed into the sediment, filtering seawater to feed on plankton. But Hensel isn’t looking for living bivalves—she’s searching the mudflat for the shells of dead clams…

Beluga or white whale, Delphinapterus leucas. courtship (by Brian Gratwicke CC BY 2.0 via Flickr).

In Alaska, a Mystery Over Disappearing Whales – Undark

In the 1980s, Kotzebue Sound’s beluga population began to dwindle…Although some stocks are healthy, beluga numbers have fallen off in around a half-dozen regions over the last 50 years…Now, even after hunting has ceased in some places, stresses such as climate change, increased ship traffic, and chemical pollutants are a gathering storm that threatens to finish the job…

Floreana Island (by eatswords CC BY-NC-ND 2.0 via Flickr).

New Research Shows People, Wildlife, and Marine Environment Benefit When Island-Ocean Connections are Restored – SCRIPPS

“By applying this knowledge to islands worldwide, we can understand the marine benefits of island restoration projects and maximize returns for our conservation management investments for people, wildlife, and the planet,” said Stuart A. Sandin, PhD, lead co-author of the perspective and a marine ecologist at Scripps Institution of Oceanography at the University of California San Diego…

Temple, Red Sea (Andrew K CC BY-NC 2.0 via Flickr).

The Red Sea’s Coral Reefs Defy the Climate-Change Odds – New York Times

…(T)he wildly colorful coral reefs in the waters outside the Egyptian Red Sea resort of Sharm el Sheikh, where the annual United Nations climate conference is taking place, are an anomaly: They can tolerate the heat, and perhaps even thrive in it, making them some of the only reefs in the world that have a chance of surviving climate change…

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