"Stability, cycling and noise propagation in a complex biogeochemical model"Lazzari, PaoloMarine ecosystem models, which describe the lower trophic levels of the food web and simulate biogeochemical processes in the sea, are increasingly being used in large-scale monitoring infrastructures (e.g. Copernicus Marine Environmental Monitoring Service - CMEMS) to analyze and predict the state of the seas and oceans or to carry out simulations of biogeochemical climate scenarios. The structure of these plankton models usually differs from the simplified general formulations used for theoretically oriented studies. To build a bridge between these two contexts, we show applications from the theoretical domain in an operational model. Thus, we investigate the relationship between the complexity of a model and its inherent stability by considering stationary, cyclic or chaotic model solutions. We also show how environmental variability and stochastic fluctuations can influence model dynamics and stability. In the absence of external perturbations, the inherent stability of plankton communities appears to be related to the presence of multiple feedbacks in the food web structure (e.g. omnivory, low centre of gravity), and suggests that food webs of realistic complexity rarely exhibit significant endogenous non-stationary dynamics. Environmental fluctuations interact with the dynamics of the deterministic model skeleton and lead to non-monotonic behaviour as a function of noise intensity, suggesting resonance effects in the non-linear regime and influencing survivability within plankton networks. |
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