The views expressed above are those of the authors and not those of the University of Southampton or the National Oceanography Centre Southampton.

Background

Fal Estuary

The Fal Estuary, located on the south coast of Cornwall, is the third largest natural harbour in the world1. Geologically it is classified as a ria as it was formed by the drowning of a river valley through a combination of tectonic subsistence and sea level rise2. Its hydrology is dominated by tidal influences, as with other rias the Fal has a relatively low freshwater input3 from its drainage basin, which includes the Fal, Truro and Tresillian rivers4. The Fal Estuary is a macrotidal estuary with a length of 18km and has a maximum spring tide of 5.3m at Falmouth, however at the head of the estuary the maximum spring tide is 3.5m and is therefore mesotidal5.  

The Fal is a Special Area of Conservation (SAC) under the EU habitat directive6 due to its large range of marine habitats supporting a rich diversity, including two important maerl species near St Mawes which create a unique habitat for other species; these maerl species are Phymatolithon calcareum and Lithothamnion corallioides. Dredging in the estuary has been proposed as part of the Falmouth Cruise Project to accommodate for larger ships and to help boost the local economy. However there is worry that dredging will damage the maerl habitats and there is resistance from scientific and fishing communities as many fish and shellfish use the maerl beds as a nursery ground, some of which have commercial importance7.

For many centuries mining activity in the Fal’s catchment area and contaminated water discharges have lead to increased heavy metal levels in the estuary. The Carnon River and Restronguet Creek have been affected the most and are relatively acidic with high levels of heavy metals, most notably Cu, Zn, As and Zn which tend to be in the order of 1500-3500 µg/g8. Some organisms have adapted to the elevated levels of copper in Restronguet Creek, for example, Nereis diversicolor which has an increased tolerance to high concentrations9. Other pollution sources include continuous and intermittent sewage discharges, boat discharges and runoff from agricultural land. There are also high concentrations of nutrients in the estuary, mostly from diffuse sources, which often cause eutrophic conditions in summer months.

Past Research and Useful Links

In 2006 Hatton wrote the Fal and Hedford SAC Management Scheme which includes the anthropogenic impacts on the area, habitat directives and regulations and the conservation objectives. Research published in 200310 discusses activities potentially affecting the condition of the SAC and the environmental permissions affecting them. The upper estuary is subject to eutrophication and toxic algal blooms were also found due to agricultural runoff. Pirrie et al.11 studied the after effects of the clay mining industry on the Fal estuary; the dock area was found to have localised contamination of the antifouling agent TBT (tributyltin) whilst high levels of zinc, copper, tin, lead, and arsenic were found in the estuary sediment.

Research on the coastal station, L1, and offshore station, E1, near Plymouth can be found on the Western Channel Observatory website. The data collected at the station includes nutrients, temperature, depth, salinity and phytoplankton composition; at L4 the data is collected weekly and bi-weekly at E1.

       Below is list of useful website links:

• General information on Fal estuary: http://projects.exeter.ac.uk/geomincentre/estuary/Main/loc.htm
• Information on the Fal and Hedford SAC: http://jncc.defra.gov.uk/protectedsites/sacselection/sac.asp?EUCode=UK0013112
• Western Channel Observatory website for data on stations L4 and E1 near Plymouth: http://www.westernchannelobservatory.org.uk/

• Falmouth weather, tides and shipping information:
• http://www.falmouth.co.uk/on-the-water/seafaring-information

• Tide times website: http://www.tidetimes.org.uk/falmouth-tide-times

References

 1http://www.destination-cornwall.co.uk/portfal.htm

2http://www.soes.soton.ac.uk/teaching/courses/soes3018/2009/group6/

main.htm

3 http://www.sssi.naturalengland.org.uk/citation/citation_photo/2000174.pdf

4 www.google.com/maps

5 Pirrie, D., Power, M. R., Rollinson, G. S., Camm, S., Hughes, S. H., Butcher, A. R. and Hughes, P. 2003. The spatial distribution and source of arsenic, copper, tin and zinc within the surface sediments of the Fal Estuary, Cornwall, UK, Sedimentology, 50, 579-594.

6http://jncc.defra.gov.uk/protectedsites/sacselection/sac.asp?EUCode=UK0013112

7 http://www.cornwallwildlifetrust.org.uk/conservation/position_statements/

fal_docks_dedge_and_the_reference_area_for_maerl

8 Bryan, G. W. and Gibbs, P. E., 1983, Heavy metals in the Fal Estuary, Cornwall: A study of long-term contamination by mining waste and its effects on estuarine organisms, Marine Biological Association of the United Kingdom, Occasional Publication No. 2.

9 Marine Pollution (4th Edition) R.B. Clark, C. Frid and M Atttrill Oxford Science Publications, 1997.

10 Langston, W., Chesman, B., Burt, G., Hawkins, S., Readman, J. and Worsfold, P. 2003. Characterisation of European Marine Sites: The Fal and Helford. Marine Biological Association Occasional, 8.

11 Duncan Pirrie, Matthew R. Power, Gavyn Rollinson, et al., no date. Mapping and visualization of historical mining contamination in the Fal Estuary, Cornwall. n.d.. Home page. [online] Available at https://projects.exeter.ac.uk/geomincentre/estuary/home.htm [Accessed: 1 Jul 2013].

Aims

Through the analysis of data collected from Fal estuary and coastal offshore waters, we aimed to investigate and gain a broader understanding of the biological, chemical, physical and geophysical processes of the Fal estuary and surrounding waters.

The initial findings of the investigation are summarized on this website.