On a cool Friday morning last month,
a dozen curious Rhode Islanders lay down on the pier at Point Judith Marina to collect
some of the squishy and crunchy creatures that were growing on the side of the
docks. Using rusted metal spatulas, they scraped the unknown life into small aquarium
nets and saved it in plastic tubs, then spent half an hour trying to identify
what they had retrieved.
With the exception of a few blue
mussels, almost nothing was recognizable. There were sea squirts and
shrimp-like things, seaweeds and green crabs, and just about everything was
covered in a mushy yellow-brown mat called a colonial tunicate.
Almost
none of it was native to New England waters. In fact, most it came from the
other side of the planet.
Colonial tunicate |
Marine
invasive species are a growing problem. According to Kevin Cute of the CoastalResources Management Council, who led the marina program sponsored by RhodeIsland Sea Grant, there is little that can be done about them. Once a new
species arrives, it’s almost impossible to get rid of it. So prevention is the key, he said.
But
preventing marine organisms from showing up where they don’t belong is harder
than you would think. Most arrive in the ballast water of ships, which pump
entire marine ecosystems from one part of the world into their hulls to improve
the ship’s stability, and then they discharge it into water bodies far from
where they originated.
Since
the biochemistry of Narragansett Bay is far different from that of the South
China Sea, for instance, most microscopic organisms cannot survive in both
places. But a few hardy specimens endure the journey, latch onto a hard surface
like a rock or marina dock, and start to reproduce. And it’s nearly impossible
to stop them.
The
colonial tunicate that covered most of the other creatures at Point Judith
Marina that day originated in Japan, showed up in Maine in 1993, and has been
spreading along the East Coast ever since. With no known predators, it grows
aggressively, fouls fishing and aquaculture gear, and smothers shellfish and
other creatures living on the seafloor.
Cute
and a team of CRMC staff and volunteers conduct monthly sampling for marine
invasive species at five sites around Narragansett Bay to keep an eye on the
known invaders and to watch for new arrivals. But, he said, “there are so many
variables – storm events, changing temperatures and salinity, predation,
competitors – if I came back next week there could be very different species
here.”
Various
regulatory agencies are doing what they can to restrict the arrival of new
organisms. Ships entering U.S. waters are now required to dump their ballast
water at least 200 miles from shore. And some ships must install on-board
chemical or ultraviolet systems for treating their ballast water before
discharging it – though many in the shipping industry are fighting these
regulations.
So
while it is getting more difficult for new species to make it to our shores,
dealing with the species that are already here is a never-ending battle. The
colonial tunicate is an especially challenging one to manage. It’s already
affecting Narragansett Bay’s eelgrass beds, which Cute calls the most important
habitat in the bay because it is a valuable nursery area for fish.
“We’re
playing ecological roulette with invasive species,” Cute said. “They’re wiping
out dinner for all of us.”
This article first appeared in the Independent on November 17, 2016.
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