There was no significant change in pH over the time series which is as expected. The salinity, figure 7, on the other hand decreased almost linearly over time because the tide was initially going out and therefore salt water was moving out of the estuary making the water fresher. However after this period, when the tide started to come back in, the salinity would be expected to rise again.
The initial findings of the pontoon sampling show water column changes that would be expected given the effect of the tide however a fuller time series will be obtained by collaborating all groups’ results giving a longer time series.
The views expressed above are those of the authors and not those of the University of Southampton or the National Oceanography Centre Southampton.
References
1Haxeltine, A. and Prentice, I. 1996. A general model for the light-
Temperature (figure 5) at 1 or 2m depth was reasonably constant, varying by less than 1°C over the time series; however at the surface there were two larger increases in temperature at 14:20 and 15:20. The latter could be linked to the decrease in cloud cover as that would increase the infrared radiation reaching the surface water. The dissolved oxygen concentration, shown in figure 6, generally decreased from 12:50 to 14:50 but this was followed by a large increase. Although dissolved oxygen usually decreases with an increase in temperature, when the temperature greatly increased between 14:50 and 15:20 dissolved oxygen also increases. This coincides with the maximum in irradiance which is known to lead to a rise in primary production1, it is also possible that the increase in temperature increased the rate of photosynthesis and therefore more dissolved oxygen was released.
Results
For a large proportion of the sampling time the cloud cover was greater than five
octants except for the final sample when coverage dropped to three octants which
correlates with surface irradiance, figure 1. In contrast to this deep water irradiance,
shown in figure 2, was lowest at 13:20 and 13:50 UTC during slack water when the
flow rate, figure 3, was slowest and therefore there was likely a higher concentration
of suspended matter in the water column. The flow rate at the surface was low for
all samples and did not exceed 0.08ms-
Introduction
As a complement to the estuarine data collected on Bill Conway, physical parameters
were measured at the Pontoon in the upper reaches of Fal estuary, situated next to
the King Harry Ferry crossing. As the transition zone between fresh and salt water,
estuaries are well-
The aim of the investigation was to collect a time series of these various physical measurements in order to compare change over part of the tidal cycle in the estuary.
Methods
Parameters were measured as a time series over part of the tidal cycle, with measurements
taking place every half an hour, at 20 past and 10 to the hour, over the course of
2.5 hours. These measurements included depth of light penetration into the water
using a Secchi disk, surface and depth irradiance using a Li-
Date: 26/06/13
Start time: 12:50
End time: 15:20
Data taken at 30 minute intervals
Location: 50°12.57'N 005°01.39'W
Cloud cover: 7/8 until 14:20 then decreased; 6/8 at 14:50 and 3/8 at 15:20.
High tide of 5.1m at 08:20(UTC) with respect to Falmouth.
Pontoon
Pontoon Location
Figure 3. Surface flow rate of water around the pontoon for each sample time.
Figure 7. Salinity at meter intervals for all sampled times.
Figure 6. Dissolved oxygen concentration at meter intervals for all sample times.
