Giant Clams: Unsung Heroes for Coral

Giant clams have been a hard-to-miss part of coral reef ecosystems for the greater part of the last 38 million years. However, experts will be quick to admit that the part they play in these incredible systems remains rather shrouded in mystery. Now a new study hopes to pull back the veil and further our understanding of these clam colossi.

The study, recently published in the journal Biological Conservation details how the giant clam is not only a member of the incredibly diverse and complex coral ecosystem, but it may be an essential founding member, serving as an assistant reef builder, shelter, algae provider, water filter, and even "pantries" for reef inhabitants.

To quantify the extent of these services in hard numbers, researchers from the University of Singapore poured over extensive archives of publications proceedings, dissertations, books, and even technical reports (481 publications in all) concerning  the giant clam (Hippopus and Tridacna species). They then compiled observations and data from this assents with data from their own field surveys to determine that 13 species of giant clam in particular serve as coral ecosystem food factories.

According to the study, these massive clams can grow up to 40 feet long and 60 pounds heavy, and often host food-making algae known as zooxanthellae. This food attracts predatory lobsters and crabs, whose feces in turn attract opportunistic feeders and scavengers like snails and their ilk.

These species are essential for keeping a growing coral colony clean free of diseased, as you can't have a city without its garbage men.

They also help build reefs directly. Dense populations of clams lead to some species producing an estimated 80 metric tons of carbonate shell material per hectare each year, which serves as initial housing for soft corals as they acquire the symbiotic algae partners they will need to keep a sturdy coral colony growing.

"They also filter large volumes of water-which can potentially counteract eutrophication," the researchers wrote, citing a process of water pollution often cause by agricultural runoff in this modern age.

"We are not proposing that giant clams are essential to the survival of coral reefs; however, there can be no doubt that they make a positive contribution to these critically important tropical ecosystems," they add.  "Based on the wide range of ecological functions they perform, giant clams are unique among reef organisms and therefore deserve attention... a greater understanding of giant clams' contributions will provide managers with 'ammunition' to justify their protection."

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