•We compared three models for calculation of eastern oyster filtration.•Both maximum filtration rates and limitation factors were assessed.•A new individual-based model was generated from the ...assessment.•The maximum filtration rate was set at 0.17m3g−1DWday−1 for a 1gDW oyster.
Crassostrea virginica, the eastern oyster, is a suspension-feeding bivalve currently at low numbers in Chesapeake Bay, where it was once abundant. Accurately describing the filtration rate of these bivalves is essential to estuarine management and associated efforts to understand the impact of oyster populations on water quality. Here, the filtration rate equations for three existing models (Cerco and Noel, 2005; Fulford et al., 2007; Powell et al., 1992) are reviewed. We examine how each of the models define the maximum filtration rate and explore the various limitation factors that modify these maximum rates via environmental conditions that include salinity, temperature, and total suspended solids. Based on the individual model strengths assessed with a model comparison and literature review, we determine a maximum filtration rate of 0.17 (±0.07)m3g−1DWday−1 for a 1g DW oyster to describe this rate process, which is then modified by a combination of limitation factors taken from a variety of sources. These include those described by Fulford et al. (2007) for total suspended solids and salinity, and a newly developed function to describe temperature dependence. Differences in size are incorporated by using a basic allometric formulation where a weight exponent alters filtration rate based on individual oyster size.
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Technological advances in water quality measurement systems have provided the potential to expand high-frequency observations into coastal monitoring programs. However, with limited resources for ...monitoring budgets in natural waters that exhibit high temporal and spatial variability in water quality, there is a need to identify the locations and time periods where these new technologies can be deployed for maximum efficacy. To advance the capacity to make quantitative and objective decisions on the selection of monitoring locations and sampling frequency, we combined high-resolution numerical model simulations and multi-frequency water quality measurements to conduct a power analysis comparing alternative sampling designs in the assessment of water quality in the Chesapeake Bay. Specifically, we evaluated candidate monitoring networks that deployed both conventional long-term fixed station monitoring in deep channel areas and short-term continuous monitoring technologies in near-shore, shallow areas to assess 30-day dissolved oxygen criteria in two Bay tributaries. We conducted a cumulative frequency diagrams analysis to quantify the accuracy of each monitoring scheme in evaluating compliance with respect to the model. We used a Monte Carlo simulation to incorporate the spatial and temporal uncertainty of criteria failure. We found that additional long-term biweekly channel and short-term continuous shallow sampling efforts can lead to statistically unbiased and improved assessments at local spatial extents (less than 0.2 proportion of the assessed water body), especially when additional sampling is added at stations representing hypoxic water areas. Stations that represented seaward regions of the tributaries were more valuable in maintaining unbiased assessments of dissolved oxygen criteria attainment. This analysis highlights the importance of statistical evaluation of ongoing monitoring programs and suggests an approach to identify efficient deployments of monitoring resources and to improve assessment of other water quality metrics in estuarine ecosystems.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Urbanization has altered the fate and transport of anthropogenic nitrogen (N) in rivers and estuaries globally. This study evaluates the capacity of an urbanizing river–estuarine continuum to ...transform N inputs from the world's largest advanced (e.g., phosphorus and biological N removal) wastewater treatment facility. Effluent samples and surface water were collected monthly along the Potomac River estuary from Washington D.C. to the Chesapeake Bay over a distance of 150 km. In conjunction with box model mass balances, nitrate stable isotopes and mixing models were used to trace the fate of urban wastewater nitrate. Nitrate concentrations and δ15N-NO3− values were higher down-estuary from the Blue Plains wastewater outfall in Washington D.C. (2.25 ± 0.62 mg L−1 and 25.7 ± 2.9 ‰, respectively) compared to upper-estuary concentrations (1.0 ± 0.2 mg L−1 and 9.3 ± 1.4 ‰, respectively). Nitrate concentration then decreased rapidly within 30 km down-estuary (to 0.8 ± 0.2 mg L−1), corresponding to an increase in organic nitrogen and dissolved organic carbon, suggesting biotic uptake and organic transformation. TN loads declined down-estuary (from an annual average of 48 000 ± 5000 kg day−1 at the sewage treatment plant outfall to 23 000 ± 13 000 kg day−1 at the estuary mouth), with the greatest percentage decrease during summer and fall. Annually, there was a 70 ± 31 % loss in wastewater NO3− along the estuary, and 28 ± 6 % of urban wastewater TN inputs were exported to the Chesapeake Bay, with the greatest contribution of wastewater TN loads during the spring. Our results suggest that biological transformations along the urban river–estuary continuum can significantly transform wastewater N inputs from major cities globally, and more work is necessary to evaluate the potential of organic nitrogen and carbon to contribute to eutrophication and hypoxia.
