Pang, H.; Ingelido, P.; Hirst, B.; Pflaumer, J.; Witt, A.; Zaman, A., and Aiello, J., 2017. Water quality condition and assessment within the Barnegat Bay watershed between 2011 and 2015. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay–Little Egg Harbor, New Jersey.
To address the ecological health of Barnegat Bay in New Jersey, a comprehensive water monitoring program has been conducted within the Barnegat Bay watershed by the New Jersey Department of Environmental Protection and multiple partners since June 2011. Barnegat Bay and its tributaries were evaluated for multiple water quality metrics and from various perspectives. The nutrient concentrations and loadings from the tributaries in the northern watershed are higher than those from the tributaries in the southern portion of the watershed. Within Barnegat Bay, higher nitrogen concentrations were observed in the northern portion, while higher total phosphorus (TP) concentrations occurred in the southern portion. Daily variability of water quality at certain locations was observed from the results of intensive sampling events (six samples per day over 4 consecutive days of sampling). Analysis of multiple years of data suggests that water quality has not varied significantly year to year from 2011 to 2015. Violation of the existing applicable numeric criterion was identified for dissolved oxygen, TP, and turbidity within some assessment units in Barnegat Bay and its watershed. A comparison made between these data and the targets used by other estuaries in the NE United States related to nutrient criteria found that portions of the bay would not achieve the water quality thresholds used by these other estuaries.
The 660-mi2 (1709-km2) Barnegat Bay watershed encompasses most of the 33 municipalities in Ocean County, New Jersey, and four municipalities in Monmouth County, New Jersey. Barnegat Bay has long been appreciated for its great aesthetic, economic, and recreational value. It supports wetlands and aquatic vegetation, shellfish beds, finfish habitats, waterfowl nesting grounds, and spectacular vistas. The land draining to Barnegat Bay has a population of more than 550,000, which increases significantly during the summer season (U.S. Census Bureau, 2012).
The entire watershed has undergone dramatic growth since 1950, resulting in land use shifting from primarily forest, wetlands, and agriculture to various forms of suburban development. This change in land use has affected the quality and quantity of storm water runoff and has modified habitats (Barnegat Bay Partnership, 2016). There has also been increased human use in the form of swimming, boating, and harvesting of fish and shellfish. In addition, the Oyster Creek nuclear-generating facility cooling water system, which commenced operation in 1969, affects bay resources through entrainment and impingement of aquatic organisms at the intake and as the result of thermal modification from the discharge of water used for cooling.
There has been growing concern about the ecological health of Barnegat Bay based on observed loss of seagrasses such as eelgrass and widgeon grass, collectively called submerged aquatic vegetation (Haag et al., 2014; Kennish et al., 2007; Kennish, Sakowicz, and Fertig, 2016; Lathrop and Haag, 2010); episodic blooms of macroalgae and brown tides (Kennish, Fertig, and Sakowicz, 2011; Pecchioli, Lathrop, and Haag, 2006); decline of hard clams (Bricelj, Kraeuter, and Flimlin, 2012); and increasing numbers of invasive species such as sea nettles (Bologna and Gaynor, 2013). The full suite of stressors and biological, chemical, and physical processes responsible for these observations is not entirely known. A multifaceted study of Barnegat Bay to understand these stressors and develop action strategies to address them is under way. The development of appropriate water quality criteria and targets is an essential step in the restoration and protection of Barnegat Bay.
On December 21, 2010, the New Jersey Department of Environmental Protection (NJDEP) took initial steps toward developing water quality criteria through the adoption of narrative nutrient criteria for coastal waters (NJDEP, 2011). However, development of numeric translators for narrative nutrient criteria has not yet been completed. To develop the numeric translators for narrative criteria and to determine whether the existing numeric criteria are protective of designated uses in the unique setting of Barnegat Bay requires a better understanding of the complex chemical, physical, and biological processes that define the water quality in the bay.
