Figure 2 shows the distribution of surface temperature observed by thermograph at 4 m of depth. When analyzed together with the hydrographic profiles it seems that the lower temperatures inshore off Suriname results from mixing with cool upwelled water. Off Guyana the cool water does not reach as far inshore as further east, probably because of the bottom configuration. Figure 3 shows the distribution of temperature, salinity and oxygen in the Maroni river profile. The isolines of these three types of observations rise over the shelf edge and lifts further over the shelf shorewards, demonstrating upwelling of intermediate water and transport shorewards across the shelf. The low-salinity surface water affected by the large river discharges has a maximum over the middle and outer parts of the shelf. Underneath this and off the slope an intermediate layer of high salinity water (>37 ) is found in abt. 50-150m. This water is of surface subtropical origin. Below this we find a Central North Atlantic water mass. A thermocline of 3-5° C is found near the bottom over the mid and outer shelf which may affect fish distribution, as may the variations in salinity found. Oxygen in the shelf water is everywhere quite high.
Also the isolines for temperature, salinity and oxygen in the Demerara river profile, Figure 3 reveal a process of upwelling of intermediate water and the existence subsurface of the same types of water as further east. The low salinity surface water is, however, less pronounced.
Upwelling is also clearly demonstrated in the Orinoco profile, Figure 3 with inshore waters affected by river discharge.