Shinnecock Bay Brown Tide Threatens Clams

While Shinnecock Bay is the easternmost of the connected lagoon estuaries that line the south shore of Long Island, and some might argue the most pristine, it isn't without its share of problems. In recent years, the western portion of Shinnecock Bay has been plagued with brown tides (as has the next bay to the west, Quantuck Bay).  There was a recent report on NBC News New York on the subject.

One of the issues, as talked about in the video, is that brown tides have a negative impact on hard clams. Brown tides affect hard clams in three ways:

1) Blooms inhibit feeding in adults. This can impact growth and survivorship, but it typically affects condition and reproductive output negatively.

2) Blooms cause a reduction in growth of larval clams. This can extend the larval period, increasing the likelihood of larval mortality. Slow larval growth can also effect metamorphosis to settlement stage. Since brown tides typically occur when larvae are expected to be in the water, this can then ultimately lead to recruitment failure.

3) Blooms shade out eelgrass. Eelgrass offers a 3-D habitat that provides shelter to a number of organisms. For hard clams, they find refuge from predation in the complex rhizome structure. Clams also grow faster in eelgrass.

So brown tides create a potential triple-whammy for hard clams, and so the blooms are likely to blame, at least in part, for low clam populations. Add to the harmful algal bloom equation deteriorating water quality in general and fishing pressure, hard clams might have a hard time recovering on their own. 

In fact, low clam populations may be partially to blame for recurrent brown tide blooms. Researchers from the School of Marine and Atmospheric Sciences, such as Dr. Robert Cerrato, have demonstrated in mesocosm — a.k.a. a large bucket — experiments that high clam densities can prevent bloom formation. So, low clam densities might enable blooms to initiate and persist, which prevent hard clams from replenishing themselves, and so on in a negative feedback.

Stony Brook researcher Chris Gobler also conducts many research projects on brown tides. His research demonstrated that poor water quality, due to increasing population on the East End leading to nutrient loading, can cause these blooms.  He has also shown the devastating impacts of these blooms on shellfish larvae.

So what can be done? One option is trying to restore shellfish to the bay. Shellfish restoration has certainly maintained success on Long Island, be it scallops in Peconic Bay or hard clams in Great South Bay. Certainly, high densities of filter feeders might help keep water clear and prevent blooms from recurring. But which shellfish are best suited to handle this "new" environment in western Shinnecock Bay still needs to be investigated.