UNITED UTILITIES
______
MANCHESTER SHIP CANAL
WATER QUALITY REVIEW
PART 2 OF 2
(APPENDIX DOCUMENT) ______
FINAL REPORT
SEPTEMBER 2007
APEM REF: 410039
APEM Scientific Report 410039
CLIENT: United Utilities
ADDRESS: Haweswater House, Lingley Mere, Business Park, Lingley Green Avenue, Great Sankey, Warrington, WA5 3LP
PROJECT No: 410039
DATE OF ISSUE: September 2007
PROJECT DIRECTOR: Dr. Keith Hendry
PROJECT MANAGER: David Campbell, M.Sc.
SENIOR SCIENTISTS: Dr Roger Baker Margaret-Rose Vogel Heather Webb Kathleen Beyer
Riverview, Embankment Business Park, Heaton Mersey, Stockport, SK4 3GN Tel: 0161 442 8938 Fax: 0161 432 6083 Website: www.apemltd.co.uk Registered in England No. 2530851
Final Report – September 2007 ii APEM Scientific Report 410039
CONTENTS 1 MONITORING LOCATIONS ...... 1 1.1 APEM WATER QUALITY MONITORING ...... 1 1.2 ENVIRONMENT AGENCY WATER QUALITY MONITORING ...... 2 2 REVIEW OF MSC PHYSICO-CHEMICAL DATA...... 6 2.1 BOD ...... 6 2.1.1 Upstream of Mode Wheel Locks ...... 8 2.1.2 Mode Wheel to Barton Locks ...... 8 2.1.3 Barton to Irlam Locks...... 9 2.1.4 Irlam Locks to Latchford Locks...... 10 2.2 AMMONIA...... 11 2.2.1 Upstream of Mode Wheel Locks ...... 12 2.2.2 Below Mode Wheel Locks...... 14 2.3 DO...... 16 2.3.1 Upstream of Mode Wheel Locks ...... 17 2.3.2 Mode Wheel Locks to Barton Locks ...... 20 2.3.3 Barton to Irlam Locks...... 22 2.3.4 Irlam to Latchford Locks...... 23 2.3.5 Continuous monitoring sonde data ...... 25 2.4 SUSPENDED SOLIDS AND TRANSPARENCY...... 29 2.4.1 Upstream Mode Wheel Locks...... 29 2.4.2 Downstream Mode Wheel Locks...... 32 2.5 NUTRIENTS ...... 34 2.5.1 Upstream Mode Wheel Locks...... 34 2.5.1.1 Total phosphorus ...... 34 2.5.1.2 Orthophosphate...... 36 2.5.1.3 Nitrate ...... 37 2.5.1.4 Nitrite...... 38 2.5.2 Downstream of Mode Wheel Locks ...... 39 2.5.2.1 Total phosphorus ...... 39 2.5.2.2 Orthophosphate...... 39 2.5.2.3 Nitrate ...... 42 2.5.2.4 Nitrite...... 44 2.6 DISSOLVED COPPER ...... 46 2.6.1 Upstream Mode Wheel Locks...... 46 2.6.2 Downstream of Mode Wheel Locks ...... 46 2.7 TOTAL ZINC ...... 46 2.7.1 Upstream Mode Wheel Locks...... 46 2.7.2 Downstream of Mode Wheel Lock...... 46 2.8 PH...... 47 2.9 CONDUCTIVITY...... 48 2.10 TOTAL RESIDUAL CHLORINE ...... 49 2.11 BACTERIOLOGY...... 50 2.11.1 Upstream Mode Wheel Locks...... 50 2.11.2 Downstream of Mode Wheel Locks ...... 51 2.12 INFLUENCE OF SEDIMENT ON WATER QUALITY ...... 51 2.13 FISH KILL IN MAY 2006 ...... 53 3 RIVER INPUTS...... 56
4 REVIEW OF MSC BIOLOGICAL DATA...... 61 4.1 HISTORICAL MACRO-INVERTEBRATE DATA: MSC...... 61 4.2 HISTORICAL MACRO-INVERTEBRATE DATA: A COMPARISON BETWEEN THE MSC AND SALFORD QUAYS 66 4.3 HISTORICAL MACRO-INVERTEBRATE DATA: RIVER INPUTS...... 68 4.4 HISTORICAL REVIEW OF ALGAL DATA...... 71 iii
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4.4.1 Monitoring from 1986 to 1988 (NWW) ...... 71 4.4.2 APEM monitoring programme 1986 - present ...... 74 4.5 CONCLUSION ...... 85 5 REFERENCES...... 86
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1 MONITORING LOCATIONS
1.1 APEM Water Quality Monitoring
APEM conducts water quality monitoring in the Manchester Ship Canal (MSC) upstream of Mode Wheel Locks year round as part of the monitoring programme conducted for Salford City Council at Salford Quays and in the summer (May to September) on behalf of United Utilities.
8 Basin 9a (Huron)
9 C2 Basin 9b (Erie) 6 C1 Basin 8 (Ontario) 7
10 Basin 7 * 3 4 5 1
Basin 6 (South Bay)
*Basin 7 from left to right – 7a. St.Francis, 7b. St.Louis, 7c. St.Peter
Figure A1.1. Aerial photo showing the location of the monitoring sites in the MSC and Salford Quays. The locations of 29 MSC sites are shown ( ), at which temperature and dissolved oxygen profiles are measured. Salford Quays current water quality monitoring sites are shown ( ), with site numbers. Oxygenation unit locations are marked in blue.
Water quality monitoring of Salford Quays is undertaken on a weekly basis from November to April and twice weekly from May to October (monitoring is conducted by boat from May to October). Two sites on the MSC are monitored as control sites in this sampling programme (one located in Basin 6, known as Site 1, and the other near the southwest corner of Basin 8, known as Site 10; see Figure A1.1). The data extends back to 1985, making these sampling locations invaluable to describing water quality improvements in the upper MSC over time. Importantly, these sites involve measurement of dissolved oxygen (DO) and temperature at 1m intervals throughout the water column. Full detail of the parameters measured along with sampling frequencies are given in Table A1.1.
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The summer monitoring on the Ship Canal is conducted in order to provide management information and monitor performance of the MSC oxygenation project, which became operational in July 2001 (APEM, 2002). The objective is to ensure that the dissolved oxygen (DO) target of 4 mg/l is maintained whilst minimising oxygen usage. Temperature and dissolved oxygen profiles (at 1 m resolution) are measured three times a week at 29 sites on the MSC from Trafford Road Bridge to Mode Wheel Locks (APEM, 2002-2007). A further four sites at Pomona docks serve as control sites upstream of the areas influenced by the oxygen injection units (Figure A1.1). Monitoring is conducted by boat to allow access to more sampling locations providing a more representative view of Turning Basin water quality.
Table A1.1 Details of the parameters measured by APEM for the monitoring programme conducted on Salford Quays. Parameter Sampling Frequency Sampling Type Weekly (November to April); Bi-weekly Temperature 1 metre resolution profile (May to October) Weekly (November to April); Bi-weekly Dissolved Oxygen 1 metre resolution profile (May to October) Total and Faecal Fortnightly Surface Coliforms Chlorophyll a Monthly Surface Surface and bottom of the water pH Monthly column Surface and bottom of the water Conductivity Monthly column Ammonia Monthly Surface BOD Monthly Surface and bottom Total phosphorous Monthly Surface Nitrogen Monthly Surface Suspended Solids Quarterly Surface and bottom Phenols Twice annually Surface Metals Twice annually Surface Pesticides Twice annually Surface
1.2 Environment Agency Water Quality Monitoring
The Environment Agency (EA) sampling of the Mersey tributary and lately the MSC began with it’s predecessor organisation in the 1970s. The earliest data available at the time of writing this report was from the River Irwell near Salford in 1975, however monitoring at this site ceased in 1999. Historical long term data are available from as early as 1978 to present, located between the River Irwell at the Searchlight premises and Latchford Locks (Figure A1.2). These sites are part of the monitoring programme undertaken by the EA river monitoring team. A second monitoring programme is also undertaken by the specialised marine team1 whose survey programme involves collecting data from seven sites since 2000. Water quality of river inputs to the MSC is also monitored on several tributaries. In addition, direct
1 Dissolved nutrient measurements were carried out on filtered samples gathered by the EA marine monitoring team, however, river monitoring team samples were analysed without filtration. It is therefore important to note, for example, that data from the marine team for orthophosphate is a measure of soluble reactive phosphorus, whereas for the river team it is a measure of total reactive phosphorus. 2
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APEM Scientific Report 410039 wastewater treatment work (WwTW) inputs are monitored from Salford, Davyhulme, Eccles and Urmston WwTWs.
The EA's river monitoring team visits the sites located on the MSC and its tributaries on a monthly basis and monitors the WwTW effluent between 20 to 44 times throughout the year. Various parameters are measured including dissolved oxygen, pH, temperature, total ammonium, total residual chlorine, un-ionised ammonia and zinc (total), which are of particular importance to the EC Freshwater Fish Directive (FFD). All EA measurements are from the surface water and sampled from the bank, no depth profiles have been taken.
In addition to the above the EA has deployed continuous monitoring sondes (water quality loggers) at various locations. The continuous monitoring sondes collect surface measurements of dissolved oxygen, pH and temperature every 15 minutes at three sites (upstream of Barton Locks, upstream of Irlam Locks and upstream of Lanstar also known as Partington). Sampling at all the EA sites is conducted on a monthly basis recording various physico-chemical, nutrient and biological parameters.
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Figure A1.2. Water quality monitoring sites on the MSC from Manchester to Irlam.
