A 6000-year record of diatom assemblages in a storm-influenced estuary (Alabama)

Diatoms were identified from a 455 cm core representing 6000 years of sediment from Weeks Bay, a sub-estuary in the south-east corner of Mobile Bay, Alabama. Over 15,529 diatoms were counted, 172 species were identified, and one new species was found. Cesium-137 and Carbon-14 data indicate mixing of sediment in the upper 70 cm. Paralia sulcata, a benthic dwelling diatom decreased significantly in the upper core. This was probably due to increased sediment load that destroyed P. sulcata's habitat. The most noticeable change in assemblages was the lack of diatoms in over 50% of the core probably due to breakage and dissolution. Sea level change and the effects of human settlement were not obvious from changes in assemblages. This was probably because storm events mixed the sediment rendering credible analysis impossible. Paleoecological research using diatom assemblages is problematical in storm influenced estuaries except over a millennia time scale.