To advance this objective, NJDEP engaged multiple partners to carry out a comprehensive water monitoring project. More than 10,000 water samples have been collected since June 2011 within the Barnegat Bay watershed. The study was designed to determine the locations and extent of water quality impairments and to calibrate and validate modeling tools that define the relationship between pollutant loads and water quality. This information will then be used, in combination with the findings of ecological research, to determine water quality thresholds, which are key to supporting the health of the various plant and animal communities that are the basis of a healthy ecology.
In June 2011, a comprehensive ambient monitoring program was launched by the NJDEP and its partners that measured both water quality and water quantity within Barnegat Bay and along the major tributaries within the watershed (NJDEP, 2011). There are two phases of the ongoing monitoring program. During Phase 1 (June 2011 to June 2013), water quality concentration was measured in 12 major tributaries and at 14 locations throughout the bay; both surface (i.e. 1 ft below the surface) and bottom (i.e. 1 ft above the bottom sediment) samples were collected from the in-bay stations. Frequency of sampling varied seasonally. Samples were collected once per week in the growing season (May–September) and twice a month in the nongrowing season. Water flow into the bay from tributaries was measured through a combination of discrete measurements and continuous flow gauges. Continuous flow was also collected at three locations within Barnegat Bay and at the three inlets from the Atlantic Ocean. Continuous water quality was collected using buoys at select locations, and intensive sampling events were conducted in the summer seasons. During intensive sampling events, six samples were taken per day (from 05:00 to 20:00, roughly one sample every 2–3 hours) for 4 consecutive days. The continuous and intensive monitoring components complemented the discrete sampling by capturing the full range of daily, tidal, and seasonal variations. Phase 1 data were primarily used to construct and calibrate a hydrodynamic and water quality model of the estuarine system.
During Phase 2 (July 2013 to present), sample location and frequency changed. The Phase 2 monitoring focused on water quality to document the change in condition over time. The stations where the water quality samples were collected are shown in Figure 1. Data used in the analysis provided in this paper are summarized in Table 1. A more complete description of the monitoring program can be found at NJDEP (2011).
The data collected through both Phase 1 and Phase 2 were used to perform three distinct analyses. First, a comprehensive evaluation was conducted to understand the current water quality conditions both in the watershed's freshwater tributaries and within Barnegat Bay. Analysis of both water quality and flow data were performed for tributary stations and used to calculate the load from the watershed to the bay. The evaluation of the conditions within the bay was focused on water quality. The analysis was performed on select parameters of interest—total nitrogen (TN), total phosphorus (TP), chlorophyll-a (Chl-a), and dissolved oxygen (DO)—and included the evaluation of concentration, load, and daily and seasonal variability. The data from the intensive sample events conducted in July and August 2012 were evaluated to determine daily variability. Year-to-year comparisons were made at stations where at least 4 years of data are available from 2011 to 2015.
Second, data collected were used to assess Barnegat Bay and its watershed by comparing the data to the applicable existing numeric water quality criterion. This assessment was performed on select parameters of interest (DO, TP, and turbidity), and followed the methods used in NJDEP's statewide assessment method (Division of Water Monitoring and Standards Staff, 2015). These three parameters were selected because they are associated with the support of aquatic life.
Data collected within defined assessment units (AUs) were used to determine existing water quality relative to established water quality standards. The Hydrologic Unit Code 14 subwatersheds have been used to delineate AUs throughout the State of New Jersey. New AUs were developed for the open waters of Barnegat Bay after evaluating the hydrological, chemical, and biological features based on the recent monitoring program (Division of Water Monitoring and Standards Staff, 2015) and ongoing model simulations completed to date (Defne and Ganju, 2014; DePaul and Spitz, 2014). Figure 2 illustrates the boundaries of the AUs used in assessment of the Barnegat Bay watershed. The numeric criteria for the parameters of interest within Barnegat Bay and its tributaries are summarized in Table 1.
Lastly, given that there are no numeric nutrient criteria applicable to Barnegat Bay, a comparative assessment was performed between Barnegat Bay data and numeric targets and standards that are used in other NE states, including New Hampshire, Delaware, Maryland, Massachusetts, and New York (Division of Water Monitoring and Standards Staff, 2014).
