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Keywords:

  • Lake Pontchartrain;
  • potential SAV habitat;
  • submersed aquatic vegetation

Abstract

The depth distribution of submersed aquatic vegetation (SAV) was studied in Lake Pontchartrain, Louisiana, to develop a model to predict changes in SAV abundance from changes in environmental quality. We conducted annual line-intercept surveys from 1997 through 2001 and monitored monthly photosynthetically active radiation at four sites with different shoreface slopes. The following relationships between SAV distribution and environmental factors were used as model parameters: (1) water clarity controls SAV colonization depth; (2) fluctuation in annual mean water level and wave mixing determines SAV minimum colonization depth; and (3) site differences in SAV areal coverage under the comparable water quality conditions are due to shoreface slope differences. These parameters expressed as mathematical components of the model are as follows: mean water clarity determines SAV colonization depth (Zmax= 2.3/Kd); mean water level and wave mixing controls SAV minimum depth (Zmin= 0.3 m); and shoreface slope angle (θ) determines the distance from Zmin to Zmax. The equation developed for the potential SAV habitat (PSAV) model is PSAV = (2.3 − 0.3 ×Kd)/(sinθ×Kd). The model was validated by comparing empirical values from the dataset to values predicted by the model. Although the model was developed to predict the PSAV in Lake Pontchartrain, it can be applied to other coastal habitats if local SAV light requirements are substituted for Lake Pontchartrain values. This model is a useful tool in selecting potential restoration sites and in predicting the extent of SAV habitat gain after restoration.