Progress and challenges in coupled hydrodynamic-ecological estuarine modeling

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Estuaries and Coasts 39 (2016): 311-332, doi:10.1007/s12237-015-0011-y.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 different 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.NKG, ALA, and RPS acknowledge support from the USGS Coastal and Marine Geology Program. DKR gratefully acknowledges support from NSF (OCE-1314642) and NIEHS (1P50-ES021923-01). MJB and JMPV gratefully acknowledge support from NOAA NOS NCCOS (NA05NOS4781201 and NA11NOS4780043). MJB and SJL gratefully acknowledge support from the Strategic Environmental Research and Development Program—Defense Coastal/Estuarine Research Program (RC-1413 and RC-2245)

New paths for modelling freshwater nature futures

Freshwater ecosystems are exceptionally rich in biodiversity and provide essential benefits to people. Yet they are disproportionately threatened compared to terrestrial and marine systems and remain underrepresented in the scenarios and models used for global environmental assessments. The Nature Futures Framework (NFF) has recently been proposed to advance the contribution of scenarios and models for environmental assessments. This framework places the diverse relationships between people and nature at its core, identifying three value perspectives as points of departure: Nature for Nature, Nature for Society, and Nature as Culture. We explore how the NFF may be implemented for improved assessment of freshwater ecosystems. First, we outline how the NFF and its main value perspectives can be translated to freshwater systems and explore what desirable freshwater futures would look like from each of the above perspectives. Second, we review scenario strategies and current models to examine how freshwater modelling can be linked to the NFF in terms of its aims and outcomes. In doing so, we also identify which aspects of the NFF framework are not yet captured in current freshwater models and suggest possible ways to bridge them. Our analysis provides future directions for a more holistic freshwater model and scenario development and demonstrates how society can benefit from freshwater modelling efforts that are integrated with the value-perspectives of the NFF. Graphical abstract: [Figure not available: see fulltext.]</p

Effects of Habitat Degradation on Biological Endpoints in the South Fork Broad River Basin, Georgia

Proceedings of the 2001 Georgia Water Resources Conference, April 26 and 27, 2001, Athens, Georgia.The effects of habitat degradation on biological endpoints were studied at 13 sites in and adjacent to the South Fork Broad river basin. Constrained ordination was used to relate benthic macroinvertebrate and fish data to habitat and environmental data. Benthic macroinvertebrates were primarily influenced by habitat, while fish were affected by stream order and secondarily by habitat. Habitat degradation was related to: a decrease in stoneflies, caddisflies, and the Clingers/Burrowers ratio; a decline in the abundance of darters and suckers; and an increase in the number of sunfish species.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors

Foodweb modeling for polychlorinated biphenyls (PCBs) in the Twelvemile Creek Arm of Lake Hartwell, South Carolina, USA

PCBs from the Sangamo-Weston Superfund Site near Clemson, South Carolina, USA, were released into the Twelvemile Creek Arm of Lake Hartwell until the early 1990s. Monitoring data have shown that while PCB concentration in sediments declined since 1995, PCB concentrations in fish have remained elevated, e.g., largemouth bass (Micropterus salmoides) concentrations have ranged from 5 to 10 ppm. The EPA aquatic ecosystem model AQUATOX was applied to this system to better characterize foodweb dynamics that lead to biomagnification of PCBs. The model was calibrated with observed fish biomass data. Simulated PCB loading over a 12-year period provided a reasonable fit to observed PCB data in fish. The model demonstrated that contaminated labile detritus loaded to the system was incorporated into the foodweb rather than deposited, thereby maintaining the PCB concentrations in fish while concentrations in the sediment declined. A dominant PCB pathway was from detritus to daphnia to shad to largemouth bass. Fish PCB concentrations showed moderate sensitivity to toxicant parameters; model runs incorporating uncertainty in these parameters predicted recovery (\u3c2ppm PCB) for all species in the range of years from 2008 to 2013. The high sensitivity of the model to parameters related to growth strongly affected PCB concentrations in fish and should be considered in future AQUATOX applications