The results are presented in three sections: water quality condition, water quality criteria assessment, and comparative assessment.
Water Quality Condition
Flow, Loading, and Nutrient Concentration at the Tributary Boundaries
Average freshwater flow into Barnegat Bay (June 2011 to June 2013) from the 12 monitored tributary stations (Figure 1) was approximately 630 cubic feet per second (cfs). About one-third of the freshwater flow into Barnegat Bay from the tributaries was contributed by the north branch of Toms River (station BT03, 214.3 cfs). Cedar Creek (BT06) had the second-highest mean flow (87.3 cfs). The two branches of Metedeconk River (BT01 and BT02) combined provided 120 cfs of freshwater into the bay. The flow from each of the three southernmost tributaries ranged from 30 to 40 cfs, and the tributaries in the central portion of the watershed contributed 10 to 20 cfs individually.
The mean TN concentration in the watershed ranged from 0.17 to 1.2 mg/L (Figure 3), with the higher concentrations occurring in the four northernmost tributary stations (BT01–BT04) and lower concentrations occurring in the southern tributary stations. The highest mean TN concentration of 1.2 mg/L was at the north branch of Metedeconk River near Laurelton (BT01). The second-highest concentration of 1.0 mg/L was at Toms River near Toms River (BT03). The south branch of Metedeconk River near Laurelton (BT02) and Wrangle Brook (BT04) had similar mean TN concentrations of about 0.8 mg/L. Mean concentration at the southern tributary stations was about one-third of the concentrations at the northern stations, with one exception at Mill Creek at Manahawkin (BT11). The mean concentration at BT11 was 0.56 mg/L. For all stations, more than 90% of the nitrogen was in the dissolved phase. Dissolved inorganic nitrogen consisted of about three-quarters of dissolved nitrogen at the northernmost four stations (BT01–BT04).
Mean TP concentration in tributaries has the same distribution as mean TN concentration: higher in the north and lower in the south (Figure 3). The highest mean TP concentration was observed again at BT01 (0.055 mg/L). The second-highest mean TP concentration was at BT05 (less than 0.03 mg/L). The other three northern tributaries had a mean concentration of around 0.02 mg/L. Five tributaries in the southern watershed had a mean TP concentration of less than 0.01 mg/L. Dissolved phosphorus was the primary form of phosphorus at the seven stations with relatively lower TP concentration. Ortho-P concentration was about half of the dissolved phosphorus concentration at 10 of 12 stations.
The sum of loading from all 12 tributaries is about 392,000 kg of TN and 10,000 kg of TP per year (Figure 3). With the highest flow and nutrient concentrations, the north branch of Toms River (BT03) provided the highest load of both TN and TP entering the bay. With respect to TN loading, 44% was from BT03, and the other three northern stations (BT01, BT02, and BT04) contributed 36%. Loading from the middle and southern tributaries contributed 20% of the summed loading. Compared to the relative TN loading, the TP contribution of BT03 to the summed TP loading was a little lower, 34% compared to 44%. But the combined TP loading from the four northern tributary stations contributes 78% of the total TP loading, similar to the finding for TN loading.
Using the annual TN load of 392,000 kg and TP load of 10,000 kg, with the total average tributary flow of 630 cfs, the flow-weighted average TN concentration is 0.697 mg/L and the flow-weighted average TP concentration is 0.018 mg/L.
Water Quality Condition within Barnegat Bay
Most of the bay is polyhaline, with salinity between 18 and 30 ppt. The southern portion of the bay has higher salinity than the northern portion of the bay. The portion of the bay where Toms River enters (BB04a) is mesohaline, with salinity lower than 18 ppt, 90% of the time, because of the large amount of freshwater entering at this location. Salinity near the inlets (BB08 Barnegat Inlet and BB14 Little Egg Harbor Inlet) are similar to the level usually seen in the ocean (about 30 ppt). Ocean water entering the bay via Barnegat Inlet affects the bay salinity below Oyster Creek, where stations BB07 and BB07a are located. Salinity measurements from both surface and bottom samples were examined. There was no significant difference between surface and bottom salinity at all stations except BB04a, the station near the mouth of Toms River. At station BB04a, the mean salinity was 13.5 ppt at the surface and 19 ppt at the bottom. There was no overlap between the 25th and the 75th quantiles of salinity readings from the surface and the bottom samples at this station.
