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Falmouth 2015 - Group 1

Figure 1: Complete sampling area from Truro River to Black Rock. (Combined data from group 1 and 13) (Click to Enlarge)

Introduction

The Fal estuary is an example of a Ria or drowned-river valley which formed during melting of glaciers from last ice age. The Carrick Roads which extend up the estuary towards Tresillian from Black Rock, approximately four miles downstream, reach maximum depths of thirty four meters; a contributing factor to making the Fal estuary the third largest natural harbour in the world. The depth of water allows a range of large vessels to utilise the estuary for transportation of goods and recreational uses with other activities on the Fal such as tourism ferry trips, marine engineering and fishing, most notably that of oysters. The estuary is supplied with fresh water directly from rivers including the Fal, Turo and Tresillian at the head of the estuary, the Carnon into Devoran and the Penryn and Percull rivers near the mouth of the estuary and Falmouth harbour. The interaction of fresh waters

containing ‘new’ nutrients and saline waters form an estuary with multiple species niches and a range of environmental conditions down the length of the Carrick Roads which also experiences influence from the tides in Falmouth harbour.

The Fal is home to a vast array of bird life which reside on the mud flats and river banks with kites, gannets and buzzards a common occurrence in the air. The marine life is also very biologically diverse with the Fal river and parts of Falmouth Bay forming a special area of conservation which protects the habitats of Eelgrass, mearl and sea grasses to name a few.

Samples were taken from near the head of the estuary in the Turo River to the pontoon (See figure 2 & 3) with outstanding samples to black rock obtained from group 13. Samples measured:

Biological parameters

• Phytoplankton
• Zooplankton
• Chlorophyll

Chemical parameters

• Silicon

• Phosphate
• Nitrate
• Oxygen

Physical parameters

• Temperature
• Conductivity
• Current velocity
• Secchi depth
• Turbidity

On-board the Bill Conway a CTD sensor was deployed containing a rosette of eight Niskin bottles at pre-planned stations. The sensors measured the various parameters with depth on the downcast and Niskin bottles were fired according to observations from the CTD data on the up-cast. Some stations, 38 and 41, were added due to failure of Niskin bottle closing on the previous stations with the skipper positioning the boat as close as possible to the original station site.

See Table 1 for high and low tides on the day of sampling. The samples were taken on the flood tide until high water at 13:17, and any samples later in the afternoon were taken on the ebb tide. This was advantageous as this meant the upper estuary was sampled close to low tide, so the lowest salinity samples were acquired.

References

Destination Cornwall, no date, The Fal estuary and Area [Online]. Available: http://www.destination-cornwall.co.uk/portfal.htm [accessed 2015, June 28th]

Cornwall Guide, 2015, The River Fal [Online]. Available: http://www.cornwalls.co.uk/Falmouth/fal

_river.htm [accessed 2015, June 28th]

Falmouth port, no date, Environmental code of practice for the ports of Falmouth, Turo and Penryn [Online]. Available: http://www.falmouthport.co.uk/commercial/html/documents/environmental

cop2010.pdf [accessed 2015, June 28th]  

Joint Nature Conservation Committee, no date, SAC selection Fal and Helford [Online]. Available:

http://jncc.defra.gov.uk/protectedsites/sacselection/sac.asp?EUCode=UK0013112 [accessed 2015, June 28th]

Table 1:High and Low tides for the Fal Estuary on 27/06/2015

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Disclaimer: The views expressed here are not associated with those of the National Oceanography Centre Southampton or the University of Southampton.

Figure 2: Stations sampled on 27/6/2015 in the estuary from Truro river to black rock. (Click to Enlarge) (White Lines show ADCP Transects)

Table 2: Metadata for Estuary Fieldwork

Introduction Physical Chemical Biological

Introduction Physical Chemical Biological

Introduction Biology