Ashley R. Smyth

Economic Valuation of Ecosystem Services Provided by Oyster Reefs

Valuation of ecosystem services can provide evidence of the importance of sustaining and enhancing those resources and the ecosystems that provide them. Long appreciated only as a commercial source of oysters, oyster reefs are now acknowledged for the other services they provide, such as enhancing water quality and stabilizing shorelines. We develop a framework to assess the value of these services. We conservatively estimate that the economic value of oyster reef services, excluding oyster harvesting, is between

Habitat-specific distinctions in estuarine denitrification affect both ecosystem function and services

5500 and

Scientific Evidence Supports a Ban on Microbeads

99,000 per hectare per year and that reefs recover their median restoration costs in 2–14 years. In contrast, when oyster reefs are subjected to destructive oyster harvesting, they do not recover the costs of restoration. Shoreline stabilization is the most valuable potential service, although this value varies greatly by reef location. Quantifying the economic values of ecosystem services provides guidance about when oyster reef restoration is a good use of funds.

Habitat context influences nitrogen removal by restored oyster reefs

Resource limitation controls the base of food webs in many aquatic ecosystems. In coastal ecosystems, nitrogen (N) has been found to be the predominant limiting factor for primary producers. Due to the important role nitrogen plays in determining ecosystem function, understanding the processes that modulate its availability is critical. Shallow-water estuarine systems are highly heterogeneous. In temperate estuaries, multiple habitat types can exist in close proximity to one another, their distribution controlled primarily by physical energy, tidal elevation and geomorphology. Distinctions between these habitats such as rates of primary productivity and sediment characteristics likely affect material processing. We used membrane inlet mass spectrometry to measure changes in N2 flux (referred to here as denitrification) in multiple shallow-water estuarine habitats through an annual cycle. We found significantly higher rates of denitrification (DNF) in structured habitats such as submerged aquatic vegetation, salt marshes and oyster reefs than in intertidal and subtidal flats. Seasonal patterns were also observed, with higher DNF rates occurring in the warmer seasons. Additionally, there was an interaction between habitat type and season that we attributed to the seasonal patterns of enhanced productivity in individual habitat types. There was a strong correlation between denitrification and sediment oxygen demand (SOD) in all habitats and all seasons, suggesting the potential to utilize SOD to predict DNF. Denitrification efficiency was also higher in the structured habitats than in the flats. Nitrogen removal by these habitats was found to be an important contributor to estuarine ecosystem function. The ecosystem service of DNF in each habitat was evaluated in US dollars using rates from a regional nutrient-offset market to determine the cost to replace N through management efforts. Habitat-specific values of N removal ranged from approximately three thousand U.S. dollars per acre per year in the submerged aquatic vegetation to approximately four hundred U.S. dollars per acre per year in the subtidal flat. Because of the link between habitat type and processes such as DNF, changes in habitat area and distribution will have consequences for both ecosystem function and the delivery of ecosystem services.

Impacts of Climate-Related Drivers on the Benthic Nutrient Filter in a Shallow Photic Estuary

Chelsea M. Rochman,*,†,‡ Sara M. Kross,†,§ Jonathan B. Armstrong,†,∥,@ Michael T. Bogan,†,⊥,@ Emily S. Darling,†,#,@ Stephanie J. Green,†,¶,@ Ashley R. Smyth,†,▲,@ and Diogo Verissimo†,▼,@ †David H. Smith Conservation Research Program, Society for Conservation Biology, Washington, DC 20001, United States ‡School of Veterinary Medicine, Aquatic Health Program, University of California Davis, Davis, California 95616, United States Department of Wildlife, Fish and Conservation Biology, University of California Davis, Davis, California 95616-8627, United States USGS Cooperative Fish and Wildlife Research Unit, University of Wyoming, Laramie, Wyoming 82071, United States Department of Environmental Science, Management and Policy, University of California Berkeley, Berkeley, California 94720-3114, United States Marine Program, Wildlife Conservation Society, New York 10460-1099, United States Department of Integrative Biology, Oregon State University, Corvallis, Oregon 97331, United States Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062, United States Andrew Young School of Policy Studies, Department of Economics, Georgia State University, 33 Gilmer Street SE, Atlanta, Georgia 30303, United States

Extending Rapid Ecosystem Function Assessments to Marine Ecosystems: A Reply to Meyer

Summary Like many ecosystem functions in marine and terrestrial environments, nutrient processing varies dramatically over small spatial scales, making efforts to apply findings within and across ecosystems challenging. In estuaries, information on the influence of habitat context on sediment nutrient cycling is lacking even though this is an important estuarine function with high societal value. We collected triplicate intact sediment cores from restored oyster reefs located in different habitat contexts (adjacent to salt marshes, seagrass beds and mudflats), as well as salt marshes, seagrass beds and mudflats without reefs (controls). Sediment denitrification and fluxes of dissolved inorganic nitrogen were measured under ambient and experimentally elevated water column nitrate levels. Under ambient nitrate, oyster reefs enhanced sediment denitrification by 18–275% over the controls, with highest rates of denitrification in the mudflat context. With experimentally elevated nitrate, the rate of denitrification was higher for oyster reefs compared to the controls in all contexts. This suggests that oyster reefs prime sediments to denitrify nitrate pulses by providing a labile carbon source for denitrifying bacteria. There was a weak positive relationship between oyster density and denitrification under ambient nitrate concentrations and a positive relationship with denitrification that became negative beyond ∼2400 individuals m−2 with elevated nitrate concentrations. The effect of the oyster reef on sediment denitrification was most pronounced in the mudflat context, due to the absence of other structured habitats and higher oyster density, compared to the other two habitat contexts investigated. The consistency of denitrification efficiency across the habitats and lack of difference between habitats with reefs and those without (controls) suggest oyster-mediated denitrification is an effective sink for nitrogen in coastal systems. Synthesis and applications. Our study indicates that oyster-mediated denitrification is dependent on the habitat context of the oyster reef, and variation in oyster density and the relative functional redundancy of oyster reefs where other structured habitats exist (e.g. seagrass and salt marshes) may explain this pattern. Efforts to model and predict ecosystem services provided through oyster reef restoration such as the removal of anthropogenically derived nitrogen should incorporate how habitat context influences ecosystem functions.

