THE ROLE OF SALT POOLS IN THE DYNAMIC SURFICIAL MOSAIC OF NORTH-TEMPERATE SALT MARSH ENVIRONMENTS

Salt pools are shallow, continuously flooded depressions common to many north-temperate salt marsh environments. Previous work from Maine suggests that salt pools are secondary and dynamic features, as opposed to primary relict features. Recent analyses of a time series of aerial photographs from Ogunquit to Lubec, ME, reveal that many pools alter their shape and size over decadal time periods, contributing to substantial surficial change. Pools drained, often via tidal creek capture, and re-vegetated at first by the low-marsh plant, Spartina alterniflora, and then either continued to accrete vertically, becoming colonized by the high marsh plant, S. patens, or they re-filled with water and reverted to pool environments. In addition, over the same time period, once-vegetated surfaces converted to open-water pool habitats. Dutch cores collected through paleo-pools confirm these transformations of the marsh surface. Salt pools are consistently recognized in the stratigraphic record by dark gray, muddy sediment of high water content that may contain macrofossils of the submerged aquatic plants Ruppia maritima and Zostera marina, and/or the mollusks, Hydrobia totteni and/or Gemma gemma. Recent work quantifies the physical variation in salt pool environments among and between sites in terms of temperature, salinity, dissolved oxygen, water depth, elevation, size, and shape. Preliminary analyses link these physical measurements to vegetation patterns and potential physical and biogeochemical processes governing change in salt pool geomorphology. These results suggest that, although salt marshes passively accrete sediment as sea level rises, salt pools play significant roles in controlling the surficial morphology and biological/geological processes in many north-temperate salt marshes. This understanding of the dynamics of salt pools expands the context within which salt marsh environments may be managed in ecologically protected systems.