ESTUARY SURVEY

BIOLOGICAL

CHEMICAL

PHYSICAL

As the high tide was at 14:04 UTC (https://www.tidetimes.org.uk, 2018), the team on RV Winnie the Pooh started sampling  the Tamar River at 10:30. Salinity and temperature measurements were taken at the surface, at 18 different sites, moving upstream from the Tamar Bridge to Calstock. Phytoplankton samples were collected using a single Niskin Bottle and preserved in Lugol’s iodine, as well as nutrient samples. Systematically, at the start, middle and end of the transect a zooplankton net was deployed, allowing it to drift at 1 metre depth  for 5 minutes, 3 minutes and 1 minute respectively due to the increasing amount of organic matter in the estuary.

On the pontoon, measurements for salinity, temperature, turbidity, oxygen saturation (%) and oxygen concentration (mg/L) were recorded using an YSI probe. A light meter as well as a Secchi disk were used to measure light penetration, whereas the flow speed and direction were measured by  a current meter. These recordings were made at 1m intervals every 30 minutes going as deep as the tide would allow.

On top of those other recordings, a Niskin bottle was used to collect water samples from the surface and at 4m every hour, these were filtered into 3x50ml samples and those filters were subsequently put in acetone for later lab analysis to calculate the chlorophyll concentrations

On board Callista, a CTD was deployed at 9 different sites along the Tamar estuary recording the salinity and temperature which were used to create a depth profile. Once deployed, Niskin bottles were fired at depths of interest to collect water samples which were later processed and stored for lab analysis to record the nitrate (μmol/L), nitrite (μmol/L), silicon (μmol/L), phosphate (μmol/L) oxygen concentrations (μmol/L) and phytoplankton. A net was also deployed at 3 sites for 5 minutes at a speed of 2kn to collect zooplankton samples and a Secchi disk was used to measure the light penetration.  ADCP transects were taken at each site to measure the flow speed and direction.

METHODOLOGY