Barnegat Bay-Little Egg Harbor Research Articles

Simulated Estuary-Wide Response of Seagrass (Zostera marina) to Future Scenarios of Temperature and Sea Level

Seagrass communities are a vital component of estuarine ecosystems, but are threatened by projected sea level rise (SLR) and temperature increases with climate change. To understand these potential effects, we developed a spatially explicit model that represents seagrass (Zostera marina) habitat and estuary-wide productivity for Barnegat Bay-Little Egg Harbor (BB-LEH) in New Jersey, USA. Our modeling approach included an offline coupling of a numerical seagrass biomass model with the spatially variable environmental conditions from a hydrodynamic model to calculate above and belowground biomass at each grid cell of the hydrodynamic model domain. Once calibrated to represent present day seagrass habitat and estuary-wide annual productivity, we applied combinations of increasing air temperature and sea level following regionally specific climate change projections, enabling analysis of the individual and combined impacts of these variables on seagrass biomass and spatial coverage. Under the SLR scenarios, the current model domain boundaries were maintained, as the land surrounding BB-LEH is unlikely to shift significantly in the future. SLR caused habitat extent to decrease dramatically, pushing seagrass beds towards the coastline with increasing depth, with a 100% loss of habitat by the maximum SLR scenario. The dramatic loss of seagrass habitat under SLR was in part due to the assumption that surrounding land would not be inundated, as the model did not allow for habitat expansion outside the current boundaries of the bay. Temperature increases slightly elevated the rate of summer die-off and decreased habitat area only under the highest temperature increase scenarios. In combined scenarios, the effects of SLR far outweighed the effects of temperature increase. Sensitivity analysis of the model revealed the greatest sensitivity to changes in parameters affecting light limitation and seagrass mortality, but no sensitivity to changes in nutrient limitation constants. The high vulnerability of seagrass in the bay to SLR exceeded that demonstrated for other systems, highlighting the importance of site- and region-specific assessments of estuaries under climate change.

Live-Dead Mismatch of Molluscan Assemblages Indicates Disturbance from Anthropogenic Eutrophication in the Barnegat Bay-Little Egg Harbor Estuary

Previous research combining data on the abundance of benthic invertebrates living in the northernmost section of the Barnegat Bay-Little Egg Harbor estuary with data on water quality suggested a community composition consistent with anthropogenic eutrophication. This part of the estuary, however, experiences both high-nutrient and low-salinity environmental conditions, which are both ecologically stressful to sensitive species and favorable to opportunistic species, complicating assessments of the direct effects of anthropogenic eutrophication. Here, geohistorical baselines were derived from molluscan death assemblages from four localities along a north-south gradient in the bay—two northern low-salinity, high-nutrient sites and two southern high-salinity, low-nutrient sites—to disentangle the effects of salinity and nutrient enrichment on the composition of benthic communities. Disturbance in the northern section of the estuary from freshwater input has been relatively consistent for thousands of years, but nutrient enrichment is a more recent stressor, developing only in the past few decades. The cause of the disturbed benthic community is unlikely to be anthropogenic eutrophication, if there is little discordance between the living and the death assemblage in the northern, low-salinity section of the bay. Comparisons of rank-order abundance (Spearman's rho) and taxonomic similarity (Jaccard-Chao index) of the living and death assemblages along the north-south gradient, however, indicate that compositional shifts occur at the northern sites only. A multivariate index analysis, M-AMBI, which integrates the AZTI Marine Biotic Index, a biotic index based on species sensitivity/tolerance to disturbances, with Shannon diversity and species richness, shows a similar pattern: ecological status shifts (from undisturbed to disturbed) in the northern but not southern sites along the north-south salinity gradient. These independent lines of evidence corroborate the inference that it is most likely anthropogenic eutrophication (and not salinity) disturbance driving observed patterns in benthic community composition. Further sampling and incorporation of geohistorical data into ongoing benthic monitoring in the estuary is recommended to establish ecological baselines where none exist, guide restoration planning, and assess the success of restoration efforts.

