Hyalocylis striata sea butterfly

Hyalocylis striata (All photos: Karen Osborn/Smithsonian)

As climate change continues to wreak havoc on land, marine ecosystems are also showing signs of environmental trauma. One group of organisms that is especially sensitive to environmental changes are tiny, free-swimming pteropods called sea butterflies. Like canaries in a coal mine, the thin shells of these sea snails make them perfect subjects to evaluate the Earth's oceanic chemistry.

About a quarter of all carbon dioxide released into the air settles into the oceans and increases water acidity. Ocean acidification is bad news for the multitude of marine life equipped with shells and exoskeletons made of calcium carbonate, which becomes scarcer and more difficult for these organisms to secrete as the pH of water decreases.

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Limacina helicina sea butterfly

A broken shell of a Limacina helicina

Found in the ocean's pelagic zone, sea snails and slugs can be divided into three groups based on their shells: Thecosomes (hard shells), pseudothecosomes (gelatinous shells) and gymnosomes (no shells).

Scientists have already observed the dissolution of thecosome and psuedothecosome shells in the Antarctic. Meanwhile, the shell-less gymnosomes may not be physically affected by the acidification, but since their entire food source consists of shelled pteropods, their prey is now in danger of disappearing.

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Clione limacina sea butterfly

Clione limacina, a gymnosome

One scientist studying the effects of ocean acidification on marine life is Dr. Karen Osborn, a Smithsonian zoologist who uses genetic research and photography to study these delicate creatures.

To capture the photos, Osborn collects living specimens while scuba diving off the coasts of Mexico and California. After bringing them aboard a research ship, the fragile organisms are placed in a shallow tank of clear water and photographed using a Canon 5D camera with a 65mm lens. To capture the subtle colors of the transluscent creatures, several flashes are used.

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Cavolinia uncinata sea butterfly

Cavolinia uncinata

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Cavolinia uncinata eggs

Eggs of a Cavolina uncinata

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Cavolinia uncinata sea butterfly

Cavolina uncinata

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Clio recurva sea butterfly

Clio recurva covered in a colony of hydroids

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Gymnosome

Gymnosome

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Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.