WP200 (WEL-1117-750779) AQUATOX as a tool to evaluate suspended sediment and nutrient stressor interactions and their management alternatives.
Start time: 8:00 AM
Wellman, M¹, Park, R², Carleton, J¹, Clough, J³, ¹ US Environmental Protection Agency, Washington, DC, USA² Eco Modeling, Diamondhead, MS, USA³ Warren Pinnacle Consulting, Inc., Warren, VT, USA
AQUATOX, a mechanistic fate and effects model, simulates the significant physical, chemical, and biological processes affecting aquatic biota. It can model multiple species of periphyton, phytoplankton, macrophytes, invertebrates, and fish as well as nutrients, sediments, organic toxicants and pesticides. AQUATOX has a very flexible structure and provides multiple analytical tools useful for evaluating the ecological effects of sediments and nutrients, alone or in combination. Identification of the most important stressor on the biota, and therefore the most effective stressor to reduce, can be aided by iterative changes in stressor loadings, or by using the automated uncertainty and sensitivity routines. Evaluation of ecological process and interactions can be facilitated by graphing time-varying biological rates and limitations on production. This may provide a greater understanding of the ecosystem functions and how they may change under different stressor regimes. Linkage to watershed models, such as HSPF in BASINS, can help evaluate whether proposed pollution reduction alternatives will be able to meet water quality goals, such as for chlorophyll a and water clarity. Users can examine whether compositional shifts are predicted for periphyton, phytoplankton, invertebrate and fish communities with changes in N, P, and sediment loadings. Sensitivity analysis may provide quantitative estimates of optimal levels of nutrients and sediments to sustain a diverse riverine community. Examples will be given from applications to four rivers in Minnesota and Alabama.

WP201 (BER-1117-738575) Winter flounder Psuedoleuronectes americanus hatching success as a function of burial depth in the laboratory.
Start time: 8:00 AM
Berry, W¹, Rubinstein, N¹, Hinchey, E¹, Klein-MacPhee, G², ¹ U.S. Environmental Protection Agency, Narragansett, RI, USA² University of Rhode Island, Narragansett, RI, USA
The winter flounder Pseudopleuronectes americanus is a commercially and recreationally important fish whose populations have declined steadily over the last 20 years and are currently at an all-time low. Previous laboratory experiments have shown that viable hatch of winter flounder eggs is reduced when the eggs are buried by as little as one half of one egg diameter (0.5 mm of sediment), but these experiments were not specifically designed to measure the effects of burial. The sensitivity of winter flounder eggs to burial has resulted in seasonal banning of dredging in several northeastern U.S. estuaries, which can greatly increase the cost of dredging. In this study, a series of three laboratory experiments was performed to better determine the effects of burial in clean sediment on the hatching success of winter flounder. Recently spawned (3-5 days after fertilization) eggs were exposed to clean, fine-grained sediment with burial depths including a control (no-sediment), dusting (<0.5 mm), and up to 9.3 mm (>10 egg diameters) of sediment until hatch. Despite variability among experiments, a trend of decreased hatch success and increased time to hatch with increasing depth of burial relative to controls was observed. Percent total hatch of eggs buried in <1.0 mm sediment was generally not statistically different from that of the controls. Percent total hatch was highly variable in eggs buried in 3.0 mm of sediment, while there was little or no hatch in eggs buried in > 3.0 mm of sediment. Delayed hatch date (compared to controls) was observed in eggs buried in as little as 1.0 mm of sediment. Overall, these results confirm that winter flounder eggs are vulnerable to burial in sediments. These findings should be considered whenever anthropogenic activities are proposed resulting in increased sediment deposition in winter flounder spawning areas.

WP202 (DOH-1117-712114) Pre-Restoration Geomorphic and Sediment Conditions of Minebank Run, Baltimore County, Maryland.
Start time: 8:00 AM
Doheny, Edward¹, Mayer, Paul², ¹ U.S. Geological Survey, Water Science Center, Baltimore, Maryland, United States² U.S. Environmental Protection Agency, Office of Research and Development, Ada, Oklahoma, United States
Urban streams frequently undergo severe incision and erosion due to flashy streamflows caused by impervious surfaces in the watershed. Such streamflows can lead to unstable sediment dynamics that can limit options for urban stream restoration. The U.S. Environmental Protection Agency, U.S. Geological Survey, and Baltimore County Department of Environmental Protection and Resource Management are collaborating to study the effects of restoration on sediment processes in a selected study reach of Minebank Run, a small urban stream in Baltimore County, Maryland that is currently being restored. The pre-restoration dimension, pattern, and profile of the stream channel at Minebank Run were quantified, and changes over time caused by storms and flooding were assessed. Changes in cross-sectional area, bed elevation, lateral migration of the stream channel, rate of bank retreat, and grain-size distribution were measured throughout the study reach. Pre-restoration longitudinal-profile surveys indicated rapid and significant changes in the distribution of riffles, pools, and runs within the study reach, indicating continuous alteration of benthic habitat. Changes in channel-bed elevations indicated alternating periods of degradation and aggradation in different locations of the study reach. Boundary shear-stress computations showed erosive power nearly an order of magnitude larger than that of similar non-urban streams, suggesting that restoration of urban streams must address highly variable flow regimes to be successful. The Minebank Run stream channel was restored during 2004 and early 2005. Post-restoration characterization of sediment dynamics is planned to determine whether specific restoration techniques enhance the stability of the dimension, pattern, and profile of the stream channel.