Aim	Equipment	Ancillary data	Vessel Information
To effectively survey and categorize benthic habitats in the Helford River using a range of geophysical and  biological techniques.	ADCP Van Veen grab Sidescan sonar Sector scan	Date: 05/07/2010 Weather: Sunny with 2/8 cloud cover Tides: HW 1100GMT, LW 1725GMT Wind: 16knots average Sea State: Calm	SV Xplorer: This vessel is ideal for both estuarine and offshore work. At 12m long and with a 1.20m draft it is able to navigate the mouth of a small estuary much easier than the larger Callista. It is also a much quicker vessel with a maximum speed of 25 knots and a cruising speed of 18 knots. It is equipped with a 1 tonne capacity winch on the stern which is used for Van Veen Grab sampling. Side scan sonar tow fish are also deployed from this vessel. It can carry 14 passengers and the wheelhouse can double up as a dry lab where the progress of the side scan sonar can be monitored.

 

Introduction

The Helford River is a ria, or a flooded river valley, fed by seven creeks. It supports many types of industries, for example different types of tourism and an oyster farm. Due to its importance to people and the organisms living within its environment, it has been a point of interest for both conservation and development groups. The Helford River is a Special Area of Conservation (SAC), a protected site under the EU Habitats Directive and is home to many rare species of marine life such as seahorses, gobies and wrasse.  It has gained status as a SAC due to its various interesting habitats including mud flats, sea inlets and sandbanks.  These different habitats support beds of the eelgrass, Zostera marina and two species of the red calcareous algae maerl, L. corallioides and P. calcareum, both of which are protected species.  The River incorporates the National Seal Sanctuary which takes on injured seals and nurses them back to health before later release back into the Atlantic Ocean. This River is also a designated Bass (Dicentrarchus labrax) nursery. 

Two separate survey sites were chosen for our study.  One of these sites was a known eelgrass area and it was chosen in order to establish growth and abundance. Due to its status as a protected species, it is important that such an area of eelgrass is surveyed repeatedly. Eelgrass supports rich invertebrate communities and lives submerged in seawater in a range of habitat conditions and its survival is subject to water clarity, sedimentation and various forms of pollution (Langston et al., 2006). According to relevant literature (Covey et al., 1987) it has been observed that Zostera marina beds have disappeared from many areas while the ones that remain have been eroded. The effect of erosion on the eelgrass beds is seen in this survey as the eelgrass abundance was observed mainly in patches and not in extensive eelgrass beds.

Images from video trawl
Patchy Eelgrass	More substantial Eelgrass Beds

 

Maerl beds around the UK, sites shown in blue.

The second site chosen was in the mouth of the Helford estuary.  This site was chosen as it would hopefully provide a different benthic habitat to that further up the estuary.  It was also presumed that this area would provide grabs containing maerl.  Maerl is a collective term for a group of red algae that form calcareous crusts on rocks, shells and other substrates. They can form extensive beds but are easily disturbed by changes in their surrounding environment, including temperature, salinity and heavy metal concentration of the water column. The Maerl beds usually consist of a mixture of two species of the algae, for example L. corallioides and P. calcareum. The exact combination of species can vary with different environments. The presence of Maerl beds has been a catalyst for the introduction of new conservation sites around the British Isles. This is due to it being threatened by environmental and anthropogenic pressures, such as the threat from industrial use as it is often dredged and turned into a powder for multiple used including a soil conditioner and in water treatment. Maerl is important in our ecosystems as it creates habitats for smaller organisms which live in the empty ‘shells’ of the Maerl, and it also affects the substrate as it contributes to biostabalisation on the sediment, making it more coarse.

Sidescan in Eelgrass beds, shown in red below

Sidescan in the Bay, shown in blue below

At both stations side scan sonar tracks were taken, 6 at the first site and only 2 at the second due to time constraints.  A drifting video trawl was also undertaken at both, allowing for a true view of the sea bed over which the tow fish had just been dragged.  Each time the fish was being towed along a transect two members of the group were positioned on the deck as observers to note down anything that may affect the sonar read out.  The wake of passing ships or the movement of moored buoys could create cloud like trails on the print out.  At the second site three grabs were performed using a Van Veen Grab.

