Text Box: Text Box:   Figure 21. Horizontal Niskin bottle for water samples at pontoon Text Box: Figure 20. CTD ready for deployment Text Box: Figure 22     where p2=highest density and p1=lowest density.

As the CTD didn’t directly record density data, density must be calculated from temperature and salinity data. Because of the impracticality of performing this calculation upon all temperature and salinity records, density has been calculated at highest and lowest temperature and salinity values. From these four values the highest and lowest density was then used in the above calculation. Often the lowest temperature and highest salinity coincided (and vice versa), demonstrating the legitimacy of this ‘back of envelope’ approach.

The phosphate concentrations show an inverse relationship with salinity throughout the tidal cycle (fig. 22). The depth profiles show that phosphate concentrations tend to be higher towards the head of estuary, concentrations up to ≈0.9μmol/l, whilst those towards the mouth concentrations tend to be lower, up to ≈0.5μmol/l. The estuarine mixing diagram displays that phosphate is added to the estuary, most significantly at 25psu with a concentration over 3.0 μmol/l.

The silicon concentrations also show an inverse relationship with salinity over the tidal cycle (fig. 23). The profiles with depth also show that higher concentrations of salinity are reached further up the estuary, up to ≈7.0 μmol/l, whereas the maximum for the bottom half of the estuary is ≈4.4μmol/l. The estuarine mixing diagram shows silicon behaves conservatively up to a psu≈15, after this salinity silicon is removed from the estuary.

The dissolved oxygen sampled in the surface waters at the pontoon (fig. 22) showed the ebb tide to bring oxygenated water, causing a dissolved O2 peak of  103.1% at 11.00GMT indicating super saturation. The flood tide appears to bring two water masses past the station, initially a water mass significantly lower in O2, a minimum  61.9% reached at 14.00GMT.  This is followed by a water mass with higher O2 saturation recovering to 89.0% by 17.00GMT.

The phytoplankton counts indicated diatoms to be at least 86% dominant at all the sampling stations and the pontoon. The most common phytoplankton families seen in the estuary were the Chaetocerotaceae (67.49%), Naked dinoflagellates (9.17%), Thalassiosiraceae (8.38%) and Skeletonemaceae (6.03%). By comparing the phytoplankton communities at the head and mouth of the estuary it can be seen there is very little change, the only significant change being an increase in the percentage of Skeletonemaceae towards the head (fig. 26). Numbers/L of both dinoflagellates and diatoms increased greatly at 12:00GMT at the pontoon; this seems to occur just after high tide.

 

  Text Box: The temperature and salinity profiles taken further towards the head of the estuary (figs. 10-15) show the water column to be stratified with a  layer of warmer fresher water overlying a layer of colder more saline water; temperature typically ≈0.5°C higher in the surface layer whilst salinity is around 8psu higher at the first station, this difference dropping to 0.5psu by station 5 as waters become more homogenous. This type of structure would be typical of a salt wedge estuary. However the profiles towards the mouth of the estuary (figs. 15-18) show the water column to be more well mixed with a less evidence of strong stratification, indicating a well mixed estuary. By Black rock (fig. 19) the profile shows warmer more saline water over colder less saline water.  Richardson number estimates can be calculated for different locations along the estuary. Various assumptions about parameters can be made in estuarine environment, such as greatest shear occurring at the seabed, such that the following equation adequately estimates the vertical stability of the water column:        where p2=highest density and p1=lowest density. As the CTD didn’t directly record density data, density must be calculated from temperature and salinity data. Because of the impracticality of performing this calculation upon all temperature and salinity records, density has been calculated at highest and lowest temperature and salinity values. From these four values the highest and lowest density was then used in the above calculation. Often the lowest temperature and highest salinity coincided (and vice versa), demonstrating the legitimacy of this ‘back of envelope’ approach. The phosphate concentrations show an inverse relationship with salinity throughout the tidal cycle (fig. 22). The depth profiles show that phosphate concentrations tend to be higher towards the head of estuary, concentrations up to ≈0.9μmol/l, whilst those towards the mouth concentrations tend to be lower, up to ≈0.5μmol/l. The estuarine mixing diagram displays that phosphate is added to the estuary, most significantly at 25psu with a concentration over 3.0 μmol/l. The silicon concentrations also show an inverse relationship with salinity over the tidal cycle (fig. 23). The profiles with depth also show that higher concentrations of salinity are reached further up the estuary, up to ≈7.0 μmol/l, whereas the maximum for the bottom half of the estuary is ≈4.4μmol/l. The estuarine mixing diagram shows silicon behaves conservatively up to a psu≈15, after this salinity silicon is removed from the estuary. The dissolved oxygen sampled in the surface waters at the pontoon (fig. 22) showed the ebb tide to bring oxygenated water, causing a dissolved O2 peak of  103.1% at 11.00GMT indicating super saturation. The flood tide appears to bring two water masses past the station, initially a water mass significantly lower in O2, a minimum  61.9% reached at 14.00GMT.  This is followed by a water mass with higher O2 saturation recovering to 89.0% by 17.00GMT. The phytoplankton counts indicated diatoms to be at least 86% dominant at all the sampling stations and the pontoon. The most common phytoplankton families seen in the estuary were the Chaetocerotaceae (67.49%), Naked dinoflagellates (9.17%), Thalassiosiraceae (8.38%) and Skeletonemaceae (6.03%). By comparing the phytoplankton communities at the head and mouth of the estuary it can be seen there is very little change, the only significant change being an increase in the percentage of Skeletonemaceae towards the head (fig. 26). Numbers/L of both dinoflagellates and diatoms increased greatly at 12:00GMT at the pontoon; this seems to occur just after high tide.    

