Brown Tide Noted Along Long Island’s South Shore as New Research Seeks to Better Manage its Blooms
Red Tide Found all Through the East End — in the waters of the Peconics, Orient, Sag Harbor, Shinnecock east of the Canal — as well as in some western Long Island Bays as New Research May Provide Insights into Bloom Development and Dynamics.
Stony Brook, NY, September 09, 2009 – In July, brown tide turned up in East End waters on the South Shore, but, as Stony Brook University (SBU) researcher Christopher says, the Peconic and Flanders bays appear safe at the moment.
As illustrated by New York Sea Grant's (NYSG) Brown Tide Research Initiative (BTRI), a research effort documented in a report series from 1998 - 2006, brown tide is a phenomenon of interest and continued concern to scientists, resource managers, government officials, fishers and users of Long Island's east end and south shore bays.
“Brown tides” are part of growing world-wide incidences of harmful algal blooms caused by a proliferation of single-celled marine plants called phytoplankton. One species of phytoplankton, the microscopic alga Aureococcus anophagefferens, may bloom in such densities that the water turns dark brown, a condition known as "brown tide." Bloom concentrations of A. anophagefferens can cause mortality in larval and juvenile stages of hard clams and have been a factor in the decline of the hard clam fishery as well as the bay scallop fishery and the loss of eelgrass meadow habitat.
As reported in BTRI Report #9, released March 2006 (click here), Long Island bays have experienced sporadic brown tide events since 1985. The last major bloom in the Peconic estuary was in 1995, while the south shore estuaries on Long Island have experienced blooms in varying degrees through 2004. In the spring 2008, a large bloom swept across the all of Long Island’s south shore bays (Great South Bay, Moriches Bay, Shinnecock Bay) for much of the spring, summer, and fall. And, this year the alga was reported to be appearing in Moriches, Quantuck and Shinnecock Bays during June and July.
Another type of harmful algal bloom, known as red tide, has appeared in local bay waters during the past three summers, including this one. Unlike the brown tide alga, which disrupts feeding cycles, the red tide organism (Alexandrium fundyense) synthesizes a lethal toxin, according to Gobler, an Associate Professor at SBU's School of Marine and Atmospheric Sciences (SoMAS). The toxin is lethal to fish and, because it accumulates in shellfish, it can be lethal to humans, too. "Fortunately, on the east and south shore of Long Island it's been found in areas that are not open to shellfishing right now," says Gobler. Some western Long Island bays that are open to shellfishing, though – in Northport and Huntington – have been closed down this year, as well as in 2006 and 2008.
Earlier this year, Gobler began a NYSG-funded study to provide insights into the development and dynamics of red tides. This research will give fisheries managers and local health departments the essential information they need to protect human health and sustain healthy ecosystems and local economies. For more on this project, click here to check out the 2009 suite of research to improve the health of Long Island Sound, funded by Sea Grant programs in New York and Connecticut.
Scientists believe these algal blooms are caused by the introduction of high quantities of nutrients, such as nitrogen, into the waterways, though no singular cause of the red or brown tides has been firmly established. Knowing that these algae are nitrogen-loving organisms, though, it makes sense to identify and try curtailing sources, like fertilizer and waste water, that contribute to nitrogen loading in our local waters.
Gobler is also currently a co-investigator on a second NYSG-funded two year study, this one to better understand and manage brown tide. "Due to the ecological impacts on economically important shellfisheries in Long Island from brown tide blooms, the importance of successful management and recovery plans hinges on adequate knowledge of bloom dynamics, ecology and physiology," says Gobler.
This study, which began this past February, will provide important information using traditional and molecular genetic techniques to characterize the entire plankton community – phytoplankton, bacteria, small zooplankton – during both bloom and non-bloom conditions. Gobler, along with principal investigator Jackie Collier and their SBU team will also examine the incorporation of nitrogen from nitrate, ammonium, urea, and glutamate into the DNA of A. anophagefferens and other plankton.
"It's been hypothesized that Aureococcus anophagefferens forms brown tide blooms by relying on dissolved organic nitrogen sources, drawing nutrient concentrations down to such low levels that no competing phytoplankton can match its net growth rate," says Gobler. However, as he and his fellow researchers on this NYSG-funded project have found, no field study has yet to examine how the whole plankton community changes during brown tides. Previous studies have also not yet measured the incorporation of specific nitrogen compounds by individual species during brown tides, despite the important managerial implications of how these blooms acquire nitrogen.
For more on brown tide and its ecological and economic effects since first appearing in local waters in 1985, click here.
— Paul C. Focazio
