Summary of Bill Conway

Summary of Bill Conway

The ADCP data, upon analysis revealed, that the flood tide observed entering the river Tamar via a northward flow, with the denser seawater moving below the lighter freshwater.

The CTD casts identified a thermocline and a stronger halocline at 5 metres suggesting a salt wedge (Figure 6) at station 6 up the Lyher River compared to the stations in River Tamar, due to much less turbulence in the Lynher.At the confluence of the two rivers (station 5) the thermohalocline had decreased to a depth of 2.5 metres due to the imprinting of the thermohalocline from the river Lynher onto the well mixed river Tamar water.Further out in Plymouth Sound, station 10, there is a very slight thermocline occurring at a depth of 2.5 metres and no halocline, possibly due to turbulent mixing at the breakwater where the water body is constricted.

Overall biological removal of silicate, phosphate and nitrate is apparent towards the marine end-member however this is neither reflected by chla levels nor strongly backed up by phytoplankton counts, although a dominance of diatoms may explain silicate concentrations. There is evidence of anthropogenic input of phosphates between 20 and 35 psu.

Dissolved oxygen levels are higher towards the marine-end member suggesting high phytoplankton production, this is supported by high phytoplankton counts at higher salinities. High dissolved oxygen levels could also be put down to lower marine water temperatures. Summary of Bill Conway

The physical profiles made of the water column (with ADCP and CTD) revealed various processes: a flood tide entering the river Tamar via a northward flow, with the denser seawater moving below the lighter freshwater (presence of salt wedge), as well as strong thermocline and halocline at 5 m depth up the river Lynher, which decrease in strength and depth moving out towards Plymouth Sound due to trubulence and mixing.