Freezing plants : exploring the effects of freeze thaw cycles on macrophyte phosphorus release

Abstract

Every year following the cold winter freeze comes the spring thaw, and with it comes an influx of nutrients that can cause eutrophication problems; even in high nutrient systems. We identified a potential source of nutrients released during the winter freeze; aquatic macrophytes and aimed to determine the quantity of total phosphorus (TP) they release. Specifically, cattails and reeds (Typha and Juncus, respectively). Stalks were harvested from 3 different sites; a pond with an agriculturally dominated watershed, the beginning of a wetland used to treat effluent waste water, and a site further along in the wetland treatment process. Samples from each site were split into four different sample types: wet freeze, dry freeze, wet control, and dry control. Control and freeze samples were placed in at 1.6[degree]C and -1[degree]C respectively, and left for equal amounts of time averaging 31.375 hours (SD 10.25). After treatment, residual water samples were analyzed for total phosphorus concentrations. Results showed that freeze thaw cycles (FTCs) did not induce TP release from macrophytes tested in the lab. These results suggest that the use of macrophytes as a sink for nutrients is a beneficial practice that managers should continue to employ.