The unpredictable timing and magnitude of precipitation events and the spatiotemporal variability of constituent concentrations are major complications to effective monitoring of watershed nutrient ...and sediment loads. Furthermore, detecting small changes in constituent loads in response to implementation of Stormwater control measures (SCMs) against natural variability is a challenge. Nevertheless, regulatory frameworks that direct reductions of pollutants to streams frequently depend on the ability to quantify changes in loads after management interventions. The before-after-control impact (BACI) sampling design is often used to assess the effects of an environmental change made at a known point in time. However, this approach may be complicated to apply to nutrient and sediment loads in streams as the relative impact of SCMs on nutrient concentration conditional on the long term variability of discharges has not been evaluated. Multi-scale monitoring studies that provide estimates of the natural temporal and spatial variability of discharge and concentrations could provide useful information in designing a BACI study. Here we use data from the Baltimore Long Term Ecological Research (LTER) sites and urban restoration sites to develop multiple statistical measures of the effectiveness of a given monitoring scheme in revealing the hypothesized restoration effects in terms of hydrology and nutrient loads. Stratified sampling over baseflow and stormflow and the use of multiple control streams were useful tools to detect long term cumulative reductions in concentrations due to SCMs. Moderate reductions in concentration (20%), however, were not detectable with the design options considered. We emphasize that appropriate pre-planning of monitoring schemes and sampling frequency is essential to determine if the effects on constituent loads resulting from a given watershed restoration activity are measurable.
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•BACI with stratification over discharge has power to detect local BMP impacts.•Moderate load reduction from concentration changes was not detected.•Planning of monitoring schemes and sampling frequency are essential.
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•The Chesapeake Bay is the largest, most productive, and most biologically diverse estuary in the continental United States.•Pressures from human population growth and agricultural intensification ...have led to excessive nutrient and sediment inputs.•The Chesapeake Bay program partnership has been developing and applying a complex modeling system as a planning tool to inform management decisions and Bay restoration efforts.•This paper provides a description of the modeling system along with specific recommendations that emerged from a 2018 workshop designed to inform future model development.
The Chesapeake Bay is the largest, most productive, and most biologically diverse estuary in the continental United States providing crucial habitat and natural resources for culturally and economically important species. Pressures from human population growth and associated development and agricultural intensification have led to excessive nutrient and sediment inputs entering the Bay, negatively affecting the health of the Bay ecosystem and the economic services it provides. The Chesapeake Bay Program (CBP) is a unique program formally created in 1983 as a multi-stakeholder partnership to guide and foster restoration of the Chesapeake Bay and its watershed. Since its inception, the CBP Partnership has been developing, updating, and applying a complex linked modeling system of watershed, airshed, and estuary models as a planning tool to inform strategic management decisions and Bay restoration efforts. This paper provides a description of the 2017 CBP Modeling System and the higher trophic level models developed by the NOAA Chesapeake Bay Office, along with specific recommendations that emerged from a 2018 workshop designed to inform future model development. Recommendations highlight the need for simulation of watershed inputs, conditions, processes, and practices at higher resolution to provide improved information to guide local nutrient and sediment management plans. More explicit and extensive modeling of connectivity between watershed landforms and estuary sub-areas, estuarine hydrodynamics, watershed and estuarine water quality, the estuarine-watershed socioecological system, and living resources will be important to broaden and improve characterization of responses to targeted nutrient and sediment load reductions. Finally, the value and importance of maintaining effective collaborations among jurisdictional managers, scientists, modelers, support staff, and stakeholder communities is emphasized. An open collaborative and transparent process has been a key element of successes to date and is vitally important as the CBP Partnership moves forward with modeling system improvements that help stakeholders evolve new knowledge, improve management strategies, and better communicate outcomes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have ...moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review, we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using différent spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a "theory of everything" for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy.
Through technological and research advances, numerous methods and protocols have emerged to estimate spectral absorption of light by particles, a
in an aquatic medium. However, the level of agreement ...among measurements remains elusive. We employed a multi-method approach to estimate the measurement precision of measuring optical density of particles on a filter pad using two common spectrophotometric methods, and the determination precision, or uncertainty, of the computational techniques for estimating a
for six ocean color wavelengths (412, 443, 490, 510, 555, 670 nm). The optical densities measured with the two methods exhibited a significant, positive correlation. Optical density measurement precision ranged from 0.061%-63% and exhibited a significant, positive correlation. Multi-method uncertainty ranged from 7.48%-119%. Values of a
at 555 nm and 670 nm exhibited the highest values of uncertainty. Poor performance of modeled a
compared to determined a
suggest uncertainties are propagated into bio-optical algorithms.
Estuarine ecosystem ecology is a dynamic field of study that has historically focused on a spectrum of compelling research topics, and here we present a series of perspectives on the major challenges ...to be overcome and key research questions to be addressed toward making progress over the coming decades. The challenges we identify include (1) maintaining and improving spatially distributed time-series datasets, (2) maximizing innovation by harnessing new technologies, (3) resuscitating experimental ecosystem research for estuaries, (4) integrating diagnostic ecological models into ecosystem research, and (5) improving basic science by linking it to applied research. We also raise a number of key research questions for the field, including (1) how does food web function respond to changing climate and nutrients, (2) what are likely trajectories of ecosystem recovery in response to restoration, (3) how does climate alter seasonality of estuarine ecosystem processes, (4) how do estuaries affect the global carbon budget and what are key feedbacks, and (5) how will tidal wetland ecosystems respond to sea level rise and climate change? Looking ahead, we envision that the field of estuarine ecosystem ecology will continue to build upon its rich tradition to address fundamental research questions with an expanded toolkit and enlightened perspective to focus basic science on the knowledge needs of society.
