We Could Do Without Invasive Tunicates in Rhode Island

By Aya Rothwell


“Invasive tunicates?” asked my friend. “Tunicates are a kind of fashionable shirt, right?” I think my friend was thinking of “tunics,” not “tunicates”. (To be honest, I've mixed them up before.) Today, however, I'm here to talk about not human garments but sea tunicates. Specifically, how invasive tunicates are the bane of oyster farmers and boaters in Rhode Island and what you can do to help.


First, a big picture of tunicates. Also called sea squirts, these amazing ocean creatures are 500 million years old. Tunicates might sport brilliant fluorescent colors or mesmerizing star-patterns. They might also look like pale blobs on rocks. (Not all tunicates get to be dazzling.) Tunicates can form colonies on surfaces, looking like underwater patches of moss, or they can grow as single creatures. Visit marinas and you can find native and invasive tunicates on the side of the docks. Rhode Island has a native tunicate called Aplidium constellatum.


But back to the non-native, invasive tunicates. Invasive species are called “invasive” because they threaten the environment, threaten the economy and threaten human health, as I will explain below.


Invasive tunicates run amok, so to speak, growing over native eelgrass and native blue mussels. Eelgrass does great things such as stopping shoreline erosion. The plant also helps house or provide food for commercially important fish. We don't need invasive tunicates smothering our eelgrass.


Invasive tunicates are bad news for local shellfish farmers as well. Rhode Island's shellfish farming was valued at over $4.2 million in 2013 (www.rismp.org). Invasive tunicates foul blue mussels, oysters and other shellfish as well as aquaculture gear. Shellfish farmers must do even more work in treating gear and shellfish to get rid of nuisance species (as Perry Raso, the owner and founder of Matunuck Oyster Bar, told me).


But how did invasive tunicates arrive and how are they spread? Non-native tunicates were originally brought through fouled hulls and ballast water of boats. Even now, invasive tunicates are a problem as they foul boat hulls and lines and potentially threaten human health and safety. Boat owners and marinas can follow best management practices to help keep boats and marinas safe and help stop invasive tunicates from spreading. You can find out more information at the Aquatic Nuisance Species Task force website (www.anstaskforce.gov). The National Oceanic and Atmospheric Administration has additional information on habitat conservation (www.habitat.noaa.gov).

For general boating and dealing with invasive species, Rhode Island Dept. of Environmental Management has information (www.dem.ri.gov/programs/water/quality/surface-water/invade.php).

The Coast Guard and the U.S. Fish and Wildlife Services sponsor information sites as well (www.protectyourwaters.net).


Finally, you -- yes, you, the public! -- can also keep an eye on invasive tunicates. Rhode Island's Coastal Resource Management Council hosts programs where the public can learn how to identify and monitor marine invaders. (http://www.crmc.ri.gov/news/2016_1014_aismonitoring.html)


By recording the species on floating docks, you can help figure out if invasive species are spreading in Narragansett Bay. You might even come across golden star tunicates, the beautiful star-patterned tunicate I described earlier. (Sadly, golden star tunicates are also highly invasive.)


Tunicates are amazing creatures. However, we could do without non-native, invasive tunicates spreading in Rhode Island coastal waters and hindering boats, shellfish farms and our native species. While it is impossible to get rid of all the invasive tunicates in Rhode Island's waters, we can manage them and make them less harmful. And you can help.


Aya Rothwell is a graduate student studying conservation biology at the University of Rhode Island.



A version of this Op-Ed was published in the Narragansett Times on December 16, 2016.

Tunicates in Indonesia (Getty Images)

Invasive Golden star tunicate (www.rimeis.org)

Tunicates fouling a boat (www.whoi.edu)

Native Aplidium constellatum (www.ascidians.com)

Monitoring tunicates (www.crmc.ri.gov)