This field trip is directed toward observation of ecological and hydrological processes in the marine/estuarine environment. The Plum Island Ecosystem (PIE) research site, located on the Northern Massachusetts coast, is part of the National Science Foundation's (NSF) Long Term Ecological Research (LTER) Network.
Human activities in rivers and watersheds have altered enormously the timing, magnitude and nature of inputs of materials such as water, sediments, nutrients and organic matter to estuaries. One of the dominant themes of estuarine research in recent decades has been the effects of inorganic nutrients on eutrophication of coastal waters. Studies have detailed how inorganic nutrient inputs from land influence primary productivity, the depletion of oxygen, habitats, and trophic relationships in coastal waters. However, another important but neglected linkage between land and coastal waters is the input of dissolved and particulate organic carbon and organic nitrogen.
Despite an awareness of large scale, long-term changes in watersheds, we do not fully understand the consequences of activities such as damming of rivers, land use conversion, and removal of floodplains. Often human influences on river systems are opposing. For instance land clearing increases drainage basin sediment yield while damming decreases sediment discharge.
Climate variability and long-term patterns of climate change also can have immense effects on the timing, magnitude and nature of material inputs. Infrequent storms can accomplish in days what normally occurs over decades. For instance, heavy rainfall associated with tropical storm Agnes increased Susquehanna River flow to record levels, which resulted in 30 years of "normal" sediment discharge occurring in one week.
Variations and long-term increases in sea level affect estuaries from their seaward end. Tides and sea level have significant effects on water and marsh sediment salinity, plant community composition, primary production, access to marsh surface habitats by nekton and sediment accretion.
The interaction of organic matter and nutrient inputs from land and variations in the external forcings (climate, land use, river discharge, sea level) regulating estuarine mixing and residence time will dictate the extent of nutrient and organic matter processing during estuarine transport and will determine the spatial patterns of productivity and trophic structure. The long-term research program at Plum Island focuses on the following question: How will trophic structure and primary and secondary productivity in estuaries be affected by changes in organic matter, nutrient and water fluxes caused by changing land cover, climate and sea level?
For more information on the Plum Island LTER, see http://ecosystems.mbl.edu/PIE. For more information about this field trip, please contact Doug Burns, +1-518-285-5662, daburns@usgs.gov, or Ellyn Terry, +1-202-777-7335, eterry@agu.org.