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Table A1.2 Gannt chart of available data for the EA monitoring sites at the WwTW and river inputs as well as in canal monitoring (Start dates and end dates are according to archived data provided by the EA and UU) 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
EA Site Name Upstream Mode Wheel Locks River Irwell at Blackfriars Bridge S S S River Irwell near Salford Station M M M M M S S S S S S S River Irwell at Searchlight Ltd. Premises, Water M M M M M M M M M M M M M M M M M M M M M M M M M M M M M St. (was above Woden St. Footbridge) MSC at Woden Street S S S MSC upstream of Pomona Docks S MSC downstream of Pomona Docks S MSC at Swing Rail Bridge M M M B M B B B M M M M M M F M S Mode Wheel to Barton Locks MSC at Mode Wheel Locks Bridge M M M M M M M M M M M M M M M M M M M M M M M M M MSC below Mode Wheel M M M M M M M Salford STW Final Effluent W W W W W W W W W W W W W W W W W W W W W W W W W W W W W MSC below Barton Bridge B B B B B B S S S M M B B S S M M M M M M M M M M M M MSC upstream of Barton Locks M M M M M M M MSC at Barton Locks M M M M M M S S S S S S S S S S Barton to Irlam Locks Davyhulme WwTW Final Effluent W W W W W W W W W W W W W W W W W W W W W W W W W W W W W MSC upstream of Irlam Locks M M M M M M M MSC at Irlam Locks M M M M M M M M M M M M M M M M M M M M M M M M M M M M M Irlam to Latchford Locks Urmston STW Final Effluent F F F F F F F F F F F F F F F F F F F F F F F F F F F F F MSC downstream of Irlam Locks M M M M M M M MSC at Cadishead Ferry M M M M M M M M M M M M M M M M M M M M M M M M M MSC upstream of Lanstar M M M M M M M MSC at Warburton Bridge S S MSC upstream of River Bollin M M M M M M M MSC upstream of Latchford Locks M M M M M M M M M M M M M M M M M M M MSC at Latchford Locks M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River inputs Eccles STW Final Effluent F F F F F F F F F F F F F F F F F F F F F F F F F F F F F Corn Brook above Confluence with MSC M M M M M M M M M M M M M M M M M M M M M M M M M M M M M Red Brook at Partington Road Bridge M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Bollin Warburton Bridge Heatley M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Glaze at Little Woolden Hall M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Irk at Red Bank above Scotland Weir M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Irwell at Foot Bridge at Salford University M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Medlock at Pinmill Brow M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Mersey at Flixton Road Bridge M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M River Mersey at Woolston Weir M M M M M M M M M M M M M M M M M M M M M M M M M M M M Salteye Brook above Confluence with MSC M M M M M M M M M M M M M M M M M M M M M M M M M M M M M Sow Brook downstream of Lymm Dam M M M M M M M M M M M M M M M M M M M M M M M M M
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2 REVIEW OF MSC PHYSICO-CHEMICAL DATA
The most intensive water quality surveys of the MSC have been undertaken by APEM upstream of Mode Wheel Locks (Figure A1.1). The EA have conducted monitoring in all of the pounds upstream of Latchford Locks and on several of the rivers flowing into the MSC (Figure A1.2). Of particular interest are the pounds between Mode Wheel and Irlam Locks, which receive a significant amount of effluent input from the WwTW inputs at Salford and Davyhulme. Both the Rivers Bollin and Mersey enter the MSC in the lowest pound between Irlam and Latchford Locks and the Mersey also flows out of this pound towards the Irish Sea. Several APEM and EA monitoring sites have been selected along the course of the MSC to represent monitoring within each pound (Table A2.1).
Table A2.1. Routine monitoring sites on the MSC between the Turning Basin and Latchford locks. Site description Site code NGR Date sampling Date sampling commenced ceased APEM Site 1 APEM 1 SJ8120296932 19/06/1985 Present APEM Site 10 APEM 10 SJ8085697053 09/07/1986 Present MSC below Mode 88020292 SJ7960097600 12/06/2000 Present Wheel MSC upstream of 88020291 SJ7560097000 12/06/2000 Present Barton locks MSC upstream of Irlam 88020293 SJ7280094300 12/06/2000 Present Locks MSC downstream Irlam 88020294 SJ7260093700 12/06/2000 Present Locks MSC upstream Lanstar 88020295 SJ7050091400 12/06/2000 Present
2.1 BOD
Biological oxygen demand (BOD) reflects the utilisation of oxygen by bacteria during the decomposition of organic matter. It is a crude index of organic (typically sewage) pollution and a measure of the level at which bacteria in the water utilise oxygen as they degrade the organic matter. More oxygen is used up with increasing organic matter content, hence giving rise to a higher BOD. In general terms BOD values between 0 and 4mg/l are considered satisfactory for fish and values over and above this may be considered organically polluted. The UK amended EU mandatory guideline for cyprinid fish for BOD is <6mg/l for 92% of samples taken and compliance against this value is tested against 12 samples per year. Since values of greater than 6mg/l are only acceptable 8% of the time and only 12 samples are required per year, any more than one BOD value of over 6mg/l will result in failure (as each sample represents 8%).
In general terms BOD increases as the River Irwell enters the MSC and flows downstream to Barton and Irlam Locks (Figure A2.1; Harper, 2000a). However, over the thirty years since monitoring began a progressive decrease in the BOD has been observed indicating a reduction in the organic waste entering the MSC. The greatest improvements in BOD have been observed in the Irwell at Salford as well as at Barton and Irlam Locks (Figure A2.1). Overall the downstream section of the MSC within the study zone (i.e. between Irlam and Latchford Locks) has historically had a lower 6
Final Report – September 2007 APEM Scientific Report 410039
BOD than the upstream sites. This is most likely due to the dilution of the upstream effluents by the tributaries Mersey and Bollin in the lower pound. The breakdown or settling out of particulate organic matter may also help to reduce BOD as the water passes down the MSC and sediment drops out of suspension as velocities decrease.
Table A2.2 Site comparison for extending Harper (2000a) historic plots of the upper canal, Manchester to Warrington. Harper (2000a) site name EA sites used to extend the plot from 2000 to 2006 SPT number Irwell Salford River Irwell at Foot Bridge at Salford University 88002348 Downstream Barton Locks MSC below Barton Locks 88002426 Irlam Locks MSC at Irlam Locks 88002440 Howley Weir River Mersey above Howley Weir 88002634 Latchford Locks MSC at Latchford 88002773 Woolston Weir River Mersey at Woolston Weir 88002631
20 Irwell Salford (Harper, 2000a) d/s Barton Locks (Harper, 2000a) Value not known but > 20 mg/l 18 Irlam Locks (Harper, 2000a) Howley Weir (Harper, 2000a) Latchford Locks (Harper, 2000a) 16 River Irwell at Foot Bridge at Salford University MSC below Barton Locks MSC at Irlam Locks 14 MSC at Latchford Locks Mersey at Howley Weir 12
10 BOD (mg/l) 8
6
4
2
0
1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Figure A2.1 Annual average BOD in the Manchester Ship Canal since 1974, adapted from Harper (2000a). Data post 2000 provided by routine EA monitoring as detailed in Table A2.2.
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2.1.1 Upstream of Mode Wheel Locks
At APEM monitoring Site 1, mean BOD since 2002 has been less than 6 mg/l, and the 92% compliance level of the Freshwater Fish Directive (78/659/EEC) (for cyprinid fish) guideline has been met for 2002, 2004, 2005 and 2006. As stated previously one failure of the guidance level (≤6mg/l) is allowed per 12 samples to achieve compliance. Prior to 2002, the mean BOD fluctuated between years with the maximum mean annual BOD of 85 mg/l being measured in 1995 (Figure A2.2). It is plausible that even higher BOD measurements occurred when storm events followed drier weather conditions. During these events the scour of riverbed deposits, urban run off and storm water inputs from combined sewage overflows introduce high concentrations of organic matter to the water column which subsequently result in higher BODs (Harper, 2000a).
90 APEM Site 1
80 Required for compliance with EC FFD guideline level for 70 cyprinid fish
60
50
40
BOD ATU (mg/l) 30
20
10
0
5 8 0 3 5 8 0 1 3 5 6 8 9 9 9 9 0 0 0 9 987 9 992 9 9 997 9 0 0 0 1 1986 1 198 1989 1 1991 1 1 1994 1 1996 1 1 1999 2 200 2002 2 2004 2 200
Figure A2.2 Mean annual BOD upstream of Mode Wheel Locks. Bars indicate minimum and maximum values recorded each year.
2.1.2 Mode Wheel to Barton Locks
The mean annual BOD in all years has been less than the guideline level of 6 mg/l required for compliance with the EC Freshwater Fish Directive (FFD) for cyprinid fish (Figure A2.3.). This guideline level has only been exceeded on three occasions over the seven year period. High BOD values may be explained by the introduction of organic pollution to the system. However it should be noted that the effects of the effluent input from Salford WwTW are not apparent at either of the EA monitoring sites (SPT 88020292 & 88020291, Table A2.1) since they are located upstream of the inflow and at the downstream limit of the pound respectively (Figure A1.2).
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MSC below Mode Wheel 20 locks (SPT: 88020292)
18 MSC u/s of Barton locks (SPT: 88020291) 16
14 Required for compliance with EC FFD guideline level for cyprinid fish 12
10
8 BOD ATU (mg/l) 6
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.3. Mean annual BOD between Mode Wheel and Barton Locks (from EA data). Bars indicate minimum and maximum values recorded each year.
2.1.3 Barton to Irlam Locks
As observed from the Harper report (Figure A2.1), BOD improves with distance down the MSC. The mean annual BOD between 2000 and 2006 at the site upstream of Irlam Locks was 3.4 mg/l compared to 4.2 mg/l during the same period at APEM Site 1 upstream of Mode Wheel Locks. However, caution must be exercised when comparing APEM data with that from the EA as APEM BOD analysis is commenced within three hours of sampling. The laboratory methodology can affect results as samples may degrade if left longer before analysis.
