Grant Agreement: 101082021Project Acronym: MARCO-BOLOProject Title: MARine COastal BiOdiversity Long-term ObservationsDeliverable Number: D5.1Work Package Number: WP5Deliverable Title: Scientific document determining biodiversity trends, underlying drivers and essential observations for predictive modellingDue Date: 30.11.2025Submission Date: 17.11.2025 The main goal of this report is to assess biodiversity trends and their drivers in marine and coastal European ecosystems. To this end, we analysed community-level biodiversity trends and species-level habitat use during the last decades using data from open sources. Biodiversity trends are paired with environmental parameters and projected into the future using Habitat Suitability Models and Random Forest Regressions. Three complementary studies are presented. Study 1 — Time series analysis: European time series for six biotic groups (birds, fish, invertebrates, macroalgae, phytoplankton, zooplankton) were analysed to estimate temporal trends (1956–2022) in richness, diversity, and abundance across regions. A total of 2,359 time series comprising 552,475 observations of 4,718 coastal and marine taxa in 2,246 different sites were assembled from open-access databases (BioTIME, EMODnet, REPHY, FishGlob, Continuous Plankton Recorder Survey). Most communities showed no significant change, suggesting no further widespread biodiversity loss during the observation period. Positive trends were found for birds and invertebrates in the Baltic, and negative ones for fish in the Atlantic. However, uneven data coverage limits this generalization, highlighting the lack of sufficient rigorous monitoring of biodiversity and of accessibility to existing data. Study 2 — Habitat suitability modelling: Habitat suitability was predicted for coastal and marine species protected under the Habitats and Birds Directives, under current and future Shared Socioeconomic Pathways (SSP) climate scenarios. Projections were made for four marine mammal species (harbour porpoise, harbour seal, common dolphin, bottlenose dolphin) in OSPAR regions II–IV using EurOBIS data (2000–2019) and environmental predictors. Results revealed clear spatial and seasonal patterns in projected suitable habitats: a southward shift for porpoises in winter, seals remaining coastal, and dolphins concentrating in the Iberian region. Future projections suggest an overall reduction in suitable habitats for all four species. While limited by sampling biases and data inconsistencies, the study demonstrates the value of open-access biodiversity data for large-scale ecological modelling. Study 3 — Causal relationships in coastal ecosystems: Climate change impacts on coastal ecosystems were examined at the Gulf of Naples (LTER Mare Chiara site). Combining long-term data, reanalysis, and machine learning, the study found salinity to be a key driver of chlorophyll (phytoplankton) variability, linking land-based freshwater inputs and ocean dynamics. Using Representative Concentration Pathways to 2070 (RCP4.5, RCP8.5), the model predicts increasing salinity and declining chlorophyll, largely driven by reduced rainfall and runoff. The findings stress the importance of long-term monitoring and indicate that land-driven changes may affect coastal productivity more than ocean warming alone. This report highlights the usefulness of publicly available data but also its limitations. As biodiversity open-source data increases in quantity and quality, the potential of future analyses will grow with it.
Arce et al. (Mon,) studied this question.