The northern portion of the bay has higher TN concentrations than does the southern portion of the bay (Figure 4). The highest mean TN concentration, 0.64 mg/L, was seen at BB04a, where Toms River enters the bay, corresponding to the high TN loading from Toms River. Concentrations in the range of 0.4 to 0.5 mg/L were shown at the stations within Bay Head Harbor and Metedeconk Estuary and Harbor. Concentrations at the southern portion, from Manahawkin Bay to Little Egg Harbor Bay, ranged from 0.2 to 0.3 mg/L.
The distribution of TP concentration within the bay was opposite of the TN concentration distribution, with the higher concentration in the southern portion of the bay and relatively lower concentration in the northern part of the bay. The highest TP concentration is at station BB11a, with a value of 0.064 mg/L. The mean TP concentrations at the southernmost stations are all around 0.05 mg/L, while Point Pleasant Canal (BB00) is the only station in the northern portion of the bay that had a mean concentration of 0.05 mg/L.
The highest mean Chl-a concentration, 10 μg/L, was seen at BB04a, while BB07a had the second-highest Chl-a concentration (9.3 μg/L). These two stations also had the top 2 mean TN concentrations in the same order. Relatively high Chl-a concentration, above 20 μg/L, was observed at various locations, with the highest concentration of 37 μg/L seen at BB04a.
Noting that the top two mean Chl-a and TN concentrations occurred at the same two stations, a plot was made for the mean TN concentration vs. the mean Chl-a concentration. A positive correlation was found between these two parameters with a R-square value of 0.77 (see Figure 10 later).
During intensive sampling events, six samples were collected each day to test for variability in the course of a day. Daily patterns were detected at some locations for some parameters and were absent at others.
During the August 2012 intensive sampling event, a daily pattern of DO concentration was found at station BB07a. In the surface layer, the DO concentration peaked in the late afternoon or early evening, while in the bottom layer, the DO decreased from morning to the afternoon (Figure 5). The average daily swing of DO concentration over the 4-day sampling period was 4 mg/L. Between the surface and the bottom layer, a difference in turbidity and Chl-a was not evident. Low DO concentration (less than 4 mg/L) was observed at 9 of 24 samples in the bottom layer.
Also during the August 2012 intensive sampling event, differences between the surface and the bottom layers were observed for DO, salinity, turbidity, and temperature at station BB04a. In the surface layer, a Chl-a concentration of 43 μg/L was collected simultaneously with a DO concentration of 9.76 mg/L during the first day of the event. The bottom layer DO was lower than that of the surface, with 5 of 24 readings less than 4 mg/L.
At BB12, the water column was generally well mixed. DO, salinity, and Chl-a in surface and bottom layers were almost identical. The change in DO concentration over the course of the day was relatively small, with one exception on day 2 of the August 2012 intensive sampling event, compared to the swing of DO observed at the other two stations.
At 7 of 10 in-bay stations, annual mean TN concentration was highest in 2015. At two stations (BB09 and BB12), 2015 mean TN concentration was the second highest, exceeded only by the mean concentration in 2011 (0.48 vs. 0.47 mg/L at BB09 and 0.5 vs. 0.43 mg/L at BB10). Three in-bay stations' mean TN concentrations are presented in Figure 6, which were selected as representative stations from north to south. The mean concentration of BB04a was relatively stable, yet the distribution of the concentration varied by year, with the widest range in 2013. For different stations, the highest annual mean TP concentration occurred at different years from 2011 to 2014, but none of them was observed in 2015. The mean concentration of Chl-a at eight of nine stations was higher in 2015 than in 2014 but lower than in the period from 2011 to 2013.
