Fig 1.
Map of the North Sea and its geographical position.
Labels correspond to the names of specific localities in terms of areas and geographic features including banks, bights and islands mentioned in the study.
Table 1.
Overview of the eight selected trait categories sorted according to traits, description and ecological relevance.
Fig 2.
Temporal trends and spatial patterns of multiple biodiversity indicators in the North Sea.
(A, D, G, J) Time-series and temporal trends of fish species richness (SRic), trait richness (TRic), species evenness (SEve), and trait evenness (TEve) as annual averages across all ICES rectangles. Significant temporal trends were observed for SRic (GAM: F = 37.45, e.d.f. = 1.92, R2 = 0.64, p < 0.001), TRic (GAM: F = 5.6, e.d.f. = 1.78, R2 = 0.33, p < 0.01) and TEve (GAM: F = 39.84, e.d.f. = 1.75, R2 = 0.71, p < 0.001). Shaded grey represent 95% confidence intervals. (B, E, H, K) Tempo-spatial patterns of biodiversity indicators represented by the slope and significance of a linear regression model fitted to each ICES rectangle across years. Green colors indicate a positive trend, while purple colors indicate a negative trend. Significant trends are indicated by black crosses (p<0.05). (C, F, I, L) Spatial patterns of biodiversity indicators shown as average value for each ICES rectangle across all years.
Fig 3.
Relative variable importance (RVI) of environmental and anthropogenic drivers and their relationship to the biodiversity indicators.
Drivers are sorted according to their cumulative importance across the four investigated biodiversity indicators. RVI>0.9 signifies high importance of a driver, RVI>0.6 signifies moderate importance, while RVI<0.6 is considered low or no importance. Relationships between drivers and biodiversity indicators based on GAMs are indicated by symbols: + indicate a positive relationship, ÷ indicate a negative relationship, ∩ indicate a unimodal relationship. If no symbol is assigned, the RVI of the driver is below 0.6.
Fig 4.
Null model results and the spatial distribution of over- and underdispersion in the North Sea.
(A) Observed (red dots) and simulated trait richness (TRic) values based on a null model. Bold black line: mean of 999 random permutations; areas shaded in dark and light grey: 50th and 95th percentiles, respectively, smoothed using a generalized additive model (GAM) function. (B) Spatial distribution of residuals of observed TRic from the null model. Areas shaded in green and red are characterized by over- and underdispersion, respectively, where the observed TRic is outside the 50th percentiles is either higher or lower than expected from its level of SRic. Black crosses (+) indicate significant deviation from the null model as described by falling outside the 95th percentile of simulated values.