Development and validation of a Benthic Flux Model for the Adriatic Sea Presenter: F. Zaffagnini Zaffagnini F. 1, Vichi M. 1,2, Frascari F. 3, Spagnoli F. 4, Marcaccio M. 5, Bergamini C. 3 1:CMCC 2:INGV 3:ISMAR CNR – Bo 4:ISMAR CNR – An 5:ARPA ER – Bo Keywords: Layer Model, Biogeochemistry, Diagenetic processes, Adriatic Sea WORKSHOP W10 Progetto VECTOR (Rimini, settembre 2007)

Geochemical Modelling: Objectives Find homogeneous biogeochemical regions in the Adriatic Sea Define initialization parameters for each facies Run the simulation and compare with available observations No predictive purposes 2/13

Geochemical Modelling Level Model Layer Model (BFM)‏ Diagenetic processes: 2 approaches Explicit depth-profile resolution 3/13

BFM: The Layer Model 3 Layers governed by different diagenetic environments Steady state analytical solutions are calculated (Berner equations) for each layer Each layer considers integrated concentrations for every parameter The evolution over time is determined through many transient solutions (Initial conditions  Equilibrium) Only vertical diffusion! K Oxic Suboxic Anoxic D1 D2 Dtot Pelagic System Benthic System Berner (1980) K1 K2 4/13

The Model Oxic layer Anoxic layer DLayer Depths D (1)‏ D (2)‏ Q c (6) penetration Q n (6) penetration D (6)‏ D (7)‏ Q p (6) penetration Q s (6) penetration D (8)‏ D (9)‏ Phosphate - Oxic Layer - Dentrification Layer - Anoxic Layer Nitrate Ammonium - Oxic Layer - Dentrification Layer - Anoxic Layer Silicate KNutrients K (1)‏ K1 (1)‏ K2 (1)‏ K (3)‏ K (4)‏ K1 (4)‏ K2 (4)‏ K (5)‏ Organic matter flow (C,N,P,Si)‏ Inorganic nutrient flow (N,P,Si)‏ Gas exchange (Bio)chemical reaction Chemotrophy Non-living Organic CFF Living Organic CFF (LFG)‏ Inorganic CFF Boundary flow KInorganic species Reduction Equivalents K (6)‏ GDissolved Gases Oxygen G (6)‏ Carbon dioxide G (6)‏ YZoobenthos Y i (1)‏ Y i (2)‏ Y i (3)‏ Y i (4)‏ Y i (5)‏ Macrobenthos Detritivores Filter feeders Meiobenthos Infaunal predators H i (1)‏ H i (2)‏ HBenthic Bacteria Aerobic Anaerobic Q i (1)‏ Q1 i (1)‏ Q i (6)‏ QOrganic Matter Semi-ref. DOM - Oxic - Anoxic Particulate OM Ingestion/Egestion Respiration Uptake/Release Excretion Dissolution Predation Uptake/Release Predation Oxidation 5/13

BFM: Output Variations of concentration in the layers Changes of the layers’ thickness Fluxes of the major geochemical species all outputs expressed over time 6/13

BFM: Adriatic Sea biogeochemical facies 5 facies: 1.High reactivity 2.Medium reactivity 3.Low reactivity 4.Negligible reactivity 5.Coastline First Station: S1 Many data Most complex area Very reactive Frascari et al /13

BFM: Initialization From ISMAR – CNR database ( ) Sediment & pore water data: Nutrients DOM and POM concentration and input Chemical-Physical parameters Benthic Fluxes 8/13

BFM: Method Initialization of variables Assignment of values measured in station S1 Model run Check the evolution of variables over 10 years Estimate the required deposition rate of Organic Matter in order to: Maintain the initial conditions Obtain a credible equilibrium Stationary conditions (no seasonality) Absence of feedback from the pelagic system Numerical validity check 9/13

BFM: Initialization Choice of the 3 layers’ thickness Starting values Fe in pore water D1=0.5 cm NO3 D2=7.5 cm Porosity POCNH3 10/13

BFM: Results Oxygen penetration depthDenitrification depth Oxygen in pelagic systemPOC 11/13

BFM: Results Ammonium Oxic Layer Suboxic Layer Anoxic Layer Phosphate !? Oxic Layer Suboxic Layer Anoxic Layer 12/13

BFM: Conclusions Considering a stationary input of oxygen and organic matter, we see: Reached equilibrium of most variables similar to startup conditions Some variables (i.e. phosphate) show problems Short term future purposes: Fix problems and uncertainities Add seasonality to external sources Medium term future purposes: Apply the BFM to the other facies in Adriatic Sea Couple the BFM with the Pelagic Model 13/13