Introduction

We have conducted an investigation of the Fal estuary, South-West England. This website contains our initial findings and thoughts of the investigation. The aim of our project was to study the biological, chemical and physical profiles of the water column throughout the estuary, as well as offshore locations, from multiple pre-selected locations on the research vessels and one stationary survey location at Mylor (King Harry Ferry pontoon).  Falmouth was selected as the survey destination because of the unprecedented dynamics unique to very deep, tidal dominated estuarine systems.

The Fal

Falmouth estuary is a unique environment, designated a special area of conservation (SAC) and site of specific scientific interest (SSSI) due to its diversity of estuarine organisms and habitats, as well as rare or endangered species.  As the world’s third deepest natural estuary (34 metres; 10 metres upriver) [1], it has served as a busy port dating back to the 1100’s, and so naturally there has been a great deal of human impact on the surrounding habitats [2].

 The estuary itself is a drowned river, valley or ria, and dates back ~10,000 years; it was formed during the last ice age, as a result of tectonic movements and riverine forcing, and a subsequent sea level rise.  The majority of the estuarine system is contained within the Carrick Roads area, which starts at Black Rock and extends four miles to Turnaware Point and the transition from the river to estuarine system, and is at least one mile wide throughout.

There are six main tributaries to the Carrick Roads, the predominant sources being the River Fal, the Truro River, and the River Carnon, as well as twenty eight creeks and smaller rivers.  Despite this, heavy sedimentation, human impact and the estuary bed morphology has limited the fresh water input upriver, resulting in a tidal dominated estuarine system.  In addition, the estuary’s [greater than average] depths create salinity gradients unique to deeper channels where tidal water input is much greater than that of fresh water, and so higher levels of salinity can be observed much further upriver than in most estuarine systems.

 Salt marshes are subsequently found further upriver, which offer further habitats for the local and migrating species and one of the main reasons behind the SAC designation.  Furthermore, the Fal Estuary contains rare species of Maerl; Phymatolithon calcareum, and Lithothamnion coralliode, as well as [Zostera sp.] seagrass beds [3].  These habitats are of great scientific importance and covered under SAC and SSSI regulations.  In recent years, the Falmouth Harbour Commissioners have been under a great deal of pressure to expand the local Ports, which would require dredging the estuary channels several metres in particular areas; debates on consequential effects of this the rare species in the area are still ongoing.

[1] Pirrie, D., Power, M., Rollinson, G., Camm, G., Hughes, S., Butcher, A. 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(3), pp.579--595.

[2] Deeble, M. and Stone, V. (1985). A port that could threaten marine life in England's Fal Estuary. Oryx, 19(02), pp.74--78.

[3] Hall-Spencer, J., Kelly, J. and Maggs, C. (2008). Assessment of maerl beds in the OSPAR area and the development of a monitoring program. Prepared for the Department of the Environment, Heritage \& Local Government (DEHLG), Ireland. 30pp.

[4] Widdicombe, C., Eloire, D., Harbour, D., Harris, R. and Somerfield, P. (2010). Long-term phytoplankton community dynamics in the Western English Channel. Journal of Plankton Research, p.127.

[5] Pirrie, D., Camm, G., Sear, L. and Hughes, S. (1997). Mineralogical and geochemical signature of mine waste contamination, Tresillian River, Fal Estuary, Cornwall, UK. Environmental Geology, 29(1-2), pp.58--65.

[6] Gibbs, P. (2009). Long-term tributyltin (TBT)-induced sterilization of neogastropods: persistence of effects in Ocenebra erinacea over 20 years in the vicinity of Falmouth (Cornwall, UK). Journal of the Marine Biological Association of the United Kingdom, 89(01), pp.135--138.

[7] Rijstenbil, J., Merks, A., Peene, J., Poortvliet, T. and Wijnholds, J. (1991). Phytoplankton composition and spatial distribution of copper and zinc in the Fal Estuary (Cornwall, UK). Hydrobiological Bulletin, 25(1), pp.37--43.

The estuary is macrotidal in the Carrick Roads with tidal ranges of 5.4 metres (tide-table included above), but transitions into mesotidal system upriver where increased sedimentation has occurred.  Due to its tidal dominated nature, the Fal Estuary is a well-mixed system, which has potential for two separate mixed layers, and very high levels of phytoplankton growth and primary production [4].  It is important to note that much of the surrounding landscapes in the Falmouth/Truro area are farmland, and so agricultural runoff as well as pollution and dumping cause a notable effect on the biological system of the estuary; there is potential for eutrophication to occur in the system, particularly in seasons of higher productivity as a result of nutrient enrichment into the inputting rivers [1].  Additional sources of pollution and nutrients were input in system from local mines, in particular the Wheel Jane tin mine located in Baldhu, which overflowed in 1992 as a result of rising groundwater levels, and carried the contaminated waters into the Fal Estuary, causing detrimental effects to much of the inhabiting species [5].  High contaminants levels were once again observed more recently as result chemicals found in anti-fouling sprays used for protecting ships; particularly the chemical tributyltin was found to be causing cases of mortality and imposex in the local gastropods [6].  While the Wheel Jane and accompanying mines have been shut down for more than two decades, the effects are still being observed and hypernutrification continues to occur in the Falmouth Estuary.  Furthermore, the effects of the metal ion enriched waters can be observed in the phytoplankton species distributed throughout the local region, providing an informative survey location for sampling productivity [7].   

Meet Falmouth 2014 Group 8!

Click on the individual photos below for names, course and contact details.