The mean annual BOD upstream of Irlam locks was consistently below the 6 mg/l guideline level for compliance with the EC FFD (Figure A2.4). Nevertheless, it should be noted that there were periods where the concentration at this site exceeded the guideline and this happened more frequently than at the two sites upstream of Barton locks. This observation may be associated with the cumulative effect of organic load from a combination of several upstream WwTW including Salford and Davyhulme.
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14 MSC u/s of Irlam locks (SPT: 88020293)
12 Required for compliance with EC FFD guideline level for cyprinid fish 10
8
6 BOD ATU (mg/l)
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.4. Mean annual BOD upstream of Irlam Locks. Bars indicate minimum and maximum values recorded each year.
2.1.4 Irlam Locks to Latchford Locks
The mean annual BOD has historically been very similar at the two EA monitoring sites in the pound between Irlam and Latchford Locks. It is only during 2005 and 2006 that higher BODs have been measured at the site upstream of Lanstar, otherwise known as Partington (Figure A2.5). Measurements at this site (located furthest downstream) have only exceeded the cyprinid fish guideline level (≤6 mg/l) required for the EC FFD on one occasion in July 2002. Occasional high BOD measurements may be associated with less dilution of organic inputs during low flow summer months. The mean BOD in this lowest pound on the MSC was 3 mg/l. Hence a distinct spatial decrease in BOD is apparent with distance downstream in the MSC even when examining EA data alone.
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10 MSC d/s Irlam locks (SPT: 88020294)
9 MSC u/s Lanstar (SPT: 88020295) Required for compliance with EC FFD 8 guideline level for cyprinid fish
7
6
5
4 BOD ATU (mg/l) 3
2
1
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.5. Mean annual BOD between Irlam and Latchford Locks. Bars indicate minimum and maximum values recorded each year.
2.2 Ammonia
Ammonia is generally present in natural waters, though in very small amounts, as a result of microbiological activity that affects the reduction of nitrogen-containing compounds. Ammonia can be used as an indication of sewage pollution when present at levels not much above 0.1 mg/l N. Depending on the pH and / or temperature of the + water column, ammonia can occur in two forms, ammonium (NH4 ) and un-ionised ammonia (NH3). Of notable importance is the un-ionised ammonia (UIA), which is extremely toxic at low concentrations to aquatic life and in particular to fish when the pH is high (alkaline). A comparatively small increase in pH (e.g. from algal photosynthesis) can have a substantial effect on UIA concentration. The FFD cyprinid mandatory requirement level for ammonium is ≤1mg/l, which must be achieved 92% of the time (with a minimum of 12 samples taken per year).
Ammonium is of particular significance in the MSC which is failing to reach the FFD cyprinid compliance level (≤1mg/l) due to high concentrations. In the MSC it is expected that the majority of ammonium originates from WwTW although there are significant industrial sources (eg Magnesium Electron Ltd on the River Irwell). A significant reduction in ammonium has been recorded since monitoring began in the 1970s (Harper, 2000a). The greatest change has been observed at Irlam Locks which are immediately downstream of the effluent input from the WwTW at Salford and Davyhulme (Figure A2.6). Improved sewage treatment, particularly since the mid 1990s is thought to be the primary driver for the improvements. Of the sites monitored the lowest ammonium concentration (certainly over the last 10 years) has been
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20 Irwell Salford (Harper, 2000a) d/s Barton Locks (Harper, 2000a) 18 Irlam Locks (Harper, 2000a) Howley Weir (Harper, 2000a) Latchford Locks (Harper, 2000a) 16 River Irwell at Foot Bridge at Salford University MSC below Barton Locks MSC at Irlam Locks 14 MSC at Latchford Locks Mersey at Howley Weir 12
10
Ammonium (mg/l) 8
6
4
2
0
1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Figure A2.6 Ammonium in the Manchester Ship Canal since 1974, adapted from Harper (2000a). Data post 2000 provided by routine EA monitoring as detailed in Table A2.2.
2.2.1 Upstream of Mode Wheel Locks
Surface monitoring of ammonium is undertaken upstream of Mode Wheel Locks at APEM Site 10. Total ammonium data from this site is presented in Figure A2.7 and with data for the un-ionised form alone in Figure A2.8.
There has been a steady long term improvement in the ammonium and UIA concentrations in the MSC upstream of Mode Wheel Locks. 2006 was the first year since monitoring commenced that saw the annual average ammonium concentration falling within the mandatory level required for the EC FFD (≤1mg/l). The guideline level of 0.2 mg/l has only been achieved sporadically at APEM Site 10 upstream of Mode Wheel locks. Clearly high ammonium concentrations are an issue particularly in relation to the non-compliance of the FFD, hence there are serious implications for the fish populations residing in the MSC.
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APEM Site 10 40
35 Required for compliance with the EC FFD mandatory level for 30 cyprinid fish Required for compliance with the EC FFD guideline level for 25 cyprinid fish
20
15 Ammonium (mg/l)
10
5
0
7 0 6 2 5 93 99 992 998 001 1985 1986 198 1988 1989 199 1991 1 19 1994 1995 199 1997 1 19 2000 2 200 2003 2004 200 2006
Figure A2.7. Mean annual ammonium upstream of Mode Wheel Locks. Bars indicate minimum and maximum values recorded each year.
Un-ionised ammonia (UIA) concentrations are of greater significance to fish than total ammonium concentrations, UIA being several orders of magnitude more toxic to fish. Concentrations of UIA at APEM Site 10 have fluctuated over the years (Figure A2.8). Prior to APEM sampling, the EA have records of UIA at Swing Rail Bridge (SPT 88002421) upstream of APEM Site 10 (Figure A2.9). UIA levels between 1990 and 1992 regularly exceeded the mandatory level required by the FFD. However, since 2003 mean annual concentrations have been lower than the mandatory level for compliance with the FFD. APEM Site 10 300
Average 547 μg/l Required for compliance with the 250 maximum 1680 μg/l EC FFD mandatory level for cyprinid fish
g/l) Required for compliance with the μ 200 EC FFD guideline level for cyprinid fish
150
100 Unionised ammoniaUnionised (
50
0
6 0 2 8 4 8 87 9 9 93 9 99 0 05 9 9 9 9 9 9 0 1985 1 1 1988 1989 1 1991 1 1 1994 1995 1996 1997 19 1 2000 2001 2002 2003 20 2 2006
Figure A2.8. Mean annual un-ionised ammonia upstream of Mode Wheel Locks. Bars indicate minimum and maximum values recorded each year. 13
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150 Swing Rail Bridge SPT 140 88002421 130 120 Required for compliance with 110 EC FFD mandatory level for 100 cyprinid fish 90 Required for compliance with 80 EC FFD guideline level for 70 cyprinid fish 60 50 40 Un-ionised Ammonia (ug/l) Ammonia Un-ionised 30 20 10 0 Jul 90 Jul 91 Jul 92 Jan 90 Jan Mar 90 91 Jan Mar 91 92 Jan Mar 92 May 90 90 Nov May 91 91 Nov May 92 Sep 90 Sep 91 Sep Sampling Date
Figure A2.9. Un-ionised ammonia (mg/l) from January 1990 to August 1992 on the Manchester Ship Canal at Swing Rail Bridge (SPT 88002421).
2.2.2 Below Mode Wheel Locks
Data for ammonia is available within all three pounds between Mode Wheel and Latchford Locks. As shown in Figure A2.10, Figure A2.11and Figure A2.12, mean annual ammonia concentrations in all pounds below Mode Wheel Locks have exceeded the guideline and mandatory level to comply with the EC FFD for cyprinid fish. The levels observed below Mode wheel Locks are generally similar to that seen upstream, in the Turning Basin since 2000 and there is an overall decreasing trend in ammonia within all pounds, which is likely due to the improvements made at the various WwTWs that discharge into the MSC.
In 2006, it is interesting to note that a peak value of 5.8mg/l occurred in June at the site downstream of Irlam Locks (SPT 88020294). This value could have been the result of increased levels of ammonia discharged from the WwTW located just upstream of the monitoring location. However, the overall decreasing trend in ammonia shows important improvements in water quality.
Data of the unionised form of ammonia was not available at the sites under study.
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MSC below Mode Wheel locks 6 (SPT: 88020292)
MSC u/s of Barton locks (SPT: 5 88020291)
Compliance required for the EC FFD mandatory level for total 4 ammonium for cyprinid fish Compliance required for the EC FFD guideline level for total 3 ammonium for cyprinid fish
Ammonia (mg/l) 2
1
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.10. Mean annual ammonia (mg/l) in the MSC between Mode Wheel and Barton Locks. Bars indicate minimum and maximum values recorded each year.
6 MSC u/s Irlam locks (SPT: 88020293)
5 Compliance required for the EC FFD mandatory level for total ammonium for cyprinid fish 4 Compliance required for the EC FFD guideline level for total 3 ammonium for cyprinid fish
Ammonia (mg/l) 2
1
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.11. Mean annual ammonia (mg/l) in the MSC between Barton and Irlam Locks. Bars indicate minimum and maximum values recorded each year.
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MSC d/s Irlam locks (SPT: 6 88020294)
MSC u/s Lanster (SPT: 5 88020295)
Compliance required for the EC FFD mandatory level for total 4 ammonium for cyprinid fish Compliance required for the EC FFD guideline level for total 3 ammonium for cyprinid fish
Ammonia (mg/l) 2
1
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.12. Mean annual ammonia (mg/l) in the MSC between Irlam and Latchford Locks. Bars indicate minimum and maximum values recorded each year.