 

 

 

Google Earth image of benthic mapping transects

 

Aim	Equipment	Ancillary Data	Vessel Information
To study how the biological, chemical and physical processes interact within the Fal estuary	ADCP CTD Niskin bottles Secchi disk Plankton net Van-Veen grab	Date: 09/07/10 Weather: Sunny, 2 Oktas Tides: LW 0805 GMT, HW 1415 GMT Sea State: Calm	The Bill Conway is a smaller vessel than RV Callista with a length of 11.34m and a beam of 3.96m. Its full load draft is 1.4m making the Conway an ideal vessel to navigate up small estuaries. It has an average speed of around 10 knots which makes it perfect for estuarine work. Two crew and twelve scientists can be carried on the Bill Conway at any one time allowing enough space for samples to be collected. The A frame on the Bill Conway is 3m high and its maximum capacity is 750kg which is ample for any sample collected within an estuary. The trawl winch is 70m which will reach the bottom of any estuary enabling good samples to be obtained.

 

Google Earth map of transects and ship track

Estuaries are bodies of semi-enclosed water that have different biological, physical and chemical characteristics compared to that of the seas into which they flow. They form a transition zone between the fresh (riverine) water environments and the ocean environments. The mix of both the seawater and freshwater provide the water column and sediment with a high nutrient concentration. This alone makes the estuary one of the most productive natural habitats in the world.

Wastes, transferring contaminants from heavily populated or industrialised areas use estuaries as a convenient channel to the coastal seas. Concentrated pollutants tend to impact an estuary first due to the area being more enclosed than coastal seas. Once the pollutants reach the sea, processes in the estuary control the form and concentrations of the various pollutants.

We took three ADCP transects (red lines) at the mouth, middle and upper part of the estuary to find the flushing time of the estuary. At the same points we took vertical profiles of the water column to determine the temperature, salinity and turbidity. Ideally we would have measured fluorometry but the fluorometer was not working. However, samples for chlorophyll from the Niskin bottles have been analysed in the laboratory. The green line shows the five points at which salinity decreased by 0.5 where we took nutrient samples to produce mixing diagrams. The river-end member has already been collected further upstream at 0 and 20.0 salinity.

It is important to note that as the survey was undertaken during a period of low rainfall, the salinity values vary very little along most of the estuary. As estuarine sampling is usually salinity-dependant, this resulted in fairly low-resolution mixing diagrams.

 

 

 

 

Depth Profiles

Fig. 1a: Temperature-Salinity plot	Fig. 1b: Temperature - Depth	Fig. 1c: Salinity - Depth	Fig. 1d Turbidity - Depth

Station 1 shows evidence of a slight thermocline (Fig. 1b), over a few degrees as the measurements were taken out in the mouth of the estuary. However, stations 2 and 3 were much shallower so a thermocline is not present but temperature does decrease with depth. The highest temperature recorded was at the surface at Station 3 where there is least turbulence (Fig. 1b) and the depth is shallowest. The highest turbidity was at station 1 (Fig. 1d) which was constant throughout the water column. Station 2 and 3 (Fig. 1c) show salinity decreasing with depth whereas station 1 has a constant salinity through the water column representative of a well-mixed water column. The T-S plot (Fig. 1a) also shows station 1 with a constant salinity and only a small change in temperature whereas stations 2 and 3 show larger decreases in temperature and increases in salinity. Station 1 at the mouth of the estuary has a light decrease in temperature but is well-mixed. Further up the estuary, with decreasing depth the surface is warmer as less water to heat up and salinity is much higher at depth as density increases.

