THE CHESAPEAKE BAY ESTUARY, DENOTED A NATIONAL TREASURE, SUPPORTS AN ACTIVE FISHING INDUSTRY AND SUPPLIES WATER AND RECREATION TO THE MID-ATLANTIC REGION. THE SURPLUS ADDITION OF FERTILIZERS CONTAINING NITROGEN AND PHOSPHORUS TO AGRICULTURAL PRACTICES IN ITS WATERSHED HAS NEGATIVELY IMPACTED WATER QUALITY DOWNSTREAM IN THE BAY. THE RESULTANT SEASONAL ALGAL BLOOMS DECREASE OXYGEN AVAILABILITY, PROMPTING HYPOXIA IN THE SUMMER MONTHS. THIS EUTROPHICATION, COUPLED WITH LAND-USE CHANGE DUE TO URBANIZATION ALONG WITH POLLUTION FROM TOXIC CHEMICALS, HAS RESULTED IN THE OVERALL DECLINE OF WATER QUALITY, AND ECONOMIC DEPRECIATION, OF THE BAY. MULTIPLE POLICIES HAVE BEEN IMPLEMENTED TO REDUCE NUTRIENT RUNOFF PRIMARILY FROM AGRICULTURAL SOURCES, BUT WATER QUALITY HAS CONSISTENTLY REMAINED SUBPAR. THE VOID BETWEEN CURRENT INVESTMENT AND ACHIEVEMENT IN COASTAL AND INLAND WATER QUALITY AND SUSTAINED POOR WATER QUALITY POINT TOWARDS A MISSING GAP IN SCIENTIFIC KNOWLEDGE. THIS PROJECT AIMS TO ELIMINATE THIS GAP BY ELUCIDATING THE CYCLING OF ONE OF THESE NUTRIENTS, PHOSPHORUS, FOCUSING ON THE IDENTITY AND STABILITY OF ITS SINKS IN SEDIMENTS AND WHAT CONDITIONS PROMOTE ITS RELEASE TO THE WATER COLUMN.THIS PROJECT SEEKS TO IDENTIFY THE CONTROL OF BOTTOM-WATER HYPOXIA ON DIFFERENT PATHWAYS OF PHOSPHORUS CYCLING, SUCH AS THROUGH PHOSPHATE BOUND TO ORGANIC OR IRON COMPOUNDS, AS THE RELEASE OF PHOSPHORUS FROM SEDIMENTS IS PARTIALLY DEPENDENT ON DISSOLVED OXYGEN LEVELS. IT WILL ALSO QUANTIFY THE DIFFERENT SINKS OF PHOSPHORUS IN SEDIMENTS, AND USE THE RELEASE OF PHOSPHORUS INTO WATER OR ITS CONTAINMENT IN SEDIMENT TO DEVELOP RELATIONSHIPS WITH WATER QUALITY. ISOTOPIC AND CHEMICAL SIGNATURES OF PHOSPHATE COMPOUNDS WILL BE USED TO TRACE SOURCES, PATHWAYS, AND SINKS OF PHOSPHORUS. ANSWERING THESE FUNDAMENTAL PROCESSES WILL ADDRESS LONGSTANDING QUESTIONS ON PHOSPHORUS CYCLING. THE SCIENTIFIC OUTPUT WILL BE INSTRUMENTAL IN PROVIDING DATA TO THE CHESAPEAKE BAY PROGRAM FOR THE ADEQUATE FORMULATION OF POLICIES THAT CAN HAVE TANGIBLE EFFECTS ON WATER QUALITY IMPROVEMENT.