Abstract
We present a new stochastic model, based on a 0-dimensional version of the well known biogeochemical flux model (BFM), which allows to take into account the temperature random fluctuations present in natural systems and therefore to describe more realistically the dynamics of real marine ecosystems. The study presents a detailed analysis of the effects of randomly varying temperature on the lower trophic levels of the food web and ocean biogeochemical processes. More in detail, the temperature is described as a stochastic process driven by an additive self-correlated Gaussian noise. Varying both correlation time and intensity of the noise source, the predominance of different plankton populations is observed, with regimes shifted towards the coexistence or the exclusion of some populations. Finally a Fourier analysis carried out on the time series of the plankton populations shows how the ecosystem responds to the seasonal driving for different values of the noise intensity.
Highlights
Marine ecosystem models describing the lower trophic levels of the food web and ocean biogeochemical processes [1,2,3] are increasingly used in large scale monitoring and assessing infrastructures (e.g. Copernicus Marine Environmental Monitoring Service - CMEMS) to analyze and predict the state of seas and oceans [4]
We have developed a Stochastic Biogeochimical Flux Model, by introducing additive noise terms in the deterministic biogeochemical flux model (BFM), in view of taking into account both the contribution of random fluctuations coming from the environment and eventual uncertainties such as intrinsic variabilities [43]
We wish to point out that additive noise sources could be used to better model random fluctuations of: i) parameters which regulate the kinetics of a given chemical process; ii) the rate of transition between two different phases caused by a certain contaminant; iii) the rate at which a biological population absorbs a contaminant; iv) the so called recycling rate, that is, the rate at which the amount of a contaminant is reintroduced into the ecosystem since it is absorbed by a biological population
Summary
Marine ecosystem models describing the lower trophic levels of the food web and ocean biogeochemical processes [1,2,3] are increasingly used in large scale monitoring and assessing infrastructures (e.g. Copernicus Marine Environmental Monitoring Service - CMEMS) to analyze and predict the state of seas and oceans [4]. Marine ecosystems are an interesting and, from a socio-economic and ecological point of view, important example of natural complex systems, characterized by nonlinear interactions [53] Their dynamics is highly affected by both deterministic forcings (daily and seasonal cycles) [26,54,55] and random fluctuations of environmental variables [30,31,32,34,37,41,42,52,56,57,58] such as the temperature [59,60]. The last section is devoted to final remarks and conclusions
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