Phytoplankton Index of Biotic Integrity and Reference Communities for Barnegat Bay–Little Egg Harbor, New Jersey: A Pilot Study

ABSTRACT Ren, L.; Belton, T.J.; Schuster, R., and Enache, M., 2017. Phytoplankton index of biotic integrity and reference communities for Barnegat Bay–Little Egg Harbor, New Jersey: A pilot study. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay–Little Egg Harbor, New Jersey. A pilot study was carried out to quantify season-salinity-specific phytoplankton reference communities and to develop a phytoplankton index of biotic integrity (P-IBI) for Barnegat Bay–Little Egg Harbor (BB-LEH) estuary, using approaches similar to those for the Chesapeake Bay. Synchronized phytoplankton and water-quality data collected between August 2011 and August 2013 from the Barnegat Bay Water Quality Monitoring Program were used as calibration data set. The results showed that one-fifth of samples were from the least-impaired habitat condition, with low turbidity and low concentrations of dissolved inorganic nitrogen and orthophosphate (PO4). Nearly 60% of samples were from un...

Status and Trends of Hard Clam, Mercenaria mercenaria, Populations in a Coastal Lagoon Ecosystem, Barnegat Bay–Little Egg Harbor, New Jersey

ABSTRACT Bricelj, V.M.; Kraeuter, J.N., and Flimlin, G., 2017. Status and trends of hard clam, Mercenaria mercenaria, populations in a coastal lagoon ecosystem, Barnegat Bay–Little Egg Harbor, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay–Little Egg Harbor, New Jersey. This review examines the historical and current status of hard clam, Mercenaria mercenaria, populations in the Barnegat Bay–Little Egg Harbor (BB-LEH) Estuary using New Jersey State stock assessments and published studies and evaluates their potential for rehabilitation under present environmental conditions. This estuary has experienced increasing urbanization, population growth, bulkheading, and changes in watershed use. Clam populations have decreased markedly since the 1960s, and in LEH, substantial areas are now devoid of clams. Landings of wild-caught hard clams, and commercial and recreational clam licenses have all declined. There is no evidence that eutrophication an...

The Comprehensive Barnegat Bay Research Program

Abstract Buchanan, G.A.; Belton, T.J., and Paudel, B., 2017. The Comprehensive Barnegat Bay Research Program. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. A comprehensive ecosystem research strategy was developed and initiated for the Barnegat Bay-Little Egg Harbor (BB-LEH) estuary in New Jersey, United States. This multiyear program (2011–15) examined several environmental management issues and questions involving concerns with water quality (e.g., nutrients) and the health of this ecosystem (e.g., eutrophication). Multiple projects ranging from the assessment of phytoplankton to fish to wetlands, as well as hydrodynamic/water quality and ecosystem modeling, were conducted each year to fill in critical data gaps and to define the bay's baseline condition for future comparisons (e.g., a nuclear generating station on the bay with a once-through cooling system will close in 2019). Issues of concern for environmental agenci...

Phytoplankton Community Structure Based on Photopigment Markers in a Mid-Atlantic U.S. Coastal Lagoon: Significance for Hard-Clam Production

ABSTRACT Fantasia, R.L.; Bricelj, V.M., and Ren, L., 2017. Phytoplankton community structure based on photopigment markers in a mid-Atlantic U.S. coastal lagoon: Significance for hard-clam production. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. Phytoplankton community structure at four contrasting sites in the Barnegat Bay-Little Egg Harbor (BB-LEH) Estuary was determined microscopically and by photopigment-CHEMTAX analysis. It was related to temperature, salinity, and weekly growth rates of juvenile hard clams, Mercenaria mercenaria, deployed at these sites during the summer in 2012 and 2013, pre- and post-Hurricane Sandy. Results indicated distinct differences in phytoplankton composition among sites, with a greater contribution of chlorophytes and cyanobacteria at the northernmost site, Island Beach State Park (IBSP). Photopigment analysis was useful in improving upon the taxonomic assessment of pico-coccoid (<3 μm) ...

