NUTRIENT EXPORT FROM RIVER WATERSHEDS IS LARGELY DEPENDENT ON SEDIMENT PLUMES OCCURRING DURING STORMFLOW EVENTS. AND YET, BIOLOGICAL NUTRIENT REMOVAL WITHIN AND DURING SEDIMENT PLUMES HAVE BEEN OVERLOOKED AND UNDERSTUDIED. SEDIMENT PLUMES MOBILIZE LARGE AMOUNTS OF SUSPENDED SEDIMENTS PROVIDING EXTENSIVE SURFACE AREA FOR MICROBIAL ACTIVITY, AND THUS OMISSION OF BIOLOGICAL NUTRIENT REMOVAL IN SEDIMENT PLUMES MAY HAVE SIGNIFICANT EFFECTS ON OUR MODELED ESTIMATIONS OF WATERSHED NUTRIENT EXPORT TO COASTAL ENVIRONMENTS. HERE, WE PROPOSE TO ASSESS BIOLOGICAL NITROGEN (N) REMOVAL (DENITRIFICATION) IN SEDIMENT PLUMES AND ITS POTENTIAL INFLUENCES ON WATERSHED NITROGEN EXPORT. TO ACHIEVE THIS GOAL WE HAVE DESIGNED A THREE-STEP PROCESS COMBINING LABORATORY MESOCOSMS, REACH-SCALE MONITORING, AND WATERSHED MODELING APPROACHES. FIRST, LIMITING FACTORS OF DENITRIFICATION RATES IN SUSPENDED SEDIMENTS WILL BE EVALUATED IN MESOCOSMS. THEN, RESULTS AND LESSONS LEARNED FROM MESOCOSMS EXPERIMENTATION WILLBE EMPLOYED TO MEASURE AMBIENT RATES OF DENITRIFICATION IN SEDIMENT PLUMES THROUGHOUT MULTIPLE STORMFLOW EVENTS AND LCOATIONS. TOTAL N LOSS BY DENITRIFICATION IN SEDIMENT PLUMES WILL BE SCALED UP PER STORM EVENT AND WATERSHED AREA AND COMPARED TO THE AMOUNT OF N EXPORTED. FINALLY, PREDICTIVE REGRESSION RELATIONSHIPS BETWEEN WATER QUALITY PARAMETERS (E.G., TURBIDITY, TEMPERATURE, PARTICLE SIZE) AND AMBIENT DENITRIFICATION RATES WILL BE EVALUATED AND TESTED TO ASSESS THEIR VALIDITY AS A MANAGEMENT TOOL FOR MODELLING N PROCESSES. WE BELIEVE THIS RESEARCH CAN HELP IMPROVE THE CHARACTERIZATION OF NUTRIENT PROCESSES IN MANAGEMENT MODELS BY BETTER QUANTIFICATION OF NUTRIENT AND SEDIMENT LOADINGS ALLOWING BETTER DECISION MAKING IN TERMS OF WHERE TO PLACE BMPS IN AGRICULTURAL WATERSHEDS.