The Richardson Number was calculated for Station 1 and 3, with an average of 11.82 and 2.68 respectively. This shows that at station one at the mouth of the Falmouth Estuary is more stable than further up the river, where ADCP data shows that the current velocity is greater. The Ri was calculated using un-calibrated salinity measurements as the calibrated data was not available at the time. This wouldn’t affect the results as the change in shear stress would still be detectable.
 

 

Station 1

Fig. 2a: Nutrient depth profile St. 1

Results
The first station sampled was a deep trough in the middle of the mouth of the Fal estuary which had a depth of 33m. Fig. 2a shows there was a slight thermocline from 15.5ºC to 13.5ºC but not much of a halocline with the salinity staying relatively constant between 33.6 and 34. The highest turbidity found during sampling was 4.397V (Fig. 1d) which was approximately constant throughout the water column. The nitrate minimum was 0.42μM at 4.4m whilst the maximum of 1μM was observed at 20m. The concentration decreases from the surface to 5m then increasing down to 20m before decreasing again at the bottom depth. The phosphate concentrations show a decrease from the surface to 5m then an increase. The maximum value for phosphate was higher in the water column at 9.25m at 0.17μM. The results gave 0 concentrations at 19.8m and 25.7m. In the first 9.25m silicate has a completely opposite trend to the two other nutrients with the concentration increasing at 4.4m then decreasing again. At 19.8m we see the maximum of 2.02μM. This station shows an initial decrease in oxygen saturation from the surface to 5 meters, and then begins to increase; the biggest increase taking place between 19.8 and 25.7 meters with an increase of approximately 10%, resulting in the highest oxygen saturation being 114.7% at 25.7m depth. (Fig. 7a) At Station 1 the phytoplankton numbers were low. This was the only station with Ceratum present and only 1,000,000 individuals could be found in 1m^-3. Dinoflagellates dominated the sample; the group consisting of unidentified dinoflagellates, Alexandrium sp., Karenia sp., and Gymnodinium sp. (Fig. 5) The Copepooda dominated the zooplankton community at Station 1, with 6375.52m-3, which is the lowest value of Copepoda recorded for all the stations we looked at. Appendicularia were abundant in the sample, with 1499.31m-3. This is a very high value compared to other stations and particularly to that of the offshore samples (Fig. 6). The chlorophyll data here is relatively low compared to the other stations, not reaching higher than 0.4746µg/L, and it is fairly uniform as it only has a range of 0.3258µg/L (Fig. 7b). The chlorophyll maximum is at the surface at 1.2m.

Discussion
The phytoplankton numbers here were the lowest of all the stations visited, which may be tied into the high turbidity observed, which would restrict the amount of light available for photosynthesis. The low chlorophyll levels at this station support the hypothesis that there are not many phytoplankton cells present here, but we can assume that they are mostly in the surface waters as the chlorophyll maximum is at 1.2m. The chlorophyll data are also relatively constant throughout the water column which is another indication of a mixed system. The low abundance of phytoplankton may be the reason for the low density of zooplankton found here, as they would have little food to graze on. The phosphate results are the highest at the surface as they are being excreted by phytoplankton, and the slowly decrease with depth as the phytoplankton numbers decrease. There is an anomalous reading where the concentration peaks at about 10m depth; this could have been caused by contamination of the sample. The Silicate has an initial increase with depth, as the phytoplankton abundance is decreasing and so less silicate is being taken up. Below this depth, the nutrients do not behave as would be expected in this part of the estuary, considering the results for factors such as chlorophyll maxima and abiotic factors which usually determine the nutrient levels throughout the water column. These results can be explained by pollution, as The Urban Wastewater Treatment Directive has classified the Fal estuary as a Sensitive Area (eutrophic) and the Nitrate Directive designated the area as Polluted Water due to eutrophication (Langston et al. 2006). The initial decrease in oxygen saturation could be due to the zooplankton which would be feeding on the phytoplankton in the surface waters, using the oxygen in respiration. The later increase in oxygen could be due to the second lesser increase in phytoplankton cells at around 20m which would reintroduce oxygen into the water.

