RESPONSE OF CARBON CYCLING TO CLIMATIC AND ANTHROPOGENIC PERTURBATIONS IN TWO NORTH AMERICAN SUBTROPICAL ESTUARIES

SUBTROPICAL ESTUARIES WORLDWIDE ARE FACING INCREASING PRESSURE FROM HUMAN POPULATION GROWTH DEVELOPMENT AND CLIMATE CHANGE PERTURBATIONS I.E MORE EXTREME STORMS WARMING SEA-LEVEL RISE HYDROLOGICAL CHANGES AND CHANGING RIVERINE LOADS OF NUTRIENTS SEDIMENTS AND ORGANIC CARBON. WE PROPOSE TO USE TAMPA BAY AND BISCAYNE BAY AS TEST BEDS FOR STUDYING SUBTROPICAL ESTUARINE CARBON CYCLING AT TEMPORAL SCALES RANGING FROM MONTHS TO DECADES. IN ADDITION WE PROPOSE TO FILL A KEY DATA GAP BY MAKING FIELD MEASUREMENTS OF NET PRIMARY PRODUCTION (NPP) WHICH ARE VERY LIMITED IN THE SUBTROPICAL ESTUARIES. THE CENTRAL OBJECTIVE OF THIS PROPOSAL IS TO UNDERSTAND HOW CARBON CYCLING IN BISCAYNE BAY AND TAMPA BAY RESPONDS TO CLIMATIC AND ANTHROPOGENIC PERTURBATIONS. TO ADDRESS OUR CENTRAL OBJECTIVE WE WILL COMPLETE FIVE MAIN TASKS: (1) SYNTHESIZE HISTORICAL WATER QUALITY DATA SETS IN BISCAYNE BAY AND TAMPA BAY. (2) MAKE IN SITU MEASUREMENTS OF KEY CARBON FLUXES CARBON STOCKS AND OPTICALLY ACTIVE MATERIALS TO BETTER CONSTRAIN THE CARBON CYCLE IN THESE SYSTEMS AND PROVIDE DATA FOR REMOTE SENSING ALGORITHMS. (3) USE DATA FROM MODIS AND SEAWIFS TO DEVELOP AND APPLY REMOTE SENSING ALGORITHMS FOR PRIMARY PRODUCTION AND DISSOLVED ORGANIC CARBON IN THE TWO ESTUARIES WHICH WILL EXTEND THE SPATIAL AND TEMPORAL COVERAGE OF IN SITU MEASUREMENTS. (4) CREATE TIME-DEPENDENT DIAGNOSTIC MASS-BALANCE BOX MODELS OF THE FLUXES OF CARBON AND RELATED CONSTITUENTS IN THE TWO ESTUARIES USING THE IN SITU AND REMOTE SENSING DATA SETS. (5) ANALYZE THE MODEL RESULTS TO DETERMINE THE FACTORS AFFECTING THE FLUXES OF CARBON AND RELATED CONSTITUENTS IN THE TWO ESTUARIES SPECIFICALLY CLIMATE AND ANTHROPOGENIC ACTIVITY. THE DERIVED ESTIMATES OF BIOGEOCHEMICAL FLUXES ALLOW US TO INVESTIGATE A NUMBER OF HYPOTHESES REGARDING THE IMPACTS OF CLIMATE AND ANTHROPOGENIC ACTIVITY ON BIOGENIC PROCESSES THAT INFLUENCE CARBON AND RELATED ELEMENTS IN SUBTROPICAL ESTUARIES. SPECIFIC HYPOTHESES THAT WE WILL TEST ARE THE FOLLOWING: (1) H1: TROPICAL CYCLONES CAUSE SUBTROPICAL ESTUARIES TO BECOME MORE AUTOTROPHIC. (2) H2: THE LONG-TERM DECLINE IN NITROGEN LOADING TO TAMPA BAY HAS CAUSED IT TO BECOME MORE HETEROTROPHIC WITH TIME. (3) H3: HIGH STREAMFLOW RESULTS IN LOW NET ECOSYSTEM PRODUCTION (NEP) THROUGH INCREASES IN SEDIMENT DELIVERY WHICH LEAD TO DECLINES IN WATER CLARITY AND NPP. (4) H4: NPP AND NEP ARE CORRELATED WITH PHOSPHORUS IN BISCAYNE BAY AND NITROGEN IN TAMPA BAY. (5) H5: SPATIAL VARIATIONS IN NEP ARE DICTATED BY THE LIGHT FIELD SUCH THAT TURBID WATERS ARE MORE HETEROTROPHIC THAN CLEARER WATERS. (6) H6: DENITRIFICATION IS ENHANCED WHEN PARTICLE FLUX TO THE SEAFLOOR IS HIGH. (7) H7: THE BIOLOGICAL SINK OF SILICATE (SI) IS LOWER THAN EXPECTED BASED ON NPP AND THE SI:C RATIO OF DIATOMS. THIS PROPOSAL IS RESPONSIVE TO THE GOALS OF NASA USDA-NIFA DOE AND NOAA WHO SEEK PROPOSALS TO IMPROVE UNDERSTANDING OF CHANGES IN THE DISTRIBUTION AND CYCLING OF CARBON AMONG THE ACTIVE LAND OCEAN COASTAL AND ATMOSPHERIC RESERVOIRS AND HOW THAT UNDERSTANDING CAN BE USED TO ESTABLISH A SCIENTIFIC FOUNDATION FOR SOCIETAL RESPONSES TO GLOBAL ENVIRONMENTAL CHANGE.