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Introduction
On the 3rd of July 2016, an offshore investigation was conducted on board the research vessel Callista, off the coast of Falmouth with the aim of investigating the stratification of the water column and types of plankton within said water column, along a spatial transect with 3 stations. The weather was poor with patches of rain, 8/8 cloud cover and a sea state of 5 (fresh breeze) on the Beaufort wind force scale.
Method and Equipment
Attached to a rosette was a CTD, fluorometer and transmissometer, which were used
to investigate the stratification (temperature, depth and conductivity parameters),
fluorescence and turbidity of the water column. In addition, Niskin bottles were
also attached to the rosette, used to sample the specific depths for phytoplankton
and nutrients. The CTD was lowered
through the water column, collecting data for
temperature, salinity and fluorescence, which was then used to determine the depths
where the Niskin bottles would sample on the way up. The Niskin bottles were triggered
remotely on the computer at these predetermined depths. When the CTD was recovered,
samples were taken from the Niskin bottles and were transferred into labelled bottles
to analyse in the boat’s wet lab and onshore chemistry and biology labs. For procedures
used in the wet lab, please see the preservation methods here.
A MiniBat was deployed at station 3 (the furthest station from shore), enabling the analysis of temperature, salinity, fluorescence, conductivity and density as distance offshore decreased. The MiniBat was towed behind the RV Callista for approximately 40 minutes, being controlled by a laptop connected to the machine. This allowed us to adjust the frequency and amplitude of the undulations by varying the angle of the wings and the speed of the boat. The maximum depth the MiniBat reached was 29m, and the minimum depth was 5m. A separate laptop, also connected to the MiniBat software, was used to record the data collected by the MiniBat.
An ADCP was used to assess the speed and direction of the flow between stations.
The ADCP recorded the relative vertical and horizontal mixing in an estuarine environment
and collected data for a series of Eulerian and Lagrangian flow measurements. 
Zooplankton were collected using a sample net with diameter 0.5m and 100 µm mesh
size, which was deployed and towed vertically at each station. The vertical samples
were taken at different depths at different stations. The depths at which the sampling
was conducted was determined by looking at the CTD profiles for interesting areas
of the water column at each station. At station 1 the net was deployed to 25m and
closed at 15m; at station 2 the net was deployed to 30m and closed at 26m; at station
3 the net was deployed to 40m and was meant to close at 15m. However, a misfire caused
the net to never close and so another sample was performed from 15-
The views expressed here are not representative of the University of Southampton.