2.3 DO
One of the most important determinands for the ecology of the MSC is dissolved oxygen (DO). The EC FFD guideline level for salmonid fish is ≥ 9mg/l for 50% of the time and ≥ 7mg/l for 100% of the time. For cyprinid fish the requirement is ≥ 8mg/l for 50% of the time and ≥ 5mg/l for 100% of the time. The mandatory level is ≥ 9mg/l for 50% for salmonid fish and ≥ 7mg/l for 50% of the time for cyprinid fish. Dissolved oxygen percentage saturation is integrally linked to the temperature of the water as the carrying capacity for oxygen is decreased at higher temperatures. Therefore water has a natural tendency to contain less DO in the warm summer months.
The Harper report (2000a) showed that the highest DO saturations were recorded in the Irwell at Salford (Figure A2.13). There is a net downstream deterioration in mean annual oxygen concentrations. A distinct change is apparent between the DO levels in the Irwell and the DO downstream of Barton Locks where the heavily modified channel reduces velocity and turbulence, limiting atmospheric re-aeration as occurs in the Irwell. An improvement in DO is apparent from more recent data downstream of Barton Locks. This may be associated with the commencement of the oxygenation project in the upper MSC upstream of Mode Wheel Locks in 2001 (APEM, 2002). It is also considered that water quality improvements at Irlam may be associated with developments in the treatment processes at the WwTW located in the upstream pounds.
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Final Report – September 2007 APEM Scientific Report 410039
Irwell Salford (Harper, 2000a) 160 d/s Barton Locks (Harper, 2000a) Irlam Locks (Harper, 2000a) Howley Weir (Harper, 2000a) 140 Latchford Locks (Harper, 2000a) Woolston Weir (Harper, 2000a) River Irwell at Foot Bridge at Salford University 120 MSC below Barton Locks MSC at Irlam Locks MSC at Latchford Locks 100 Woolston Weir Mersey at Howley Weir
80
60 Dissolved oxygen saturation(%)
40
20
0 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Figure A2.13 DO saturation (%) in the Manchester Ship Canal since 1974, adapted from Harper (2000a). Data post 2000 provided by routine EA monitoring as detailed in Table A2.2.
2.3.1 Upstream of Mode Wheel Locks
The pound upstream of Mode Wheel Locks is the only area of the MSC in which both surface and bottom measurements of DO have been routinely monitored. Profile measurements at 1 m intervals have been undertaken since sampling commenced at APEM Site 1, Salford Quays Basin 6 in 1985. During summer months a clear gradient is apparent between the surface and bottom water DO saturation (e.g. summer 2004). In recent years, operation of the helixors in Basin 6 and the oxygen injection units in the Turning Basin have artificially mixed the water, impacting upon how the water is stratified. However at Pomona (upstream of the oxygen injection system) stratification resulting in reduced DO concentration in the lower depths is often apparent.
During the summer months additional monitoring (between Trafford Road Bridge and Mode Wheel locks) is undertaken by APEM at 29 sites to manage the operation of the oxygen injection system (Figure A1.1). The APEM summer monitoring programme in the MSC is specifically designed to monitor thermal stratification and water column oxygen concentrations. Measurements of temperature and DO (mg/l) are recorded three times a week between May and September and are used to manage the DO concentration above 4 mg/l as well as optimise oxygen usage (Figure A2.14). Although affording considerable ecological benefits, the 4 mg/l target was derived from empirical measurements during intensive studies in the early 1990s. When oxygen concentrations were at or above 4 mg/l, foul odours, excessive gaseous bubbling and the ‘sloughing off’ of sewage derived sediment rafts was considerably reduced (APEM, 2001b).
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Final Report – September 2007 APEM Scientific Report 410039
17-05-06 b
9740
9720
9700
9680
9660
7960 7980 8000 8020 8040 8060 8080 8100 8120 8140 12-05-06 b
9740
9720
9700
9680
9660
7960 7980 8000 8020 8040 8060 8080 8100 8120 8140 Figure A2.14 Typical bottom water dissolved oxygen (mg/l) contour plots used for oxygen dosing management comparing typical plots when the units are on (top) and off (bottom). Yellow line indicates the 4 mg/l management target. Areas in red indicate oxygen levels below 4 mg/l.
Conversely when the oxygen injection system is not operational, the contour plots (Figure A2.14) reveal the effect of the morphological change imposed by the Canal on oxygen concentrations. Oxygen levels previously maintained by re-aeration from the higher velocities and turbulence experienced in the River Irwell are rapidly reduced as Sediment Oxygen Demand (SOD) and BOD within the basin are exerted on the almost stagnant water. The deep nature of the Manchester Ship Canal (up to 9m), combined with vertical walls renders the canal prone to stratification. In addition, a high retention period in the Turning Basin pound (up to 3 days) means that oxygen concentrations are rapidly depleted particularly the bottom water which can become completely anoxic (Figure A2.15). It follows that oxygen input to the downstream pounds (Barton and Irlam) can be virtually non existent under these conditions.
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Final Report – September 2007 APEM Scientific Report 410039
120 Surface dissolved oxygen (%) Bottom dissolved oxygen (%)
100
80
60
40 Dissolved Oxygen Saturation (%)
20
Bottom water anoxia
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure A2.15 Dissolved oxygen (mg/l) profile from APEM Site 1 on the Manchester Ship Canal from January to December 2000 prior to oxygen injection.
Returning to the long term record of annual averages, a gradual improvement in the surface DO (mg/l) over twenty years of monitoring was apparent at APEM Site 1 (upstream of Mode Wheel Locks). During the first 15 years of monitoring the lowest DO measurements were frequently less than 10%. However, since the installation of the oxygenation system in 2001 the surface DO in this pound has stabilised and the minimum DO is rarely less than 50% (Figure A2.16); bottom DO is maintained at a similar level. This indicates the success of careful artificial management of DO in this section of the MSC. The two plots (Figure A2.14) illustrate the effectiveness of the oxygen injection system in elevating DO levels above the target concentration. This is confirmed by dissolved oxygen concentration readings, which show that for the last six years the mean concentrations of DO at APEM Site 1 have exceeded 5 mg/l (which is the guideline level required by the Freshwater Fish Directive (FFD) for cyprinid fish) (Figure A2.17). This is an improvement on the previous 12 years when the minimum DO concentration was consistently less than the EC FFD compliance concentration of 5 mg/l.
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Final Report – September 2007 APEM Scientific Report 410039
350
APEM Site 1 300
250
200 ) DO (% 150
100
50
0 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Figure A2.16 Mean annual DO (%) from APEM Site 1 upstream of Mode Wheel Locks. Bars indicate minimum and maximum values recorded each year.
APEM Site 1
100% compliance required for EC FFD 20 guideline level for cyprinid fish 50% compliance required for EC FFD guideline level for cyprind fish 50% compliance required for EC FFD 15 mandatory level for cyprinid fish
DO (mg/l) DO 10
5
0
8 4 87 8 91 93 9 97 01 03 05 9 9 9 0 0 1985 1986 1 19 1989 1990 1 1992 19 19 1995 1996 1 1998 1999 2000 2 2002 20 2004 2 2006
Figure A2.17 Mean annual DO (mg/l) from APEM Site 1 upstream of Mode Wheel Locks. Bars indicate minimum and maximum values recorded each year.
2.3.2 Mode Wheel Locks to Barton Locks
EA surface measurements of dissolved oxygen % saturation have been taken at both sites in this pound since June 2000 (Figure A2.18). The mean annual DO is consistently higher at the upstream site compared with the site at the lower end of the pound. It is also worthy of note that the second site is downstream of Salford WwTW, 20
Final Report – September 2007 APEM Scientific Report 410039 although the anticipated higher BOD at this site has not been recorded (see section 2.1.2).
180 MSC below Mode Wheel locks (SPT: 88020292) 160 MSC u/s of Barton locks (SPT: 88020291) 140
120
) 100
DO (% 80
60
40
20
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.18. Mean annual DO (% saturation) between Mode Wheel and Barton Locks. Bars indicate minimum and maximum values recorded each year.
The DO data have also been presented as oxygen concentration in mg/l for both sites in this pound since 2004 (Figure A2.19). Once again the DO concentrations were higher below Mode Wheel locks compared with upstream Barton locks. In 2004 the mean annual concentration of DO below Mode Wheel locks (SPT: 88020292) exceeded the guideline compliance level of 8 mg/l. This was the only occasion that this standard has been exceeded and may have been influenced by the oxygen scheme immediately upstream of the Turning Basin. However, both sites during all three years have had a mean annual concentration that exceeds the ≥5 mg/l guideline limit for cyprinid fish (which requires 50% compliance).
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Final Report – September 2007 APEM Scientific Report 410039
MSC below Mode Wheel locks (SPT: 88020292) MSC u/s of Barton locks (SPT: 88020291) 10 100% compliance required f or EC FFD guideline level f or cyprinid f ish 50% compliance required for EC FFD mandatory level for cyprinid fish 50% compliance required for EC FFD guideline level for cyprinid fish 8
6 DO (mg/l) DO 4
2
0 2004 2005 2006
Figure A2.19. Mean annual DO (mg/l) between Mode Wheel and Barton Locks.
2.3.3 Barton to Irlam Locks
From EA data a gradual improvement in the dissolved oxygen saturation has been observed upstream of Irlam locks (SPT: 88020293), particularly in 2004, 2005 and 2006 when the mean annual surface saturation levels were 63, 56 and 59 % respectively (Figure A2.20). This represents an improvement compared to the mean annual DO at the start of the data set in 2000 of 48%.
120 MSC u/s of Irlam locks (SPT: 88020293) 100
80 ) 60 DO (% DO
40
20
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.20. Mean annual DO (% saturation) upstream of Irlam Locks. Bars indicate minimum and maximum values recorded each year. 22
Final Report – September 2007 APEM Scientific Report 410039
Monitoring of dissolved oxygen concentration was carried out upstream of Irlam locks between 2000 and 2006 (Figure A2.21). Measurements were intermittent prior to 2004 and no measurements were taken in 2001 or 2003. Since 2004 the mean annual DO has exceeded 5 mg/l which is the guideline level required 100% of the time for compliance with the EC FFD for cyprinid fish. However, minimum concentrations in all three years have dropped below this level on numerous occasions during the summer months, the lowest being in July 2006 when DO dropped to 1 mg/l. These low DO concentrations are likely to have detrimental impacts on the aquatic ecology and particularly fish populations residing in or migrating through the MSC.
