Falmouth Field Trip 2014- Group 3

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Produced by: Alice Duff, Philippa Fitch, Joanna Gordon, William Harris, Thomas Jefferson, Eirian Kettle, Jesse Marshall, Dominique Mole, Emma-Jo Pereira, Joshua Walton

Home Geophysics Estuary Pontoon Offshore Appendix

Aim

Investigate diurnal variations in physical and biological parameters of the Fal estuary over a short time period (8 hours).

Objectives

Determine how current varies with depth over the time period using a flow meter.

Investigate changes in multiple parameters (temperature, salinity, turbidity, pH, dissolved oxygen concentration and chlorophyll) with depth using a YSI multi-sensor probe over the time period.

Determine the variation in surface chlorophyll over the time period by taking and filtering water samples.

Introduction

Diurnal variations can be large in some estuaries (Cronin, 1975). It is therefore important to investigate daily changes in estuarine conditions. Within the Fal estuary, factors influencing diurnal variations in physical and biological changes including tidal regime, weather conditions and human activities which may take place. A short time series, measuring multiple parameters has been carried out from a pontoon within the Fal estuary in order to examine the variation observed within this time period.

Methods

On the 28th June 2014, data collection was carried out from a pontoon located within the Fal estuary (50°08.682N, 005°01.661W). The same procedure for collecting results was completed every half an hour from 07:30 to 15:00 UTC (although measurements for 10:00 UTC are missing due to the transition between the two groups sampling in the morning and afternoon).  A current meter was used to collect speed and direction of flow at 1m intervals. Maximum depth was recorded using meter indications on the wire of the flow meter and A YSI multi-sensor probe was used to take measurements. Temperature, salinity, turbidity, pH, dissolved oxygen concentration and chlorophyll concentration were all recorded using this instrument. Water samples were taken from the surface every half an hour using syringes (2 repeat samples). 50ml was filtered through glass fibre filters, which were each added to 6ml of 90% acetone. These samples were then analysed for chlorophyll concentrations ex situ using a fluorometer.

See Appendix for further details

Pontoon