You are here:
Tampa Bay Water Clarity Model (TBWCM): As a Predictive Tool
Citation:
Rogers, Johne AND M. Russell. Tampa Bay Water Clarity Model (TBWCM): As a Predictive Tool. 2016 Ocean Sciences Meeting, New Orleans, LA, February 21 - 26, 2016.
Impact/Purpose:
Describe Tampa Bay Water Clarity Model at ASLO Conference.
Description:
The Tampa Bay Water Clarity Model was developed as a predictive tool for estimating the impact of changing nutrient loads on water clarity as measured by secchi depth. The model combines a physical mixing model with an irradiance model and nutrient cycling model. A 10 segment bifurcated box model based on salt and water balance which assumed complete mixing of each segment at each time step was used to physically mix the Bay. The irradiance model predicted light levels just below the Bay surface from atmospheric conditions appropriate for Tampa Bay. The nutrient cycling model was primarily based on the growth of phytoplankton, their death and the recycling of inorganic nutrients as described in WASP. Secchi depths were calculated from Kd values based on light absorption by water, total chlorophyll (a, b and c), colored disolved organic matter, and the effects of turbidity. The model was calibrated against monthly salinity, total chlorophyll, ammonia, total kjeldahl nitrogen, and dissolved oxygen data collected during 1985 through 1991. The model was calibrated in two stages: (1) by first calibrating the exchange coefficients using the box model and (2) by calibrating selected nutrient cycling parameters using the complete water clarity model. Validation of the model was conducted with a similar data set collected during 1992 through 1994. We assessed the sensitivity of the model to changes in nutrient load by running the model in predictive model. Inputs from gauged river and unguaged drainage basins were adjusted by factors of (0.5 to 5.0). A straight line relationship was found between nutrient inputs and the average secchi depths, ammonia levels, and total chlorophyll levels for the seven year (1985-1991) model runs. A 5-fold increase in gauged river input resulted in a 10 percent decrease in secchi depth which resulted in a 30 percent decrease in the maximum depth for seagrass growth in the middle portion of Old Tampa Bay.