Alkalinity in Tidal Tributaries of the Chesapeake Bay Najjar, Raymond G.; Herrmann, Maria; Cintrón Del Valle, Sebastián M. ...
Journal of geophysical research. Oceans,
January 2020, 2020-01-00, 20200101, Volume:
125, Issue:
1
Journal Article
Peer reviewed
Open access
Despite the important role of alkalinity in estuarine carbon cycling, the seasonal and decadal variability of alkalinity, particularly within multiple tidal tributaries of the same estuary, is poorly ...understood. Here we analyze more than 25,000 alkalinity measurements, mostly from the 1980s and 1990s, in the major tidal tributaries of the Chesapeake Bay, a large, coastal‐plain estuary of eastern North America. The long‐term means of alkalinity in tidal‐fresh waters vary by a factor of 6 among seven tidal tributaries, reflecting the alkalinity of nontidal rivers draining to these estuaries. At 25 stations, mostly in the Potomac River Estuary, we find significant long‐term increasing trends that exceed the trends in the nontidal rivers upstream of those stations. Box model calculations in the Potomac River Estuary indicate that the main cause of the estuarine trends is a declining alkalinity sink. The magnitude of this sink is consistent with a simple model of calcification by the invasive bivalve Corbicula fluminea. More generally, in tidal tributaries fed by high‐alkalinity nontidal rivers, alkalinity is consumed, with sinks ranging from 8% to 27% of the upstream input. In contrast, tidal tributaries that are fed by low‐alkalinity nontidal rivers have sources of alkalinity amounting to 34% to 171% of the upstream input. For a single estuarine system, the Chesapeake Bay has diverse alkalinity dynamics and can thus serve as a laboratory for studying the numerous processes influencing alkalinity among the world's estuaries.
Plain Language Summary
Alkalinity, which is the capacity of a water body to neutralize acid, is a useful quantity when studying the cycling of carbon in water bodies, including estuaries. Here we analyze alkalinity measurements in tidal tributaries of the Chesapeake Bay. Average alkalinity levels in the freshest parts of the estuaries varied by sixfold among seven tidal tributaries. Alkalinity was also found to increase over several decades at several locations, partially due to alkalinity increases in the rivers draining to Chesapeake Bay and also probably due to a reduction in the processes that remove alkalinity from estuarine waters. Evidence also supports the role of an invasive species, the Asiatic Clam, in the alkalinity removal in the Potomac River Estuary. More generally, we found evidence that tidal tributaries fed by high‐alkalinity rivers consumed alkalinity while tidal tributaries that are fed by low‐alkalinity rivers produce alkalinity. For a single estuarine system, the Chesapeake Bay has a wide range of alkalinity levels and a wide variety of processes that influence its alkalinity. Therefore, the Chesapeake Bay can serve as a laboratory for studying the alkalinity of many of the world's estuaries.
Key Points
The long‐term means of alkalinity in fresh waters of the Chesapeake Bay vary by a factor of 6 among seven tidal tributaries
Tidal tributaries fed by high‐alkalinity rivers have alkalinity sinks and those fed by low‐alkalinity rivers have alkalinity sources
The alkalinity sink in the Potomac River Estuary declined from 1986 to 2013, leading alkalinity to increase in this system
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Cornwell, J.C.; Owens, M.S.; Boynton, W.R., and Harris, L.A., 2016. Sediment-water nitrogen exchange along the Potomac River estuarine salinity gradient. Observations of N2 efflux in estuarine ...sediments across the salinity gradient of the tidal Potomac River, a eutrophic subestuary of the Chesapeake Bay, were used to evaluate environmental controls of microbial denitrification. Rates of denitrification were measured using N2:Ar ratios in core incubations and were similar to other nitrogen-enriched estuaries, with summer and spring N2-N efflux rates averaging 54 ± 47 and 153 ± 97 μmol m−2 h−1, respectively. The paradigm of higher denitrification rates at lower salinities was not supported by observations during summer and spring conditions along this estuarine salinity gradient. Low bottom water oxygen concentrations in the lower, more saline part of the estuary resulted in low rates of coupled nitrification/denitrification. The most favorable region for denitrification in the tidal Potomac River occurred where changes in salinity were most rapid and oxygen concentrations were not depleted, with high rates observed within the estuarine turbidity maximum (ETM) zone. Overall, the key role of salinity in the tidal Potomac River in controlling denitrification appears to be in the focusing of materials into ETM and providing stratification in the lower estuary that restricts the vertical exchange of oxygen necessary for coupled nitrification/denitrification.
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