Harry V. Wang

Importance of Metapopulation Connectivity to Restocking and Restoration of Marine Species

We examine the impact of spatial processes on the efficacy of restocking in species with varying forms of population or metapopulation structure. Metapopulations are classified based on spatial complexity and the degree of connectedness between populations. Designation of effective restocking sites requires careful attention to metapopulation dynamics; populations in the metapopulation can differ dramatically in demography and connectivity, and the sites they occupy can vary in habitat quality. Source populations, which are optimal for restocking, can be distinct geographically and may be a small percentage of the metapopulation. Sink areas, where restocking is almost certain to be fruitless, can nonetheless serve as productive locations for habitat restoration since larvae from source reefs are likely to recruit to these areas. Effective restocking of metapopulations is most likely to be attained by selection of optimal source populations; inattention to metapopulation dynamics can doom restoration efforts with marine species.

Modeling particles and pelagic organisms in Chesapeake Bay: Convergent features control plankton distributions

A two-dimensional Lagrangian particle trajectory model is described and used to study how surface currents transport particles and, by analogy, plankton in Chesapeake Bay, United States. It is shown that persistent patches of high particle concentration develop in well-defined regions along the eastern shore and in the lower reaches of some western shore tributaries due to a combination of passive accumulation of particles in areas where the flushing rate is low and convergence. In the model the highest particle concentrations in the Chesapeake consistently develop in the lower bay (latitude 37.1°–37.7° N) in two specific regions near the shore of Cape Charles where convergence and downwelling occur. It is shown that one of these is associated with a strong and persistent, residual cyclonic eddy located over an abrupt change in bottom topography. Recent bay wide field surveys reveal that various planktonic groups, including phytoplankton, zooplankton, and bay anchovy eggs and larvae, have maximum abundances in the vicinity of this eddy. It is argued that these convergent areas are important features that have a strong influence on plankton distributions and that they provide consistently high food concentrations for higher trophic levels.

Assimilating high‐resolution salinity data into a model of a partially mixed estuary

[1] A three-dimensional circulation model of the Chesapeake Bay is used to validate a simple data assimilation scheme, using high-resolution salinity data acquired from a ship-towed undulating vehicle (a Scanfish). The simulation period spans the entire year of 1995 during which the high-resolution Scanfish data were available in July and October, lasting a few days each. Since Scanfish data were irregularly distributed in time and space, only salinity fields are nudged in the model for simplicity. Model improvements through data assimilation are evaluated from a pair of experiments: one with data assimilation and one without. Data from scattered Chesapeake Bay Program monitoring stations and a few stations maintained by the National Ocean Service inside the bay are used independently to check the model performance. In general, the simple assimilation scheme leads to visibly improved density structures in the upper and middle reaches of the bay. The improvement in the lower bay is equally pronounced after data assimilation but diminishes in a shorter timescale because of faster flushing from the adjacent coastal ocean. Moderate to weak nudging normally enhances the gravitational circulation. Strong nudging may produce transient overshooting, during which the gravitational circulation is renewed vigorously.

Validation and Application of the Second Generation Three Dimensional Hydrodynamic Model of Chesapeake Bay

The validation and subsequent application of the current three-dimensional numerical hydrodynamic model of Chesapeake Bay is presented. The numerical model solves conservation equations for water mass, momentum, salinity, and heat on a boundary-fitted grid in the horizontal plane and a Cartesian z-grid in the vertical. A generalized ADI finite difference scheme is employed in conjunction with mode splitting technique, solving external and the internal modes. The 10-year boundary conditions including tide, slinity, temperature, wind, heat exchange coefficient, river and non-point source flows were constructed. Model validation was accomplished by demonstrating the models ability to reproduce observed data over time scales ranging from tidal to seasonal periods. The major parameters compared include tidal elevation, intra-tidal and residual velocities, salinity, temperature, stratification, and flux calculated through the Bay mouth.After validation, the model was applied to simulate bay hydrodynamics for the 10 years of 1985–94. These results were used to drive the three-dimensional water quality model of Chesapeake Bay, which is discussed in a companion paper.