The TN concentration at the tributary stations showed a mixed trend over the years. One-third of the stations showed an increased mean concentration in 2015, one-third showed a decreased concentration in 2015, and the rest showed no variability throughout the years. Three tributary stations were chosen to represent the condition spatially (Figure 7). Mean TN concentration at BT01 was in a slightly upward trend from 2011 to 2015, with the highest mean concentration of 1.37 mg/L in 2015. At BT03, mean TN concentration in 2015 was again the highest, and the mean concentrations in 2012 to 2014 were nearly the same. At BT11, mean TN concentration reached the highest in 2014, dropping slightly in 2015, but the differences among the 5 years of means were small. Mean TP concentrations were lower in 2015 at 9 of 14 tributary stations.
Water Quality Criteria Assessment
Several AUs did not attain the applicable numeric water quality criteria for DO, turbidity, and TP (Figure 8). Eleven AUs violated the DO criteria: three AUs in the bay and eight AUs in the tributaries. DO levels at BB04a and BB07a during the intensive sampling event resulted in the determination of DO impairment in Barnegat Bay AUs 4 and 5, respectively. The 30-day average turbidity criterion was violated in three in-bay AUs: Barnegat Bay 3, 8, and 9. There is no TP criterion applicable to estuarine water. Violation of the freshwater TP criteria occurred in three tributary AUs.
There is no numeric translator for nutrient criterion applicable for Barnegat Bay. To illustrate the condition of Barnegat Bay, data in each AU was compared to the range of values considered adequate to support a healthy estuarine ecosystem in estuary systems elsewhere in the NE (Tables 2 and 3). The Barnegat Bay results relative to the thresholds set by other studies are presented using the station with the best water quality and the worst water quality, relatively speaking, in each AU. The parameters that are presented later are DO, DO saturation, total suspended solids (TSS) or clarity, Chl-a, and TN.
Barnegat Bay AUs 1, 4, 5, 8, and 9 would be the AUs that don't achieve the target when using an instantaneous DO concentration greater than or equal to 5 mg/L as the threshold (Table 2). When using an annual average DO concentration greater than or equal to 6 mg/L, all AUs meet the threshold. When considering the 30-day average of DO greater than or equal to 5 mg/L, five bay AUs extending from Toms Estuary in the north and to Manahawkin Bay and Upper Little Egg Harbor in the south would not achieve the target.
Delaware Inland Bay (Watershed Assessment Section Staff, 1998) required the 75th percentile of TSS during the growing season to be less than or equal to 20 mg/L. Except for two stations located within Metedeconk Bay and its lower tributaries, all other stations would fail to meet that threshold (Table 3).
In Massachusetts's Back Bays (Division of Water Monitoring and Standards Staff, 2014), the habitat quality was considered healthy when the mean Chl-a concentration is less than 5 μg/L. In Great Bay (Throwbridge, 2009), the 90th percentile Chl-a concentration goal was less than or equal to 10 μg/L, while in Delaware's Inland Bays (Watershed Assessment Section Staff, 1998), the 90th percentile of Chl-a concentration was required to be less than 20 μg/L. As shown in Figure 9a,b, there were four stations with a mean Chl-a higher than 10 μg/L and two stations with a 90th percentile higher than 20 μg/L. Toms Estuary (Barnegat Bay 4) is the one with the highest Chl-a concentration, both the mean and the 90th percentile value. Metedeconk Estuary and Bay (Barnegat Bay 2 and 3) contained three stations that had Chl-a above the threshold (Figure 9a,b).
In Great Bay (Throwbridge, 2009), the target is an annual median TN concentration less than or equal to 0.45 mg/L to protect the DO concentration and an annual median TN concentration less than or equal to 0.25 to 0.30 mg/L for the protection of eelgrass habitat. When evaluating the median TN concentration in Barnegat Bay (Figure 9c), four AUs would exceed the 0.45 mg/L median concentration, specifically the three northernmost AUs plus Barnegat Bay 8 (Manahawkin Bay and Upper Little Egg Harbor). If the median concentration of the 0.25 mg/L target is considered, all eight AUs would exceed the target where data were available.
