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Modelling phytoplankton in the Northern Adriatic Claire Spillman Limnology Seminar 16 th April 2004. Hypothesis. Hypothesis: The Northern Adriatic Sea is a productive system, a sink for nutrients and highly sensitive to eutrophication.
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Modelling phytoplankton in the Northern Adriatic Claire SpillmanLimnology Seminar 16th April 2004
Hypothesis Hypothesis: The NorthernAdriatic Sea is a productive system, a sink for nutrients and highly sensitive to eutrophication. Outcome: Circulation, nutrient loading and stratification regimes. Phytoplankton abundance and succession. Model calibrated with field data. Po River entering Adriatic
The Adriatic Sea • Overall cyclonic circulation • 3 distinct basins • Northern Adriatic - shallow shelf, with bulk of riverine inputs • Po River - major source of nutrients & freshwater Croatia Po Delta Barbamarco Lagoon Italy Adriatic Bathymetry
Forcing Data • Barbamarco meteorological data: • wind speed and direction • relative humidity • air temperature • solar radiation • Global Tidal Model
CAEDYM Inputs • Riverine Inputs • Po River (~1600 m3s-1) • Northern Italian rivers • Emilia-Romagna rivers • Adige River • Nutrients • Phytoplankton Degobbis 1990
Initial Conditions • Stratified temperature & salinity • Set N, P & Si values for entire domain • Horizontal sheet for chlorophyll a Gilmartin & Revelante 1983
Temperature • Stratified in summer • Overturn in spring and fall June Oct
Circulation • Circulation strongly influenced by: • Po inputs • Stratification regime • Coriolis effects • Summer: Semi enclosed gyre • Winter: Increased water transport from Northern Adriatic Gilmartin et al 1990
Po Plume Po Tracer Freshwater Plume
Nutrient inputs • Po River ~50% of total nutrient inputs • Phosphorus is limiting nutrient • Regeneration ~ riverine inputs • Regeneration important under stratified conditions • River inputs important when high Po discharge
Adriatic Phytoplankton • Two size classes: 1. Nanoplankton (2-20μm) 2. Microplankton (>20μm) • Nanoplankton dominates biomass except in spring and fall • Major increases in biomass due to microplankton blooms Plot of chla mdiat:nano Gilmartin & Revelante 1976-1983
Phytoplankton Species • Nanoplankton Naked flagellates & silicoflagellates • Microplankton Spring/Fall: Diatoms (N. seriata, S. costatum) Dominate biomass Summer:Dinoflagellates (P. micans) Co-dominant with nanoplankton Skeletonema costatum
Phytoplankton results • SeaWiFS images Marine diatoms Nanoplanktpn
Northern Adriatic = Nutrient sink? • Settling velocities of phytoplankton Nanoplankton: small size low settling velocity Microplankton: Larger size higher settling velocity • Summer circulation patterns • Regeneration of nutrients
Next steps… • Regeneration of nutrients? • Include dinoflagellates – vertical migration? • Complete fine tuning of CAEDYM for Northern Adriatic • Outputs as forcing for Barbamarco Lagoon