In Situ Benthic Nutrient Flux and Sediment Oxygen Demand in Barnegat Bay, New Jersey

Wilson, T. and DePaul, V., 2017. In situ benthic nutrient flux and sediment oxygen demand in Barnegat Bay, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey.The U.S. Geological Survey, in cooperation with the New Jersey Department of Environmental Protection, measured sediment oxygen demand (SOD) and benthic nutrient fluxes throughout Barnegat Bay, New Jersey. SOD was determined in situ using chambers equipped with optical dissolved oxygen sensors. The benthic nutrient fluxes of ammonia (NH3), nitrite nitrate ( plus ions; here, referred to as NO32), soluble reactive phosphorous (SRP), and dissolved silica (SiO2) were measured with in situ equilibrium dialysis samplers. Measurements were made at nine stations around the periphery and at three mid-Bay locations from August 2012 to October 2013. The SOD ranged from −1.5 to −8.4 g of oxygen (O2) m−2 d−1. The SOD rates varied as a function of water temperature and followed the van't Hoff rate equation for change in reaction rate with temperature, with a temperature coefficient (Θ) that varied among sites and averaged 1.083. The highest SOD rates in the bay were measured near the mouth of the Toms River embayment. Concentrations in the upper 1 m of sediment pore water were found up to 23 mg N L−1 for NH4 and 6.7 mg P L−1 for SRP. Maximum measured fluxes into the overlying water were 3.0 × 10−2 g NH3–N m−2 d−1, 7.0 × 10−4 g NO32–N m−2 d−1, 1.9 × 10−3 g P m−2 d−1, and 3.6 × 10−3g SiO2 m−2 d−1. Using the measured benthic N and P fluxes, daily nutrient inputs derived from sediment recycling are shown to be comparable in scale to freshwater tributary inputs to the bay.

Salt Marsh Denitrification Provides a Significant Nitrogen Sink in Barnegat Bay, New Jersey

ABSTRACT Velinsky, D.J.; Paudel, B.; Quirk, T.; Piehler, M., and Smyth, A., 2017. Salt marsh denitrification provides a significant nitrogen sink in Barnegat Bay, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. Denitrification in salt marshes can be an important removal mechanism for inorganic nitrogen, particularly in coastal estuaries subject to high nutrient loading and eutrophication. Barnegat Bay, New Jersey has had high nutrient loading in the northern part of the Bay and has exhibited symptoms of eutrophication. The first goal of this study was to examine seasonal denitrification, other N fluxes, and sediment oxygen demand in salt marshes of Barnegat Bay where inputs and concentrations of nutrients vary spatially within the Bay. Second, differences in N process rates among emergent vegetated marsh and permanently flooded isolated ponds were investigated. Finally, the percentage of the N load to the Bay re...

The Relative Importance of the Sedge Island Marine Conservation Zone for Adult Blue Crabs in Barnegat Bay, New Jersey

ABSTRACT Jivoff, P.R.; Moritzen, L.; Kels, J.; McCarthy, J.; Young, A.; Barton, A.; Ferdinando, P.; Pandolfo, F., and Tighe, C., 2017. The relative importance of the Sedge Island Marine Conservation Zone for adult blue crabs in Barnegat Bay, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. Marine protected areas have become an important tool for the management of commercially important species. The Sedge Island Marine Conservation Zone (SIMCZ) in Barnegat Bay is 15 years old, but its effectiveness has never been assessed. This study evaluated the relative importance of the SIMCZ for adult blue crabs by comparing the abundance and size frequency distribution of crabs inside the SIMCZ with physically similar locations outside the SIMCZ that (1) were nearby, providing straight-line access to Barnegat Inlet but varying in habitat, and (2) varied in distance from an inlet but shared the same habitat. The SIMCZ contain...

Phosphorus Dynamics in the Water Column and Sediments of Barnegat Bay, New Jersey

ABSTRACT Paudel, B.; Weston, N.; O'Connor, J.; Sutter, L., and Velinsky, D., 2017. Phosphorus dynamics in the water column and sediments of Barnegat Bay, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. Phosphorus (P) loadings are higher in northern Barnegat Bay, New Jersey, relative to southern Bay, whereas ambient dissolved P is higher in the southern part of the Bay. This study investigated the mechanism for higher water-column P in the southern part of the Bay relative to the northern Bay. The authors hypothesized that sediments may be the source of P to the water column in the southern Bay. Water-column samples and sediment cores were collected from 20 stations along the N-S gradient of the Bay on three dates (spring, summer, and fall) in 2014–15. Benthic sediment P flux experiments were conducted under oxic and anoxic conditions. Phosphorus was sequentially extracted from sediments into five operationally d...

