Richard A. Batiuk

Assessing Water Quality with Submersed Aquatic Vegetation

Estuaries throughout the world are experiencing water quality problems as the result of human population growth in coastal areas. By establishing the habitat requirements of critical submerged aquatic vegetation, water quality can be evaluated and restoration goals can be made. This study used submerged vegetation in Chesapeake Bay to examine the habitat and health of the Bay. Both natural distributions and transplant survival in different studies were analyzed. The five habitat requirements used were light attenuation, total suspended solids, chlorophyll, dissolved inorganic nitrogen, and dissolved inorganic phosphorus. Water-quality conditions supporting vegetation growth to one meter depth was used. This study represents the first attempt at linking habitat requirements of a living resource to water quality standards in an estuarine system. It allows for predictive capability without detailed knowledge of the precise nature of vegetation/water quality interactions.

Long-term nutrient reductions lead to the unprecedented recovery of a temperate coastal region

Significance Human actions, including nutrient pollution, are causing the widespread degradation of coastal habitats, and efforts to restore these valuable ecosystems have been largely unsuccessful or of limited scope. We provide an example of successful restoration linking effective management of nutrients to the successful recovery of submersed aquatic vegetation along thousands of kilometers of coastline in Chesapeake Bay, United States. We also show that biodiversity conservation can be an effective path toward recovery of coastal systems. Our study validates 30 years of environmental policy and provides a road map for future ecological restoration. Humans strongly impact the dynamics of coastal systems, yet surprisingly few studies mechanistically link management of anthropogenic stressors and successful restoration of nearshore habitats over large spatial and temporal scales. Such examples are sorely needed to ensure the success of ecosystem restoration efforts worldwide. Here, we unite 30 consecutive years of watershed modeling, biogeochemical data, and comprehensive aerial surveys of Chesapeake Bay, United States to quantify the cascading effects of anthropogenic impacts on submersed aquatic vegetation (SAV), an ecologically and economically valuable habitat. We employ structural equation models to link land use change to higher nutrient loads, which in turn reduce SAV cover through multiple, independent pathways. We also show through our models that high biodiversity of SAV consistently promotes cover, an unexpected finding that corroborates emerging evidence from other terrestrial and marine systems. Due to sustained management actions that have reduced nitrogen concentrations in Chesapeake Bay by 23% since 1984, SAV has regained 17,000 ha to achieve its highest cover in almost half a century. Our study empirically demonstrates that nutrient reductions and biodiversity conservation are effective strategies to aid the successful recovery of degraded systems at regional scales, a finding which is highly relevant to the utility of environmental management programs worldwide.

Assessment of Impact of Storm on Point Source Pollutant Transport in Estuary by Dissolved Tracer Modeling

A continuously discharged dissolved conservative tracer was simulated with the Chesapeake Bay Estuary Model Package to study pollutant transport in the estuary in response to point source loads and the impact of the November, 1985 storm. A visualization technology is applied to show 3-dimensional concentration variations in a continuous daily time sequence. The differential responses of daily net transport during storms versus inter-storm periods can be observed from an MPEG movie. It may take 2–3 months for a tracer to travel from the fall-line to the mouth of a river during relatively dry seasons, only 2 weeks in some medium storms, and less than 5 days in a big storm. Plots of daily concentrations from eleven selected locations in the estuary provide quantitative information on the response of tracer concentration to flows. The magnitude and time of tracer peaks related with different weather events in these locations reflect the combined effects of flows from various directions to these locations. The lower tributaries (which are closer to the Bay mouth) are affected more than the upper tributaries by a source discharged at a mid-tributary. A storm can transport materials more effectively to the Bay and affect adjacent tributaries more severely.

Influence of Reservoir Infill on Coastal Deep Water Hypoxia

Ecological restoration of the Chesapeake through the Chesapeake Bay total maximum daily load (TMDL) requires the reduction of nitrogen, phosphorus, and sediment loads in the Chesapeake watershed because of the tidal water quality impairments and damage to living resources they cause. Within the Chesapeake watershed, the Conowingo Reservoir has been filling in with sediment for almost a century and is now in a state of near-full capacity called . The development of the Chesapeake TMDL in 2010 was with the assumption that the Conowingo Reservoir was still effectively trapping sediment and nutrients. This is now known not to be the case. In a TMDL, pollutant loads beyond the TMDL allocation, which are brought about by growth or other conditions, must be offset. Using the analysis tools of the Chesapeake TMDL for assessing the degree of water quality standard attainment, the estimated nutrient and sediment loads from a simulated dynamic equilibrium infill condition of the Conowingo Reservoir were determined. The influence on Chesapeake water quality by a large storm and scour event of January 1996 on the Susquehanna River was estimated, and the same storm and scour events were also evaluated in the more critical living resource period of June. An analysis was also made on the estimated influence of more moderate high flow events. The infill of the Conowingo reservoir had estimated impairments of water quality, primarily on deep-water and deep-channel dissolved oxygen, because of increased discharge and transport of organic and particulate inorganic nutrients from the Conowingo Reservoir.

Volume Analysis for Attainability of Water Qualuty Criteria for Three Loading Constitutents

This paper presents a method to analyze the outputs of an estuarine water quality model to determine the attainability of water quality criteria for designated-use-areas in the Chesapeake Bay estuary using different levels of reduction of nitrogen, phosphorus, and sediment loads. From a set of water quality model scenarios with different nitrogen (N), phosphorus (P) and sediment (S) loads, a relationship between a water quality index (W) and the loading-constitutents N-P-S, i.e., W = f(N,P,S), in a designated-use-area, can be established through regression. In a designated-use-area, we may obtain a percentage of non-attainment (or violation, V) of a water quality criterion accumulated over time and water-volume versus the entire simulated time and volume for a model scenario. From a ser of model scenarios, a relationship between W and V, i.e., W = g(V), can be established. The value of the water quality index (Wo) equivalent to near-zero violation (Vo) of the criteria can be projected, i.e., Wo = g(Vo). Using W = Wo as a constraint for the function W = f(N, P, S), we can plot a 3-dimenstional surface of minimum water quality attainment, Wo, versus N, P, and S loads for the designated-use-area. This surface divides the 3-dimensional N-P-S “loading volume” into regions of attainment and non-attainment of the water quality criterion in the designated-use-are. This plot can be used to analyze tradeoffs among N-P-S load restrictions that still ensure attainment of the water quality criteria, providing useful information for optimal nutrient and sediment controls in water quality management.

Recast of the outputs of a deterministic model to get a better estimate of water quality for decision makings

The outputs of a deterministic water quality model are retreated to recast the model simulation. A multi-variance regression method is used for daily model outputs versus observed data to assess the systematic errors in model simulation of individual model cell. The model outputs are re-adjusted to better represent the actual values, and to yield a better model calibration. Such a recast is important to model application for water quality analysis, especially for TMDL (Total Maximum Daily Load) which requires accurate simulation to exam criteria attainment. This paper addresses the recast method, its prerequisites, and how the results are extended for the scenarios with various load reductions.