Text Box: Figure 46. Station 6 Text Box: Figure 45. Station 5 Text Box: Figure 44. Station 4 Text Box: Figure 43. Station 3 Text Box: Figure 42. Station 2 Text Box: Figure 41. Station 1 Text Box: DISCUSSION The physical structure of the estuary is variable, towards the head the water column is more characteristic of a salt wedge estuary whereas towards the mouth it is more characteristic of a well mixed estuary. This is reflected in the Richardson numbers calculated for each station, there is a decrease in Ri down the estuary indicating a lesser stratified water column. This could be attributed to the tidal regime along the Fal estuary; it has been shown to be mesotidal at Truro whilst being macrotidal at Falmouth (Pirrie et al 2003). The increased tidal strength towards the mouth would promote greater mixing of the water column. The tidal cycle could also be influencing the structure, the stations showing stratification were sampled before low tide (12.26GMT) whereas those showing a better mixed water column were sampled on the flood tide. The preceding warm calm weather conditions would have also increases stratification by increasing the temperature of the freshwater inputted. The physical structure of the offshore water column is driven by changes in temperature; the influence of salinity is not a dominant factor as it is in the estuary as the water column offshore is well mixed in terms of salinity. It can be seen that the strongest thermoclines occur at the stations furthest offshore. Whereas, those either side of Dodman point and those at mouth of the Fowey and Fal estuary show weaker thermoclines; due to the influence of bottom friction and mixing of marine and estuarine waters. Differing Ri numbers above and below the thermocline at the mouth of the Fowey and Fal could be attributed to the tidal state, the Fowey was sampled on the ebb and the Fal on the Flood tide, but further investigation would be needed to positively determine this. By comparing stations 1and 3 with offshore stations from group 6 it appears that the windy weather on that day caused the surface waters to begin to mix and become more homogenous. The behaviour of silicon in the Fal is non-conservative at salinities above 15psu. There is evidence for the removal of silicon; the plankton data for the estuary show that diatoms are dominant at all points over the estuary. Therefore the removal of silicon is likely to be from diatoms taking up silicon to form frustules (Vaulot, 2006). The inverse relationship between silicon and salinity observed in the estuary continues offshore with the lowest concentrations recorded at the offshore stations. Phosphate is also non-conservative in the Fal estuary, phosphate undergoes addition to the estuary at lower salinities. A possible source of this addition is runoff from fertilizer; high annual rainfall and impermeable bedrock results in the area having a high natural runoff, this coupled with the development of intensive farming techniques has resulted in the addition of phosphate to the Fal over the last 60 years (Langston et al., 2003). Phosphate concentrations also follow an inverse relationship with salinity with concentrations within the estuary lower at lower salinities and the lowest concentrations recorded offshore. Both the silicon and phosphate offshore showed no obvious trend with depth with behaviour varying between stations, this is likely a result of only 2 samples taken at each station, however it can be seen phosphate increases at the head of the Fowey and Fal estuary. The dissolved oxygen measurements at the pontoon appear to demonstrate the passing of different water masses over the tidal cycle, on the ebb fresher water is more dominant and this has a higher O2%, possibly a result of increased photosynthethic activity causes by the addition of phosphate. The flood tide appeared to bring two masses one with low O2% causing the O2 minimum; this coincided with the observation of brown water at the pontoon, possibly higher in organic matter and therefore higher in bacterial respiration. The following water mass is higher in O2 causing the O2% to rise. The O2 measurements offshore do not show many significant trends due to the lack of samples taken, however, there appears to be a trend of higher O2% nearer the surface, as would be expected as it is closer to the atmosphere-ocean boundary where gas exchange takes place.   