Tidal Marsh Record of Nutrient Loadings in Barnegat Bay, New Jersey

Velinsky, D.J.; Paudel, B.; Belton, T.J., and Sommerfield, C.K., 2017. Tidal marsh record of nutrient loadings in Barnegat Bay, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey.Sediment and nutrient burial in tidal marshes of Barnegat Bay was investigated using age-dated sediment cores collected along a north-to-south transect. Measurements of radionuclides (210Pb and 137Cs) and stable isotopes (13C and 15N) were accompanied by nutrient and organic matter concentrations. Sediment accumulation rates, measured using 210Pb and 137Cs chronology, ranged from 48 to 81 mg cm2 y−1, whereas corresponding accretion rates ranged from 0.16 to 0.30 cm y−1. Sediment nitrogen (N) accumulation rates increased twofold at an upper bay site, starting in the mid-1950s, whereas at other locations, only small to no increases were seen with time. Phosphorus (P) accumulation was minimal with time. N and P accumulation rates were higher between the 1940s to 1950s at stations BB-1 and BB-3, while higher accumulation rate in the down-bay (BB-4) was identified in the early 1990s. Results indicate that bay marshes can sequester approximately 79 ± 11% of N and 54 ± 34% of P entering the Bay from upland sources; thus, these marshes perform an important ecosystem service in the form of nutrient sequestration. Marsh accretion rates at the coring sites fall at, to just below, rates of relative sea-level rise recorded by nearby tide gauges. These relatively low rates of accretion render the marsh vulnerable to inundation should the rate of sea-level rise accelerate in the future.

Zooplankton Community Dynamics in a Western Mid-Atlantic Lagoonal Estuary

ABSTRACT Howson, U.A.; Buchanan, G.A., and Nickels, J.A., 2017. Zooplankton community dynamics in a western mid-Atlantic lagoonal estuary. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. Zooplankton are an integral component of the food web in estuarine ecosystems. The most recent studies of zooplankton in Barnegat Bay, New Jersey, occurred almost 40 years ago. Since then, this coastal lagoon estuary has been affected by anthropogenic impacts that threaten its ecological integrity, including nutrient enrichment, algal blooms, alterations of freshwater inputs, and extensive development around the bay and its watershed. Assessing the zooplankton community in this ecosystem provided updated information on the status of this important component of the bay's living resources. Zooplankton samples were collected from the upper meter of the water column with horizontal surface net tows using bongo plankton nets monthly during the w...

Sediment Diatoms as Environmental Indicators in New Jersey Coastal Lagoons

ABSTRACT Desianti, N.; Potapova, M.; Enache, M.; Belton, T.J.; Velinsky, D.J.; Thomas, R., and Mead, J., 2017. Sediment diatoms as environmental indicators in New Jersey coastal lagoons. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. The goal of this study was to explore the possible use of sediment diatoms as environmental indicators in New Jersey coastal lagoons. Diatom samples were collected from 100 sites in Barnegat Bay and Great Bay representing both subtidal and intertidal habitats. A total of 603 diatom taxa were found, with most samples characterized by high species diversity. A strong north-to-south salinity gradient in the study area was a major factor influencing composition of diatom assemblages. Subtidal sediments, especially in highly productive areas in the northern part of the Barnegat Bay, contained a high proportion of planktonic diatoms, especially small-celled Cyclotella and Chaetoceros species. Habita...

Toward a Comprehensive Water-Quality Modeling of Barnegat Bay: Development of ROMS to WASP Coupler

ABSTRACT Defne, Z.; Spitz, F.J.; DePaul, V., and Wool, T.A., 2017. Toward a comprehensive water-quality modeling of Barnegat Bay: Development of ROMS to WASP coupler. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. The Regional Ocean Modeling System (ROMS) has been coupled with the Water Quality Analysis Simulation Program (WASP) to be used in a comprehensive analysis of water quality in Barnegat Bay, New Jersey. The coupler can spatially aggregate hydrodynamic information in ROMS cells into larger WASP segments. It can also be used to resample ROMS output at a finer temporal scale to meet WASP time-stepping requirements. The coupler aggregates flow components, temperature, and salinity in ROMS output for input to WASP via a hydrodynamic linkage file. The coupler was tested initially with idealized cases designed to verify the water mass balance and conservation of constituent mass using one-to-one and one-to-many connectiv...

