The little gelatinous blobs on the beach? Salps.
Swimmers venturing into the ocean on Block Island have been experiencing what feels like baby jellyfish, small organisms in the water. Chris Littlefield, Director of The Nature Conservancy on Block Island, and Dave Prescott and Adam Kovarsky from Save the Bay, told The Times that the creatures are marine invertebrates.
“Salps are not jellyfish,” said Littlefield. “They are a primitive animal called a colonial tunicate. Unlike jellyfish, they are filter feeders and eat microscopic plants, phytoplankton, pumping water through their body and filtering out the plankton. They are not harmful. Whales eat them.”
“I read that tunicates use jet propulsion to move water through their bodies to feed on phytoplankton,” said Kovarsky. “Tunicates are distantly linked evolutionarily to people. They have a developmentally primitive form of a spinal cord called a notochord.”
“They have a backbone,” said Prescott, who noted that he has seen tunicates while surfing. “They’re really cool, simple animals. They eat phytoplankton, microscopic marine algae.”
Prescott added, “Tunicates don’t sting. They are not going to kill you. Although, I would not advise eating them.” He noted that tunicates are also not sea lice, which can sting, and cause rashes. Sea lice, which are jellyfish larvae, have been in the news recently with swimmers in Ocean City, New Jersey complaining of skin irritation.
Prescott said that tunicates appear annually at this time of year when they feed on algae blooms. “This is very common,” he said. “They’re everywhere right now. When phytoplankton are plentiful you’ll find them. When they eat too much phytoplankton they sometimes beach on the shoreline.”
Tunicates have been seen on Fred Benson Town Beach, looking like diamonds glistening on the sand.
“They have a very rapid life-cycle and can become really abundant when there is an abundance of phytoplankton,” said Littlefield. “So apparently conditions are right for them now. They usually bloom in late July to around now, and it usually doesn’t last too long. A few years ago we had a big bloom in the fall, which included the Great Salt Pond. I have never seen them thicker than they were in the pond that fall.”
Littlefield said he gets questions about tunicates “every year. It definitely seems to be an annual event of sorts.”
Prescott said tunicates form long chains in the water, like a string of pearls, by attaching to each other. “Tunicates float in the water, and swim along with the ocean’s tides and currents. They’re a great little thing to observe.”
Littlefield said, “You should check them out at night when they are backlit. It is especially interesting to observe them at night at the marinas. It’s best when illuminated by those cool green or blue underwater lights that some people have on their boats.”
Kovarsky said, “There are many species of tunicates; not all are planktonic. If people ever want to come to the Save The Bay Aquarium in Newport (www.savebay.org/aquarium) we have other species of tunicates on display they can see and learn about as well.”