Text Box: PHYSICAL STRUCTURE AT STATIONS At stations 1 and 3 there are the strong thermoclines with a difference in temperature between the surface and the bottom of the water column of 3-3.5oC. This is most likely the result of their position which is further out to sea and in deeper water and so less mixing occurs. Stations 2 and 6 were at the mouths of the Fowey and Fal estuaries respectively. This allows some comparison between the estuaries and their effect on the surrounding coastal waters. Both of these stations have much weaker thermoclines of around 0.5oC. This may be the result of the mixing of the estuarine water and the oceanic water. There can be seen to be a difference in the flows of the two sections of the water column at these stations using the Richardsons number………… Stations 4 and 5 have stronger thermoclines than 2 and 6 but not as strong as at 1 or 3. This is because they are either side of Dodman point and in shallow water close to shore. This means that they are shallower than stations 1 and 3 but also that there is more mixing as a result of eddies that will be formed from the headland. The Richardsons number for Station 2 for above the thermocline of 7.57 shows that there is very strong flow out of the estuary with laminar flow and below the thermocline there is turbulent flow (Ri = 0.22) and mixing with weaker flow into the estuary. This is expected as the tide was ebbing at this station. The Ri number for station 6 above the thermocline is 0.19 and shows mixing in this part of the water column. Below the thermocline the Ri is 3.80 and therefore it is laminar flow. This makes sense as the tide was flooding at the time of data collection for this station. Chlorophyll for station 1 shows a rapid decrease at the thermocline. At this time of year the majority of the phytoplankton are diatom populations therefore they cannot move out of the mixed layer so these results would be expected. Station 2 has a slight decrease in chlorophyll down through the water column with a peak at 12m however this may be an anomaly and not a true chlorophyll maximum. Station 3 chlorophyll matches that of station 1 and decreases down through the water column with the thermocline. At station 4 there is not much change in chlorophyll through the water column but this is to be expected with the stronger mixing around Dodman point. Station 5 is the same as station 4 but has slightly more of a difference in chlorophyll but it is still much smaller than other stations. Station 6, like stations 2, 3 and 4 is well mixed and therefore there is no real change in the amount of chlorophyll through the water column. For station 1, silicon and phosphate concentrations both decreased with increasing depth, which may be due to the mixing within the water  At station 2, however silicon and phosphate concentrations increased with increasing depth. It should be noted that the proportion of change at station 2 was a very small increase, whereas the decrease at station 1 was much greater. For station 3 the silicon and phosphate concentrations show different relationships to each other with increasing depth. Silicon shows a large increase with increasing depth, whereas phosphate shows a slight decrease with increasing depth. At station 4 no water samples were collected due to the very similar CTD compared to station 3. Station 5 shows a decrease in silicon through the water column and there was very low phosphate so that when compared to the blanks there was negative values of phosphate so these have been counted as 0. At station 6 there is very small increase in silicon but a very large increase in phosphate through the water column. RESULTS At all stations temperature decreases with depth. At station 1 there is a thermocline at 15m as there is a drop in temperature from 15.3°C to 14.2°C and there is a difference of 2.6°C between surface waters and 30m depth. Station 3 shows a similar strong thermocline at 15m with a difference between surface waters and 33m depth being 2.9°C. Station 2 has a difference in temperature of 1.7°C between surface and 15m. Stations 6 show weaker less distinctive thermocline with a difference of 0.7°C between surface and 26m. Stations 4 and 5 have a difference of 1.2°C between the surface and deep waters for both stations. The Richardsons number for Station 2 above the thermocline is 7.57 showing laminar flow and below the thermocline there is turbulent flow (Ri = 0.22). The Ri number for station 6 above the thermocline is 0.19 giving turbulent flow. Below the thermocline the Ri is 3.80 and therefore it is laminar flow. Chlorophyll for station 1 shows a rapid decrease at the thermocline with a difference between the surface waters and 30m of 1.5 μg/L. Station 2 has a slight decrease in chlorophyll down through the water column with a peak of 16.5 μg/L at 12m however this may be an anomaly and not a true chlorophyll maximum. Station 3 chlorophyll matches that of station 1 and decreases down through the water column with the thermocline. At station 4 there is not much change in chlorophyll through the water column. Station 5 is the same as station 4 but has slightly more of a difference in chlorophyll but it is still much smaller than other stations. Station 6, like stations 2, 3 and 4 is well mixed and therefore there is no real change in the amount of chlorophyll through the water