Recent Trends of &amp;lt;i&amp;gt;Zostera marina&amp;lt;/i&amp;gt; (Eelgrass) in a Highly Eutrophic Coastal Lagoon in the Mid-Atlantic Region (USA)

Spatial and temporal characteristics of Zostera marina (eelgrass) in the Barnegat Bay-Little Egg Harbor Estuary are compared before (2004-2011) and after (2012-2013) major fertilizer legislation (Fertilizer Law A2290) was enacted in New Jersey (USA) to reduce nutrient inputs from fertilizers to water bodies in the state. A significant decrease of Z. marina biomass and areal cover occurred in this eutrophic estuary between 2004 and 2011 concomitantly with increasing nitrogen and phosphorus loading from the watershed. The rate of decline in aboveground and belowground biomass was significantly sharper during 2004-2006 than during 2008-2010. In 2010, Z. marina biomass dropped to a very low level (mean aboveground biomass = 7.7 g dry wt m&#452; mean belowground biomass = 27.0 g dry wt m&#452), persisting through the last sampling period (October-November) in 2013. Biomass and areal cover of Z. marina decreased even further after Fertilizer Law A2290 was enacted in January 2012, with the lowest values recorded from August to November each year. These low values are the result of ongoing eutrophication of the system. More seagrass monitoring and research are necessary in future years to determine if the fertilizer law will have a positive effect on Z. marina condition in the estuary over the long term.

Evolution of Mid-Atlantic Coastal and Back-Barrier Estuary Environments in Response to a Hurricane: Implications for Barrier-Estuary Connectivity

Assessments of coupled barrier island-estuary storm response are rare. Hurricane Sandy made landfall during an investigation in Barnegat Bay-Little Egg Harbor estuary that included water quality monitoring, geomorphologic characterization, and numerical modeling; this provided an opportunity to characterize the storm response of the barrier island-estuary system. Barrier island morphologic response was characterized by significant changes in shoreline position, dune elevation, and beach volume; morphologic changes within the estuary were less dramatic with a net gain of only 200,000 m3 of sediment. When observed, estuarine deposition was adjacent to the back-barrier shoreline or collocated with maximum estuary depths. Estuarine sedimentologic changes correlated well with bed shear stresses derived from numerically simulated storm conditions, suggesting that change is linked to winnowing from elevated storm-related wave-current interactions rather than deposition. Rapid storm-related changes in estuarine water level, turbidity, and salinity were coincident with minima in island and estuarine widths, which may have influenced the location of two barrier island breaches. Barrier-estuary connectivity, or the transport of sediment from barrier island to estuary, was influenced by barrier island land use and width. Coupled assessments like this one provide critical information about storm-related coastal and estuarine sediment transport that may not be evident from investigations that consider only one component of the coastal system.

Model-to-data comparisons reveal influence of jellyfish interactions on plankton community dynamics

Taxonomic shifts can alter predator feeding preference and modify ecosystem dynamics through top-down control. In Barnegat Bay-Little Egg Harbor Estuary (New Jersey, USA), sea nettle Chrysaora quinquecirrha abundances have increased in the northern portions of the estuary. We evaluated the geographical variation in top-down influence of C. quinquecirrha on plankton community dynamics. We simulated a range of jellyfish- to copepod-dominated eco- systems using a size-resolved nutrientphytoplanktonzooplankton (NPZ) model. Zooplankton feeding was parameterized as a community average based on predatorprey size ratios and breadth of prey sizes of dominant species. We compared model outputs to data collected in the estuary during 2 summer months of high C. quinquecirrha abundance. We predicted that data from the northern region would be more similar to the jellyfish-dominated model outputs, because C. quinquecirrha abundance is higher in the north. Contrary to expectations, all northern sites had observational data more similar to the copepod-dominated model outputs, and the site that was most similar to the jellyfish-dominated model outputs was in the C. quinquecirrha-free southern region. These results may indicate complex interactions between C. quinquecirrha and the ctenophore Mnemiopsis leidyi, a voracious copepod predator that is nearly absent in the northern region despite having wide environmental tolerances. Predation by C. quinquecirrha may limit the distribution of M. leidyi and indirectly strengthen copepod dominance in the northern region of the estuary. These results suggest that top-down control by jellyfish can be strongly influenced by competition among gelatinous taxa.

