Monday, November 13, 2006

Subaqueous Soil/Landscape Relationships of Estuaries near Cedar Key, Fl.

Larry Ellis, Mary Collins, and G. W. Hurt. Univ of Florida, Soil & Water Science Dept, 2169 McCarty Hall A, PO Box 110290, Gainesville, FL 32611

Recent advances in pedology have demonstrated that the concept of soil is valid under water.  Thus underwater bottoms have been termed subaqueous soils and have been studied by pedologists from a soils-based perspective.  An important part of the soils-based perspective is that soils are related to, and thus predictable by, landscapes.  The subaqueous soil/landscape relationships examined thus far have been in temperate systems in bays and lagoons.  Presented here are subaqueous soil/landscape relationships of shallow, open grassflats that occur near Cedar Key, FL.  This area is typical of the nearshore marine environments along much of Florida’s Gulf coast.  The grassflat was the dominant shallow (<3m) landform in the area.  Some of these flats occurred as expansive areas several km away from shore (termed offshore) while others occurred as flats (termed nearshore) along the margins of barrier islands.  A conceptual soil/landscape model was constructed based on the subaqueous soil forming factors outlined by Demas and Rabenhorst (2001).  The model could not explain the morphological differences between the offshore and nearshore grassflats.  The addition of a new factor, geographic position, refined the model allowing for the consideration of barrier island effects on grassflats.  The soils occurring on the offshore grassflats were finer in texture and higher in organic matter than near-shore grassflats.  Furthermore, those soils had thick (>1m) A horizons.  Soils occurring on the nearshore grassflats had poly-value morphologies and coarser particle size distributions.  Both soils had n values < 0.7 as determined in the field.  The soils in the offshore grassflats appear to satisfy all the criteria of the Mollisol order.  Thus, the soils occurring on offshore grassflats near Cedar Key, FL are the first documented subaqueous Mollisols.  Additional work is needed to confirm these relationships in other areas where offshore grassflats and nearshore grassflats occur.