column with a difference of 0.1μg/L between the surface and 27m. For station 1, silicon (0.87 μmol/L at the surface to 0.51 μmol/L at 23m) and phosphate (0.00 μmol/L to 0.021 μmol/L at 23m) concentrations both decreased with increasing depth. At station 2, silicon and phosphate concentrations increased with increasing depth. Silicon went from 084 μmol/L to 0.87 μmol/L and phosphate went from 0.033 μmol/L to 0.03 μmol/L. For station 3 the silicon and phosphate concentrations show different relationships to each other with increasing depth. Silicon shows a large increase with increasing depth (0.58 μmol/L to 1.48 μmol/L), whereas phosphate shows a slight decrease with increasing depth (0.057 μmol/L to 0.051 μmol/L). At station 4 no water samples were collected due to the very similar CTD compared to station 3. Station 5 shows a decrease in silicon through the water column from 1.07 μmol/L at 0m to 1.09 μmol/L at 23m and there was very low phosphate so that when compared to the blanks there was negative values of phosphate so these have been counted as 0. At station 6 there is very small increase in silicon but a very large increase in phosphate through the water column. Silicon went from 1.07 μmol/L to 1.09 μmol/L and phosphate went from 0.039 μmol/L to 0.093 μmol/L.   Text Box: Table 6. Zooplankton data Text Box: Figure 36. Comparison of phytoplankton species found offshore and in the fal estuary   Text Box: Figure 37. % of each phytoplankton family present at each station Text Box: At stations 1, 2, 5 and 6 diatoms make up at least 90% of the sample collected, whereas at station 3 they decrease to being only 81% of the sample collected. The total numbers of phytoplankton has an average of approximately 600,000/L at stations 1, 4 and 5, with a larger average of 1.1million/L at station 2 and a much lower average of 145,000/L at station 6. Station 2 was sampled during an ebb tide at the mouth of the Fowey estuary, whereas station 6 was sampled during a flood tide at the mouth of the Fal estuary (Black rock). The ebb tide would carry phytoplankton out of the Fowey estuary, therefore increasing the numbers found at the mouth. On the ebb tide however, the inflowing waters would cause the water column to become more mixed and therefore the phytoplankton would be more widely distributed within it. The different tidal cycle stages between these two stations could therefore be part of the large difference in phytoplankton numbers.  The most common phytoplankton families seen were Cheatocerotaceae (51.19%), Rhizosoleniaceae (15.16%), Thalassiosiraceae (8.43%) and Skeletonemaceae (8.18%). When comparing the planktonic communities between the estuary and the offshore sites it is clear that there are similarities between the dominant species seen at each site (Chaetocerotaceae, Thalassiosiraceae and Skeletonemaceae). At the offshore sites it is clear that there are much fewer numbers of phytoplankton; approximately 1million/L is the highest recorded number of phytoplankton offshore, whereas in the estuary it is 7 times greater. Text Box: Figure 35. Bongo zooplankton sample Text Box: Figure 34. Zooplankton number of species offshore   Text Box: Stations 1 3 5 6 Bongo (no. In m-3) Holoplankton no. in 500ml 1800 12200 9560 4250 16264 Meroplankton no. in 500ml 200 5150 3900 6100 1955 Total no. in 500ml 2000 17350 13460 10350 18219   Text Box: BONGO NET: In the case of the Bongo net sample, which was a 5 minute long vertical trawl, there is, like in all other samples, a large dominance of Hyrdomedusae for the Holoplankton (65%). The second largest group of Holoplankton is Chaetognatha (30%). The high presence of Chaetognatha is interesting as there is no significant presence of it in the depth samples. The Meroplankton of the bongo net sample shows the strongest group of Echinodermata larvae (59%) and a surprisingly high amount of fish larvae (15%).     Text Box: When comparing the samples in regard to the relationships between Holoplankton and Meroplankton, the samples show that there is a higher amount of Holoplankton which represents at least 70% of the sample. The exception being station 6, where Meroplankton is more abundant than Holoplankton, representing 60% of the sample. It is clear that at all stations, Holoplankton is largely dominated by Hydromedusae. Other dominant Holoplankton groups are Siphonophorae (15% and 16%) in station 1 and 3, Copepoda (18% and 26%) in station 3 and 6 and Chtenophora (14%) in station 5.  There is more variation of Meroplankton in terms of species between each station. In station 1 only Echinoderm and Polycheate Larvae are present and represent 5% each of the whole sample. In station 3 Polychaete Larvae and Copepod Nauplii are dominant (each 28%). In station 5 mainly Cirripedia (31%) and Polychaete larvae (26%) were measured and in station 6 Echinoderm (33%) and Gastropod larvae (25%) occurred.  