16 MSC u/s of Irlam locks (SPT: 88020293)
100% compliance required for guideline 14 level EC FFD for cyprinid fish 50% compliance required for mandatory 12 level EC FFD for cyprinid fish 50% compliance required for guideline level EC FFD for cyprinid fish 10
8 DO (mg/l) DO 6
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.21. Mean annual DO concentration (mg/l) upstream of Irlam Locks. Bars indicate minimum and maximum values recorded each year.
2.3.4 Irlam to Latchford Locks
With the exception of 2002, dissolved oxygen saturation has been consistently higher at the downstream site at Lanstar (Partington) (Figure A2.22). Since 2000 some improvement has been seen in the mean DO statistics, although it should be noted that a low DO event occurred in July 2006 which resulted in a DO saturation of just 8%.
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Final Report – September 2007 APEM Scientific Report 410039
120 MSC d/s Irlam locks (SPT: 88020294)
100 MSC u/s Lanster (SPT: 88020295)
80 ) 60 DO (%
40
20
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.22. Mean annual DO (%) between Irlam and Latchford Locks. Bars indicate minimum and maximum values recorded each year.
Although measurements of DO saturation have been taken routinely since 2000, the concentration of dissolved oxygen in mg/l was not measured during 2001 (Figure A2.23). Only sporadic measurements had been taken prior to 2004. An improvement in maximum DO concentration is apparent since 2004 although minimum concentrations have continued to fall below the mandatory level of 5 mg/l which is required for compliance with the EC FFD for cyprinid fish. The lowest DO concentration was recorded downstream of Irlam locks in July 2006 when it fell to just 0.7mg/l. Bearing in mind that this is a surface sample, DO concentrations this low throughout the water column are likely to have detrimental impacts on fish populations and the aquatic ecology as a whole.
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Final Report – September 2007 APEM Scientific Report 410039
MSC d/s Irlam locks (SPT: 88020294) 16
MSC u/s Lanstar (SPT: 88020295) 14 100% compliance required for guideline level EC FFD cyprinid fish 12 50% compliance required for mandatory level EC FFD for cyprinid fish 10 50% compliance required for guideline level EC FFD for cyprinid fish 8 DO (mg/l) 6
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.23. Mean annual DO concentration (mg/l) between Irlam and Latchford Locks. Bars indicate minimum and maximum values recorded each year.
2.3.5 Continuous monitoring sonde data
Monitoring of a limited suite of water parameters in three of the pounds has been carried out by the EA using continuous monitoring sondes since 2004. These sondes were located at routine EA monitoring sites (upstream of Barton Locks; upstream of Irlam Locks and upstream of Lanstar also known as Partington) (Figure A1.2) Measurements of DO (mg/l2 and % saturation)3 were recorded using YSI 6920 sondes at fifteen minute intervals twenty-four hours a day. The sondes were in fixed positions targeted to collect surface measurements (the sondes are occasionally exposed to the air when water level in the Canal drops). Typically the results were downloaded on a fortnightly basis and each sonde was cleaned and recalibrated before further measurements were taken.
The hourly mean values from the three sondes during 2006 are presented in Figure A2.24, Figure A2.25 and Figure A2.26. The greatest variability in dissolved oxygen (%) saturation was observed from the sonde upstream of Barton locks (the furthest upstream of the three locations). Peak values of DO exceeding 300 % were measured during the summer months. Dissolved oxygen saturations over 100 % are known as supersaturation and occur as a result of algal photosynthesis. Whilst a high oxygen concentration can be problematic (see associated fish review report, APEM 2007c), algal respiration during the hours of darkness can cause an oxygen sag of equal magnitude. An event of this type was observed at the sonde upstream of Barton Lock on the 2nd of July 2006 (Figure A2.28). This can exert extreme stress on the ecology of the system, particularly the fish representing a common cause of summer fish kills. The effects of algal blooms on dissolved oxygen are discussed further in section 2.13.
2 Measurements of dissolved oxygen (mg/l) commenced in February 2006. 3 pH, conductivity and temperature are also recorded using the sondes. 25
Final Report – September 2007 APEM Scientific Report 410039
It is also important to note that periods of bottom water anoxia can lead to the release of phosphorus, metals and other chemicals locked within the sediments. This is of particular importance in the Manchester Ship Canal due to the presence of possibly toxic substances in the Canal sediments.
u/s Barton Lock
350
300
250 Fish kill reported between Mode Wheel and Barton Locks 200
150
Dissolved oxygen (%)saturation 100
50
0
5 6 6 6 /0 0 /0 0 0/05 2 7/06 8/06 0 1 1 02/ /03/06 /05/06 0 0 1 11/ /01/07 /03/07 5/ 4/ 2/ 4 3 1/ 0/ 9/ 8 9 2 1 0 2 1 02/ 2 1 2 1 0 Figure A2.24 Continuous monitoring sonde data for dissolved oxygen (%) saturation from the EA monitoring location upstream of Barton Locks (SPT 88020291).
u/s Irlam Lock
160
140
120
100
80
60 Dissolved oxygen (%)saturation 40
20
0
1/05 1/06 3/06 4/06 6/06 8/06 1 0 0 0 0 0 /12/06 4/ 3/ 4/ 9 2 1 0 23/ 12/ 01/ 20/09/06 09/11/06 2 Figure A2.25 Continuous monitoring sonde data for dissolved oxygen (%) saturation from the EA monitoring location upstream of Irlam Locks (SPT 88020293)
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Final Report – September 2007 APEM Scientific Report 410039
u/s Lanstar (Partington)
200
180
160
140
120
100
80
60 Dissolved oxygen (%)saturation
40
20
0
1/05 1/06 3/06 4/06 6/06 8/06 1 0 0 0 0 0 /12/06 4/ 3/ 4/ 9 2 1 0 23/ 12/ 01/ 20/09/06 09/11/06 2 Figure A2.26 Continuous monitoring sonde data for dissolved oxygen (%) saturation from the EA monitoring location upstream of Lanstar (Partington, SPT 88020294)
50 u/s Barton Lock 45 u/s Irlam Lock u/s Lanstar (Partington) 40
35
30
25
20
Dissolvedoxygen (%) saturation 15
10 Fish kill reported between Mode Wheel and Barton Locks
5
0
18:00 13th 00:00 14th 06:00 14th 12:00 14th 18:00 14th 00:00 15th 06:00 15th 12:00 15th 18:00 15th 00:00 16th 06:00 16th 12:00 16th 18:00 16th 00:00 17th 06:00 17th 12:00 17th 18:00 17th 00:00 18th 06:00 18th 12:00 18th 18:00 18th 00:00 19th 06:00 19th Figure A2.27. Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 13th and 19th of May 2006.
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Final Report – September 2007 APEM Scientific Report 410039
250 u/s Barton Lock u/s Irlam Lock u/s Lanstar (Partington)
200
150
100 Dissolved oxygen (%) saturation
50
0
18:00 29th 00:00 30th 06:00 30th 12:00 30th 18:00 30th 00:00 01th 06:00 01th 12:00 01th 18:00 01th 00:00 02th 06:00 02th 12:00 02th 18:00 02th 00:00 03th 06:00 03th 12:00 03th 18:00 03th 00:00 04th 06:00 04th 12:00 04th 18:00 04th 00:00 05th 06:00 05th Figure A2.28 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 29th June and 5th of July 2006.
60 u/s Barton Lock u/s Irlam Lock 50 u/s Lanstar (Partington)
40
30
20 Dissolved oxygen (%) saturation (%) oxygen Dissolved
10
0
00:00 08th 06:00 08th 12:00 08th 18:00 08th 00:00 09th 06:00 09th 12:00 09th 18:00 09th 00:00 10th 06:00 10th 12:00 10th 18:00 10th 00:00 11th 06:00 11th 12:00 11th 18:00 11th 00:00 12th 06:00 12th 12:00 12th 18:00 12th 00:00 13th Figure A2.29 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 8th and 13th August 2006.
The benefit of continuous monitoring sondes recording DO at 15 minute intervals is obvious in that these nocturnal oxygen sags are detected (Figure A2.29), whereas spot sampling during the day would merely present the supersaturation values observed. However, since the data presented are mean hourly values it is possible that dissolved oxygen (%) saturation levels exceeded those presented here.
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It is also apparent from Figure A2.24, Figure A2.25 and Figure A2.26 that the frequency of mean daily DO saturation falling below 50 % increases during the summer months. During lower flow conditions the MSC is less able to absorb organic loads, there being less capacity for dilution. Furthermore increased summer temperatures mean that the bacterial uptake of oxygen during degradation of organic material can exceed the rate at which it is replenished from the atmosphere therefore resulting in anaerobic conditions.
A fish kill event was reported in the MSC on 15th May 2006 as discussed in Section 2.13. The continuous monitoring sonde located upstream of Barton Locks recorded the event (Figure A2.27). It is useful to note that from the routine samples collected at approximately monthly intervals that this low dissolved oxygen event would not have been recorded without the aid of the continuous monitoring sonde.
2.4 Suspended solids and transparency
Suspended solids is a measure of the quantity of matter suspended within the water column. It consists of fine particulates which may never settle or those which are kept is suspension by flowing water. The solids may be derived from a number of sources, such as organic pollution and urban particulate run-off, but may also consist of algal cells. In the context of the MSC, the level of suspended solids is crucial, as it is a major driver in controlling light penetration into the water column. By limiting light penetration, high levels of suspended solids inhibit the growth of algae and limit the onset of severe algal blooms that would otherwise be prevalent in the MSC’s nutrient rich waters. As such any future reductions to suspended solid levels may have a detrimental impact upon algal levels in the Canal. The EC FFD guideline for both salmonid and coarse fish for suspended solids is for the average level to be ≤25mg/l.