Fig. 8a shows the limited mechanical mixing through out the water column, with some mixing occurring at 10 to 12 meters. This corresponds to the Brunt Vaisala frequency which is lowest at that depth, but which also shows a very stable water column.

 

Station 2

Fig. 2b: Nutrient depth profile St. 2

Results
At Station 2 the water temperature decreases with depth from 16.51°C at the surface to 13.80°C at 15.3m depth. The salinity increases with depth from 34.02 to 35.05. The transmissometer reading increased from 4.10v to 4.26v, indicating increased turbidity at the seabed compared to the surface. The nitrate concentrations follow a strange pattern but this time in reverse. At Station 2 the nitrate maximum is at 3.18m (0.83 μM) and the minimum is at 9.75m (0.17μM). The phosphate concentration behaves in the same way as nitrate at station 1 with it decreasing at the surface but then increasing again before decreasing near the sea bed. The phosphate maximum was 0.26μM at 9.75m. The silicate decreases very slowly from the surface to 9.75m and then suddenly increasing from 2.3μM to 9.0μM at 15.3m. Station 2 had approximately the same number of total phytoplankton m-3, 27000000, though a lower diversity; only diatoms and Alexandrium sp. Were present (Fig. 2b). The chlorophyll maximum is 1.224µg/L, near the surface at 1.28m (Fig. 7b). The zooplankton community at Station 2 was composed almost exclusively of the Copepoda, with a value of 159815.24m-3; the copepods were very dense as well as very dominant compared to other stations (Fig. 6). The most abundant zooplankton after the Copepoda were larvae of the Gastropoda with a frequency of 392.61 m-3, however this value was very small and did not deviate greatly from the frequency of other organisms. Station 2 shows an initial increase in oxygen saturation from the surface to 3m and peaks here at 110.5%. After this, a huge decrease of 13% occurs between 3.18m and 7.47m. It then gradually increases again as the depth decreases (Fig. 7a).
 

Discussion
There is no thermocline but a halocline at Station 2, probably due to its position in the estuary. It is situated approximately in the middle of the estuary between the sea and the rivers, so the water column is likely to be partially mixed with more freshwater overlying more saline water. All nutrients are shown in Fig. 2b to fluctuate between extreme values, at depths which do not always correspond to other factors such as chlorophyll maxima. This can be explained by eutrophication and pollution; The Urban Wastewater Treatment Directive has classified the Fal estuary as a Sensitive Area, and the Nitrate Directive have designated the area as Polluted Water due to eutrophication (Langston et al. 2006). The oxygen saturation peaks near the chlorophyll maximum, then decreases as the phytoplankton abundance, indicated by chlorophyll concentration, decreases. This is because phytoplankton create large amounts of dissolved oxygen at the surface. The turbidity is highest near the seabed because increased friction causes turbulence. The very high number and density of the Copepoda can be explained by eutrophication. It is possible that due to the pollution of the estuary by nitrates and phosphates a eutrophic event could have occurred causing a large phytoplankton bloom. The zooplankton would then have multiplied greatly as they fed on the bloom, reducing the bloom to more natural levels of phytoplankton in the estuary, and resulting in a zooplankton population explosion, where the Copepoda outcompeted all other zooplankton Groups.

 

Station 3

Fig. 2c: Nutrient depth profile St. 3

Results

Fig. 2c illustrates data collected right up the estuary so one would expect to see low salinities and high dissolved nutrient concentrations.  It could be argued that there is a slight thermocline between 1.5 and 3.5m where the temperature decrease 2ºC from 18ºC to 16ºC.  The salinity is incredibly high for the study area, possibly due to lack of freshwater inputs.  The lowest salinity value was at the surface, 31, with it increasing over the 5.25m to 33.2.  The turbidity increases from 3.96 to 4.14 at 2.87m before decreasing to 4.08.  Here the nutrient concentrations are at their greatest.  The nitrate maxima is at the surface at 9.6μM and it decreases linearly to 2.3μM at 5.25m.  The phosphate ranges from 0.59μM to 0.27μM.  The silicate behaves in the same way as the nitrate with the maxima at the surface at 8.4μM.  This is the only station at which the nutrients have all followed a similar pattern and decreased with depth. 

