As we wrap up our waterbody prioritization surveys for the summer, the LIISMA team took two days this past month surveying the Carmans River. One of Long Island’s largest rivers, all of it is designated by New York state as either a “Scenic River” or a “Recreational River.” The river is approximately 10 miles long, starting as a freshwater river in Yaphank that is fed 95% by groundwater, and meanders into an estuary for two miles as it feeds out into the Great South Bay. We focused on the northern portion, between the Long Island Expressway, down to Sunrise Highway.
Geared with our kayaks, rake toss, and waterproof tablet loaded with SASpro for data collection, we set out at the 3 Yaphank ave launch, just across the road from Lower (Lily) Lake. Immediately, we were overwhelmed with the diversity of species along and within the water, from the climbing hemp vines (Mikania scandens) to bright yellow Bidens flowers, to the ebony jewelwing dragonflies (Calopteryx maculata) darting around us. As well, we immediately noticed invasive species like watercress (Nasturtium officinale), phragmites (Phragmites australis), and eurasian watermillfoil (Myriophyllum spicatum).
On several of our tosses near the beginning of the river, we came across some tiny clams embedded in the aquatic macrophytes that we later identified as the invasive Asian clams (Corbicula fluminea); an underreported but widespread invasive species (tier 4) in LIISMA. The key ID features for this species to separate them from the native Fingernail clams are:
- The three cardinal teeth along the base of the interior of the shell, just above the umbo
- Finely serrated lateral teeth along each side.
These invasive clams can hurt our waterways by over-filtering phytoplanktons that would otherwise be consumed by our native filter-feeders, as well as contributing to higher levels of nitrogen in the waters that can support increased algae and aquatic macrophyte growth. While they do not attach themselves to hard substrates the way invasive zebra mussels (Dreissena polymorpha) do, they can be a similar nuisance. They can clog underwater intake pipes of water treatment systems as juveniles flow into, settle, begin to reproduce within them, and then become transported deeper into the system. They will however attach themselves to algae and aquatic plant matter, which can be tangled and transported to non-infested waters on boats or animals.
As we approached the Southaven County Park boat launch area, just before the river runs under sunrise highway, we began to pull up much heavier rake tosses, with an array of native Nitella spp, Chara spp, as well as invasive Cabomba (Cabomba caroliniana), and more Eurasian watermilfoil. Both of these invasive species have become widely established throughout the LIISMA region, largely due to the aquarium dumping as well as watercraft transport. Forming large, dense mats, they crowd out native vegetation and disrupt the microhabitats of native fauna. These plants also enjoy the ability to reproduce from tiny plant fragments, making control difficult.
LIISMA plans to return to the Carmans River in the upcoming weeks as weather permits to more precisely map the locations and size of the watercress patches along the slower moving margins of the river. We also look forward to continuing to coordinate with Suffolk County Parks to understand how we can reduce the impact and spread of these invaders within this high priority waterbody.
As summer closes out and we try to squeeze in some final warm days of boating and fishing, remember to keep cleaning, draining, and drying your gear so we can all help to prevent the spread of aquatic hitchhikers in our local water bodies!