Quantifying the Residence Time and Flushing Characteristics of a Shallow, Back-Barrier Estuary: Application of Hydrodynamic and Particle Tracking Models

Estuarine residence time is a major driver of eutrophication and water quality. Barnegat Bay-Little Egg Harbor (BB-LEH), New Jersey, is a lagoonal back-barrier estuary that is subject to anthropogenic pressures including nutrient loading, eutrophication, and subsequent declines in water quality. A combination of hydrodynamic and particle tracking modeling was used to identify the mechanisms controlling flushing, residence time, and spatial variability of particle retention. The models demonstrated a pronounced northward subtidal flow from Little Egg Inlet in the south to Pt. Pleasant Canal in the north due to frictional effects in the inlets, leading to better flushing of the southern half of the estuary and particle retention in the northern estuary. Mean residence time for BB-LEH was 13 days but spatial variability was between ∼0 and 30 days depending on the initial particle location. Mean residence time with tidal forcing alone was 24 days (spatial variability between ∼0 and 50 days); the tides were relatively inefficient in flushing the northern end of the Bay. Scenarios with successive exclusion of physical processes from the models revealed that meteorological and remote offshore forcing were stronger drivers of exchange than riverine inflow. Investigations of water quality and eutrophication should take into account spatial variability in hydrodynamics and residence time in order to better quantify the roles of nutrient loading, production, and flushing.

Comparison of remotely-sensed surveys vs. in situ plot-based assessments of sea grass condition in Barnegat Bay-Little Egg Harbor, New Jersey USA

With the increasing appreciation that sea grass habitats are in global decline, there is a great need to be able to efficiently and effectively assess and characterize the status and trends of sea grass in our coastal ecosystems. This paper examines the utility of remotely sensed vs. in situ plot-based monitoring using the Barnegat Bay-Little Egg Harbor (BB-LEH), New Jersey, USA estuarine system as a case study. Eelgrass (Zostera marina) is the dominant species, while widgeon grass (Ruppia maritima) is also common in lower salinity regions of the BB-LEH. Aerial imagery collected during the months of July and August 2009 was interpreted and mapped using object based image analysis techniques, similar to techniques used in the 2003 mapping survey of this system. Boat-based in situ monitoring data were collected concurrently with the aerial photography to assist the image interpretation and for an independent accuracy assessment. We compared the remotely-sensed mapping of sea grass cover change (in 2003 vs. 2009) vs. in situ plot-based monitoring conducted from 2004 through 2009. Comparison of the remotely-sensed vs. the in situ plot-change analysis suggests that the two methodologies had broadly similarly results, with the percent area showing declines in sea grass cover greater than those that exhibited increases. In conclusion, the two studies provide corroborating evidence that sea grass has declined in percent cover in the BB-LEH system during the decade of the 2000’s. While remotely-sensed surveys provide synoptic information for a “big picture” view on sea grass distribution, site specific in situ sampling is required to determine other aspects of sea grass status, e.g. above vs. below-ground biomass, blade length, shoot density, epiphytic loading, etc. Either method alone gives an incomplete picture. As demonstrated in this study, to fully characterize the spatial extent, health, and density of sea grass meadows across the entire estuary, combining remote sensing surveys concomitantly with comprehensive in situ assessment provides the most robust approach.

Changing eelgrass (Zostera marina L.) characteristics in a highly eutrophic temperate coastal lagoon

Previous investigations of eelgrass (Zostera marina L.) beds in the Barnegat Bay-Little Egg Harbor Estuary, New Jersey (USA) revealed a significant decline in plant biomass associated with ongoing nitrogen enrichment of the system and declines in light availability. Here, we update trends in eelgrass characteristics (aboveground and belowground biomass, shoot density, percent cover, blade length) for 2008–2010 and compare these to previous datasets (2004–2006). Analysis of quadrat, core, and hand samples collected at 120 transect stations in 4 disjunct eelgrass beds of the estuary showed a distinct, continued reduction in Zostera biomass. In 2010, Z. marina biomass decreased to its lowest level ever recorded in the estuary (mean aboveground biomass=7.7gDWm−2; mean belowground biomass=27.0gDWm−2). Reduced biomass and other characteristics indicated that eelgrass beds had not recovered from previous reductions observed 2004–2006. The rate of decline was related to nutrient loading and associated symptoms of eutrophication. Additionally, the rate of degradation changed over time. The decline in plant parameters was evident in all of the eelgrass beds investigated, indicating that an estuary-wide stressor was responsible.