Introduction

Estuaries are semi-enclosed variable environments in terms of chemical, physical and biological properties. By measuring these properties the physical structure such as the extent of mixing, classification and flushing within the estuary can be calculated and therefore the conservative/non conservative nature of the nutrients can be determined (Liss, 1976). The Fal River and estuary is a drowned river formed during the last glacial maximum valley known as a ria and is geographically located near populated settlements and the industrial port of Falmouth. Anthropogenic inputs from these may cause changes in the properties of the estuarine environment and in turn can affect the biota residing within the estuary (Somerfield et al, 1994; Bryan and Gibbs, 1983; Somerfield et al, 1994).    

The study was carried out on the vessel Bill Conway on 28/06/2013 starting at 8.30am.

The equipment used was a CTD rosette, an ADCP (Acoustic Doppler Current Profiler), plankton trawling net, and a Secchi Disk.

Stations are marked on map below.

Conditions

Lab methods

Laboratory methods to determine phosphate and silicon levels were in accordance with the procedures described by Maita and Lalli (1894). The method involved adding reagents and measuring colour intensity, and determining unknown concentrations of samples by means of a calibration curve from working standards of dissolved phosphate/silicon solutions.

Dissolved oxygen levels were determined by titration with sodium thiosulphate using the method described by Grasshoff, Kremling and Ehrhardt (1999).

Chlorophyll levels were determined using a 10 AV Fluorometer followed by data conversion to seawater concentrations.

Water samples from each station were analysed for nitrate using a flow injection system as described in Johnson and Petty (1983).

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Figure 4: A map to show the locations of the sample stations. Click on yellow dots for ADCP data from each station

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