Damaging Brown Tide Emerges Across Great South Bay

An intense and potentially damaging brown tide has emerged across Great South Bay, monitoring by The Gobler Laboratory of Stony Brook University has revealed.

A brown tide that began to develop earlier in May has intensified to more than 600,000 cells per milliliter in Patchogue Bay and more than 200,000 cells per milliliter in Bay Shore.

Experts say the pattern of this year’s brown tide bloom is particularly troubling as it is a full month ahead of most prior years. It is paralleling 2017 when the bloom also began in May and persisted until nearly August.

The brown tide alga, Aureococcus anophagefferens, has been notorious on Long Island, having caused the demise of the largest bay scallop fishery on the East Coast in the Peconic Estuary, the loss of eelgrass across Long Island and the inhibition of hard clam recovery efforts in Great South Bay. Densities above 50,000 cells per milliliter are harmful to marine life, particularly clams.

Densities in the Great South Bay are now 10-times higher than this. Densities are presently lower in the eastern Long Island regions, such as Moriches Bay and Shinnecock Bay.

“The outbreak of brown tide in this early in the season is a troubling sign for Long Island.” said Dr. Christopher Gobler, professor of marine science at Stony Brook University. “These early events often last a long time and are, in turn, very damaging to marine life.”

Gobler noted that intense and extended blooms in Great South Bay have been associated with the mass-die-off of seed clams and thus have prevented the recovery of these populations.

Decades of research on brown tide at Stony Brook University has identified high levels of organic nitrogen and poor flushing as factors promoting blooms on Long Island. And while the new ocean inlet in the bay has improved water quality in the eastern Great South Bay and western Moriches Bay, other regions remain poorly flushed, and brown tides have recurred every year since 2012 in the Great South Bay.

“The bays along the south shore of Long Island have the precise combination of conditions that leads to brown tides and other harmful algal blooms: Intense nitrogen loading from septic tanks into a shallow water body that is poorly flushed by the ocean," Glober said. “As efforts move forward to address nitrogen loading, this region must be a high priority.”

The timing of the current brown tide is particularly double trouble for hard clam populations. Beyond the toxicity of these blooms to seed clams set in 2017, June marks the once per year event when adult hard clams reproduce and any newly spawned hard clams will be highly vulnerable to the 2018 brown tide. The fate of these young-of-the-year clams may rest on the duration of the current brown tide which usually intensifies through June and into July until water temperatures get into the mid- or high-70s.