SEASONAL AND ENVIRONMENTAL TRENDS OF BENTHIC FORAMINIFERA IN CHINCOTEAGUE BAY, DELMARVA PENINSULA, USA

Sedimentological, geochemical, and faunal properties of surface sediments from Newport and Chincoteague Bays were investigated to determine environmental gradients and seasonal variability (early spring/early fall) in the bay and surrounding marshes. Analyses included grain-size distribution, metals, dead/live (rose Bengal stained) benthic foraminiferal assemblages, stable and percent carbon and nitrogen. Additional offshore samples were examined for foraminifera.

The bay is characterized by low-salinity species. Preliminary data (live, dead, spring, fall) show that Ammonia parkinsoniana is found in all samples containing foraminifera throughout the bay, whereas Elphidium excavatum dominates at the bay inlet and in offshore samples. Living foraminiferal densities are higher in the spring than the fall and include Buccella frigida, which co-occurs with E. excavatum in bay inlet samples. Living and dead Cribroelphidium poeyanum are found primarily along the eastern shore of Chincoteague Bay. These sediments also record increased organic matter and phosphorous values most likely resulting from fragmentation and erosion of coastal wetlands. Live assemblages have geographically expanded ranges and densities (three clusters: A. parkinsoniana, E. excavatum, and C. poeyanum) when compared with dead assemblages (two clusters: A. parkinsoniana and Ammotium salsum). The difference may be explained by taphonomic loss of both calcareous and agglutinated tests over the winter months. Consequently, higher dead foraminiferal densities are found in early fall and lower dead densities occur in the early spring. Trends that may be useful to environmental and paleoenvironmental reconstructions include E. excavatum as a salinity signal (inlet breach) and C. poeyanum as an indicator of coastal marsh erosion.