Document Type

Report

Department/Program

Virginia Institute of Marine Science

Publication Date

6-29-2018

Abstract

In 2014, a user-friendly, web-accessible model was developed that allowed restoration practitioners and resource managers to easily estimate the TMDLrelated benefits of oyster reef (Crassostrea virginica) restoration per unit area, run restoration scenarios in Harris Creek, MD to optimize restoration planning and implementation, and calculate the benefits of the chosen plan. The model was rooted in scientifically defensible data and was readily transferrable to systems throughout the Chesapeake Bay and Eastern Shore. The model operated in five vertically well-mixed boxes along the main axis of the creek. Exchanges among creeks were computed using a tidal prism approach and were compared to exchanges provided from a high resolution 3D hydrodynamic model. Watershed inputs for the model were obtained for the Harris Creek sub-watershed from the Phase V Chesapeake Bay Program Watershed Model. The base model simulated daily concentrations over an annual cycle of chlorophyll-a, dissolved inorganic nitrogen (N) and phosphorus (P), dissolved oxygen, total suspended solids, the biomass of benthic microalgae, and the water column and sediment pools of labile organic carbon (C) and associated N and P. Water quality data for model forcing and calibration were obtained from the Chesapeake Bay Program, the Choptank Riverkeeper, the University of Maryland Center for Environmental Science, and the Maryland Department of Natural Resources. An oyster sub-model was coupled to this base model to compute the volume of water filtered, removal of phytoplankton, suspended solids, and associated nutrients via filtration, recycling of nutrients and consumption of oxygen by oyster respiration, production of feces, N and P accumulation in oyster tissues and shell, oyster-enhanced denitrification, and N and P burial associated with restored reefs. The completed model was served online and operated through a web browser, enabling users to conduct scenario analysis by entering box-specific values for acres restored, restored oyster density, and restored oyster size, as well as the economic value of associated N and P removal.

The updated model incorporates all aspects of the previous model but replaces oyster related data collected outside Harris Creek with site-specific data, and now includes restored oyster populations and water quality data through 2016. It also incorporates the impacts of two common, reef-associated filter feeding organisms: the hooked mussel Ischadium recurvum and the sea squirt Molgula manhattensis. Additional data collected in Harris Creek and incorporated into the model include: biomass of benthic microalgae, biogeochemical fluxes in relation to oyster biomass, and the biomass density and distribution of the dominant non-oyster reef filter feeders (I. recurvum, and M. manhattensis). The revised model incorporates an improved estimate of annual oyster growth, uses an improved method for estimating N and P sequestered in tissues and shells, and accounts for the prerestoration oyster population in Harris Creek. The model also incorporates data on the filtration capacity of I. recurvum and M. manhattensis in relation to C. virginica collected as part of a previous study (not in Harris Creek) by Kellogg and Newell (unpublished data).

DOI

https://doi.org/10.25773/7a75-ds48

Keywords

Oysters. Oyster culture--Maryland. Water--Pollution--Total maximum daily load--Maryland. Restoration ecology--Maryland.

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