ecological modelling 211 ( 2 0 0 8 ) 77–89 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ecolmodel Modeling oyster growth rate by coupling oyster population and hydrodynamic models for Apalachicola Bay, Florida, USA Hongqing Wang a,* , Wenrui Huang b , Mark A. Harwell a,1 , Lee Edmiston c , Elijah Johnson a , Ping Hsieh d , Katherine Milla d , John Christensen e , Jessica Stewart c , Xiaohai Liu b a Environmental Cooperative Science Center, Environmental Sciences Institute, Florida A&M University, Tallahassee, FL 32307, USA b Civil Engineering Department, College of Engineering, Florida A&M University and Florida State University, Tallahassee, FL 32310, USA c Apalachicola National Estuarine Research Reserve, Florida Department of Environmental Protection, Apalachicola, FL 32320, USA d College of Engineering Sciences, Technology & Agriculture, Florida A&M University, Tallahassee, FL 32307, USA e National Centers for Coastal Ocean Science, National Oceanic & Atmospheric Administration, 1305 East West Highway, Silver Spring, MD 20910, USA article info Article history: Received 29 April 2007 Received in revised form 2 August 2007 Accepted 22 August 2007 Published on line 24 October 2007 Keywords: Eastern oyster Oyster population modeling Coupled biological–physical models Estuaries Bay salinity Freshwater inflow Apalachicola Bay Hydrodynamic model abstract The eastern oyster (Crassostrea virginica) plays an important role both ecologically and economically in Apalachicola Bay, Florida. Oyster population features such as population size, age structure, spawning, growth, and reproduction are closely related to bay salinity, which is often affected by freshwater flows from the Apalachicola River. Existing model- ing approaches have used statistical models to examine the effects of changing freshwater inflow/salinity regime on oyster growth rates in Apalachicola Bay. However, little has been done using population process-based models. In this study, we adapted an oyster population model that simulates a diversity of population processes (including ingestion, assimila- tion, respiration, reproduction, spawning, recruitment, and mortality) and coupled it with a hydrodynamic model to examine the effects of changes in freshwater flow/salinity on oyster growth rates. We simulated oyster populations at two sites, Cat Point, a less-freshwater- influenced oyster reef, and Dry Bar, a more-freshwater-influenced oyster reef. The model simulations agree reasonably well with field measurements (r 2 = 0.84). Statistical analyses suggested that oyster growth rates are significantly related to salinity. Lowest oyster growth rates tend to occur in mid-spring due to lowest salinity caused by highest Apalachicola River freshwater inflows whereas the growth peaks tend to occur in mid-summer because of the warm temperature and high food supply. Meanwhile, changes in freshwater inflows affect oyster growth rates through influencing salinities as well as other environmental factors such as food availability; and the magnitudes of the change in oyster growth rates depend on the difference between salinity and salinity range for optimal growth. The salin- ity range for optimal growth (≥2.0 mg AFDW oyster -1 day -1 ) is between 20 and 25 ppt at Cat Point and 17–26 ppt at Dry Bar. Only at the optimal salinity level can oysters achieve the max- imum growth rates. Our simulations indicate that coupling oyster population process-based ∗ Corresponding author. Current address: Center for Louisiana Inland Water Studies, University of Louisiana at Lafayette, Lafayette, LA 70503, USA. Tel.: +1 850 443 7870; fax: +1 337 482 0698. E-mail address: hxw7894@louisiana.edu (H. Wang). 1 Current address: Harwell Gentile & Associates, LC, Palm Coast, FL 32164, USA. 0304-3800/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2007.08.018