 

 

 

 

 

 

 

 

Text Box: REFERENCES Bosence D. & Wilsion J., 2003. Maerl growth, carbonate production rates and accumulation rates in the northeast Atlantic. AquaticConserv: Mar. Freshw. Ecosyst. 13: S21 – S31. Google Earth Screen Shot, 2011, Infotera Ltd &Bluesky Image copywrite 2011 Getmapping PLC. Irvine L. & Chamberlain Y., 1994. Seaweeds of the British Isles – Volume 1 Rhodophyta Part 2B Corallinales, Hildenbrandiales. London: HMSO. Royal Haskoning (2009). Port of Falmouth Developing Initiative Environmental Statement, Section 8 – Marine Coastal Ecology. From: http://www.falmouthport.co.uk/commercial/html/PortofFalmouthDevelopmentInitiative.php  Langston,W. Chesman,B. Burt,G. Hawkins,S. Redman,J. Worsfold,P. 2003. The Fal and Halford (candidate) Special Area Conservation. Marine Biological Association Occasional Publication. Vol 8 pp91-94 Pirrie,D. Power,M. Rollison,G. Camm,S. Hughes,S. Butcher,A. Hughes,P. 2003. The spatial distribution and source of arsenic, copper, tin and zinc within the surface sediments of the Fal estuary, Cornwall, U.K. Sedimentology. Vol 50 issue 3 pp 579-595  Vaulot, D., 2006. Phytoplankton. eLS. Langston, W.J., Chesman, B.S., Burt, G.R., Hawkins, S.J., Readman, J. and Worsfold, P. 2003, ‘Site characterisation of the South West European Marine Sites, Fal and Helford cSAC’, Plymouth Marine Science Partnership. Braby, C.E. 2001, Phytoplankton blooms [online]. Available:  http://www.mbari.org/staff/conn/botany/phytoplankton/phytoplankton_blooms.htm [accessed 2011, July 06th]. NOAA, Acoustic Current Doppler Profiler (ADCP) [online]. Available: http://oceanexplorer.noaa.gov/technology/tools/acoust_doppler/acoust_doppler.html [accessed 2011, July 06th]. WHOI, Conductivity, Temperature, Depth (CTD) sensors [online]. Available: http://www.whoi.edu/instruments/viewInstrument.do?id=1003 [accessed 2011, July 06th).   Text Box: METHODS The spatial investigation of the Fal took place on 01 July 2011 on RV Bill Conway (fig. 6). The weather was clear skies and low winds at the start of the day. By 1000 GMT there was intermittent cloud cover and slightly higher winds.   Text Box: GEOPHYSICS Text Box: Figure 4. Satellite image of transet tracks (click to enlarge) Text Box: Text Box: Figure 3. Visual representation of findings from sidescan sonar data (click to enlarge) Text Box:   Text Box: Figure 2. Van veen grab deployment Text Box:

 

 

 

 

Text Box: Figure 25. Time series of % value of each phtyoplankton family found whilst surveying at the pontoon Text Box: Figure 26. Comparison between phytoplankton % found at the head & mouth of Fal estuary Text Box: Figure 24. Amount % that each phytoplankton family contributes to the total number of phytoplankton/L

 

 

 

