Numerical modeling of eutrophication dynamics in the shallow coastal ecosystem: A case study in the Maryland and Virginia coastal bays

Shallow coastal bays and lagoons (mean depths \u3c2-3 meters) are important buffer zones and links between terrestrial and deep marine ecosystems. They are inherently vulnerable to eutrophication, and are normally dominated by benthic primary producers such as seagrass, benthic micro- and macroalgae. There is an urgent need for quantitative models that are specifically designed for studying eutrophication dynamics in shallow coastal ecosystems. In this study, a hydrodynamic and water quality modeling system consisting of the hydrodynamic model UnTRIM and the water quality model CE-QUAL-ICM was applied to a representative shallow coastal bay ecosystem, the Maryland and Virginia Coastal Bays (MVCBs). A high-resolution unstructured model grid was generated to resolve the complex geometry. to address the important role played by benthic macroalgae, a benthic macroalgal module, which assimilated macroalgal kinetics from literature and recent laboratory studies, was incorporated into the water quality model framework. The module includes two representative macroalgal species, Ulva lactuca and Gracilaria vermiculophylla , common in the MVCBs, and employs the internal nutrient-limited growth kinetics proposed by Droop. The numerical modeling system has been calibrated against a comprehensive field monitoring data collected by the Maryland Department of Natural Resources in the MVCBs. The data include water level, current velocity, salinity, and major water quality variables, such as chlorophyll a, dissolved oxygen, and nutrients. The calibrated hydrodynamic model was used to calculate the physical transport time scales. The model estimated flushing time for the entire system is on the order of 2-3 months, which are much longer than typical time scales required by most biological processes. In addition, the local residence time is found to be extremely variable throughout the system. Depending on locations, the local residence time can vary from 0 to more than 200 days. The calculated transport time scales were further compared with spatial water quality distributions in the system. The comparisons demonstrate that physical circulations could substantially modulate biological processes in the system. By using the Droop equation, the benthic macroalgae\u27s unique property, the so-called luxury uptake, was satisfactorily captured. Furthermore, the characteristic boom-and-bust life cycle of benthic macroalgae was qualitatively simulated using a box model. The expanded water quality model that includes the benthic macroalgal module reproduced both temporal and spatial distributions of observed benthic macroalgae and major water quality variables reasonably well in the MVCBs. The model results indicate that benthic macroalgae are highly important in regulating ecosystem metabolism in areas where they are abundant. Moreover, spring phytoplankton bloom was substantially suppressed when benthic macroalgae were present. The incorporation of a benthic macroalgal module also improved the model\u27s predictive capability in simulating dissolved oxygen in shallow ecosystems affected by benthic macroalgae. In terms of nutrient budget, the model estimated that benthic macroalgae retain approximately 10% of annual nonpoint source nitrogen inputs from the watershed based on the simulation of year 2004. This is lower than that contributed by benthic microalgae reported in other shallow coastal bays such as the Lynnhaven Bay. It is suspected that the restricted distribution of benthic macroalgae in the MVCBs limited their role from the whole bay perspective. With the incorporation of a benthic macroalgae module, the overall water quality model prediction capability is improved

Evaluation of the Effect of Saturated Silty and Fine Sand Foundation Improved by Vibro-Flotation in Seismic Area

The improvement of liquefaction foundations in seismic region has been concerning many engineers. The authors had carried out experimental studies on the improvement of saturated silty and fine sand foundations at the suburbs of Beijing by vibroflotation method. The test results are described and the improvement effects are evaluated in this paper

A High-resolution Tidal Hydrodynamic Model for Sequim Bay, WA to Support Marine Renewable Energy Research

Marine renewable energy (e.g., tidal current and wave energy) comprises resources that do not generate carbon emissions. Because of high energy potential, the Salish Sea and adjacent coastal waters have been identified among the top candidate sites in the U.S. for marine energy development. To better support a variety of marine energy related research and development activities, Pacific Northwest National Laboratory’s Marine and Coastal Research Laboratory in Sequim, WA has been preparing Sequim Bay as a testbed for researchers to utilize its unique tidal and geographic setting for pilot-scale tidal energy, ocean technology, and environmental monitoring research. In this study, we present our work in developing a high-resolution tidal hydrodynamic model for Sequim Bay, which provides essential hydrodynamic information to marine energy researchers. The hydrodynamic model is based on the unstructured-grid Finite Volume Community Ocean Model (FVCOM) and resolves tidal channels with a fine grid resolution of ~10 m. The model has been systematically validated with high-quality field observations of water level and velocity. The validated model was further applied to characterize tidal circulation and tidal energy distribution in Sequim Bay. Additional efforts on energy extraction, analysis tool development and data dissemination to support tidal current energy development are also discussed

Liquefaction Risk Evaluation During Earthquakes

A simplified method is herein presented to evaluate liquefaction risk, where we modified the form of liquefaction potential index suggested by Iwasaki, Tokida and others (1980, 1982). Based upon the investigations of structure damage induced by soil liquefaction during Tangshan earthquake, four categories for evaluating liquefaction risk and the principles of engineering treatment are proposed. Several typical liquefaction sites are analyzed by this method

Allosteric p97 inhibitors can overcome resistance to ATP-competitive p97 inhibitors for potential anti-cancer therapy

A major challenge of targeted cancer therapy is the selection for drug‐resistant mutations in tumor cells leading to loss of treatment effectiveness. p97/VCP is a central regulator of protein homeostasis and a promising anti‐cancer target because of its vital role in cell growth and survival. One ATP‐competitive p97 inhibitor, CB‐5083, has entered clinical trials. Selective pressure on HCT116 cells treated with CB‐5083 identified 5 different resistant mutants. Identification of p97 inhibitors with different mechanisms of action would offer the potential to overcome this class of resistance mutations. Our results demonstrate that two CB‐5083 resistant p97 mutants, N660K and T688A, were also resistant to several other ATP‐competitive p97 inhibitors, whereas inhibition by two allosteric p97 inhibitors NMS‐873 and UPCDC‐30245 were unaffected by these mutations. We also established a CB‐5083 resistant cell line that harbors a new p97 double mutation (D649A/T688A). While CB‐5083, NMS‐873, and UPCDC‐30245 all effectively inhibited proliferation of the parental HCT116 cell line, NMS‐873 and UPCDC‐30245 were 30‐fold more potent than CB‐5083 in inhibiting the CB‐5083 resistant D649A/T688A double mutant. Our results suggest that allosteric p97 inhibitors are promising alternatives when resistance to ATP‐competitive p97 inhibitors arises during anti‐cancer treatment

Hydrodynamic Modeling Analysis of Union Slough Restoration Project in Snohomish River, Washington

A modeling study was conducted to evaluate additional project design scenarios at the Union Slough restoration/mitigation site during low tide and to provide recommendations for finish-grade elevations to achieve desired drainage. This was accomplished using the Snohomish River hydrodynamic model developed previously by PNNL

Assessment of Tidal Energy Removal Impacts on Physical Systems: Development of MHK Module and Analysis of Effects on Hydrodynamics

In this report we describe (1) the development, test, and validation of the marine hydrokinetic energy scheme in a three-dimensional coastal ocean model (FVCOM); and (2) the sensitivity analysis of effects of marine hydrokinetic energy configurations on power extraction and volume flux in a coastal bay. Submittal of this report completes the work on Task 2.1.2, Effects of Physical Systems, Subtask 2.1.2.1, Hydrodynamics and Subtask 2.1.2.3, Screening Analysis, for fiscal year 2011 of the Environmental Effects of Marine and Hydrokinetic Energy project