Architecture of a Community Infrastructure for Predicting and Analyzing Coastal Inundation

The Southeastern Universities Research Association (SURA) has advanced the SURA Coastal Ocean Observing and Prediction (SCOOP) program as a multi-institution collaboration to design and prototype a modular, distributed system for real-time prediction and visualization of the coastal impacts from extreme atmospheric events, including hurricane inundation and waves. The SCOOP program vision is a community “cyberinfrastructure” that enables advances in the science of environmental prediction and coastal hazard planning. The system architecture is a coordinated and distributed network of interoperable, modularized components that include numerical models, information catalogs, distributed archives, computing resources, and network infrastructure. The components are linked over the Internet by standardized web-service interfaces in a service-oriented architecture (SOA). The design philosophy allows geographically disparate partnering institutions to provide complementary data-provider and integration services. The overall system enables coordinated sharing of resources, tools, and ideas among a virtual community of coastal and computer scientists. The distributed design builds on the notion that standards enable innovation, and seeks to leverage successes of the World Wide Web by creating an environment that nurtures interaction between the research community, the private sector, and government agencies working together on behalf of the nation.

Modeling water exchange between Baltimore Harbor and Chesapeake Bay using artificial tracers: Seasonal variations

Understanding the dynamics of water exchange between Baltimore Harbor and the Chesapeake Bay is essential when evaluating transport and fate of dissolved substances in both of these systems. Conservative artificial tracers are used in this study to investigate transport processes through a three-dimensional hydrodynamic model (CH3D). The model well reproduced the three-layered circulation pattern in Baltimore Harbor. Several numerical experiments are performed to trace the water mass coming from different sources. The results indicate that both the upper and lower layers of the Harbor are the dominant pathways of transporting dissolved substances from Susquehanna River to the Harbor. Such inward transport is intensified (suppressed) during the high-discharge (low-discharge) period. The upper layer inflow transports water mass with high concentrations of dissolved substances while the inflow from the lower layer transports water mass with low concentrations of dissolved substances. The bottom layer is the dominant pathway for transporting dissolved substances from the lower Bay to the Harbor. Lower river discharge and stronger along-Bay pressure gradient (resulting in stronger landward residual flow in the bottom layer of the Bay) facilitate the bottom intrusion of dissolved substances from lower Bay to the Harbor. Once contaminants are transported into the Harbor, they usually stay for a longer time in the mid-depth of the Harbor than those in other layers due to the three-layer circulation in the Harbor. The time needed for the contaminants being transported out of the Harbor during a typical low-discharge period is about 1 month longer than that needed during a typical high-discharge period. The results, from the environmental perspective, provide new insights for quantitative evaluation on the transport processes of the dissolved biogeochemical substances between Baltimore Harbor and Chesapeake Bay.

Forecasting system predicts presence of sea nettles in Chesapeake Bay

Outbreaks of noxious biota, which occur in both aquatic and terrestrial systems, can have considerable negative economic impacts. For example, an increasing frequency of harmful algal blooms worldwide has negatively affected the tourism industry in many regions. Such impacts could be mitigated if the conditions that give rise to these outbreaks were known and could be monitored. Recent advances in technology and communications allow us to continuously measure and model many environmental factors that are responsible for outbreaks of certain noxious organisms. A new prototype ecological forecasting system predicts the likelihood of occurrence of the sea nettle (Chrysaora quinquecirrha), a stinging jellyfish, in the Chesapeake Bay.