Text Box: Trawl 2 took place at 1125 GMT and was the mid-estuary sampling site for plankton. This sample had less dominance of different zooplankton groups, the largest being the holoplankton Copepod larvae (37214 per m2) closely followed by Gastropod larvae (52405 per m2) (fig. 28). The largest meroplankton groups found were Copepod nauplii with 63634 per m2 and Gastropod larvae, 52405 per m2. Trawl 3 was the sample that took place nearest the mouth of the estuary at 1519 GMT. The majority of this sample (43%) is Chaetognatha (fig. 29). Mysidacea represent  nearly a quarter of the sample and Copepods are also present in significant numbers. Smaller amounts of other larvae and Cladocera make up the rest of the sample. This sample site differed from the first two in that holoplankton are much more abundant than meroplankton making up 82% of individuals found.     Text Box: The trawls were conducted with a net with a mesh size of 200 µm and diameter of 47 cm. Trawl 1 took place at 0941 GMT and was the sample point nearest the mouth of the estuary. Here the dominant group of zooplankton are copepods (36%) and copepod nauplii (29%) (fig. 27). The differences in holoplankton and meroplankton were noted. Holoplankton are species which spend their whole lives as plankton and whereas meroplankton spend just part of their lives as plankton. At this site meroplankton made up the larger proportion (66%) of individuals found with 300,485 per m3 meroplankton to 155080 per m3 holoplankton found. Copepods made up the vast majority, 84%, of holoplankton and the rest consisted of Cladocera, Chaetognatha, Mysidacea and Appendicularia. The meroplankton were dominated by Decapoda larvae and Copepoda nauplii which each formed 35% of the sample. The rest of sample contained Gastropda and Cirrepdia larve and small amounts of Polychaete and Echinoderm larvae.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Text Box: OFFSHORE DATA COLLECTION

 

 

 

 

 

 

 

Text Box: back to top

Text Box: back to top

Text Box: INTRODUTION The offshore boat work was carried out to investigate the chemical, physical and biological processes occurring spatially within the water column from the mouth of the Fowey estuary along the south coast of Cornwall to the mouth of the Fal estuary. Coastal regions are diverse areas with complex habitats and environments which are also influenced by the proximity to human populations along the coastline (Jahnke et al., 2008). The aim of the offshore investigation is to use a combination of instruments to observe the vertical mixing processes affecting the planktonic communities occurring within the water column. From previous studies it is known that there is summer thermal stratification in the English Channel (Smyth et al., 2010). Looking at the stratification of the water column gives the physical properties, which can be linked to the distribution of phytoplankton which are expected to be in high abundance around the thermocline (Smyth et al., 2010) as at this depth there is a compromise between high solar radiation and the availability of nutrients which decrease in the upper water column over the summer months due to the thermal stratification and being depleted during the spring phytoplankton bloom (Obata, 1996). The zooplankton populations are expected to occur in the highest abundance below the phytoplankton, avoiding prey from above as well as feeding on the phytoplankton. Dissolved oxygen gives an indication of the balance between autotrophy and heterotrophy whilst phosphate and silicon were also collected to observe the vertical mixing of the chemical processes occurring along the Cornwall coastine.  

 

 

Text Box: ESTUARINE CHEMISTRY AND BIOLOGY ANALYSIS

 