Discussion

The plankton data (Fig. 5, Fig. 6) show that this station was the most diverse; it had the largest range of species for both zooplankton and phytoplankton. Favourable conditions encourage different phytoplankton species to grow, which in turn promote zooplankton growth by providing a range of feeding niches. The chlorophyll maximum is at the surface, showing that it reflects the number of phytoplankton at this station. It is also the highest of the chlorophyll maxima (Fig. 7b), probably due to the conditions in the estuary. Station 3 had the highest nutrient levels and the maxima were at the surface (Fig. 2c). This is good news for the plankton community, but it could lead to eutrophication. Eutrophication can lead to harmful algal blooms, such as the red tide event of 1995-96, studied by Langston et al. (2006). Our studies at this station support this study; several species of toxic phytoplankton where found such as Alexandrium species and Karenia mikimotoi. The CTD data show that there was a fair amount of mixing going on, due to the combination of shallow water and tidal mixing. Turbidity increases with depth, which indicates that tidal shear has more of an effect at 5m than at the surface, however, the euphotic zone extended to the bottom, allowing phytoplankton to photosynthesise all the way down.

At this station where the flow was greatest, there is strong mixing seen near bottom of the water column - likely due to the frictional shear stress over the river bed. This can be seen in Fig. 8b where Ri numbers are around 0.0094, well below the mixing critical value of 0.25. This data also corresponds well with Fig. 1d, showing a high amount of turbidity at around 3m depth.

 

Light data

Fig. 3: Solar Irradiance - Depth

Light will behave differently in water to air.  In water light is scattered and absorbed by particles in the water column and is quickly attenuated.  The rate at which this occurs can be quantified by the value k.  K can be calculated in two ways, using data from a secchi disk or alternatively data from a light sensor.  The formula for calculating k using a secchi disk is very simple; k = 1.44/secchi disk depth.  This is however, not a very accurate form of measuring the attenuation coefficient.  Therefore one can use the ratio between irradiance at depth (Ez) and surface irradiance (Eo).  The equation, Ez = Eo e^-kz can be rearranged to find k.  This process is simplified by creating a graph of Ln(Ez/Eo) against depth, finding the equation of the line, and dividing 1 by the gradient.

The irradiance readings from the light sensor have allowed for the construction of a graph illustrating the change in solar irradiance with depth at each station. Fig. 3 shows that at all three of the stations the irradiance decreases exponentially, with rapid decrease in the surface layers and then a slow decrease at depth. As one moves up the estuary the depth at which light can penetrate decreases, due to increased particulate matter in the water column. In just a metre the irradiance has dropped from over 1000 at the surface to around 300μmol m^-2s^-1 at station 3 whereas at station 1 it is at 920μmol m^-2s^-1. This illustrates how the surface layer of the estuary will absorb or block a large amount of the incoming solar radiation from reaching the water beneath. Fig. 3 shows how the irradiance figure at Station 1 does not drop below 200μmol m^-2s^-1 until about 6m, whilst it occurs at much lower depths at both Station 2 and 3. Station 2 appears to have the sharpest decline due to the fact that the irradiance at the surface was very high. However, it then follows a very similar pattern to Station 1, ending a metre above the sea bed with an irradiance of about 50μmol m^-2s^-1. In accordance with the k values in Table 3, more light is able to penetrate to greater depths at Station 1. A lower k value implies that less of the light is scattered or absorbed by particles in the water column and therefore the irradiance figures will be higher than that of a station with a high k value.
 

