| | | 19.7 Temporal vs. spatial variability |
High seasonal differences in the phytoplankton community structure and sedimentation characterise the southern Gulf of Riga [356]. However, the high within-season temporal variability dominates over the variability between different areas of the southern Gulf. For most of the suspended and sedimented parameters studied at the spatial stations, the recorded variability is significant in all seasons [295][387]. The temporal variation found in the centre of the Gulf was even higher than the spatial variation. The situation off the mouth of the Daugava river is, however, different. This station is affected by resuspended matter at depth and by the suspended loads from the river runoff in the upper water column.
The sedimentation in the southern and central Gulf of Riga is influenced by river discharge, stratification and wind [387]. Wind causes high temporal variability in nutrients, suspended matter and vertical fluxes. In particular the wind direction changes the concentration of suspended matter and influenced stratification of the surface water that is influenced by both the river Daugava and by water entering through the Irbe Straight. The influence from the river on the sedimentation rates and retention of nutrients in the Gulf is difficult to evaluate since short-term variation exceeded the spatial variation in the Gulf.
| | | 19.7 Temporal vs. spatial variability |