Coastal Dynamics and Pre‐Columbian Human Occupation in Horseshoe Cove on the Northern Gulf Coast of Florida,USA

Site‐specific paleoenvironmental reconstructions are necessary to isolate environmental factors from social forces that influence shifting human practices in the coastal environment. This interdisciplinary study included the collection and analysis of marine and freshwater pond sediment cores and terrestrial sediment samples along with archaeological excavations at three directly associated pre‐Columbian sites in Horseshoe Cove on the northern Gulf Coast of Florida. This research shows a strong correlation between environmental change, the timing of initial occupation, and the morphological characteristics chosen for settlement by the pre‐Columbian residents of this area. Specific attributes sought for new settlements included elevated landforms in protected areas away from the immediate shoreline, access to fresh water from nearby spring‐fed ponds or tidal creeks, and easy access to marine resources via tidal creeks. The result of this study can be useful as a model for locating and identifying archaeological sites in similar environmental settings.     

Couplings of watersheds and coastal waters: Sources and consequences of nutrient enrichment in Waquoit Bay,Massachusetts

Human activities on coastal watersheds provide the major sources of nutrients entering shallow coastal ecosystems. Nutrient loadings from watersheds are the most widespread factor that alters structure and function of receiving aquatic ecosystems. To investigate this coupling of land to marine systems, we are studying a series of subwatersheds of Waquoit Bay that differ in degree of urbanization and hence are exposed to widely different nutrient loading rates. The subwatersheds differ in the number of septic tanks and the relative acreage of forests. In the area of our study, groundwater is the major mechanism that transports nutrients to coastal waters. Although there is some attenuation of nutrient concentrations within the aquifer or at the sediment-water interface, in urbanized areas there are significant increases in the nutrient content of groundwater arriving at the shore’s edge. The groundwater seeps or flows through the sediment-water boundary, and sufficient groundwater-borne nutrients (nitrogen in particular) traverse the sediment-water boundary to cause significant changes in the aquatic ecosystem. These loading-dependent alterations include increased nutrients in water, greater primary production by phytoplankton, and increased macroaglal biomass and growth (mediated by a suite of physiological responses to abundance of nutrients). The increased macroalgal biomass dominates the bay ecosystem through second- or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events. The increases in seaweeds have decreased the areas covered by eelgrass habitats. The change in habitat type, plus the increased frequency of anoxic events, change the composition of the benthic fauna. The data make evident the importance of bottom-up control in shallow coastal food webs. The coupling of land to sea by groundwater-borne nutrient transport is mediated by a complex series of steps; the cascade of processes make it unlikely to find a one-to-one relation between land use and conditions in the aquatic ecosystem. Study of the process and synthesis by appropriate models may provide a way to deal with the complexities of the coupling.