Brown Tide Assessment - Newsletters

Newsletter Number 6 - October 2002

The NJ Department of Environmental Protection conducted a field monitoring program consisting of water sampling and analysis of the brown tides and other water quality parameters in cooperation with the NJ Sea Grant/NJ Marine Sciences Consortium; U.S. Environmental Protection Agency, Region 2; Rutgers University; and the University of Southern California. This report includes results of data collected April through September, 2002. A more comprehensive analysis of data collected in past years is underway.

The goal of the assessment is to characterize the spatial and temporal extent of brown tide blooms caused by a minute alga, Aureococcus anophagefferens, at eleven water quality network stations in the coastal waters of New Jersey. The brown tide concentrations were evaluated using the Brown Tide Bloom Index (Gastrich & Wazniak, 2002) that relates concentrations of the brown tide organism, A. anophagefferens, to potential negative impacts on natural resources including shellfish, seagrasses and protozoa.

Highlights of 2002 Brown Tide Blooms

Preliminary spatial patterns from 2000-02 show that Aureococcus was detected at every coastal station monitored for three years. Aureococcus concentrations, mainly Category 2 and 3 blooms, which may have significant potential impacts on natural resources, specifically hard clams and eelgrass, were found in Raritan Bay, Barnegat Bay, Little Egg Harbor and south in Great Egg Inlet.

Results from monitoring stations from north to south are presented below. Figure 1 shows the one station monitored in northern Barnegat Bay (1635E) near the Toms River. While this station had a Category 1 brown tide bloom (< 3.5 X 10 cells ml-¹) (see legend below) on April 22, 2002, Aureococcus concentrations increased to a Category 2 bloom on May 20 (1.4 X 10⁵ cells ml-¹). By June 3, concentrations increased to a Category 3 bloom (242,000 cells ml-¹) with the highest concentration of 2.8 X 10⁵ cells ml-¹ on June 10. The 2002 brown tide concentrations were higher at this station than in 2001. Therefore, it will be important to monitor brown tide blooms at this station in the future to determine whether blooms are increasing in severity.

The highest concentrations of Aureococcus in monitored New Jersey coastal bays occurred over the last three years in stations in Little Egg Harbor. Figure 2 below shows the highest concentrations of brown tide in the southern Barnegat Bay and Little Egg Harbor for 2002. The concentrations in 2002 were similar to those at the same stations in 2000 and 2001. Category 2 bloom levels were already occurring in April at some stations (1651D, 1675, and 1719E) and concentrations at most stations increased to Category 2 and Category 3 blooms by May 20, which is early for the more severe blooms, which usually occur in June. Seven of the eleven stations monitored had Category 3 blooms on May 20 with concentrations ranging from 2.5 X 10⁵ to 8.5 X 10⁵ cells ml-¹. By June 3, all stations in Little Egg Harbor had Category 3 blooms with the highest concentration of 8.42 X 10⁵ ml-¹ on June 17 at Station 1719E. While Aureococcus concentrations were higher in Little Egg Harbor in June in 2000 and 2001 (>1.0 X 10⁶ cells ml-¹) than in 2002, the area has experienced Category 3 blooms for four consecutive years. Station 1703C, in Ship Bottom (Stafford TWP), located under the Rte. 72 bridge and causeway, had the highest Aureococcus concentrations of 1.56 X 10⁶ cells ml-¹ on June 20 while station 1719E in Beach Haven Terrace (Long Beach TWP) had the second highest concentration (1.2 X 10⁶ cells ml-¹) on June 26. While station 1820A, located north of Tuckerton in Little Egg Harbor TWP, experienced Category 3 blooms in 2001 and 2002 at concentrations similar to other Little Egg Harbor stations, this station had the highest recorded Aureococcus concentration in June 2000 at 2.2 X 10⁶ cells ml-¹.

Figure 3 below shows the highest concentrations of Aureococcus in Great Bay and in bays to the south. One station sampled at the mouth of the Little Egg Harbor Inlet (1824B) had a Category 1 bloom in April, which increased to a Category 2 bloom on May 20 but the concentration did not exceed 5.5 X 10⁴ cells ml-¹ (June 10) and dropped to < 3.7 X 10⁴ cells ml-¹ by July 24. While one station in Great Egg Inlet (2720B) was only monitored once on June 2002, it had low concentrations (Category 1) but in 2000 and 2001, this station had Category 2 blooms. Additional monitoring for brown tide should be conducted at this station and others further south.

These early findings not only warrant consideration of continued monitored at existing stations to track these blooms but also extended monitoring to Raritan Bay and other bays south of Great Bay during April through September.

Preliminary temporal patterns of brown tide blooms in 2002 show a similarity to previous years. Figure 4 shows the highest concentrations of Aureococcus at monitored stations from May through September, 2002, Category 1 concentrations (often < 35,000 cells ml-¹) during April increase to Category 2 blooms in May, and again, increase to Category 3 blooms in June. Generally, this increase in concentration occurs as the salinity increases to greater than 26 ppt. Higher salinities have been shown to be associated with brown tide blooms in other states. However, in 2002, some stations had Category 3 blooms earlier, in May, than in previous years. Aureococcus concentrations gradually decreased to Category 2 blooms in July and August. However, some stations in Little Egg Harbor show a secondary Category 3 bloom in September.

