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Inshore Water Column

Profiles

The CTD vertical profile of the Tamar estuary starting at station A (Calstock) and ending at station J (Eastern Channel) showed a well-mixed water column with little temperature fluctuation.

A horizontal profile of chlorophyll (μg/L) against salinity was plotted with Falcon Spirit’s dataset (Figure.1). There is a noticeable dip at salinity 32 and a major peak at salinity 32.9. After salinity 32.9 the chlorophyll starts to decrease until reaching zero at salinity 34.5. The next salinity measurement decreases to 34.2 resulting in a 0.4 μg/L increase in chlorophyll.

A horizontal profile of oxygen saturation (%) against salinity was also plotted using the Falcon Spirit stations (Figure.2). The general trend of oxygen saturation in the lower Tamar estuary was a steady increase between 31.0 salinity and 34.2 salinity, though saturation increased more rapidly between station F and G, peaking at 104.5(%) at station G.

ADCP transects

ADCP data was collected by the Falcon Spirit on the 03/07/19 in the lower Tamar estuary, from the Tavy confluence down to the Easter Channel. Low tide was at 13:10UTC(+1) (0.88m) and therefore the tidal flow was moving down the estuary. A transect at station C (N50°24.627’, W004 °12.234’) was recorded near Saltash between 09:36UTC and 09:41UTC(+1) in direction west to east. This station is at the top of the lower estuary and the ADCP velocity contours present a maximum flow at the centre of the transect (Figure.3). A transect at station F (N50°22.600’, W004 °11.427’) was recorded near Torpoint Ferry between 10:35UTC(+1) and 10:36UTC(+1) in direction west to east. It is located where the Tamar river meanders to the southeast and the velocity contours show a faster flow on the right side of the transect (Figure. 4). Finally, a transect at station J (N50°20.050’, W004 °08.013’) was recorded near the Eastern Channel between 12:33UTC(+1) and 12:37UTC(+1). It is located near the open channel and the flow across the entire transect is stronger than in any of the previous stations (Figure.5). The vertical profile of flow magnitude at the centre of the estuary is stronger in the upper 20m and decreases with depth to 1250-2000mm/s in every station, while the flow direction remains constant with depth.