Overview

Causes of Brown Tide in the Peconics

Status of Brown Tide in the Peconics

PEP Brown Tide management goals

What the PEP is doing to reduce the effects of Brown Tide

Overview

Brown Tide is a bloom (excessive growth) of small marine algae (Aureococcus anophagefferens).  Although algae of many types are found in all natural freshwater and marine ecosystems, blooms of the Brown Tide organism literally turn the water deep brown, making it unappealing to swimmers and fishermen alike.  While not harmful to humans, the presence of the Brown Tide is a problem for bay scallops and eelgrass, and to a lesser degree other finfish and shellfish.  Brown Tide is unlike most other algal blooms because of its unusually high concentrations, the extent of area it covers and the length of time it persists. 

Soon after Brown Tide blooms began in 1985, the population of bay scallops declined significantly, leading to a near collapse of the commercial shellfishing industry in the Peconics.  Many people considered this to be a “warning shot across the bow” for the estuary and its watershed. 

As more is learned about Brown Tide, it becomes clear that both the estuary’s problems and their solutions are characterized by the interrelationship among habitat, living resources, water quality and humans.  Understanding and resolving what causes the Brown Tide problem will likely require small steps on many fronts, sustained over a long period of time by many stakeholders, from homeowners to farmers to sewage treatment plant operators. 

Causes of Brown Tide in the Peconics

Numerous theories have been investigated, but scientists still do not have a clear explanation of what causes Brown Tide blooms.  Some accepted research at this point concludes that:

• Compared to other algae, Brown Tide can photosynthesize under extremely low light conditions.
• Brown Tide usually acts like an autotroph (plant), producing its own food through photosynthesis.  However, in low light conditions, Brown Tide may behave like a heterotroph (animal) metabolizing organic carbon and nitrogen. 
• Brown Tide bloom onset conditions may be optimized by elevated ratios of available dissolved organic nitrogen (high “DON”) in surface waters, with respect to the supply of dissolved inorganic nitrogen (low “DIN”).  These nitrogen constituents may be related to groundwater inputs and weather patterns – onset conditions could be optimized in a dry year (low DIN supply from groundwater) that follows a wet year.
• Clams and other suspension-feeders can exert significant feeding pressure on phytoplankton, including Brown Tide at low levels.  In an experimental setting, hard clams have been shown to play a pivotal role in determining whether Brown Tide blooms become established.

Status of Brown Tide in the Peconics

Brown Tide blooms persisted in high concentrations for extended periods in all or part of the Peconics from 1985 through 1988, 1990 through 1992, 1995, and 1997.  Brown Tide has not bloomed in high concentrations in the Peconics since then, but it continues to be an important management topic, especially as efforts are mounted to restore shellfisheries and eelgrass.

In 1982, the harvest of 500,000 lbs of bay scallops from the Peconic Estuary accounted for 28% of all U.S. commercial landings and had a dockside value of $1.8 million.  After the appearance of the Brown Tide in 1985, the bay scallop population was virtually eliminated. 

PEP Brown Tide management goals

• Determine environmental factors responsible for Brown Tide blooms
• Develop and implement strategies to prevent or mitigate Brown Tide, and its effects on estuarine resources
• Restore the natural resources affected by Brown Tide

What the PEP is doing to reduce the effects of Brown Tide

Continued research, monitoring, and information sharing is needed to find out the cause of Brown Tide and actions that can be taken to prevent, or at least mitigate, the effects of Brown Tide.