Effects of Salt Marsh Impoundments Upon Ruppia and Macroinvertebrates
- Gore, James F.
University of Maine Graduate School
A study was made in a Maine salt marsh to test the influence of holding shallow depths of water in drainage ditches upon certain plants and animals that are important in the diets of some species of ducks. Three natural ditches served as controls while three other ditches were plugged with 8-inch dikes and three more ditches were plugged with 16-inch dikes.
It was found that the number of snails was increased by impounding, while the biomass of snails increased in both the control and experimental ditches. Impounding water in ditches did not initiate growths of Ruppia. However germination tests of Ruppia seed collected from ditches revealed that the seed was unviable in contrast to seed collected from adjacent pannes. Further testing showed that Ruppia seeds of proven viability germinated in impounded ditches. Impounding did not result in increased production of salt marsh mosquitoes, primarily because these areas supported populations of mummichogs that prey upon mosquito larvae.
The soil and water properties of ditches did not vary greatly between control and impounded ditches. However, 8-inch impoundments had slightly less turbidity during the summer than did controlled ditches or 16-inch impoundments.
The simple design of the ditch plugs used in the study was sturdy enough to impound water up to 16 inches deep. The cost of the materials for making the plugs was low and the plug construction was relatively easy.
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