Figures 5, 6, and 7 show the annual change in concentrations of the brown tide blooms, caused by Aureococcus concentrations from May through September, at selected stations. Station 1703C had the highest concentrations of Aureococcus in 2002 and 2001 and Aureococcus concentrations are similar at other Little Egg Harbor stations. Stations are characterized by low concentrations (Category 1 blooms) in April that increase to Category 2 blooms in May and Category 3 blooms in June. Bloom concentrations usually drop sharply in July/August but this may vary and a secondary bloom may appear at some stations (e.g., 1703C in 2001) in September. Figure 7, Station 1824B, which is the southern reference point, shows much lower concentrations than the other stations. This is an area at the mouth of the Little Egg Harbor where there is substantial tidal action and influence. The lower concentrations in this area throughout the year (< 60,000 cells ml-¹) may result from increased flushing due to the tidal action mixing, which may not promote or sustain substantial blooms.

In conclusion, preliminary results show:
· Aureococcus concentrations were detected at every coastal station monitored over the last three years.
· Preliminary spatial patterns of brown tide blooms indicate that Category 3 blooms occurred every year for three years mainly June, and sometimes in May, in stations in Little Egg Harbor and southern Barnegat Bay. Category 2 blooms occurred over the same geographic area in Little Egg Harbor and throughout Barnegat Bay and other coastal bays including Raritan Bay and to the south in Great Egg Inlet.
· Preliminary temporal patterns of Aureococcus concentrations show an increase from background levels in April to Category 2 blooms in May to Category 3 blooms in June which may decrease in July and August; in some cases, secondary Category 3 blooms may occur in some stations in September; Category 2 blooms may occur for longer periods than Category 3 blooms which may contribute to increased environmental pressure on natural resources. Brown tide blooms increase during June when juvenile hard clam growth and new growth of seagrasses were reported, which may cause potentially harmful impacts to these natural resources that are already impacted by multiple stressors.
· Concentrations of brown tide in New Jersey coastal waters for the last three years (2000-2002) are high enough to contribute to significant potential impacts to shellfish and seagrasses in areas of Barnegat Bay and Little Egg Harbor.
· Other coastal bays may be at risk for brown tide blooms. Because brown tide blooms have recurred for the last three years in Barnegat Bay, Little Egg Harbor, Great Bay, and Great Egg Inlet, New Jersey (and occur further south in Maryland), additional monitoring for brown tides is needed in coastal waters farther south in New Jersey.

Recommendations for additional monitoring and studies include the following:
· Continue monitoring of Aureococcus concentrations at the 11 existing water quality network stations monitored for brown tide in 2000-2002 throughout the year (a similar recommendation was made by scientists and managers in the mid-Atlantic region at the Brown Tide Workshop in April 2001 at Monmouth University).
· Extend monitoring to additional water quality stations north in Raritan Bay and to water quality stations south from Great Bay.
· Continue to monitor water quality parameters associated with brown tide (e.g., salinity, temperature) and nutrients, especially dissolved organic nitrogen, and other environmental parameters simultaneously with brown tide counts at these stations.
· Assess and document impacts of brown tides on natural resources (e.g., hard clams, seagrasses) to identify potential harmful effects and to identify areas at risk.

A comprehensive report summarizing the results of the three year study and an assessment of potential environmental factors that may promote brown tide blooms, as well as geographic areas which may be at risk for blooms (e.g., seagrass habitats), is available.

For more information or to report a brown tide bloom, contact Dr. Mary Downes Gastrich, Brown Tide Assessment Project Manager, in the Division of Science, Research and Technology at (609) 292-1895 or email Mary.Downes-Gastrich@dep.state.nj.us.

Reference:
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 Ecosystem Health and
Management. Vol. 33, No. 2, pp. 175–190.

Figure 1. 2002 Brown Tide Assessment Project Stations: Brown Tide Bloom Index Results in Raritan Bay and Northern Barnegat Bay.

Figure 2. Brown Tide Assessment Project Stations 2002: Brown Tide Bloom Index Results in Southern Barnegat Bay and Little Egg Harbor.

Figure 3. 2002 Brown Tide Assessment Project Stations: Brown Tide Bloom Index Results in Little Egg Harbor South to Great Egg Inlet.

Figure 4. Highest concentrations of Aureococcus at New Jersey coastal stations during 2002.

Figure 5. 2002 Brown tide concentrations at the northern reference point station in Barnegat Bay at Seaside Park (1635E).

Figure 6. 2002 Brown Tide Concentrations at the Ship Bottom station (1703C) in Little Egg Harbor near the Route 72 Causeway Bridge to Long Beach Island.

Figure 7. 2002 Brown Tide Concentrations at the southern reference point station (1824B) at the mouth of Little Egg Harbor.

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