MedSens data is a dataset including the abundance of selected Mediterranean marine species, collected by trained volunteers (EcoDivers, i.e. scuba divers, free divers and snorkelers) according to the Reef Check Mediterranean Underwater Coastal Environment Monitoring (RCMed U-CEM) protocol (Cerrano et al., 2017), and maintained by the non-profit association Reef Check Italia. This dataset is a subset of 25 selected species from the Reef Check Med - key Mediterranean marine species dataset, and it is specifically intended to calculate the MedSens index developed by Eva Turicchia, Carlo Cerrano, Matteo Ghetta, Marco Abbiati and Massimo Ponti (Turicchia et al., 2021). MedSens data is provided as ESRI shapefiles in WGS84 geographic coordinates (EPSG:4326). MedSens abstract Citizen science (CS) projects may provide community-based ecosystem monitoring, expanding our ability to collect data across space and time. However, the data from CS are often not effectively integrated into institutional monitoring programs and decision-making processes, especially in marine conservation. This limitation is partially due to difficulties in accessing the data and the lack of tools and indices for proper management at intended spatial and temporal scales. MedSens is a biotic index specifically developed to provide information on the environmental status of subtidal rocky coastal habitats, filling a gap between marine CS and coastal management in the Mediterranean Sea. The MedSens index is based on 25 selected species, incorporating their sensitivities to the pressures indicated by the European Union’s Marine Strategy Framework Directive (MSDF) and open data on their distributions and abundances, collected by trained volunteers (mainly scuba divers, but also free divers and snorkelers) using the Reef Check Mediterranean Underwater Coastal Environment Monitoring (RCMed U-CEM) protocol. The species sensitivities were assessed relative to their resistance and resilience against physical, chemical, and biological pressures, according to benchmark levels and a literature review. The MedSens index was calibrated on a dataset of 33,021 observations from 569 volunteers (2001 to 2019), along six countries’ coasts. A free and user-friendly QGIS plugin allows easy index calculation for areas and time frames of interest. The MedSens index was applied to Mediterranean marine protected areas (MPAs) and the management and monitoring zones within Italian MPAs. In the studied cases, the MedSens index responds well to the local pressures documented by previous investigations. MedSens converts the data collected by trained volunteers into an effective monitoring tool for the Mediterranean subtidal rocky coastal habitats. MedSens can help conservationists and decision-makers identify the main pressures acting in these habitats, as required by the MSFD, supporting them in the implementation of appropriate marine biodiversity conservation measures and better communicate the results of their actions. By directly involving stakeholders, this approach increases public awareness and the acceptability of management decisions, enabling more participatory conservation tactics. References Cerrano C, Milanese M, Ponti M (2017) Diving for science - science for diving: Volunteer scuba divers support science and conservation in the Mediterranean Sea. Aquat Conserv 27:303–323 https://doi.org/10.1002/aqc.2663 Turicchia E, Cerrano C, Ghetta M, Abbiati M, Ponti M (2021) MedSens index: The bridge between marine citizen science and coastal management. Ecol Indic 122:107296 https://doi.org/10.1016/j.ecolind.2020.107296

{"references": ["Cerrano C, Milanese M, Ponti M (2017) Diving for science - science for diving: Volunteer scuba divers support science and conservation in the Mediterranean Sea. Aquat Conserv 27:303\u2013323 http://dx.doi.org/10.1002/aqc.2663", "Turicchia E, Cerrano C, Ghetta M, Abbiati M, Ponti M (2021) MedSens index: The bridge between marine citizen science and coastal management. Ecol Indic 122:107296 https://doi.org/10.1016/j.ecolind.2020.107296"]}