| Summary: | One of the key features of environmental field studies is their high variability at many different time and space scales. Because of these external influences and of the stochasticity introduced by the reproduction, population dynamics are also characterised by high variability over time and space. The search for universal scaling laws in ecology often involves considering a form of power-law distribution, power laws can emerge in population dynamics or in patterns of abundance, distribution, and richness. Using the polychaetes, group that colonises a large range of soft and hard marine sediment habitats, from intertidal to hadal zones, and are considered to be good surrogates to identify the main environmental conditions that control the structure and functioning of benthic communities, we try to identify the spatiotemporal changes in biodiversity for this characteristic benthic group. First, we discuss the dynamics of polychaete populations. Based on long-term series of three soft-bottom communities, we study the dynamics of polychaete populations using different statistical techniques; we characterise extreme events in abundance data and we show how to apply some quantification methods to highly erratic and intermittent biological series. Then, we discuss the spatial distribution of polychaete species aiming to: identify latitudinal, longitudinal and bathymetric patterns on the European northeast Atlantic continental shelf; and test the existence of general, perhaps universal, patterns for characterising biodiversity i.e. increasing diversity with sampled area, its decay from the equator to the poles and the increase in richness with the total abundance of individuals. Les systèmes environnementaux présentent une grande variabilité spatio-temporelle. En raison des influences extérieures et de la stochasticité introduite par le processus de reproduction, la dynamique des populations est également caractérisée par une grande variabilité. La recherche de lois universelles en écologie implique souvent une ...
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