Effects of stream topology on ecological community results from neutral models

While neutral theory and models have stimulated considerable literature, less well investigated is the effect of topology on neutral metacommunity model simulations. We implemented a neutral metacommunity model using two different stream network topologies, a widely branched network (wide tree) and a narrowly branched network (high tree), both represented as binary trees. The wide tree had fewer exceedances of carrying capacity, higher final number of individuals per community, and greater community (α) diversity than the high tree. The difference in diversity increased with increasing dispersal rate. We infer that the greater connectivity of the wide tree facilitated more even spatial dispersal, which limited carrying capacity exceedances and associated random deletions, which, in turn, resulted in higher diversity. Effects specifically due to topology should be considered in analyses of community patterns for mobile aquatic species.KEYWORDS: Neutral model, Stream network, Metacommunity, Species richness, Topolog

Trend Analysis of Water Quality Monitoring Data for Cobb County, GA

Proceedings of the 2007 Georgia Water Resources Conference, March 27-29, 2007, Athens, Georgia.The Cobb County Water Protection Division Water Quality Laboratory has conducted quarterly chemical monitoring from 1995-2005. Here we analyze these data for temporal trends at 45 sites in 10 Piedmont streams in the Chattahoochee and Etowah river basins. The strongest overall trend was for increases in conductivity, chlorides, TKN, and NOx. Some sites showed a decrease in turbidity, TSS, and percent dissolved oxygen saturation. To the extent that the changes in water quality have resulted from land use change and increasing urbanization and development in the watershed, the best indicators of land use change in Cobb County may be conductivity and TKN. This dataset provides a unique opportunity to examine water quality trends for a rapidly developing region of Georgia.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors

Beyond The Indices: Relations of Habitat and Fish Characteristics in the Georgia Piedmont

Proceedings of the 2003 Georgia Water Resources Conference, held April 23-24, 2003, at the University of Georgia.Multivariate statistical techniques were used to gain additional insight about ecological variability and the dominant environmental gradients in biological and habitat data from Piedmont streams sampled by the Georgia Department of Natural Resources. Principal components analysis indicated that relevant patterns in the fish assemblage were related to the number of benthic invertivore, cyprinid, and simple lithophilic species; and pioneering versus sunfish species. In addition, principal components analysis indicated that habitat variability was related to number of riffles, sediment deposition and embeddedness, bank stability, and stream width and depth. Multiple regression analysis of fish assemblage metrics indicated that the number of benthic invertivore, cyprinid, and lithophilic species appeared to be negatively associated with many substrate characteristics that are indicative of sedimentation. Results also indicate that from a management perspective it may be necessary to evaluate small headwater streams separately from larger streams

Economic Value of Stream Degradation across the Central Appalachians

This study demonstrates a method to calculate the economic value of the loss of a highly valued ecosystem service—the provision of recreational fishing—across a multi-state assessment region. We estimated annual freshwater fishing expenditures foregone from degraded conditions in wadeable streams that are potential habitat to one or more of four sportfish species. Using probability-based federal surveys for data on sportfish presence, we developed range models for the four species in the mountainous portions of four U.S. mid- Atlantic states based on geophysical stream variables unrelated to habitat condition. From these models, we determined the proportion of the wadeable stream resource (44.2%) that could potentially host sportfish and allocated an estimate of annual regional freshwater fishing expenditures (US$826 million) from the National Survey of Fishing, Hunting, and Wildlife- Associated Recreation to these stream segments. We attributed the absence of sportfish in these segments to stream degradation; an additional US$239 million was estimated as lost freshwater fishing expenditures. These figures suggest a considerable annual economic incentive for stakeholders to restore and protect stream habitat for the maintenance of sport fisheries. This method is readily transferable to other U.S. regions where long-term surveys that collect metrics linked to ecosystem services are in place

Foodweb modeling for PCBs in the Twelvemile Creek arm of Lake Hartwell, GA/SC

The U.S. EPA is conducting a series of studies on the Sangamo-Weston Superfund Site near Clemson, SC, to examine the pollution of the Twelvemile Creek arm of Lake Hartwell by PCBs that were released from the site until the early 1990s. Monitoring data have shown that while PCB concentration in sediments declined since 1995, PCB concentrations in fish have not. The EPA aquatic ecosystem model AQUATOX has been applied to examine this system. This model provides an understanding of food web dynamics, characterization of bioaccumulation, and identification of most sensitive ecosystem components. The model may eventually be used in prediction of future PCB concentrations in fish under different scenarios for management.Sponsored by: Georgia Environmental Protection Division U.S. Geological Survey, Georgia Water Science Center U.S. Department of Agriculture, Natural Resources Conservation Service Georgia Institute of Technology, Georgia Water Resources Institute The University of Georgia, Water Resources Facult