Falmouth Group 8

DISCLAIMER! This website does not necessarily reflect the views expressed by the National Oceanography Centre or any of its staff.

Station 3

The range in values reached here is an estimated 4.18-4.26. Specific depth ranges are approximately 0.04, although at the surface this becomes particularly substantial at a range of 4.16-4.22. From values of an average 4.18 this peaks in value at around 7 m depth, where the average value was approximately 4.24. This again remains consistent for the rest of the water column. A possible anomalous value of 4.20 can be observed at 9m.

Transmissivity-Figure 3

Silicate: Low (34) at surface, increases to 34.8 in top 10m, remains relatively constant (increases to 35) down to 22.5m depth.

This profile of fresher water overlying saline water is statically stable, freshwater input from the river remains on top of the higher salinity sea water that is introduced to the channel by the tide.

Phosphate: Follows same pattern as Salinity. Low (1.5*10-4umol/L) at surface, increases to 7*10-4 in top 10m, remains relatively constant down to 22.5m depth.

Low concentrations that increase with depth in the surface waters above the 1% irradiance depth indicate that phosphate is being utilised by the biology that live in the estuary surface waters. Hence, phosphate is at lower concentrations where the biology is abundant and at higher concentrations that varies little with depth where the biology is less abundant.

Silicon: High (1.95umol/L) at surface, decreases in top 10m to 1.65umol/L, decreases further to 1.5umol/L down to 22.5m depth.

River water has a higher concentration of silicon than sea water, as river water contains dissolved rock particles, most of which are high in silica. Therefore, if low salinity in the surface waters is caused by freshwater river input, the surface waters should be higher in dissolved silicon than the underlying saline seawater. This is what is observed.

Nitrate: High (4.8umol/L) at surface, decreases in top 10m to 3.4umol/L and then increases to 3.8umol/L down to 22.5m depth.

Due to the high agriculture in the Fal River catchment area, fertiliser runoff will leech into the river increasing the concentration of nitrate. At station 3, where stratification between the low salinity surface river water and the high salinity sea water bottom water is set up, the concentration of nitrate will be higher in the surface, and lower at depth.

Nutrients-Figure 2

Fluorescence-Figure 1

Error Range: 0.5-0.41 = 0.09

Fluorescence increases in the first 7m from an average of 0.380 at 1.2m to an average of 0.464 at 6.8m. From 7m the rest of the water column has a stable fluorescence of about 0.466.The graph shows 4 erroneous data plots the most noticeable at 22.5m with a fluorescence of 0.696.    

ADCP Transect-Figures 4,5,&6

The backscatter pattern is generally uniform with no significant changes throughout the estuary.

There is some evidence for the tidal flow at the surface layer of the estuary moving outwards in a southerly direction down to approximately -0.5 m/s, whilst the flow at the bottom of the estuary was moving generally inwards in a northerly direction at up to 0.5 m/s.

Click graphs to enlarge

Top

Station 4 →