Elkorn and staghorn coral collected in the 1920s can be seen in the Milstein Hall of Ocean Life in the two-story diorama of the Andros Coral Reef in the Bahamas, curated by Roy Waldo Miner. Completed in 1935, with a background painting based on underwater sketches, the display is a unique picture of the reef at its most vibrant.
But that’s just a sampling. Tucked among the Museum’s invertebrate zoology collections are 4,000 coral specimens, some of which date back to the late 1800s. The Museum recently embarked on a three-year project, with a grant from the Institute of Museum and Library Services, to conserve, rehouse, and document the holdings, which include specimens such as this elkhorn coral (Acropora palmata).
Collected in the Bahamas in 1942, this specimen offers researchers a window into a time when elkhorn coral was one of the most abundant species in the Caribbean. Along with its close relative, staghorn coral, elkhorn coral is considered to be a key reef builder, and the fast-growing, large branches that inspired its name create crucial habitats for many reef species.
But since the 1980s, multiple threats—including coral disease, bleaching from warming waters, overfishing, pollution, and damage from hurricanes—have led to devastating losses, estimated at 95 percent in some locales.
And while it’s too soon to gauge the long-term effects of the severe hurricanes that hit the Caribbean last fall, the risks to coral reefs posed by the storms are real. Pounding waves can break reefs apart, and runoff from flooding introduces pollutants and smothering silt. There is, however, a chance that cooler water dredged up from the deep might offer relief from bleaching.
In addition to several coral diseases—white pox, white band, and black band among them—coral bleaching remains a grave threat. Elkhorn corals obtain their brilliant hues from microscopic algae-like protozoa called zooxanthellae that feed coral polyps with nutrients through photosynthesis. Under the stress of above-average water temperatures, zooxanthellae are expelled, and the loss of food from photosynthesis leaves them weak and more susceptible to disease. “They go into a spiral that is not very good for them,” explains Estefanía Rodríguez, associate curator in the Division of Invertebrate Zoology and an expert on Cnidaria, the phylum that includes corals, jellyfish, and anemones.
Elkhorn coral was placed on the Critically Endangered Species List in 2008 by the International Union for Conservation of Nature (IUCN). David Obura, chair of the IUCN, warned in late September 2017 in the journal Science that the Paris Agreement’s aim to keep the rise in global temperature well below 2°C is “the only chance for coral reef survival.” He urged “action on an unprecedented scale” to curb greenhouse emissions, pollution, and overfishing, and to accelerate genetic research on heat-resistant corals.
For scientists looking to understand how environmental conditions affect corals, and for ways to protect them, the Museum’s collection is an invaluable resource. “All corals are actually threatened,” says Dr. Rodríguez. “And some are not there anymore. So, if we want to know what was there, and what actually made them disappear, this collection is crucial.”
Learn more about the preservation of the Museum's dry coral collection in the video below. And to see elkhorn coral on display, visit the Milstein Hall of Ocean Life.
A version of this story originally appeared in the Winter 2018 issue of Rotunda, the Member magazine.