Rapid changes of sediment dynamic processes in Yalu River Estuary under anthropogenic impacts

Abstract The response of the Yalu River Estuary to human activities was investigated. Changes of sediment dynamics during the past 10 years were explored through hydrodynamic calculation, as well as heavy mineral and grain size analysis. In addition, the characteristics of estuarine geomorphological evolution were compared with historical data. The long-term sediment dynamic process and geomorphological evolution were primarily affected by the decrease of water discharge and sediment supply resulting from human activities. The entire estuarine system of Yalu River Estuary has also undergone significant changes since 1941 that are associated with water reduction and sediment discharge affected by construction reservoirs. The estuary eventually formed the current patterns in the 1980s. Compared with variations of water and sediment discharge, sand dredging directly affected the estuarine sediment dynamics in the past 10 years. Data from six hydrodynamic stations measured in 2009 indicated that the bedload transport flux has substantially decreased during a tidal cycle compared with that surveyed in 1996. The bedload transport direction also changed from seaward in 1996 to landward in 2009. In addition, the estuarine bed load movement changes were: (a) sediment from areas with water depth being less than 5 m was transported from the sea towards the land; (b) sediment transport from areas with water depth between 5 to 20 m was oriented towards the sea; and (c) sediment from areas with water depth greater than 20 m was conveyed from the sea towards the land.

Erratum to: Relative Importance of Nutrient Load and Wind on Regulating Interannual Summer Hypoxia in the Chesapeake Bay

To analyze the correlations of summer anoxia/hypoxia in the Chesapeake Bay with watershed input and wind conditions, statistics were applied to nearly three decades of monitoring data. The results of Pearson correlation coefficients, multivariate regression analysis, and cluster analysis indicate that anoxia/hypoxia has a strong positive correlation with nutrient load and a moderate negative correlation with wind speed. Physical relationships among the relevant constituents were analyzed. Nutrient loads and the subsequent decay of organic matter are the primary factors that control the oxygen demand causing summer anoxia and hypoxia, while episodic wind can partially erode stratification and reduce anoxia/hypoxia. Although the extent of anoxia/hypoxia reduction differs with wind direction, higher wind speeds result in more destratification and anoxia/hypoxia reduction than lower wind speeds and are more important than the effect of wind direction. The influences of freshwater discharge, stratification, and temperature were also analyzed. Computer modeling results were used to obtain dissolved oxygen conditions at finer temporal and spatial scales to supplement the scattered and discrete observations from monitoring stations and for better understanding of anoxia/hypoxia development under episodic wind events.

An Integrated Coastal Observation and Flood Warning System: Rapid Prototype Development

This paper describes the rapid prototype development of an inaugural capability for an Integrated Coastal Observation and Flood Warning System (ICOFWS), initially focused in the tidal Potomac River. A collaboration of the Virginia Institute of Marine Science (VIMS), NOAA National Weather Service (NWS) Forecast Offices in Wakefield and Sterling, Virginia, and Mitretek Systems developed the capability for a high-resolution hydrodynamic storm-surge model, coupled with the newest generation Weather Research and Forecast model and high resolution digital elevation LIDAR data, to predict land inundation from storm events in the Washington Metropolitan Area and the tidal Potomac River. This prototype capability then uses emerging Geographic Information Systems (GIS) visualization technologies to present forecast information in a manner that can be integrated into operations systems of local jurisdiction emergency managers and other planners. Initial steps have been taken to document a proposed process to bring this capability into operational status within the standard NWS forecast cycle as a tool to support storm surge products. It is being explored for use by partners of the Chesapeake Bay Observing System (CBOS) within the Integrated Ocean Observing System (IOOS) Mid-Atlantic Coastal Ocean Observing Regional Association (MACOORA) to demonstrate the interaction of organizations operating in, and providing support within, the Chesapeake Bay region, as well as potential use of this collaborative procedure within other IOOS regional associations throughout the United States. This focused systems engineering approach allows for the more-rapid-than-typical development of prototype systems that can be evaluated for use within the broader IOOS and Global Earth Observation System of Systems (GEOSS) to provide more timely support to those with the responsibility to prepare for, and react to, environmental effects on critical infrastructure and our society