Brown Tide Assessment Project in NJ Coastal Waters: A comparison of three bloom years (2000-2002) with two non-bloom years (2003-04): Research Project Summary



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Trenton, N.J. : New Jersey Department of Environmental Protection, Division of Science, Research and Technology


Brown tides are caused by the rapid population growth (“bloom”) of a minute alga, Aureococcus anophagefferens. To determine whether these blooms are a threat to coastal waters in New Jersey, the Division of Science Research and Technology implemented the Brown Tide Assessment Project from 2000-2004. The primary objectives of this study are to (1) characterize the spatial and temporal occurrence of brown tides in Barnegat Bay-Little Egg Harbor, (2) identify those environmental factors that may promote the development and maintenance of brown tides, and (3) analyze the risk of brown tides to submerged aquatic vegetation communities. Category 2 (> 35,000 cells ml-1) and Category 3 (> 200,000 cells ml-1) A. anophagefferens blooms occurred throughout the study area in 2000-2002 (mean abundances exceeded 190,000 cells ml-1), while none of the monthly means in 2003/04 were classified as a Category 2 or 3 bloom. Category 3 blooms generally occurred during months with mean water temperatures above 14 C, and a minimum temperature above 13.5 C; and with mean salinity between 26 and 31 ppt, and a minimum salinity of at least 17 ppt. However, these environmental conditions do not always result in the occurrence of a Category 3 bloom. Concentrations of total nitrogen, dissolved organic nitrogen, and nitrite + nitrate were higher during the bloom year of 2002 compared to the non-bloom years of 2003/04. In contrast, ammonia showed lower concentrations during 2002. Category 3 brown tides did not occur in any month where the Toms River flow exceeded 200 ft3 sec-1. A Cartographic and Regression Tree Analysis identified ammonia and dissolved organic nitrogen concentrations, and the Toms River flow, as factors that distinguished Category 1 (< 35,000 cells ml-1) and Category 3 A. anophagefferens blooms. However, it appears that the observed differences in nitrogen species concentrations may be a result of A. anophagefferens blooms impacting nutrient cycles, rather than nutrient levels initiating the brown tides. Analysis of the risk of brown tides to submerged aquatic vegetation habitat indicated that 50% of the mapped habitat in Barnegat Bay-Little Egg Harbor is potentially at risk of negative impacts. Graphic displays of the spatial patterns of A. anophagefferens abundance and selected environmental factors can be viewed at:



New Jersey, Brown tide - New Jersey