A student prepares to drop a corer to the bottom of Mud Lake in Dingle Marsh (southern Idaho, USA).
To take a core, the weighted cylinder with a plastic insert is dropped to the bottom of the lake, brought back to the surface and removed from the device.
This core was taken to measure sediment oxygen demand (SOD) and phosphorus regeneration. 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 contributes substantially to sustained productivity in natural waters, especially in shallow wetlands such as Mud Lake.