Working Group on Towards a EURopean OBservatory of the non-indigenous calanoid copepod Pseudodiaptomus marinUS(WGEUROBUS; outputs from 2024 meeting).

The vision of the WGEUROBUS is to promote the understanding of the different aspects related to the distribution, biology, and ecology of the non-indigenous calanoid copepod Pseudodiaptomus marinus Sato, 1913. This is achieved through the development of different lines of research, each focusing on a specific topic, whose combination allows to build an integrated view of this species’ ability to establish itself in a diverse set of environments. Over the 2022–2024 term, research activities have focused on the spreading distribution of P. marinus, on the physiological traits supporting its establishment, on its molecular taxonomy and its trophic position in introduced sites.

The occurrence of P. marinus in ICES ecoregions has significantly increased over the analysed time window, and the species is currently in eight out of the ten subregions identified in the Marine Strategy Framework Directive. Its ecological role in selected introduced areas has been investigated, clarifying the role of this species within the zooplankton community and its nychthemeral cycle. The suitability of P. marinus for large-scale rearings was tested in the laboratory, demonstrating its ability to grow and reproduce across a wide range of temperature and salinity values. Molecular investigations highlighted the occurrence of strongly interconnected haplotypes in ICES waters, with no distinct phylogeographic patterns. Preliminary results on the trophic position of P. marinus unveiled its role as both predator and prey at selected sites. The scientific outcomes of the WGEUROBUS have been presented in scientific publications and in conference presentations, while the research lines have been central in the presentation of projects. Interactions with online information systems on the occurrence of non-indigenous species (AquaNIS, EASIN) have been established to provide real-time, up-to-date distribution data of P. marinus.

The research activities planned for the 2025–2027 time frame will prioritise the themes outlined in the Terms of Reference, with the goal of identifying the mechanisms that promote the colonization and establishment of P. marinus in receiving areas.