A long term calibration and verification of a submerged aquatic vegetation model for Lake Okeechobee

Introduction:Submerged aquatic vegetation(SAV)has multiple functions in Lake Okeechobee.It provides critical habitat for fish and wildlife,stabilizes sediments,reduces phosphorus(P)concentration in the water column by preventing re-suspension of P-rich sediments,and provides a substrate for attached algae,which also helps to remove P from the water column.Ten year water quality and SAV growth simulations are presented and compared with observed SAV and water quality data collected in the nearshore zone in Lake Okeechobee.Methods:The SAV theory and approach used in the LOEM are modified from the Chesapeake Bay model and incorporate three state variables:shoots(above the bed sediment),roots(in the bed sediment),and epiphytes(attached to the shoots).The SAV model has direct linkages with the water quality model,including(1)a link between the growth and decay of SAV and the nutrient pool of the water quality model;(2)a link between the photosynthesis and respiration of SAV and dissolved oxygen dynamics,and(3)the ways in which settling of particulate organic matter and nutrient uptake affect nutrient levels in the water column and in the sediment bed.Results:Total suspended solids affect light attenuation and are another major driving factor for SAV growth in the nearshore and littoral zone area.The model performs reasonably well in reproducing the spatial distribution of SAV.Conclusions:The theoretical analysis and model sensitivity tests indicate that SAV growth is primarily controlled by light and nutrients.The light available for SAV growth depends on the water depth and the turbidity.In this full scale simulation,the water depth comes from the LOEM hydrodynamic model,and the turbidity depends on the suspended sediment concentration and algal concentration.