VARIABILITY IN THE PALEOECOLOGICAL RECORD OF SEDIMENT CORES IN THE CHESAPEAKE BAY DUE TO LOCATION

Biological and geochemical indicators of changes in climate and land use are reflected differently in sediment cores in the Chesapeake Bay depending on the location of the cores. Pollen and seed records from cores in three different tributaries show synchronous changes in the flora due to climate change throughout the Holocene, but the floras differ for each time interval, depending on the soil substrate of the forests from which the pollen and seeds originated. Climate changes are thus superimposed on the soil template which governs the distribution of terrestrial plant species.

Likewise, land use is reflected in geochemical constituents of cores differently, depending on the location of the core with respect to its position in the Bay, whether at the mouth of a tributary in the upper Bay or closer to the ocean. Geochemical records (total organic carbon, total nitrogen, total phosphorus, total sulfur and carbon and nitrogen stable isotopes) of two cores, one largely influenced by the Chester and Susquehanna Rivers and the other in the main stem above the Patuxent River, changed simultaneously but differently in response to similar changes in land use.

The records of these cores demonstrate how biological and geochemical indicators can be used not only to infer temporal changes but also to interpret local influences of soil substrate, tidal influence and position within the estuary.