Text Box: Table 4. Estuarine time series data at pontoon Text Box: Table 3. Estuarine boat stations Text Box: Figure 30 and 31. Dolphins spotted offshore at station 3 Text Box: Fig 19. Station 10 Text Box: Fig 18. Station 9 Text Box: Fig 17. Station 8 Text Box: Fig 16. Station 7 Text Box: Fig 15. Station 6 Text Box: Fig 14. Station 5 Text Box: Fig 13. Station 4 Text Box: Fig 12. Station 3 Text Box: Fig 11. Station 2 Text Box: Fig 10. Station 1 Text Box: RESULTS Depth profiles for all stations (click to enlarge)                   Text Box: Figure 9. Zooplankton net deployed on trawls Text Box: Figure 8. Onboard filtration of samples Text Box: Figure 7. Particularly scummy water at station 1 Text Box: NOTES ON DATA COLLECTION Three samples of phytoplankton were taken using a Niskin bottle at CTD station 1, 2 and 3 and two trawls of zooplankton using a zooplankton net were taken at CTD station 1 and 5. Nutrient samples were taken at every CTD station using Niskin bottles. One sample of nutrients was taken underway at 1103 GMT after CTD station 4. Chlorophyll was also sampled using Niskin bottles at all CTD stations and dissolved oxygen was collected at stations 1, 3 and 5. A T/S probe from the boat gave a continual measurement of the temperature and salinity of the surface water for a comparison with the CTD data. Investigation of the bottom of the estuary was carried on by group 10. The temporal investigation took place on a pontoon next to King Harry Ferry at 50° 13.010 N 005° 02.500 Group 10 started the investigation in the morning at 0800 GMT until 1100 GMT, taking hourly samples of phytoplankton using a Niskin bottle, turbidity measured using a transmisometer, nutrients using a Niskin bottle, chlorophyll, PH, salinity and temperature all measured using a probe. The sampling was then carried on from 1200 GMT till 1600 GMT by group 02.   Text Box:   Start End Transect Time (GMT) Location (Lat and Long) Distance from shore (m) Time (GMT) Location (Lat and Long) Distance from shore (m) 1 0921 50° 14.339 N 005° 00.857 W 93 0923 50° 14.344 N 005° 00.975 W 87 2 1027 50° 12.243 N 005° 02.443 W 64 1031 50° 12.145 N 005° 02.115W 77 3 1049 50° 11.921 N 005° 03.151 W 71 1057 50° 11.911 N 005° 02.384 W 650 4 1105 50° 11.519 N 005° 03.091 W 459 1109 50° 11.583 N 005° 02.692 W 1120 5 1249 50° 11.207 N 005° 01.789 W 180 1301 50° 10.413 N 005° 02.726 W 313 6 1325 50° 10.535 N 005° 01.386 W 115 1337 50° 10.465 N 005° 02.573 W 180 7 1402 50° 10.051 N 005° 02.770 W 90 1412 50° 10.041 N 005° 01.712 W - 8 1447 50° 09.005 N 005° 02.750 W 122 1459 50° 09.337 N 005° 01.607 W 65 9 1532 50° 08.539 N 005° 01.036 W 132 1546 50° 08.654 N 005° 02.474 W 70   Text Box: Station Location (Lat and Long) Time (GMT) Depth (m) 1 50° 44.394 N 005° 00.885 W 0840   4.44 1.76 1.27 2 50° 13.699 N 005° 00.950 W 0937   7.91 4.10 1.26 3 50° 12.242 N 005° 02.342 W 1016   13.5 7.23 1.36 4 50° 11.860 N 005° 02.600 W 1040   13.07 9.12 3.51 1.05 5 50° 11.523 N 005’ 02.842 W 1114 14.30 10.24 4.82 1.18 6 50° 11.052 N 005° 01.949 W 1229 19.00 10.15 1.30 7 50° 10.413 N 005° 01.588 W 1310 25.52 6.50 1.24 8 50° 09.907 N 005° 02.361 W 1346 25.42 15.84 5.20 1.49 9 50° 09.202 N 005° 01.935 W 1423 26.93 8.18 1.25 10 50° 08.628 N 005° 01.425 W 1509 33.33 9.07 1.36   Text Box:     Figure 6. Sampling vessel; Bill Conway Text Box: INTRODUCTION The estuarine boat work took place on the Fal estuary to look at the temporal and spatial change of constituents within the estuary. By taking regular Acoustic Doppler Current Profile (ADCP) transects and CTD samples a spatial view of the Fal and a temporal view came from hourly sampling in one location in the estuary. The ADCP gives the speed and direction of the current within the estuary (NOAA) while the CTD gives the conductivity, temperature and depth (WHOI). Samples of nutrient, chlorophyll and dissolved oxygen were also taken from both the pontoon and boat to give chemical and biological content of the estuary. Langston et al. (2003) found that 90% of the nutrient input to the estuary came from diffuse or natural inputs, such as runoff from farm fertiliser which can contribute 719mm to the Fal annually, the atmosphere and offshore. A small percentage enters the system from anthropogenic sources such as urban waste from Truro, enhancing the nitrate input upstream. In estuaries phosphate is often adsorbed onto particles then released in turbid fresh water sea water interfaces such as that seen in the Fal (Langston et al., 2003). This can give variable values for the removal of phosphate over a tidal cycle. Dissolved oxygen is not well documented for the Fal, however it is known that 3-5mg l-1 is required for the biology within the estuary (Langston et al., 2003). Measurement of the chlorophyll will give an indication of the numbers of phytoplankton present within the estuary. It is expected there will be relatively high chlorophyll content due to high solar input to the estuary bringing stratification and an increase in the rate of photosynthesis, and nutrients available from external inputs as well as recycling within the estuary (Braby, 2001).   Text Box:  

 

 

Text Box: Figure 29. Zooplankton from trawl 3 Text Box: Figure 28. Zooplankton from trawl 2 Text Box: Figure 27. Zooplankton from tawl 1 Text Box: Figure 23. All pontoon data variables

