Micronekton indicators evolution based on biophysically defined provinces

Abstract

Abstract. Micronekton are mid-trophic marine organisms characterized by a size range of 2 to 20 cm, gathering a wide diversity of taxa (crustaceans, fish, molluscs). They are responsible for an important active carbon export to the deep ocean because of their diel vertical migrations and constitute the main prey for pelagic predators. A new method has been proposed in the literature to define provinces that identify micronekton functioning patterns based on environmental variables. Following this methodology, we define homogeneous provinces using environmental variables computed from Copernicus Marine Service products. These provinces represent a relevant way to define regions of interest, offering a regional scope of study for micronekton indicators and their evolution in time. In this study, we observe the evolution of the provinces in time from 1998 to 2023 to account for the decadal to climatic variability. We focus on the variations in surface area and average latitude of each province. We observe a global shrinking of productive provinces and polar provinces in favour of equatorial and tropical provinces' expansion. Additionally, tracking the geographical changes in the provinces over time shows that most are shifting toward the poles.