INVESTIGATIONS OF OXIDES AND DIVERSITY OF BACTERIA IN SOIL HORIZONS DEVELOLPED IN HOLOCENE BEACH RIDGES, TAHQUAMENON BAY, MICHIGAN

Tahquamenon Bay is a northward opening embayment along the southern shore of Lake Superior. Approximately 80 beach ridges ~0.5 to 3.0 m in relief occur in the Tahquamenon Bay strandplain and are believe to have ages that vary from approximately 1000 to 4200 years. Sesquioxide pans (Bs horizons), such as placic and ortstein horizons are common in spodosols developed on these beach ridges. Transmission electron microscopy (TEM) indicate oxide minerals in these soils are largely amorphous but show distinct sponge-like and platy textures as well as apparent bacterial casts. A wide range of chemical compositions exist in the particles. Scanning transmission electron microscopy (STEM) indicates spatial distribution of elements on nanoparticles is complex and not systematic. Potassium is the only chemical parameter that seems to correlate well with progressive ridge age. Length heterogeneity polymerase chain reaction (LH-PCR) fingerprinting analysis indicates that there are 37 species of bacteria taxa present in the samples. An apparent correlation between the older beach ridges and lower diversity is observed. Furthermore there is a clear correlation to high K2O content averages in particles and lower diversity. Thus, there is an apparent link between K2O content of clay particles, age of ridge, and diversity. Deviations form age relationships however suggest that K2O content has a stronger correlation on bacterial diversity. Lower K2O contents are attributed to progressive leaching in soil development. The correlations observed indicate a possible mineralogical effect on the total diversity of bacteria in Bs horizons for this environment.