October 3, 2011
Based on post-storm queries to the Virginia Institute of Marine Science (VIMS) in Gloucester Point, Virginia following Hurricane Irene, one impact remains a mystery—what are those “gray blobs” floating atop waterways and strewn along beaches?
Blob reports and queries have been streaming into VIMS since Irene passed by on the last weekend of August. The blobs—encountered by boaters and beachgoers from tidewater Virginia to Long Island—have been routinely described as being of “various sizes,” with the smallest “around the size of a baseball.” Reports of their texture range from “kind of rubbery or leathery” to “kind of soft.” They’ve also been described as “ash gray” and “foul smelling.”
Theories about the identity of the objects have proven to be as numerous as the incoming reports: Old crab floats? Sewage? Tar balls? Ambergris from whales? Sea turtles?
VIMS professor Emmett Duffy has a much simpler explanation. “They’re potato sponges,” he says.
Prof. Duffy explains that like other sponges, potato sponges make a living by filtering microscopic food from seawater. They draw the water into and through channels in their porous bodies by the beating of countless tiny hairs (flagella) on their cells.
Potato sponges, which comprise a diverse group within the genus Craniella, are normally inconspicuous animals (yes, they are animals) that inhabit shallow coastal habitats around the world, growing to about the size of a soccer ball. They look like, well, potatoes and attach to the seafloor with a network of protein fibers and glassy, needle-like “spicules” that form something like an anchor.
But when weather conditions cause large waves and strong currents to scour the seafloor, they can dislodge large numbers of these sponges, freeing them to float to the surface and wash ashore. Clogged with storm debris and no longer able to filter feed, the sponges die. Then they start to smell as decay and bacteria move in to consume the carbohydrates and collagen that form their body.
According to VIMS scientists, potato sponges are not poisonous, nevertheless, they caution people to avoid touching them as a precaution.