Besides DO concentration, DO saturation is used as an indicator to examine the water quality support of aquatic life. In Great Bay (Throwbridge, 2009), a daily mean DO saturation greater than 75% is required but a daily mean DO saturation of less than 75% occurred at all stations sampled in Barnegat Bay (Figure 9d), with the greatest deviation from the target occurring at stations in Barnegat Bay AUs 3, 4, 5, and 8.
The nutrient loadings based on the observed water quality at tributary stations are lower than the annual TN (ranging from 455,000 to 857,000 kg) and TP loading (ranging from 17,000 to 32,000 kg) estimated by the U.S. Geological Survey (USGS; Baker et al., 2014). The 12 monitored tributary stations are all located above the head of tide, and the drainage shed of these tributaries encompasses about 70% of the entire Barnegat Bay watershed. A portion of the watershed is below the head of tide, as are a few smaller tributaries that are not accounted for in the tributary loading estimates based on monitoring, which is the primary reason for the difference compared to the USGS land use–based loading estimate. While the actual magnitude differs between the two methods of estimation, in both cases, the higher nutrient concentration and the higher loading occur in the northern portion of the watershed. This is believed to be associated with the greater land area, as well as magnitude and density of development in the northern portion of the watershed.
Mean concentration of TN at the southern tributary stations was about one-third of the concentrations at the northern stations, with one exception at Mill Creek at Manahawkin (BT11). This anomaly may be because of a localized impact from a landfill located upstream of the station (Wieben, Baker, and Nicholson, 2013). Dissolved inorganic nitrogen consisted of about three-quarters of dissolved nitrogen at the northernmost four stations (BT01 to BT04). Given that dissolved inorganic nitrogen is the highly bioavailable format, nitrogen loading from these two major tributaries can have a significant impact on the productivity within the bay.
The relative higher TP concentration observed in the southern part of the bay is inconsistent with the finding that there are higher TP loadings contributed by the northern tributaries. This suggests a source of load in the southern portion of the bay that is not captured by the tributary monitoring. One possibility is that sediment in the southern portion of the bay could be contributing phosphorus into the water column. However, a sediment study concluded that the sediment in the southern part of the bay acts as a sink, not a source, of the phosphorus in the water column (Velinsky, Weston, and Paudel, 2015). Another possibility may be the extensive wetlands adjacent to the bay in the southern portion of the bay, which would be below the point of tributary monitoring. Nutrients from seawater related to the upwelling could also be the possible source of phosphorus. The reason the southern portion of the bay has a higher TP concentration compared to the northern bay while the estimate of loading from the southern tributaries is lower than from the northern tributaries requires further study.
Noting that the top 2 mean Chl-a and TN concentrations occurred at the same two stations, a plot was made for the mean TN concentration vs. the mean Chl-a concentration. A positive correlation was found between these two parameters with a R-square value of 0.77 (Figure 10). This indicates that TN concentration has an impact on the level of productivity within the bay. A log-log relationship between nutrients and Chl-a was also examined. The associated R-square value is 0.68, lower than the linear correlation.
It was previously thought that because of its shallow depth, the bay would be well mixed throughout the water column. The data from the intensive sampling events show that the degree of mixing depended on the location and is likely influenced by factors that vary over time, such as temperature and wind. At BB04a and BB07a, certain parameters were distinctly different in samples taken from the surface compared to those taken from the bottom. The low DO concentration found in the bottom layer at BB04a and BB07a during the August 2012 intensive sampling event caused the listing of DO as an impairment for the associated AUs. The degree of difference between the surface and the bottom layers at the same two stations during the July 2012 intensive sampling event was less significant. Station BB12 was observed to be well mixed at both the July 2012 and the August 2012 intensive sampling events. The significant difference between surface and bottom at BB04a could also be related to the impact of the freshwater entering the bay before it is fully mixed with the bay water.
