Biogeography of Submerged Aquatic Vegetation (SAV) in the Pontchartrain Basin: Species Salinity Zonation and 1953–2016 Lake Pontchartrain Trends

Abstract

A biogeographic study of submerged aquatic vegetation (SAV) in the Pontchartrain Basin of southeastern Louisiana was conducted. These plants provide numerous essential ecosystem services. Eighteen species occurred in different salinity zones ranging from freshwater to the saline waters of the Gulf of Mexico. Lake Pontchartrain SAV coverage was reduced by 70 percent from 1953 to 1990 due to increased turbidity from urbanization and shell dredging. A La Niña drought (1998–2001) increased SAV to 80 percent of the 1953 coverage, but declines occurred after the drought and there was extensive damage from Katrina and other hurricanes between 2005 and 2012. Coverage in 2016 is about 10 percent of the 1953 level. In these subtropical waters, some species were abundant during the winter and spring, but declined during the summer. Lower Basin SAV is also changing due to high rates of relative sea level rise and erosion of marsh and barrier islands.