by Dr. Mary Downes-Gastrich, Division of Science and Research, Research and Technology

What happened to Barnegat Bay's water color this year? The southern portion of the bay turned golden brown. This unattractive color is caused by the brown tide organism, (Aureococcus anophagefferens)-a member of the golden brown algae group. While there is no danger to human health either from swimming in waters containing a brown tide bloom or in eating fish or shellfish taken from affected waters, this algae is considered a "harmful algal bloom" because of its potential deleterious ecological effects. Algal blooms are defined as the rapid proliferation of single-cell marine plants known as phytoplankton. Concentrations of algal cells coloring the water from pigments they contain are known as "red tides," "green tides," and "brown tides" depending upon the species involved. Some algal blooms are part of a global trend in harmful algal blooms that may cause ecological and/or health problems because of the toxin they produce. The organisms may also deplete dissolved oxygen in the water column (which can affect fish).

In the mid-1980s, severe brown tide blooms were reported in the bays of New York's eastern Long Island, especially the Peconic Bay, Great South Bay and Moriches Bay; Narragansett Bay, Rhode Island; and possibly in Barnegat Bay. Since then, the brown tide has occurred periodically with variable intensity in the bays of Long Island and in Barnegat Bay. It was not until 1995, that the first known bloom of the brown tide organism was reported in Barnegat Bay and Little Egg Harbor. While there are no known effects of the brown tide on human health, there are potentially significant ecological impacts. In Peconic Bay and the Long Island Bays in New York, the brown tide devastated the scallop industry, worth approximately $2 million per year. In addition, detrimental effects of brown tide have been noted in oysters, hard clams, and possibly blue mussels. In 1995, there was an observed reduction in hard clam growth in a commercial aquaculture facility in Tuckerton Bay, New Jersey, which coincided with a substantial brown tide bloom in the area. It has been hypothesized that this reduction in growth may be related to a toxic or inhibitory substance on the cell surface of the brown tide organism that reduces the feeding response of some shellfish, such as the hard clam or bay scallop. Brown tide blooms can also play a role in reducing habitat. With decreased light penetration in an intense brown tide bloom, submerged aquatic vegetation such as eelgrass beds, which serve as spawning and nursery grounds for shellfish and finfish, may be adversely impacted. Recent research indicates that decreased light penetration may damage eelgrass by causing the plants to "slough" or lose their leaves prematurely. Eelgrass also has a "wasting disease" caused by another organism and may be related to eutrophication factors. Coupled with decreased light penetration, the eelgrass system is subjected to multiple stressors that may impair its vitality. There are several hypotheses as to the cause of brown tide but no single cause has been identified. More likely, the occurrence of brown tide is an example of an "ecological phenomenon" having multiple interactive factors, including physio-chemical, biological, and meteorological factors that may all play a role in the development and sustenance of these blooms.

The brown tide organism prefers higher salinity, cooler water temperatures, shallow bays, and possibly, the longer flushing times (58 days) in bays like Barnegat Bay. However, there are other factors such as nutrients and reduced grazing pressures of zooplankton predators that may also influence the duration of blooms. There is growing interest in another factor, the presence of viruses in natural populations of brown tide, that needs to be studied in combination with other factors to better understand how to control blooms. Recently, viruses were observed in field populations of brown tide cells taken from Barnegat Bay.

Scientific studies are needed to gain knowledge about the complex relationships and factors promoting chronic brown tide blooms. An understanding of these environmental factors, both natural and anthropogenic, will lead to the effective management of harmful algal blooms. Currently, the DEP's Division of Science, Research and Technology is conducting a preliminary investigation of potential factors that may promote brown tide blooms in New Jersey coastal waters. To report a brown tide occurrence, contact the DEP's 24-hour hotline at 1-877-WARNDEP (1-877-927-6337). For a brochure about brown tide, contact Dr. Mary Downes-Gastrich at (609) 292-1895.