Matisoff, G. Case Western Reserve University, gxm4@po.cwru.edu
Soster, F. M. DePauw University, fsoster@DEPAUW.EDU
McCall, P. L. Case Western Reserve University, plm4@po.cwru.edu
Robbins, J. A. NOAA/Great Lakes Environmental Research Laboratory, robbins@glerl.noaa.gov

 
A MODEL OF PORE WATER GEOCHEMICAL SUCCESSION FOLLOWING SEDIMENT DISTURBANCE IN THE GREAT LAKES
 
Sediment disturbances that provide open (uninhabited) space initiate successions of freshwater macrobenthos. Tube-building, filter-feeding C. plumosus (Chironomidae) larvae actively migrate into unoccupied sediment soon after disturbance and may reach population densities twice as high as in nearby, undisturbed sediments within a few weeks. Head-down, deposit-feeding tubificid worms migrate into unoccupied sediments slowly, taking at least several months to reach population densities similar to those in surrounding areas. The differential response of these functionally different taxa to sediment disturbance appears to drive a geochemical succession. Early colonizing C. plumosus larvae increase the flux of dissolved silica, ammonium, and bicarbonate (alkalinity) from sediments into overlying water and decrease the pore water concentrations. They also increase the flux of nitrate into the sediment. Ferrous iron and phosphate concentrations also are depressed in the pore water, but do not show enhanced fluxes, because iron is precipitated near burrow walls after contact with oxygen and adsorbs phosphate. In the late successional stage, dominated by tubificid worms, pore water concentrations of silica, ammonium, bicarbonate, phosphate and iron begin to increase, but fluxes out of the sediments remain low until a concentration gradient from the sediment to the overlying water is re-established.
 
Day: Thursday, Feb. 4
Time: 11:15 - 11:30am
Location: Hilton of Santa Fe
 
Code: SS30FR1115S