Do rooted macrophytes increase sediment phosphorus release?

Sediment cores were collected from two of the Norfolk Broadsandtwo of the West Midland Meres, to test the hypothesis thatrootedmacrophytes increase the sediment release rate of phosphorusduringthe growing season.These were taken from inside and outside plant beds (mixedMyriophyllum spicatum and Chara sp. in Hickling BroadandNuphar lutea in Burntfen Broad, Mere Mere and LittleMere).The overlying water was replaced with a standard waterdesigned tomimic lowland freshwater. After an overnight ‘batch’incubation thewater was analysed for TP and SRP. From this their releaserateswere calculated. Interstitial measurements of SRP were alsomadefor some of the Broads cores at the end of the incubationperiod.The data were analysed using General Linear Models. TP and SRPwerethe responses for both data sets. Factors for the Broads wereinside/outside plant beds, date, and site, whilst for theMeres thefactors of date and site could not be delineated.Release rates in this study were affected by a number offactors(plants, site and date). The picture emerging so far is thatwhenrooted macrophytes have a significant effect on phosphorusreleasethey increase it. However the large variability betweenreplicateshighlights the logistical difficulties in running suchexperiments