Table 3 also gives the depth of the euphotic zone, the depth below which there is not sufficient light for photosynthesis. This figure was calculated by multiplying the secchi disk depth by 3. The euphotic zone for Station 1 continues past the depth of the profile in Fig. 3, but one can look at the amount of radiation reaching the boundary at station 2 and 3. At station 2 the boundary of the euphotic zone is 8.58m. The photosynthetic active radiation figure at this depth is 43.7μmol m^-2s^-1. The euphotic zone for station 3 also continues past the recorded depth of the light metre to 6.3m. This depth is within 10cm of the sea bed, implying that phytoplankton would be able to photosynthesise almost anywhere in the water column. Although 6.3m was not recorded and one cannot definitely say that the irradiance would be 40μmol m-2s-1 or less, it would be foolish to suggest that the amount of light would increase at this depth.

Station	Secchi disk, k m-1	Ez/Eo k value, m-1	Euphotic Zone, m
1 (50°08.659N,005°01.420W)	0.238	0.211	18.15
2 (50°12.178N,005°02.429W)	0.503	0.333	8.58
3 (50°14.395N,005°00.883W)	0.686	0.630	6.3

Table 3: Light data for all stations

Table 2 shows that the further you travel up the estuary the greater the k value becomes and therefore the euphotic zone decreases.  The euphotic zone will also decrease, however, due to the decreasing water depth.  At station 3 both k values are within 0.06m^-1 of each other.  If the Ez/Eo value is accepted as a truer value then k = 0.630 (3dp).  Due to a smaller volume of water up the estuary all of the absorptive material such as nutrients, SPM and pollutants will be concentrated into a smaller area and therefore the amount of light being scattered or absorbed will greater.  In contrast, the k value at station 1 in the mouth of estuary was much lower at 0.211 (3dp), indicating that light will travel to much greater depths through the water column.  This is because the volume of water is much larger here and the scattering particles are dispersed throughout the water.  Station 2 is the only station which has k values that are not within 0.1m^-1 of one another.  This could be due to a change in the sunlight intensity between the two measurement times.  For example it could have been very sunny when the secchi disk was deployed, leading to inaccurate depth estimation and cloudy when the light probe was used. 

 

Estuarine Mixing Diagrams

Fig. 4a: Nitrate Mixing Diagram - Removal	Fig. 4b: Phosphate Mixing Diagram - Addition	Fig. 4c: Silicate Mixing Diagram - Removal

• Nitrate mixing diagram (Fig. 4a) shows non-conservative behavior of the constituent with all the data bellow the theoretical dilution line which suggests that nitrate was subject to removal from the estuary. Most of nitrate removal was shown at salinities 32 to 35.

• Phosphate mixing diagram (Fig. 4b) showed the strongest non-conservative behavior. Along the estuary the concentration of phosphate was increasing since the data points on the plot where above the TDL.  Most of phosphate addition took place closer to the mouth of the estuary at salinities 32 to 35.

• Silicate mixing diagram (Fig. 4c) shows non conservative behavior of the constituent with an overall removal near the mouth of the estuary at salinity 32 to 35.

The nutrients, nitrate (NO₃), phosphate (PO₄), silicate (Si) enter the open ocean through rivers via estuaries, groundwater flow, and coastal zones. Dissolved silicon is drained from land by natural chemical weathering of silicate materials. The mean concentration of dissolved Si in river water is much higher than the concentration of NO₃ and PO₄ and within an estuary Si concentration decreases towards the sea (Venucopalan et al., 2006). Si concentration showed same pattern as suggested from the relevant literature mentioned above i.e. the concentration was decreasing towards the sea.  Si is also an important limiting nutrient for diatoms, thus the removal can be accredited on the utilization of Si by diatoms in the water column.  Phytoplankton (diatoms and dinoflagellates) were found during our survey up the Fal estuary. The removal of nitrate, shown by the mixing diagram, can be owed to the utilization by phytoplankton.  The strong non-conservative behavior of phosphate can be attributed to anthropogenic input like agriculture, sewage and other small inputs. In order for the mixing diagrams to show a more reliable image of the nutrients’ behavior in an estuary the amount of samples collected for each nutrient must be around 50 or more, over a range of salinities, as suggested by Head (1985).