2.4.1 Upstream Mode Wheel Locks
Routine measurements of suspended solids have been taken at APEM Site 1 upstream of Mode Wheel Lock (Figure A2.30) since 1985 at both the surface and bottom. On the majority of sampling occasions concentrations were less than 25 mg/l and as such the annual average complied with the guideline level in the EC FFD for salmon and coarse fish for most years. There were, however, several occasions where individual suspended solids concentrations were in excess of 25mg/l such as in October 1994, although it is possible that this sample was collected during a period of dredging in the Turning Basin. In recent years the suspended solids in surface samples have been consistently lower than the guideline level with the exception of 2006 when concentrations were closer to those seen prior to commencement of the oxygenation project (a concentration of 33 mg/l was collected in March 2006). The guideline threshold of 25mg/l was exceed more frequently in bottom samples, but the yearly means have remained below 25mg/l in recent years and therefore comply with the EC FFD for cyprinid fish. A recent exception to this was in 2006, where the annual mean for bottom samples was 35mg/l and again, a combination of dredging activity and high flow conditions may have contributed to the higher values.
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Final Report – September 2007 APEM Scientific Report 410039
250 APEM Site 1
200 Required for compliance with EC FFD guideline leve for cyprinid fish
150
100 Suspended solids (mg/l)
50
0
5 8 0 1 3 5 6 8 0 1 3 5 6 8 8 9 9 9 9 0 0 0 9 987 9 9 992 9 9 997 9 0 0 0 1 1986 1 1 1989 1 199 1 1 1994 1 199 1 1 1999 2 200 2002 2 2004 2 200
Figure A2.30 Mean annual surface suspended solids upstream of Mode Wheel Locks. Bars indicate minimum and maximum values recorded each year.
Transparency is primarily determined by algal and/or suspended solids concentration. The prevailing weather conditions at the time of the survey may also affect the transparency in two ways; firstly, through disturbance of fine solids from the Canal bottom resulting in an increase in suspended solids and, secondly, through poor light or agitation to the water surface by wind and rain. Measurements taken at APEM Site 1 indicate that the mean annual Secchi extinction depths are less than 1 m and have been fairly consistent since 1985 (Figure A2.31). In line with the expected trend, water transparencies were highest during the winter months when algal densities are lower, with the converse occurring during the summer months as shown during a three year period in Figure A2.32.
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Final Report – September 2007 APEM Scientific Report 410039
2.5 APEM Site 1
2
1.5
1 Secchi depth (m) depth Secchi
0.5
0
6 8 0 2 3 5 7 9 1 2 4 6 8 8 9 9 9 0 0 0 9 987 9 989 991 9 9 9 998 000 0 0 0 1985 1 1 1 1 199 1 199 1 1994 1 1996 1 1 199 2 200 2 2003 2 2005 2
Figure A2.31 Mean annual secchi extinction depth changes in the MSC from 1985 to 2006 (APEM Site 10). Bars indicate minimum and maximum values recorded each year.
2.5
Winter Winter 2.0
1.5
Winter Summer Summer Summer Summer 1.0 Secchi extinction depth (m) depth extinction Secchi
0.5
0.0 Apr-03 Apr-04 Apr-05 Apr-06 Oct-03 Oct-04 Oct-05 Oct-06 Jun-03 Jun-04 Jun-05 Jun-06 Feb-04 Feb-05 Feb-06 Aug-03 Aug-04 Aug-05 Aug-06 Dec-03 Dec-04 Dec-05 Figure A2.32 Annual secchi extinction depth changes in the MSC (APEM site 10).
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2.4.2 Downstream Mode Wheel Locks
Measurements of suspended solids have been taken at all EA sites (Table A2.1) in the MSC, with data generally extending back until 2000. The suspended solid concentrations are reasonably consistent below Mode Wheel Locks with annual means between 7 and 20mg/l (Figure A2.33, Figure A2.34 and Figure A2.35). The highest annual mean was observed in the Irlam to Latchford pound in 2000, where the annual mean was 33mg/l and above the EC FFD guideline for cyprinid fish. It is interesting to note that in the Irlam to Latchford pound, the monitoring site just down stream of Irlam Locks (SPT 88020294) has consistently lower suspended solids annual means that the site further down stream at Lansar (Partington) (SPT 88020295). A possible explanation for this could be due to the inflow of the River Mersey above the Lansar monitoring site, introducing catchment derived suspended solids.
Overall, suspended solids in all pounds have generally remained below the EC FFD guideline for cyprinid fish.
250 MSC below Mode Wheel locks (SPT: 88020292)
200 MSC u/s of Barton locks (SPT: 88020291)
Required for EC FFD 150 guideline level for cyprinid fish
100 Suspended solids (mg/l)
50
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.33 Mean annual suspended solids in the MSC between Mode Wheel Locks and Barton Locks. Bars indicate minimum and maximum values recorded each year.
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Final Report – September 2007 APEM Scientific Report 410039
250 MSC u/s of Irlam locks (SPT: 88020293)
Required for EC FFD 200 guideline level for cyprinid fish
150
100 Suspended solids (mg/l) 50
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.34 Mean annual suspended solids in the MSC between Barton and Irlam Locks. Bars indicate minimum and maximum values recorded each year.
250 MSC d/s Irlam locks (SPT: 88020294)
200 MSC u/s Lanstar (SPT: 88020295)
Required for EC FFD guideline 150 level for cyprinid fish
100 Suspended solids (mg/l)
50
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.35 Mean annual suspended solids in the MSC between Irlam and Latchford Locks. Bars indicate minimum and maximum values recorded each year.
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Final Report – September 2007 APEM Scientific Report 410039
2.5 Nutrients
Both phosphorous and nitrogen are essential nutrients, incorporated within the protein, DNA, phospholipids and nucleic acids of all living organisms. They are therefore essential for plant growth and can often limit the amount of growth attainable in a given waterbody. As a result, the nutrient status of a waterbody plays an important role in phytoplankton composition and biomass. By monitoring concentrations, predictions can therefore be made about the development of algal blooms, since high nutrient levels form the necessary conditions for algae to flourish and bloom.
Research has shown that phosphorous is the key nutrient limiting algal growth in freshwater. To a lesser extent, nitrogen is also important but the ratio between the two nutrients plays a significant role. The importance of phosphorous is principally in regard to the phenomenon of eutrophication (nutrient enrichment). Whilst there is much debate over the availability of the various forms of phosphorous, orthophosphate is generally regarded as the most readily available form for uptake by plants and algae.
Nitrogen is not usually a limiting nutrient in the UK, with high levels of rainfall occurring throughout the year precipitating nitrogen compounds into water bodies. However the ratio between various nitrogenous compounds can be a useful tool in water quality management. Four nitrogen compounds are generally measured for - - analysis, including total nitrogen (TN), nitrate (NO3 ), nitrite (NO2 ) and total + ammonia (NH4 ) (discussed earlier).
2.5.1 Upstream Mode Wheel Locks
2.5.1.1 Total phosphorus
This is an important parameter to assess the eutrophic state of the water as total phosphorus not only includes orthophosphate but also the particulate matter which is biologically available for algal uptake. Measurements of total phosphorus (TP) have been taken at APEM Site 1 between 1985 - 2000. Monthly analysis of samples for TP ceased in 2000, although, as with total and un-ionised ammonia, measurements have continued at APEM Site 10 on a quarterly basis (Figure A2.36). The mean annual concentration at Site 10 in 2006 was 456 μg/l. This was a substantial decrease from previously when in 1992 TP was 966μg/l. However, concentrations of TP are clearly very high in the MSC and, although in freshwater aquatic systems phosphorus is widely acknowledged as being the limiting nutrient for algal growth, it is clearly not limiting in the MSC (Harper, 1992). The contrast between TP in the MSC and closed basins of Salford Quays is also clearly shown in Figure A2.36, highlighting the beneficial effect of isolation.
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Final Report – September 2007 APEM Scientific Report 410039
3,000 5,630ug/l in MSC on 07-May-91 Inner Basins MSC 2,500
2,000 Downward trend in total phosphorus in MSC
1,500
1,000 Total phosphorus (µg/l_P)
500
0 27-Jul-05 08-Jul-92 28-Apr-00 14-Apr-94 31-Oct-03 22-Oct-97 29-Jun-01 30-Jan-02 30-Jun-95 24-Jan-96 19-Feb-99 27-Mar-03 23-Feb-06 10-Feb-93 05-Mar-97 30-Nov-94 21-Sep-99 05-Dec-00 29-Aug-02 15-Dec-04 28-Sep-06 04-Dec-92 06-Sep-93 28-Aug-97 20-May-04 07-May-91 28-May-98 Figure A2.36 Total phosphorus measurements from the MSC at APEM site 10 and within the inner basins of Salford Quays.
A TP concentration of 20 µg/l P (0.02 mg/l P) has been defined as a trigger level for eutrophication in surface waters (Champ, 1998), therefore the MSC clearly has the potential to be eutrophic and even the potential to be a hypereutrophic system. However, the mean annual concentrations of chlorophyll a would need to exceed 25 μg/l in order to classify this system as hypereutrophic. As discussed earlier, high suspended solids in the MSC reduce the water transparency and restrict algal growth. However, further reductions in suspended solid concentrations will undoubtedly improve transparency allowing the available phosphorus to fuel potentially extreme algal blooms.