Text Box: back to top Text Box: Text Box: The views and opinions stated in this website are those of the creators and not those of the University of Southampton and the National Oceanography Centre Southampton or any of its affiliates. Our thanks go to Falmouth Marine School for use of their facilities during the field course.   Text Box: Figure 40. Sattelite image of stations and transects Text Box: Figure 39. Velocity magnitude Text Box: Results Both figures indicate a consistent, apparently anomalous, flow feature between 4&5m depth, indicating greater flow magnitude and divergent direction to ambient waters. This feature may indicate the presence of an internal wave, forced by pressure gradients generated by bathymetric change (Wells, N., 2011, pers. comm., 7th July). Its consistency over the transect within bins covering a two metre depth range may however indicate it as an artefact of ADCP operation (Statham, P., 2011, pers. comm., 7th July). Large scale velocity magnitude patterns are clearly indicated in figure 39, with two regions of higher than average flow speeds of approximately 0.50-0.75 m/s. The first of these occurred in the shallower waters of between 16 and 25m depth, close to the Roseland Peninsula at the beginning of the transect (left of figure ?). The second region occurs in the middle of the transect where the bathymetry rises sharply to shallower depths of approximately 17m. This section of the transect is, like the first region, close to land, and just off the tip of a peninsula mentioned in the sea shanty ‘Spanish Ladies’ [time 1:11] called Dodman Point. Flow velocities in the rest of the transect were generally <0.4m/s, with flows to the east of Dodman point (right side of figure 39) typically less than those to the west. The generally east north-easterly headed flow direction in the first region of increased velocity was little different from the slower moving water to its east, all the way to the approach to Dodman point. Here, in the faster moving shallower waters, the flow direction changed to head in a south-easterly direction, following approximately the orientation of the Dodman headland. To the west of Dodman point weaker flow velocities headed in a north north-westerly direction (red and purple region of figure ?). In a zone between these two contrasting flow directions of about 400m width and occurring throughout the water column just east of Dodman, flow travelled east. This indicates water moving, or being entrained, from the south-easterly flow into the region of northerly flow. These flow patterns indicate the movement of eddies of water in the bays both sides of Dodman point, with the water moving offshore of the headland originating in the west. Conclusion & Discussion The flow patterns demarcated by Dodman Point indicate the movement of eddies in the bays both sides of Dodman point, with the water moving offshore from the headland originating in the west. The data was recorded on an ebbing tide, when the net movement of water from the Western English Chanel will have been in the direction of the Atlantic. That the general flow recorded on the transect was to the east, particularly west of Dodman (i.e. contrary to the net tidally driven flow direction) indicate the presence of wind driven circulation patterns persisting over the tidal cycle. They may also however indicate residual tidal flow patterns particular to this region of the coastal sea. Admiralty charts provided no useful tidal diamond information for the area of interest and thus discriminating between these possibilities requires further investigation. This transect line should be repeated at different stages of the tidal cycle to examine local tidal effects, as well over a longer time series to identify the temporal persistence of the identified circulation patterns. Spatial coverage should also be increased to cover the areas inside the bays as well as further offshore.     Text Box: Figure 38. Flow direction Text Box: FLOW PATTERNS IN THE COASTAL SEAS OFF THE CORNISH ROSELAND COAST Introduction On the 5th July 2011 during a cruise on RV Callista, ADCP data was recorded over a series of near shore English Channel transects off the Cornish coast of the UK, indicated on figure 40. The longest of these (start and end 000, figure 40) covered a distance of approximately 35km and was completed over 1hour 38 minutes from 08:22 to 10:00, with a high spring tide at 07:42.. It began less than a kilometre off St. Anthony’s head and ended 3.7km from the mouth of the River Fowey. The ADCP data for the entire transect, showing velocity direction and magnitude is shown in figures 38 & 39. Text Box: Table 5. Offshore stations Text Box: Group 2. Left to Right. Emma Chisholm, Gavin Teakle, Helene Hoffmann, Philip Chapman, Philip New, Sophie Copson, Lydia Deacon, Antony Birchill, Annabelle Bond Text Box: Figure 33. CTD was used at each station however rosette sampler was not working, therefore had to collect water samples manually. Text Box: Figure 32. Deployment on Callista during choppy weather Text Box: Station Location (Lat and Long) Time (GMT) Depth (m) 1 50° 17.700 N 004° 37.639 W 1040 23.3 0.0 2 50° 19.172 N 004° 38.593 W 1050 15.0 0.0 3 50° 15.520 N 004° 41.775 W 1204 28.0 0.0 4 50° 13.571 N 004° 47.002 W 1337 19.0 0.0 5 50° 13.016 N 004° 47.124 W 1341 20.0 0.0 6 50° 08.705 N 005° 01.450 W 1549 23.0 0.0