Sediment resuspension effects on alkaline phosphatase activity

Sediment cores, including the associated lake water, were collected from a shallow hypereutrophic lake located in central Florida. Alkaline phosphatase activity (APA) was measured as an indicator of potential organic P mineralization. In both the sediment and water columns, APA was mainly associated with particulate matter; < 10% of APA was within the soluble phase. This suggests that for enzymatic hydrolysis to occur the hydrolyzable organic compounds must be in close proximity to the particle-bound enzyme complex. Both total P (TP) and APA decreased with depth in the sediment, whereas soluble reactive P increased in the 20–40 cm fraction. Resuspension of surficial sediments resulted in an immediate increase in APA, total suspended solids, TP, total Kjeldahl N, and total organic C within the overlying water column. However, these concentrations decreased rapidly following cessation of turbulence and settling of the sediments, emphasizing the close association of these parameters with the sediment.