Data from: Trait-dependent time lags amid global change in marine observed and dark diversity on the Dogger Bank (North Sea)

Understanding delayed biodiversity responses to global changes is crucial
for anticipating future ecosystem dynamics and informing conservation.
Here, we analysed a 32-year time series of benthic megafauna from the
North Sea (Dogger Bank) to assess extinction debt and immigration credit
using a probabilistic species pool framework. Within this framework, we
generated suitability estimates for both observed diversity (i.e., species
locally present) and dark diversity –the set of suitable but locally
absent species. We defined extinction debt as species persisting locally
under declining suitability and immigration credit as suitable species
remaining in dark diversity over time. We evaluated these dynamics across
101 epibenthic species (from demersal fishes to macroinvertebrates) and
tested their association with sea warming and species traits such as body
size and motility. Despite no net change in species number, the
suitability of observed diversity decreased over time, indicating
extinction debt. At the species level, 72% of species exhibited
time-lagged responses, with large-bodied and motile species being more
often in extinction debt, whereas smaller and less motile species were
more often in immigration credit. Consequently, in relation to temperature
change, the North Sea’s species pool is slowly shifting toward
smaller-bodied and less motile taxa, with several cold-adapted and
commercially important species in extinction debt. These delayed responses
and potential compositional shifts may weaken trophic interactions and
affect ecosystem resilience. As marine systems experience increased
warming, integrating trait-based approaches and time-lag responses within
the species pool framework can offer early warnings of biodiversity
reorganization and, therefore, windows of opportunity for conservation.