Rust never sleeps. Though famous as Neil Young’s exceptional album, this phrase also describes a dastardly dinoflagellate that could threaten the health of our local waters.

Rust tide is in the news again, reported recently in Long Island waters. Local shellfish guru and director of the Martha’s Vineyard Shellfish Group, Rick Karney, has sounded the alarm to look for it in our waters, sharing that it has been observed in both Lagoon Pond and Lake Tashmoo.

The organism that causes the condition known as rust tide is Cochlodinium polykrikoides, and becomes a problem when it is present in high concentrations. The term rust tide describes the hue the water takes on after a population explosion, commonly called a bloom. Rust tide is, however, not the same as the better-known red tide, since the condition is the result of a different organism than the one that causes red tide.

Cochlodinium is a type of marine plankton with peculiar characteristics. Described as mixotrophic, it can produce its own food by photosynthesis or, if it prefers, eat other organisms instead of making its own food.

But it is not a harmless character in the marine environment. When blooms occur, wildlife and aquatic health can suffer.   

Blooms can be the result of high water temperatures that we are seeing as the result of climate change and/or excess nutrients, such as nitrogen, that are coming from fertilizers, runoff, septic systems and other sources. Late summer and fall are generally times for blooms, since temperatures below 60 degrees are not conducive to Cochlodinium’s survival. Trouble can recur in future years since resting cysts of Cochlodinium can persist in sediments until conditions again become favorable.

Cochlodinium causes problems in two ways. The amount of dissolved oxygen in water is reduced during blooms, causing low (hypoxic) or no oxygen (anoxic) conditions. This occurs when large numbers of dinoflagellates become food for bacteria that use oxygen, leading the oxygen-consuming bacteria population to increase and use up available oxygen. Oxygen levels then plummet.

Some research has also showed that Cochlodinium can also produce mucus and a toxin. The mucus could clog fish gills, causing fish kills and mass fish mortality events. Luckily fish can swim away to avoid affected areas.

Shellfish, which are more sessile, are not so lucky. They cannot escape so may also be on the mortality list along with plankton and many other marine organisms. Rick notes that the shellfish in both ponds seem to not directly affected. People are not harmed by this dinoflagellate.

Scientists and others believe that Cochlodinium is an Asian species that has travelled far and wide in ballast waters and has been moved around during transfer of shellfish stocks. Though it has been known in the Chesapeake and Long Island Sound for some time, it has more recently come to our waters. The first report of this organism in Buzzards Bay came in 2006, and since then folks have been on high alert to monitor its presence elsewhere in the area.

We should be thankful that the likes of Rick Karney and others are working to keep an eye on this and other threats to our waters. In the case of Cochlodinium, we must be vigilant, since as American actress Helen Hayes observed: “If you rest, you rust.”

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.