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Bad Valentine: Red Algae Turns LI Waters Pink

It's not Mother Nature sending an early Valentine but if you love Long Island's waters, you should know about the red algae that's been swirling around in and coating our icy shores pink. Dasysiphonia japonica is a seaweed native to Asia and is known for its bushy scarlet fronds that can cover the sea floor. As it breaks apart and begins to decay, the color can range from a striking bright pink to purple to brownish red. It's recently been found in both Southold and the Great South Bay.

Something to take to heart: this invasive macro-algae (or seaweed) isn't toxic to humans; however it could alter the seascape and the marine food web if it disrupts or displaces native- species.

Here’s What You Should Know

According to researchers studying it, this algae species was first reported in Rhode Island in 2007 and was then subsequently found in 19 sites from Maine to Long Island Sound in 2012. A recent photo taken in Great South Bay caught the attention of two Long Island marine researchers who confirmed the species identification and are now enlisting citizens to help. If you want to know what it looks like and to help map it, check out this page.

For the moment, scientists aren't sure what impact this species will have in our local waters, like Great South Bay. But every few years, we get a new species that takes up residency in our waters. Only time will tell how well it acclimates and how other species adapt to it. But since the arrival of D. Japonica our waters have certainly become much more colorful.

What’s the Difference Between this Red Algae and “Red Tide?”

D. Japonica is a type of red macro-algae, commonly called seaweeds.   It’s not harmful to humans and it can be seen with the naked eye. But we don’t fully understand its impact to wildlife and the marine environment. There are other macro-algae found around Long Island, and of many different colors (some are native and some are even red).

By contrast, a “red tide” is a harmful micro-algal bloom of phytoplankton (microscopic creatures that cannot be seen with the naked eye, however in large concentrations they can change the color of the water). Red algae creates a toxin that can trigger deadly paralytic shellfish poisoning in animals and humans that eat polluted shellfish.

Algae thrives on nitrogen and sometimes “blooms” therefore causing them to be visible to humans.  Nitrogen pollution from sewage and fertilizers, like we have in most Long Island waterways, often results in excessive growth of algae that can have cascading impacts on our waterways.    

You can check out our previous blog post on red tides for more information on this toxic phenomenon.

What Can We Do About Algae?

We may not have control of the distribution of algae in our waters, but we can help keep our waters healthy and resilient by reducing our fertilizer usage, pumping our cesspools and thinking about upgrading to advanced wastewater treatment. For more information on how you can help, visit LICWP’s website.