DISCLAIMER: These opinions and views are those of the individuals concerned and not those of the University of Southampton.

Home About Us  Habitat Mapping Pontoon Estuary Offshore

Abstract:
We conducted a series of measurements on the pontoon using an Exo-Sounder to measure temperature, salinity, pH and dissolved oxygen, a flow meter to measure flow, a light meter to measure LUP % and a Niskin bottle to gather chlorophyll data. We found that the flow speed (ms-1) increases as depth increases to a point (generally between 3-4m and a change of approximately 0.1ms-1), where the flow begins to decrease by up to 0.2ms-1, and that that maximum chlorophyll concentration (mgL-1) is observed closer to the bed of the estuary due to resuspension of benthic algae.

Introduction:

The aim of this survey was to investigate temporal variations of physical and biological parameters of the Fal estuary over a short time period (3 hours). Within the Fal estuary, factors influencing diurnal variations in physics and biology include tidal regime, weather conditions and human activities which may take place.

A short time series, measuring multiple parameters has been carried out from the Trelissick pontoon within the Fal estuary in order to examine the variation observed within the period.

Methodology:

The pontoon was situated by the King Harry Ferry dock up the Fal estuary, therefore Life Jackets were worn by all members of the working group to ensure safety. The equipment was assembled on site with sub groups that pre-tested the calibration of the data to be recorded. All the equipment was deployed every half an hour in accordance with the ferry time table to minimise disruption and errors over a 3 hour period.

Exo-Sounder:

The Exo-Sounder provides a profile of a variety of measurements; including dissolved oxygen, temperature, salinity and pH when lowered through the water column. The probe is kept partially submerged at all times to ensure the sensors work appropriately. Density can be calculated using the temperature and salinity values.

Light sensing:

To determine the light attenuation, 2 light sensors were used on the pontoon. One was used to get the surface ambient irradiance (on the deck), and the other was used to get an in-situ reading (in the water column), at different depths. The initial readings of the surface ambient and in situ readings were used to calculate a correction ratio. A depth profile was taken, along with the surface ambient irradiance for each reading. In-situ irradiance was taken every 1 metre decent in the water column.

TEMPORAL PONTOON SURVEY:

Niskin Bottle:

The Niskin bottle was deployed at metre intervals from the surface to obtain a water sample.  Then a 50ml sample is syringed into a separate bottle through a filter which is retained and placed into labelled test tubes containing acetone.  This process is repeated for each sampling station.  It was then necessary to refrigerate the samples overnight for fluorescence analysis at a later date to determine the chlorophyll concentration (mg/l).

Flow meter:

The flow meter was deployed from the pontoon and lowered through the water with flow (m/s) and direction (° from North) every 1 meter. Flow is measured by the rate of the impellor’s rotation which was caused by the movement of the water.

Hover  over image for  description:

Station Conditions : Click to expand