A student holds a sediment core taken near the discharge point of a wastewater treatment plant into the Cutler Reservoir wetland. The core was taken to measure sediment oxygen demand (SOD) and nutrient regeneration (phosphorus). The oxygen demand from the sediments contributes to anoxia in the water column, and the nutrient regeneration fuels additional phytoplankton (algae) growth in the water column. This "internal loading" of nutrients is a serious problem contributing to eutrophication of polluted waters. Notice the filamentous periphyton (algae) at the top of the core.