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

In shallow photic systems, the benthic filter, including microphytobenthos and denitrifiers, is important in preventing or reducing release of remineralized NH4+ to the water column. Its effectiveness can be impacted by climate-related drivers, including temperature and storminess, which by increasing wind and freshwater delivery can resuspend sediment, reduce salinity and deliver nutrients, total suspended solids, and chromophoric dissolved organic matter (CDOM) to coastal systems. Increases in temperature and freshwater delivery may initiate a cascade of responses affecting benthic metabolism with impacts on sediment properties, which in turn regulate nitrogen cycling processes that either sequester (via microphytobenthos), remove (via denitrification), or increase sediment nitrogen (via remineralization, nitrogen fixation, and dissimilatory nitrate reduction to ammonium). We conducted a seasonal study at shallow stations to assess the effects of freshwater inflow, temperature, wind, light, and CDOM on sediment properties, benthic metabolism, nitrogen cycling processes, and the effectiveness of the benthic filter. We also conducted a depth study to constrain seasonally varying parameters such as temperature to better assess the effects of light availability and water depth on benthic processes. Based on relationships observed between climatic drivers and response variables, we predict a reduction in the effectiveness of the benthic filter over the long term with feedbacks that will increase effluxes of N to the water column with the potential to contribute to system eutrophication. This may push shallow systems past a tipping point where trophic status moves from net autotrophy toward net heterotrophy, with new baselines characterized by degraded water quality.

Differential effects of bivalves on sediment nitrogen cycling in a shallow coastal bay

Meyer et al. [1] propose a series of assays constituting their rapid ecosystem function assessment (REFA) to quickly and inexpensively survey terrestrial ecosystem processes. In this reply we extend their framework to estuarine and coastal marine ecosystems, which provide invaluable services to humanity. We propose an analogous suite of assays that are equally simple and easily deployed by a variety of end users, including scientists, managers, and citizens. We aim to facilitate cross-system comparisons, test ecological theory, engage society, and provide rigorous quantitative data on the consequences of global change and biodiversity loss for the worlds oceans.

Saltwater Intrusion Modifies Microbial Community Structure and Decreases Denitrification in Tidal Freshwater Marshes

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 removed by denitrification in the salt marshes of Barnegat Bay was calculated. It was hypothesized that denitrification rates would be the highest in summer and depend on water-column nutrient concentration. In addition, denitrification rate would be higher in vegetated marsh than in inundated ponds because of the aerobic/anaerobic interfaces present in marshes required by coupled nitrification–denitrification. Denitrification rate was three times greater in July than in October (p < 0.05). There were significant differences among marshes in N fluxes related to local availability of nutrients in the water column. Denitrification rates in vegetated marsh on thin sediment layers were more variable than in ponds. Overall, denitrification removed an average of 27.9% ± 6.9% of the total N load transported to the Bay, highlighting the important ecosystem service that the marshes provide to the Bay.

Correction to Scientific Evidence Supports a Ban on Microbeads.

In coastal ecosystems, suspension-feeding bivalves can remove nitrogen though uptake and assimilation or enhanced denitrification. Bivalves may also retain nitrogen through increased mineralization and dissimilatory nitrate reduction to ammonium (DNRA). This study investigated the effects of oyster reefs and clam aquaculture on denitrification, DNRA, and nutrient fluxes (NOx, NH4+, O2). Core incubations were conducted seasonally on sediments adjacent to restored oyster reefs (Crassostrea virginica), clam aquaculture beds (Mercenaria mercenaria) which contained live clams, and bare sediments from Smith Island Bay, Virginia, USA. Denitrification was significantly higher at oyster reef sediments and clam aquaculture site than bare sediment in the summer; however, DNRA was not enhanced. The clam aquaculture site had the highest ammonium production due to clam excretion. While oyster reef and bare sediments exhibited seasonal differences in rate processes, there was no effect of season on denitrification, or dissimilatory nitrate reduction to ammonium (DNRA) or ammonium flux at the clam aquaculture site. This suggests that farm management practices or bivalve metabolism and excretion may override seasonal differences. When water column nitrate concentration was elevated, denitrification increased in clam aquaculture site and oyster reef sediments but not in bare sediment; DNRA was only stimulated at the clam aquaculture site. This, along with a significant and positive relationship between denitrification and sediment organic matter, suggests that labile carbon limited nitrate reduction at the bare sediment site. Bivalve systems can serve as either net sinks or sources of nitrogen to coastal ecosystems, depending mainly on the type of bivalve, location, and management practices.