Offshore

Introduction Biological Findings Chemical Findings Physical Findings

Figure 1. Track from RV Callsta’s onboard computer showing sampling stations.

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 AIM

To investigate the horizontal and vertical variation of phosphate and silicate concentrations, zooplankton abundance, chlorophyll, turbidity, irradiance, temperature and salinity levels at 3 stations offshore of Plymouth Sound.





 INTRODUCTION

Weather:           Partly to very cloudy, dry, WSW wind

Temperature: 25 degrees celcius

High Water:     03:36, 16:08 UTC

Low Water:      10:05, 22:35 UTC


On the 10th July 2018, we travelled aboard the RV Callista, from Mayflower Marina offshore to sample six stations for physical, chemical and biological data from each. The first station was C42 and was the closest to shore, next was C43, C44, C45, C46 and finally C47, which was the furthest from the shore (10km SW from Plymouth and close to the L4 Station).


Three people worked on the back deck of Callista ensuring the safe deployment and retrieval of the CTD. The CTD is mounted with a rosette of Niskin bottles which collecst the samples. The CTD records; depth, salinity and temperature as well as fluorescence, which measure the concentration of chlorophyll and beam transmission which records the amount of light absorbed by phytoplankton.


Onboard the RV Callista there is a power supply that connects to the CTD, this sends a message to the CTD which closes the Niskin bottles, thus, collecting our sample of water at a desired depth.


We ran ADCP transects travelling between stations and took CTD data and 1-4 niskin bottle samples while we had stopped at each station. From the Niskin samples, we then sampled oxygen, phosphate, phytoplankton and chlorophyll from each. At stations C43 and C45 we deployed a zooplankton net for 2 minutes to recover a 1L sample.


A time series was also conducted near L4 by deploying the CTD every hour between 12:30 and 2:30 UTC. This allowed us to see how different parameters change at the same site over time. All of the samples collected were then analysed in the lab the next day.