1st International Congress on Environmental Modelling and Software - Lugano, Switzerland - June 2002
Keywords
food web model, classic food chain, microbial food web, morris method
Start Date
1-7-2002 12:00 AM
Abstract
The Gulf of Trieste is located in the northernmost part of the Adriatic Sea. It exhibits high variable hydrodynamical and trophic conditions, due to the interactions among the wind regime, characterised by impulsive strong wind events (Bora), the fresh water –nutrient rich- run off, especially from Isonzo river, the interaction with the general circulation of North Adriatic Sea, the seasonal heating and cooling of water and alternation of mixing and stratification of water column. Gulf is also characterised by occurrence of anomaly events as mucilagine. Despite the high inter-annual biological variability, it is possible to recognise the seasonal succession of two trophic structures: the classical food chain which starts with the spring diatom bloom and the microbial food web during summer stratification. As a first step in the formulation of a comprehensive model for the Gulf of Trieste, able to reproduce the fundamental functioning of the ecosystem and to investigate the occurrence of anomalies, we have developed a food web model describing the fluxes of carbon and of phosphorous, the later being thought as the limiting nutrient in the Gulf. The model considers two groups of phytoplankton: diatom and nano-pico phytoplankton; two groups of zooplankton: the first represented by mixed filter feeders, and the second consisted by microzooplankton and by fine filter feeder, mainly represented by summer cladocera Penilia avirostris. Heterotrophic bacteria are explicitly included in the model, in order to describe their role in P cycle either as remineralization agents or as nanophytoplankton competitors, and their role in DOC degradation. The content of P and C in POM and DOM compartments are also included to better reproduce the uncoupling of the P and C cycles in seawater system. The model, forced by nutrient availability and climatological factors, reproduces the seasonal succession between classical food chain and microbial food web. Sensitivity analysis (Morris’s method) applied to the model permits to highlight the most important factor in controlling the evolution of the system.
A model for the trophic food web of the Gulf of Trieste
The Gulf of Trieste is located in the northernmost part of the Adriatic Sea. It exhibits high variable hydrodynamical and trophic conditions, due to the interactions among the wind regime, characterised by impulsive strong wind events (Bora), the fresh water –nutrient rich- run off, especially from Isonzo river, the interaction with the general circulation of North Adriatic Sea, the seasonal heating and cooling of water and alternation of mixing and stratification of water column. Gulf is also characterised by occurrence of anomaly events as mucilagine. Despite the high inter-annual biological variability, it is possible to recognise the seasonal succession of two trophic structures: the classical food chain which starts with the spring diatom bloom and the microbial food web during summer stratification. As a first step in the formulation of a comprehensive model for the Gulf of Trieste, able to reproduce the fundamental functioning of the ecosystem and to investigate the occurrence of anomalies, we have developed a food web model describing the fluxes of carbon and of phosphorous, the later being thought as the limiting nutrient in the Gulf. The model considers two groups of phytoplankton: diatom and nano-pico phytoplankton; two groups of zooplankton: the first represented by mixed filter feeders, and the second consisted by microzooplankton and by fine filter feeder, mainly represented by summer cladocera Penilia avirostris. Heterotrophic bacteria are explicitly included in the model, in order to describe their role in P cycle either as remineralization agents or as nanophytoplankton competitors, and their role in DOC degradation. The content of P and C in POM and DOM compartments are also included to better reproduce the uncoupling of the P and C cycles in seawater system. The model, forced by nutrient availability and climatological factors, reproduces the seasonal succession between classical food chain and microbial food web. Sensitivity analysis (Morris’s method) applied to the model permits to highlight the most important factor in controlling the evolution of the system.