Comparing multiple years of data, the observed changes in TN concentration didn't synchronize with the observed changes in TP at the same station. Annual mean TN concentration was the highest in 2015 at 7 of 10 in-bay stations, while the highest annual mean TP concentration didn't occur in 2015 at any of these 10 stations. The concentration at each tributary station will reflect the land-based activities that result in deposition of nutrients that are then washed into the waterbodies. One factor may be the implementation of the new fertilizer law, which became effective January 5, 2013 (NJDEP, 2013).
Reviewing the assessment results of the data compared to existing criteria, Barnegat Bay 4 (Toms Estuary) would be found to be an area of concern. AUs in the northern part of the bay fail to achieve the targets set for other estuaries more frequently than the AUs in the southern portion of the bay. Even though the violation of existing DO criteria was identified for Barnegat Bay 9, it may be related to an ocean upwelling event. During an upwelling, the nutrient-rich bottom water comes to the surface and is then carried into the inlet and surrounding area. Barnegat Bay 8 (Upper Little Egg Harbor) is the primary area of concern in the southern portion of the bay. These results indicate that it may be appropriate to develop different pollutant reduction strategies for the different portions of the bay. The ongoing USGS/NJDEP modeling will be the key to determine how loadings from various sources affect water quality in different parts of the bay.
While it is not possible to draw definitive conclusions for Barnegat Bay based on this comparison because of important differences among these estuaries, it is useful to get a general sense of the condition of Barnegat Bay relative to the range of targets identified for other estuaries. Even though New Jersey has a numeric criterion for DO, this criterion may need to be revised to reflect a level that would be consistent with supporting a healthy ecosystem that would be indigenous to Barnegat Bay.
As seen in other estuarine programs, water quality targets were established in terms of parameters that affect productivity or respond to productivity. There is variability in the metrics considered, how the metrics are measured, and the value selected as the threshold for impairment. This emphasizes the importance of determining the correct metrics to protect ecological health specifically in Barnegat Bay, considering its unique physical, chemical, and biological characteristics. Some research project findings have shown promising results, linking the water quality condition within Barnegat Bay with the health of benthic macroinvertebrate-sensitive species (Taghon et al., 2016). Data collected from other trophic levels of the ecological community (Ren and Belton, 2016) are also under review to determine whether it is possible to identify the water quality level appropriate for other aspects of a healthy community. A key objective of the monitoring, modeling, and other research is to identify the numeric water quality criteria that will support the ecological health of the bay and then identify management strategies that can achieve those water quality criteria. Such strategies would complement management strategies that address use-related stressors to achieve the overall objective of restoring Barnegat Bay.
The Barnegat Bay watershed monitoring conducted by NJDEP since 2011 is a comprehensive program that provides data needed to make a thorough evaluation of the water quality condition within the bay and its tributaries. The northern portion of the watershed contributes a significant amount to nutrient loading into the bay. There is variability of water quality within the bay, spatially and temporally. Assessing the water quality condition with both existing water quality criteria and targets used by other estuarine programs indicates that in some areas of the bay, the current water quality condition cannot fully support the designated use and ecological health of the bay. This highlights the need for appropriate site-specific water quality targets for Barnegat Bay that translate narrative nutrient criteria so as to direct restoration efforts. A greater understanding of the water quality condition and what nutrient and other loadings can be assimilated is needed and is expected to be forthcoming from the findings of ecological research projects and the construction or simulation of the dynamic model developed for Barnegat Bay.
We thank Kim Cenno, Jill Lipoti, Jeff Reading, Leslie McGeorge, and Bruce Freidman of the NJDEP for their support of this effort. We also thank the Bureau of Freshwater Biological Monitoring and Bureau of Marine Water Monitoring, especially Chris Kunz and Bob Schuster, for their support of the monitoring program. In addition, we extend our gratitude to all of our partners, without whom the monitoring project would not have been possible. We also thank Debbie Kratzer of NJDEP for editorial assistance, Tonia Wu of NJDEP for the literature search, and Leigh Lager of NJDEP for GIS analysis. Lastly, we are appreciative of the reviewers for their constructive comments.