Modelling Chlorophyll from Total Phosphorus
In any aquatic system, gaining an appreciation for primary productivity is important, both in terms of understanding processes along the food chain and the potential for water quality problems caused by excessive algal and macrophyte growth. In terms of a fishery, for example, the potential sustainable yield is ultimately dictated by the amount of primary productivity. In the MSC, virtually an endless supply of nutrients are available for take up by algae and macrophytes and as such, there is a potential for a large yield of coarse fish. However, as discussed elsewhere in this report, other factors such as oxygen stress and organic pollution are a limiting factor for fish within the MSC.
Using equations, developed from Dillon and Rigler (1974) and Vollenweider (1976) it is possible to predict the level of primary production in a water body by modelling chlorophyll a from total phosphorus concentrations. The two equations are shown below.
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Final Report – September 2007 APEM Scientific Report 410039
Log10 (Chl) = 1.45 Log10 (Ptot) -1.14 (Dillon and Rigler)
Log10 (Chly) = 0.91 Log10 (Ptot) -0.435 (Vollenweider)
Where, Chl = mean summer chlorophyll, in µg/l Chly = mean annual chlorophyll, in µg/l Ptot = total phosphorus, in µg/l
Using the available total phosphorus data since 1991 in the Turning Basin a chlorophyll prediction can be made using both of the above equations. The mean summer phosphorous since 1991 (860 µg/l) predicts chlorophyll at 1304 µg/l using the Dillon and Rigler model. The mean annual total phosphorus in the Turning Basin (764 µg/l) since 1991 predicts chlorophyll at 154 µg/l using the Vollenweider equation.
The accuracy of these models is typically thought to be half an order of magnitude either way, however, a mean of the two predictions should provide an improved estimate, which is calculated to be 729 µg/l. This would appear to be an over estimate, given that the measured chlorophyll in the Turning Basin is more typically 30 µg/l (although it has peaked at over 200 µg/l in the past). This overestimation is most likely due to the poor water clarity in the MSC preventing light penetration and inhibiting algal growth in the ‘real world’. However, it does show the potential that exists for primary productivity to increase should water clarity improve, given the high levels of phosphorus available to fuel algal growth. This is supported by the data from Salford Quays following isolation. Here, water clarity improved after the Quays were separated from the MSC and chlorophyll concentrations reached over 800 µg/l.
2.5.1.2 Orthophosphate
Orthophosphate concentrations as a proportion of TP have generally been very high within the MSC. In 2006 the mean annual orthophosphate concentration at APEM Site 104 was 0.331 mg/l, representing 73% of the TP (Figure A2.37). Thus the majority of phosphorus is present in the available orthophosphate from, necessary to fuel algal growth. The available orthophosphate is therefore not being utilised by algal growth and, as discussed earlier, limited light penetration inhibits algal growth in the MSC resulting in the low level of orthophosphate uptake by algae.
During periods of algal blooms, orthophosphate concentration may be extremely low, due to all of the available orthophosphate being utilized by algal activity. This highlights the importance of measuring the total phosphorus concentration to characterise the phosphorus in all available forms rather than just soluble reactive phosphorus alone. Currently the majority of total phosphorus data available in the MSC is above Mode Wheel Locks.
4 Analysis of samples for Orthophosphate, Nitrate and Nitrite ceased at APEM Site 1 in 2000, although measurements have continued at APEM Site 10 on a quarterly basis and a monthly basis since 2002. 36
Final Report – September 2007 APEM Scientific Report 410039
100
80
60
40
20 Amount of TotalPhosphorus Orthophosphate as (%) % of TP as Orthop
0 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Figure A2.37 Percentage of Total Phosphorus as Orthophosphate in the MSC at APEM Site 10
2.5.1.3 Nitrate
The mean surface concentration of nitrate at Site 10 in 2006 was 4104 μg/l. Concentrations are far in excess of those seen in Salford Quays where concentrations in 2006 ranged from 60 μg/l to 810 μg/l. It is thought that improved water quality conditions and the successful growth of macrophytes within the isolated basins have utilised much of the nitrate and are a useful resource for ‘mopping up’ excess nutrients that would otherwise be potentially available for algal development. In contrast the MSC continues to receive a supply of nitrate from upstream, as well as that arising from the bacteriological oxidisation of ammonia. As can be seen in Figure A2.38 nitrate levels fluctuate quite dramatically between sampling occasions. There doesn’t appear to be any declining or increasing trends since data records began in 1987 and levels have remained high. In combination with available phosphorus, there is therefore a plentiful supply of nutrients to fuel algal growth.
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Final Report – September 2007 APEM Scientific Report 410039
18000
16000
14000
12000 g/l_N) μ 10000
8000
6000 Surface nitrate (
4000
2000
0
Figure A2.38 Surface water nitrate concentration recorded in the MSC (site 10)
2.5.1.4 Nitrite
Nitrite occurs naturally in freshwaters and exists as part of nitrogen cycling from ammonium, to the more oxidised form nitrate. Nitrosomonas sp. bacteria play an important role in this, as they oxidize ammonia to nitrite. Then, as part of the cycle, Nitrobacter bacteria, convert nitrite to nitrate. Importantly, this bacterial oxidiation of ammonia strips oxygen from the water column, adding to the DO problem caused by BOD. However, under certain conditions nitrite concentrations can build up. This is caused by environmental conditions such as low DO differentially affecting the latter bacteria (Nitrobacter) and preventing conversion of nitrite to nitrate before Nitrosomonas sp. is affected. As a consequence, nitrite concentrations routinely exceed the FFD guideline value of <0.03mg/l (30μg/l) for designated cyprinid waters. In fact the mean annual concentration of nitrite at Site 105 in 2006 was 227 μg/l. These grossly exceed the limit stipulated within the EC Fisheries Directive for cyprinid fish (30 μg/l), although it must be stated that there is an abundance of fish in the MSC.
Nitrite is toxic to fish because it is actively transported across the gills and readily oxidizes haemoglobin to form methaemoglobin. Methaemoglobin is unable to transport oxygen in the blood and hence can result in hypoxia severe enough to cause death. However, nitrite toxicity is dependent on the rate at which the fish can convert methaemoglobin back to haemoglobin and the presence of several other water quality parameters including the concentration of chloride ions, pH, nitrate and phosphate. Toxic levels of nitrite have been reported as ranging from 0.19 mg/l to 190 mg/l depending on the species and concentration of other water quality parameters.
5 Analysis of samples for Orthophosphate, Nitrate and Nitrite ceased at APEM Site 1 in 2000, although measurements have continued at APEM Site 10 on a quarterly basis and a monthly basis since 2002. 38
Final Report – September 2007 APEM Scientific Report 410039
Chloride ions compete with nitrite ions at the gills, if the chloride concentrations are high enough then they prevent the transport of nitrite across the gills. Although not available in the Turning Basin, data for chloride ions is available below Mode Wheel Locks. The annual average concentration of chloride ions here was 158 mg/l (Figure A2.39), an order of magnitude larger than the nitrite concentrations. This suggests the high chloride concentrations may be contributing to the survival of fish populations within the MSC.
450
400
350
300
250
200 Chloride ions (mg/l)
150
100
50
0 Apr 01 Apr 02 Apr 03 Apr 04 Apr 05 Apr 06 Oct 00 Oct 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Jun 00 Jun 01 Jun 02 Jun 03 Jun 04 Jun 05 Jun 06 Feb 01 Feb 02 Feb 03 Feb 04 Feb 05 Feb 06 Aug 00 Aug 01 Aug 02 Aug 03 Aug 04 Aug 05 Aug 06 Dec 00 Dec 01 Dec 02 Dec 03 Dec 04 Dec 05 Figure A2.39. Chloride concentrations recorded at the EA monitoring site below Mode Wheel lock.
2.5.2 Downstream of Mode Wheel Locks
2.5.2.1 Total phosphorus
No measurements of total phosphorus have been made at any of the EA sites downstream of Mode Wheel Locks.
2.5.2.2 Orthophosphate
At the sites under consideration downstream of Mode Wheel Locks, orthophosphate has been measured since 2000. In general orthophosphate levels ranged between 0.3 and 2mg/l, with peak values of 2.4mg/l in 2001 between Barton and Irlam locks and a minimum of 0.1mg/l in the same pound in 2002. In general, these figures are broadly similar to the levels observed upstream of Mode Wheel Locks and there is therefore little spatial variability within the upper MSC. However, in the Mode Wheel to Barton Locks pound, the upstream site (MSC below Mode Wheel locks SPT: 88020292) has consistently higher orthophosphate concentrations than the downstream site. Because corresponding total phosphorus data are not available downstream of Mode Wheel
39
Final Report – September 2007 APEM Scientific Report 410039
Locks, it is difficult to ascertain reasons for this. More phosphorous may be held within algal cells in the downstream site and therefore reflect greater algal activity, but without total phosphorus data it is not possible to be sure. For this reasons it difficult to draw conclusions about any temporal or spatial trends down stream of Mode Wheel locks. However, the data available in each pound shows high orthophosphate concentrations, and demonstrate that the MSC is a nutrient rich water body with the potential for extensive algal growth.
2.5 MSC below Mode Wheel locks (SPT: 88020292) MSC u/s of Barton locks (SPT: 88020291) 2.0
1.5
1.0 Orthophosphate (mg/l) Orthophosphate
0.5
0.0 2000 2001 2002 2003 2004 2005 2006
Figure A2.40. Mean annual orthophosphate concentrations between Mode Wheel and Barton Locks. Bars indicate minimum and maximum values recorded each year.
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Final Report – September 2007 APEM Scientific Report 410039
2.5 MSC u/s of Ir lam loc ks ( SPT: 88020293)
2.0
1.5
1.0 Orthophosphate (mg/l) Orthophosphate
0.5
0.0 2000 2001 2002 2003 2004 2005 2006
Figure A2.41. Mean annual orthophosphate concentrations between Barton and Irlam Locks. Bars indicate minimum and maximum values recorded each year.
