Troy University environmental science faculty recently developed an oyster habitat suitability model for the Choctawhatchee Bay as part of a $114,843 grant from the Choctawhatchee Basin Alliance and Northwest Florida State College.
Dr. Chris Boyd, Assistant Professor of restoration ecology in the Department of Biological and Environmental Sciences, collaborated with Dr. Xutong Niu, Associate Professor and Chair of the Department of Geospatial Informatics, and graduate student Taylor Rose Horn to create the online model. The model was created to provide state, federal and non-governmental natural resource managers, city and county planners and future oyster aqua-culturalists with a readily available online source that displays multiyear essential historic water quality data to evaluate oyster site suitability for specific locations in the Choctawhatchee Bay.
From mid-April through June, the trio traveled along the shorelines of the Choctawhatchee Bay to collect water samples and other data. The Choctawhatchee Bay Habitat Suitability Model was completed on June 30.
Boyd said they were able to acquire about seven years of water quality data from over 70 monitoring stations collected by the Florida Department of Environmental Protection for the state’s Watershed Information Network (WIN) database.
“The Florida Department of Environmental Protection has pretty strict quality control guidelines, so that data is really good. They have collected water samples at different depths, so we were able to tweak the data to where it had top water and bottom water data,” Boyd said. “Dr. Niu, Rose Horn and I were able to acquire the data, and I worked with Jason Storrs, the WIN Coordinator from the WINS database. We then researched all the different oyster habitat suitability models that have been run around the United States.”
Boyd explained the two main factors for oyster growth are salinity and temperature, but the team took the model a step further and incorporated dissolved oxygen, pH and bottom hardness.
“Traditionally, oyster reefs grow on the Bay bottom or on the side of the shoreline in the intertidal zone, depending on the location. Initially, the model was made for subtidal oysters,” he said. “In theory, the model is made for oysters to grow on the bay bottom, so we analyzed the data with historical water quality values and then ran the five-parameter model.”
Boyd soon ran into a question—the water quality and data showed optimal conditions for oyster growth, so why were oysters not growing in certain regions of the Choctawhatchee Bay? He thinks ocean acidification, levels of dissolved oxygen and overharvesting all play a part. Boyd hopes the model will help play a role in future efforts to re-grow the oyster population.
“Unfortunately, there’s problems worldwide with oysters growing because of overharvesting and other factors. But in particular, it could be something to do with ocean acidification and the Bay getting too acidic,” he said. “That’s why we looked at pH, but what I’m also seeing is the bottom dissolved oxygen can become low at certain times of the year. Oysters breathe air like us, but their oxygen is actually in the water. Where our model showed the most suitable locations had pretty good oxygen a majority of the year, but the problem is that we also noticed that there were some short term really low dissolved oxygen levels that need to be examined further.
“We generated an online GIS viewer from which users can check for the most suitable oyster habitat locations, along with the oxygen levels at the top and bottom of the water. The model and associated online viewer weren’t necessarily created for oyster aquaculture, but I decided since we were funded for this project already to give them all the tools that they can use to support the oyster revitalization in Choctawhatchee Bay.”
Research was performed in collaboration with the Choctawhatchee Basin Alliance, Northwest Florida State College and the Environmental Section of the Walton County Board of County Commissioners Public Works Department.