The effect of physiographic regions on benthic riffle communities in the Kokosing River (Ohio)

Background/Question/Methods

Geology, physiographic history, and land use are among the most important factors influencing benthic community structure and distribution in surface waters, especially lotic systems. During the Pleistocene Epoch, large sheets of ice altered much of the surface of Ohio by eroding and depositing large quantities of till across much of the state’s landscape while other areas of Ohio were not impacted. Given the higher till concentrations in glaciated regions, does this impact the quality of riffle habitats and associated benthic communities? The objective of this study was to examine the influence of glacial history on benthic stream communities and physicochemical variables of a river in central Ohio. The 57-mile long Kokosing River transitions through several physiographic regions within Ohio including the Till Plains, the Glaciated Allegheny Plateau and the Unglaciated Allegheny Plateau. In the first year of this study, we focused on comparisons across two of these regions. Periphyton, macroinvertebrates, fish and selected physicochemical parameters were collected in riffle habitats at nine sites along the Kokosing River, spanning the Till Plains (N = 3) and two different areas of the Glaciated Allegheny Plateau – the Killbuck Glaciated Allegheny Plateau (N = 2) and the Illinoian Glaciated Allegheny Plateau (N = 4).

Results/Conclusions

ANOVA analyses indicated that specific conductance and pH were both higher in the Till Plains when compared to the Killbuck Glaciated Allegheny Plateau and the Illinoian Glaciated Allegheny Plateau (Specific conductance: ANOVA F(2, 6) = 36.03, p < 0.001; pH: ANOVA F(2, 6) = 8.60, p = 0.017). Higher specific conductance and the elevated pH in the Till Plains could be a result of increased groundwater contributions from limestone aquifers that are prevalent in this physiographic region. Further investigation next year will expand comparisons across a third physiographic region, the Unglaciated Allegheny Plateau.