Figure 1.
(A) Map of the Central Baltic Sea with its three basins (BB = Bornholm Basin, GD = Gdansk Deep, GB = Gotland Basin) including the sampling station of the different datasets. (B) Schematic vertical profile of the hydrology together with the copepod (1 = Acartia spp., 2 = Temora longicornis, 3 = Pseudocalanus acuspes) and predator distribution (4). (C) Horizontal profile of the hydrology in August 2001, i.e., the gradient in temperature and salinity at different water depths. The respective depth ranges were chosen based on the species most affected by these parameters in our analysis.
Table 1.
Summary of the F-ratio tests comparing species- and season-specific long-term trends modeled across basins or for each basin separately.
Figure 2.
Observed and predicted long-term trends based on the best performing Generalized Additive Model (GAM).
Spring and summer biomass anomalies of Acartia spp. (green boxes), significantly differed between the Bornholm Basin (BB), the Gdansk Deep (GD), and the Gotland Basin (GB), while trends for Temora longicornis (red boxes), and Pseudocalanus acuspes (blue boxes) were not basin-specific and rather consistent within the entire Central Baltic Sea (CBS) region. Open circles (BB), triangles (GD) or crosses (GB) represent the observed values in each basin, while the continuous lines indicate the predicted trends from the GAM based on basin-specific smoothers or a single smoother fore the entire CBS region. The shaded areas indicate the pointwise 95% CI.
Figure 3.
Statistical model results of Acartia spp., T. longicornis, and P. acuspes.
Partial plots of significant covariates in the final spring and summer GAMs are presented for each basin separately or together depending on the significance and model performance. Values on the y-axis indicate the effect that the term on the x-axis has on the biomass anomaly. The solid lines indicate the smoothed (non-) parametric trend, shaded areas indicate the pointwise 95% CI.
Table 2.
Summary of final Generalized Additive Models of species-specific responses to predation and hydro-climatic drivers in spring and summer.