Figure 1
Maps of the Bilbao and Urdaibai estuaries, showing the usual extent of water masses of 35, 34, 33, 30 and 26 salinity below the halocline during neap tides and high water. The map of the river catchment areas, showing the location of the meteorological and hydro-meteorological stations is also shown.
Figure 2
Averaged inter-annual, seasonal and residual variability (SDy,m,ε) of air temperature, rainfall for the sites of Sondika (S), Abusu (A) and Muxika (M) and river flow for the Kadagua (K), Ibaizabal-Nerbioi (I-N) and Oka (O) rivers
Figure 3
Averaged inter-annual, seasonal and residual variability (SDy,m,ε), and time-series average values of the stratification index (ST) and Secchi disk depth (SDD, m) in the estuaries of Bilbao (A and C) and Urdaibai (B and D)
Figure 4
Averaged inter-annual, seasonal and residual variability (SDy,m,ε), and time-series average values of temperature below the halocline (A and B) and in the halocline (C and D) in the estuaries of Bilbao and Urdaibai. 30* – above the halocline and 35* – the whole water column
Figure 5
Averaged inter-annual, seasonal and residual variability (SDy,m,ε), and time-series average values of DOS below the halocline (A and B) and in the halocline (C and D) in the estuaries of Bilbao and of Urdaibai. 30* – above the halocline and 35* – the whole water column
Figure 6
Averaged inter-annual, seasonal and residual variability (SDy,m,ε), and time-series average values of chlorophyll a in the estuaries of Bilbao (A) and Urdaibai (B)
Figure 7
Principal component analysis of the seasonal changes in the water environmental variables (ST: Stratification index; SDD: Secchi disk depth; WTT: Water temperature for the total water column; WTB: Water temperature below the halocline; WTH: Water temperature in the halocline; WTS: Water temperature in the surface layer above the halocline; DOT: Dissolved oxygen for the total water column; DOB: Dissolved oxygen below the halocline; DOH: Dissolved oxygen in the halocline; DOS: Dissolved oxygen in the surface layer above the halocline; CHL: Chlorophyll a at different salinity sites of the Bilbao and Urdaibai estuaries
Figure 8
Cumulative sums of month scores from January to December in PC1 and PC2 for different salinity sites of the Bilbao (A and C) and Urdaibai (B and D) estuaries. *Inverse values: positive values are reported as negative values and vice versa.
Figure 9
Patterns of seasonal (SDm) and inter-annual (SDy) variability of water temperature at 35, 34, 33, 30 and 26 salinity sites in the estuaries of Bilbao (A, C, E and G) and Urdaibai (B, D, F and H). BH and H indicate below halocline and halocline waters, respectively. The dashed line for the above halocline layer at the 30 salinity site in the Bilbao estuary. At 35 salinity in the estuary of Urdaibai, the data are provided for the whole water column.
Figure 10
Principal component analysis of inter-annual changes in water environmental variables (acronyms as in Figure 7) at different salinity sites in the estuaries of Bilbao and Urdaibai
Figure 11
Cumulative sums of year scores from 1998 to 2008 in PC1 and PC2 for different salinity sites in the estuaries of Bilbao (A and C) and Urdaibai (B and D)
Table 1
Results of (Spearman rank) correlation analyses of the first (C1) and second (C2) components of PCA with the annual anomalies in rainfall, Kadagua and Oka river flows (RF) and summertime air temperature anomalies from different salinity sites (35, 34, 33, 30, 26) of the Bilbao (B) and of Urdaibai (U) estuaries. Only the p-values of significant correlations (in bold) are shown.
| Site | PCA component | Air temperature | Rainfall | Kadagua (RF) | Oka (RF) |
|---|---|---|---|---|---|
| B35 | C1 | -0.036 | 0.459 | 0.066 | |
| C2 | 0.882 (p<0.001) | -0.041 | -0.005 | ||
| B34 | C1 | 0.736 (p<0.01) | 0.166 | 0.107 | |
| C2 | -0.409 | 0.139 | -0.158 | ||
| B33 | C1 | 0.609 (p<0.05) | -0.230 | -0.358 | |
| C2 | -0.018 | 0.283 | 0.066 | ||
| B30 | C1 | -0.027 | 0.472 | 0.674 (p<0.05) | |
| C2 | -0.327 | 0.251 | 0.110 | ||
| U35 | C1 | 0.891 (p<0.001) | 0.096 | 0.093 | |
| C2 | 0.227 | -0.318 | -0.353 | ||
| U33 | C1 | 0.700 (p<0.05) | -0.041 | -0.201 | |
| C2 | -0.364 | 0.271 | 0.263 | ||
| U30 | C1 | 0.773 (p<0.01) | 0.057 | -0.048 | |
| C2 | -0.109 | 0.042 | 0.040 | ||
| U26 | C1 | 0.491 | 0.295 | 0.184 | |
| C2 | 0.100 | -0.718 (p<0.05) | -0.748 (p<0.01) |