FALMOUTH FIELDCOURSE

Group 5

The views expressed are those of the individuals concerned and do not express the views of the University of Southampton or those of the National Oceanography Centre Southampton.

Estuarine boat methodology

R.V. Bill Conway:

Four stations were sampled on the Conway, one at Black Rock, one at the top of the estuary ad two in between. At each station a CTD was lowered to gather data on the profile. Using this data, the depth at which to deploy the niskin bottles was determined. The water samples collected from the niskin bottles was then prepped on board to be analysed in the lab on a later date.

There was a slight issue with the 2 bottles misfiring (Stations 37 and 40), however, this occurred at the surface so a sample could be collected by lowering a bucket over the side of the boat. Secci disk depths were also taken at all stations.

ADCP transects were also taken at each station, travelling from one shore to another, across the estuary.

Two zooplankton nets were lowered off of Conway, one at the lowest end of the estuary and one at the upper end of the estuary. These nets were towed slowly for five minutes.

Winnie the Pooh:

An additional four stations were sampled on Winnie the Pooh further up the estuary towards Truro. As it is a smaller vessel, no CTD or ADCP data could be taken. At each station, the temperature and salinity was measured using a T/S probe. A water sample was also taken using a singular niskin bottle that was lowered to just below the surface. This sample was then prepped to be analysed in the lab the next day. However, no oxygen samples could be taken due to lack of equipment. Also only three phytoplankton samples were taken due to a lack of lugols iodine.

Two zooplankton nets were lowered off of Winnie the Pooh, one at the lowest end of the estuary and one at the upper end of the estuary from this survey. These nets were towed slowly for five minutes.

Above: 4 members of the group on Winnie-the-Pooh (Photo credit - Eleanor Spencer)

Above: R.V. Bill Conway (Photo credit-University of Southampton)

Site Reasoning

RV Bill Conway:

The sites were selected based on location and convenience. As the Conway was travelling to a pontoon at the top of the estuary, it made sense to sample at four locations, each further up the Fal. The locations chosen allowed the estuary to be sampled at fairly regular intervals, showing how the water changes as you move from high salinities to lower ones. Other factors had to be taken into account, for example the water depth as if the water was too shallow the ADCP readings would not be as accurate. Therefore areas with a deeper channel were selected.

Winnie the Pooh:

As the Winnie the Pooh is a much smaller boat, it allowed further exploration up the estuary. Here the sites were chose based on the location and the geological and anthropogenic surroundings. Sites near tributaries and near the sewage treatment plant were specifically selected to try and determine if these made a difference to the water chemistry and biology. The top site was selected as it was the furthest up the river the boat could travel and therefore the lowest salinity we could record.

Above: R.V. Bill Conway stations

Above: Winnie-the-Pooh stations

Click below to see a breakdown of our Estuarine data