 

	Phytoplankton
Ceratum fusus		Diatom chain

Fig 5: Phytoplankton data for all stations

 

 

		Zooplankton
Hydromedusae	Echinoderm larvae		Copepod	Mysidacea

Fig 6: Zooplankton data for all stations

 

Dissolved Oxygen	Chlorophyll
Fig 7a: Dissolved O2 for all stations	Fig 7b: Chlorophyll data for all stations

 

Richardson numbers
Fig 8a: Station 1 Ri Numbers	Fig 8b: Station 3 Ri Numbers

Summary

The biotic and abiotic factors of the stations studied are expected of their position within the estuary; the results for Station 1 show that of a well mixed water column in terms of temperature and salinity, however the nutrient profiles are not as expected due to pollution. Station 2 shows similar nutrient profiles as a result of this pollution. Station 2 is in between the sea and the rivers entering the estuary, therefore it shows a partially mixed water column. Station 3 appears not to be as polluted as the other stations, resulting in typical nutrient profiles, however this would have to be confirmed by further research. Station 3 is atypical of a river in terms of the water column; it is well mixed. This can be attributed to the lack of freshwater input due to limited rainfall, and the position of the tides at the time of sampling.

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Concluding statements

The offshore and estuarine areas both displayed a great degree of interaction between biological, chemical and physical properties. The offshore showed that the degree of mixing had a strong impact on the abundance of plankton communities. A similar pattern was seen in the estuary, where the physics influenced the nutrients promoting phytoplankton growth. The benthic mapping study gave a clear, visual (through sidescan and video data) representation of how the physical processes affect benthic communities.
 

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References

Covey, R. & Hocking, S., 1987. “Helford River Survey. Report for the Heinz”, Guardians of the Countrysideand World Wide Fund for Nature,pp 121.

Grasshoff, K., K. Kremling, and M. Ehrhardt. 1999. Methods of seawater analysis. 3rd ed. Wiley-VCH.

Herdson D. M., “The  Helford river fish leaflet”, Helford voluntary marine conservation area, pp 4

Howard P., Pinder D., 2003, “Cultural heritage and sustainability in the coastal zone: experiences in south west England”, Journal of cultural heritage, vol: 4, p.p.:57-68.

Johnson K. and Petty R.L.1983  “Determination of nitrate and nitrite in seawater by flow injection analysis”.  Limnology and Oceanography, vol: 28, p.p.:  1260-1266.

Langston W.J., Chesman B.S., Burt G. R., Taylor M., Covey R., Cunningham N., Jonas P., Hawkins J. S., 2006, “Characterisation of the European Marine Sites  in South West England: the Fal and Helford candidate Special Area of  Conservation (cSAC)”, Marine Biodiversity, vol:183, pp: 321-333.

Parsons T. R. Maita Y. and Lalli C. (1984) “ A manual of chemical and biological methods for seawater analysis” 173 p. Pergamon.

Pirrie D., Power R.M.,*, Rollinson  G., Camm G. S., Hughes H. S., Butcher R. A., 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, vol: 50, p.p.; 579–595.

Younger, P.L., 2002, “Mine water pollution from Kernow to Kwazulu-Natal: geochemical remedial options and their selection in practice”, Geoscience SW England, vol:10, p.p.: 254–265.

Head P. C., Practical estuarine chemistry, 1985, Cambridge University Press, New York

Venugopalan I., Unger D., Humborg C., Tac An N., 2006 ,The Silicon Cycle: Human Perturbations and Impacts on Aquatic Systems, Scientific Committee on Problems of the Environment , USA. Wollast R., Chou L.
 

Disclaimer

The views, opinions and scientific analyses expressed in this website are those of the authors and do not necessarily represent those of the University of Southampton or the National Oceanography Centre, Southampton.

No animals were hurt in the duration of the field course, other than a Seahorse and several thousand plankton.

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