The Effect of Terraces on SAV in Three Southwest Louisiana Marshes
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Chris Cannaday
School of Renewable Natural Resources
Louisiana State University
Baton Rouge, LA 70803
(Presented by Andy Nyman)
Abstract
The coast of Louisiana is one of the largest contiguous marshes in the world, but it is converting to shallow open water at a rate of 25 square miles per year. Various techniques have been developed to slow or reverse these losses. One technique used in southwestern Louisiana in recent years is terracing. Terracing uses soil from the bottom of shallow marsh ponds (tidal or nontidal) to create open ended levees that reduce wave action. This is expected to slow erosion of nearby marsh by reducing wave action. Terraces also create a small amount of marsh, and create edge habitat that is favorable for nekton. Terraces are believed to enhance submerged aquatic vegetation (SAV) productivity and abundance by reducing turbidity. Though this is a logical assumption, the effect of terraces on SAV remains unknown. Only two studies have looked at terraces' effects on SAV and the results are inconclusive. This study compares three pairs of terraced and natural shallow marsh ponds in southwest Louisiana in an attempt to understand how terracing affects SAV. Data was collected on SAV biomass and frequency using rake transects, cores, and 1m2 throw traps every other month from April 2004 to April 2005. Data collection from the field is complete but analysis is ongoing. However, preliminary results indicate that terraces may indeed increase biomass and diversity of SAV in terraced ponds.
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