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Since 2019, the Copernicus Marine portfolio is providing a new model-based product on Zooplankton and Micronekton, representing the low and mid-trophic levels (LMTL) of the ocean food chain (Global Ocean low and mid trophic levels biomass multi year product: ). Zooplankton are organisms in the size range of less than 1 to a few millimeters (e.g., copepods) constituting prey of all fish larvae and small pelagic fish species (e.g herring, sardines and anchovies). Micronekton are also relatively small but actively swimming organisms such as crustaceans, fish, and cephalopods that are typically about 1 to 10 centimeters in size. Micronekton are prey of large fish and other oceanic predators. They are also predators of fish larvae. Therefore, zooplankton and micronekton distributions are key explanatory variables to understand fish recruitment mechanisms, individual behaviour of satellite tracked individuals of protected species (e.g., marine turtles, seabirds, sharks and marine mammals), and dynamics of large populations of fish species either targeted by fisheries (mackerel, tuna, swordfish, etc.) or strictly controlled in by-catch (e.g., bluefin tuna or sharks). The product includes 2-dimensional (latitude-longitude) maps of biomass for zooplankton and groups of micronekton on a weekly basis from 1998 to 2018 at a 25 km horizontal resolution. It is a model-based estimation of micronekton biomass, relying on the most possible realistic forcings (temperature, currents and primary production) assimilating satellite and in situ data. Continuous progress in the development and validation of these new models and products will help to reduce our knowledge gaps and will also support the Science & Climate sector as zooplankton and micronekton are key to better quantifying the carbon uptake and storage in the ocean, known as the “biological carbon pump”.

SEAPODYM-LMTL is the Lower (zooplankton) and Mid (micronekton) Trophic levels model of the Spatial Ecosystem And POpulation DYnamic Modeling framework. Currently, there is one zooplankton and 6 micronekton functional groups defined according to their vertical behavior and development times. The model is global and spatially explicit with transport described through a system of advection-diffusion equations. The vertical dimension is simplified into three layers -- epipelagic, upper and lower mesopelagic -- defined relatively to the euphotic depth. There are three vertically migrant and three non-migrant functional groups. The model is parsimonious with only a few parameters (6 for the zooplankton and 11 for the micronekton) that control the energy transfer efficiency from the primary production and the mortality and time of development that are linked to the water temperature. A data assimilation framework has been implemented to estimate those parameters. We present briefly the latest results and future challenges of this model. They include the validation of vertical layer boundaries, the first zooplankton and micronekton parameters estimation using existing biomass observations, and the developments needed to use large global datasets of acoustic data.