Jars filled with alcohol were once the preferred method for preserving marine invertebrates like sea slugs for future study, but the specimens tended to fade and lose their shape. In the late 1800s father-and-son glassmakers Leopold and Rudolf Blaschka found a more aesthetic and longer-lasting method: making startlingly intricate and colorful glass replicas.

More than a century later scientists are using the Blaschkas’ handiwork as a time capsule to compare the status of today’s oceans with that of the late 19th century. One such marine biologist is Drew Harvell, who has linked ocean acidification to severe effects on underwater life. She has been comparing the models with what is currently swimming out there—and is finding that the delicate glass figures mirror the fragility of the world’s oceans, which she says face a serious crisis due to acidification.

“The surface waters in the Puget Sound region [of Washington State] are currently corrosive to shelled invertebrates six months of the year,” Harvell says. “Shelled pteropods (free-swimming snails and sea slugs) are showing up with corroded, pitted and dissolved shells.” The Cornell University professor of ecology and evolutionary biology has written a book, “A Sea of Glass: Searching for the Blaschkas’ Fragile Legacy in an Ocean at Risk,” about her work on how climate change is affecting the oceans. Her research has also found that cold-water corals like Corallium rubrum and Balanophyllia elegans—also Blaschka models—are threatened by acidification and warming in the Mediterranean Sea.

Harvell has devoted much of her career to researching impacts of global change such as warming and ocean acidification, which is the result of carbon dioxide being released into the atmosphere. According to the National Oceanic and Atmospheric Administration (NOAA), oceans absorb a quarter of all carbon dioxide emissions, resulting in an increase of ocean acidity by 30 percent over the past 200 years. In her research Harvell has found that one life-form in particular is showing the telltale marks of acidification to an alarming degree: invertebrates. And thanks to the Blaschkas’ painstakingly intricate glass models, Harvell can get a historical snapshot of marine biodiversity. Luckily for her, the glassmakers cut no corners when making their models.

Working in their studio in Dresden, Germany, they used molten glass and tweezers to create intricate models of sea anemones, octopuses, jellyfish and other ocean dwellers. The Blaschkas, who kept an aquarium filled with live sea creatures in their studio, created hundreds of these stunningly lifelike glass models, and Cornell University acquired 570 of them in 1885 to use for future study. (Here is a scanned catalogue of Cornell’s collection.) Now, more than a century later, 70 restored models are on display through January 8 next year at the Corning Museum of Glass in Corning, N.Y., in an exhibition called “Fragile Legacy: The Marine Invertebrate Models of Leopold and Rudolf Blaschka.”

Harvell helped the museum select specimens for the show and hopes her research will offer insight into whether there has been any invertebrate extinction in the 150 years since the Blaschkas made their first models. “It’s too soon to tell if any [species] has become extinct,” she says. “If they were fish, whales or sharks, we could find out by going to the International Union for Conservation of Nature’s endangered species list, but we can’t because they [marine invertebrates] are not tracked carefully enough. The best way to check on how they’re doing is to look for them in the ocean and compare our findings to the Blaschka models.”