Harmful Algal Blooms

Recurring algal blooms have been documented in the Barnegat Bay. Sometimes the growth is so explosive it creates an algal “bloom” with millions of organisms discoloring the water. This excessive growth causes an unhealthy increase in the amount of organic matter, a process called eutrophication. These blooms are typically characterized by the explosive growth of a single phytoplankton species, which can lead to negative impacts.

An underwater photo in Barnegat Bay shows heavy algae growth.
An underwater photo in Barnegat Bay shows heavy algae growth. © Mark Yokoyama

Excessive growth of some phytoplankton species generates harmful algal blooms (HABs), such as brown tides, yellow tides, red tides, and other types. The toxic forms are particularly dangerous to numerous organisms, including shellfishes, finfishes, and even humans. Secondary impacts include shading effects, altered grazing patterns, and changes in trophic dynamics that are detrimental to estuarine function. A number of HAB-forming species have been recorded in the Barnegat Bay-Little Egg Harbor Estuary, including Dinophysis spp., Gymnodinium (Karlodonium) spp., Heterosigma sp., and Prorocentrum spp.) (Olsen and Mahoney, 2001).

Brown-tide blooms, caused by the minute alga, Aureococcus anophagefferens, were first reported in New Jersey coastal bays in 1988, with initial blooms documented in 1995, 1997, 1999, 2000, 2001, and 2002. No significant bloom was documented in 2003. These algal blooms can discolor the water brown and may cause negative impacts on shellfish, notably the ecologically and commercially important hard clam and scallop, as well as on seagrasses. Adverse shellfish impacts include a reduction in the growth of juvenile and adult shellfish (e.g., hard clams and mussels), reduced feeding rates in adult hard clams and other shellfish, recruitment failures, and even mortality of shellfish (Gastrich and Wazniak 2002). The dense shading of these blooms may also contribute to the loss of seagrass beds, which serve as important habitat for fish and shellfish. Monitoring for brown tide was discontinued in 2004.

More recently, emphasis has been placed on macroalgal blooms in shallow eutrophic estuaries. Green-tide forming taxa (e.g., Enteromorpha and Ulva) may be particularly problematic. When exposed to elevated nutrient levels, these plants can grow very rapidly to form sheet-like masses that drift along the bay bottom. Such high biomasses of macroalgae often degrade benthic habitats and communities.

Useful Harmful Algal Bloom Websites

Brown Tide in New Jersey (Rutgers/CRSSA)

NJDEP Brown Tide Newsletters (2000)
Brown Tide Bloom Index Report (Gastrich, M. D. and C. E. Wazniak. 2002)

Ecology and Oceanography of Harmful Algal Blooms


Gastrich, M. D. and C. E. Wazniak. 2002. A brown-tide bloom index based on the potential harmful effects of the brown-tide alga, Aureococcus anophagefferens. Aquatic Ecosystems Health & Management 33: 175–190.


Olsen, P. S. and J. B. Mahoney. 2001. Phytoplankton in the Barnegat Bay-Little Egg Harbor estuarine system: species composition and picoplankton bloom development. In: Kennish, M. J. (Ed.), Barnegat Bay-Little Egg Harbor, New Jersey: Estuary and Watershed Assessment. Journal of Coastal Research, Special Issue 32, pp. 115-143.

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