2.5 MSC d/s Irlam locks (SPT: 88020294)
MSC u/s Lanster (SPT: 88020295)
2.0
1.5
1.0 Orthophosphate (mg/l) Orthophosphate
0.5
0.0 2000 2001 2002 2003 2004 2005 2006
Figure A2.42. Mean annual orthophosphate concentrations between Irlam Locks and Latchford locks. Bars indicate minimum and maximum values recorded each year.
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2.5.2.3 Nitrate
Nitrate concentrations below Mode Wheel Locks have displayed a reasonably consistent trend over time (Figure A2.43, Figure A2.44 and Figure A2.45). There does not appear to be any declining trend in nitrate concentration since 2000 and in fact mean nitrate in 2005 an 2006 was higher than previous years in both the Barton to Irlam and Irlam to Latchford pounds. 2007’s data will reveal if these years represent a temporary rise in nitrate levels, or if a more sustained increasing trend is occurring.
Overall the pound between Mode Wheel Locks and Barton Locks display lower nitrate concentrations than the other pounds, having a mean concentration of 3.6mg/l over the sampling period compared to 6.6mg/l in the Barton to Irlam pound and 6.1mg/l in the Irlam to Latchford pound. Within the lower pound the upstream site below Irlam Locks (SPT 88020294) has consistently higher nitrate concentrations than the downstream site at Lanster (SPT 88020295). This is most likely due to close proximity of the upstream site to the WwTW at Irlam. MSC below Mode Wheel 16 locks (SPT: 88020292) MSC u/s of Barton locks 14 (SPT: 88020291)
12
10
8
Nitrate (mg/l) 6
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.43. Mean annual nitrate concentrations between Mode Wheel and Barton Locks. Bars indicate minimum and maximum values recorded each year.
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16 MSC u/s of Ir lam loc ks ( SPT: 88020293)
14
12
10
8 Nitrate (mg/l) Nitrate 6
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.44. Mean annual nitrate concentrations between Barton and Irlam Locks. Bars indicate minimum and maximum values recorded each year.
16 MSC d/s Irlam locks (SPT: 88020294)
14 MSC u/s Lanster (SPT: 88020295)
12
10
8
Nitrate (mg/l) 6
4
2
0 2000 2001 2002 2003 2004 2005 2006
Figure A2.45. Mean annual nitrate concentrations between Irlam Locks and Latchford locks. Bars indicate minimum and maximum values recorded each year. 43
Final Report – September 2007 APEM Scientific Report 410039
2.5.2.4 Nitrite
As was the case for upstream of Mode Wheel Locks, all three pounds below Mode Wheel grossly exceed the EC FFD guideline level for cyprinid fish (≤0.03mg/l). Such levels of nitrite reflect the heavy organic pollution in the MSC.
Nitrite concentrations were similar in all three pounds below Mode Wheel Locks (mean since 2000 of 0.21mg/l Mode Wheel to Barton; 0.21 mg/l Barton to Irlam; 0.25 mg/l Irlam to Latchford). These were similar to the mean value above Mode Wheel Locks of 0.24mg/l for the same period.
MSC below Mode Wheel 3.0 locks (SPT: 88020292)
MSC u/s of Barton locks 2.5 (SPT: 88020291)
Required for EC FFD 2.0 guideline level for cyprinid fish
1.5 Nitrite (mg/l) Nitrite 1.0
0.5
0.0 2000 2001 2002 2003 2004 2005 2006
Figure A2.46. Mean annual nitrite concentrations between Mode Wheel and Barton Locks. Bars indicate minimum and maximum values recorded each year.
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3.0 MSC u/s of Irlam locks (SPT: 88020293)
2.5 Required for EC FFD guideline level for cyprinid fish 2.0
1.5 Nitrite (mg/l) Nitrite 1.0
0.5
0.0 2000 2001 2002 2003 2004 2005 2006
Figure A2.47. Mean annual nitrite concentrations between Barton and Irlam Locks. Bars indicate minimum and maximum values recorded each year.
3.0 MSC d/s Irlam locks (SPT: 88020294)
MSC u/s Lanstar (SPT: 88020295)
2.5 Required for EC FFD guideline level for cyprinid fish
2.0
1.5 Nitrite (mg/l) 1.0
0.5
0.0 2000 2001 2002 2003 2004 2005 2006
Figure A2.48. Mean annual nitrite concentrations between Irlam Locks and Latchford locks. Bars indicate minimum and maximum values recorded each year.
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2.6 Dissolved copper
Copper is a naturally occurring element that, although not toxic to humans, is toxic to fish. The toxicity of copper to fish varies with the hardness (mg/l CaCO3) of the water, therefore the EC FFD has varying guideline levels for dissolved copper depending on the hardness of the water in question.
2.6.1 Upstream Mode Wheel Locks
Measurements of dissolved copper were taken at APEM Site 1 on 5th May 1987 at the surface, mid-depth and bottom. Concentrations were 23.5, 22 and 10 μg/l respectively. A similar survey was undertaken on 12th July 1988 and the reverse was seen with the highest concentrations of copper in the bottom rather than surface waters (10, 10 and 16 μg/l from the surface, mid-depth and bottom respectively). All concentrations were lower than the guideline level of 40 μg/l required by the EC FFD.
2.6.2 Downstream of Mode Wheel Locks
The only measurements of dissolved copper downstream of Mode Wheel Locks have been recorded at the EA site Manchester Ship Canal at Barton locks on a series of dates in 1978 and then on one occasion each year during 1985, 1987 and 1988. The highest value of 50 μg/l was recorded on 21st June 1978. The MSC tends to have a hardness of between 100 to 300 mg/l and the FFD guideline levels for these hardnesses are 40 μg/l and 112 μg/l respectively. The concentration of copper recorded in 1978 was lower than the upper guideline but slightly exceeded the lower guideline set by the Freshwater Fish Directive. Unfortunately more recent data are not available.
2.7 Total zinc
Zinc occurs within waterways due to both industrial discharge and domestic sources via the WwTW. As with copper, the toxicity of zinc to fish is dependent upon hardness and, as such, the EC FFD stipulates a range of mandatory levels depending on the hardness of the water.
2.7.1 Upstream Mode Wheel Locks
Measurements of total zinc were carried out on the same sampling occasions as the dissolved copper surveys. Concentrations in surface, mid-depth and bottom samples in 1987 were 36, 37.5 and 35 μg/l respectively. Concentrations were lower during the second survey with measurements of 16.5, 24.5 and 25 μg/l being recorded. The guideline standard for total zinc is 40 μg/l, therefore all these measurements complied with the FFD.
2.7.2 Downstream of Mode Wheel Lock
The only monitoring of total zinc within the MSC downstream of Mode Wheel Locks has been carried out at the site at Barton locks. Surveys were undertaken on the same dates as dissolved copper monitoring and a maximum value of 150 μg/l was recorded 46
Final Report – September 2007 APEM Scientific Report 410039 on 23rd June 1978. More recently the river team monitoring at Irlam Locks has been used for monitoring total zinc. The mean annual concentration in 2006 was 24.4 μg/l which is less than the FFD guideline of 1,000 μg/l.
2.8 pH
The pH of water is a measure of its acidity or alkalinity, which relates to the amount of soluble carbon dioxide in the water. During the day, photosynthesising algae and macrophytes utilise carbon dioxide in the water, altering the carbon dioxide-hydrogen carbonate balance, and subsequently increasing the pH. During the night, the main biological activity is respiration, which produces carbon dioxide and causes a subsequent decrease in pH.
Measurements of pH have been taken at all sites on an approximately monthly basis. No marked change in the pH has been noted over the last twenty years at APEM Site 1 (Figure A2.49). Values have remained within the range of 6 to 9 required by the EC FFD (78/659/EEC) for cyprinid fisheries. However, it is interesting to compare data for the adjacent water in Salford Quays. Although the Quays’ enclosed basins are isolated from the MSC and hence receive no sewage derived organic load, in other respects the chemical constituents of the water, the ionic composition, buffering capacity, etc. are similar. Hence examining pH data from the Quays provides a reasonable indication of what might be anticipated in the MSC in the event of the predicted increase in algal activity, once water clarity improves as suspended loads decrease (see Section 2.4 Suspended solids and transparency).
10
9
8
7
6
5 pH
4 APEM Site 1 3 Upper limit required for EC FFD 2 guideline level for cyprind fish
1 Lower limit required for EC FFD guideline level for cyprind fish 0
6 0 5 01 987 993 997 999 003 1985 198 1 1988 1989 199 1991 1992 1 1994 1995 1996 1 1998 1 2000 20 2002 2 2004 200 2006
Figure A2.49. pH in the MSC above Mode Wheel Locks at APEM Site 1
Figure A2.50 reveals marked increases in pH in the Quays during the construction phase of the isolation bunds (Jan 1986 – June 1987). The bunds were lined with a concrete filled membrane. The elevated pH was not caused by photosynthetic activity but was the result of the construction works. Cement has an extremely high alkalinity, 47
Final Report – September 2007 APEM Scientific Report 410039 which can force the pH to rise in waters in contact with the cement. Such effects are most prevalent as the concrete cures over the 2-3 months following pouring. The high pH levels found also resulted in low water column phosphate levels (below limits of detection) as the phosphates precipitated out of solution as calcium phosphate.
12.00
pH S pH B Impoundment 11.00 Helixors
10.00
9.00
8.00
7.00
6.00 1-Jul-84 1-Jul-85 1-Jul-86 1-Jul-87 1-Jul-88 1-Jul-89 1-Jul-90 1-Jul-91 1-Jul-92 1-Jul-93 1-Jul-94 1-Jul-95 1-Jul-96 1-Jul-97 1-Jul-98 1-Jul-99 1-Jul-00 1-Jul-01 1-Jan-84 1-Jan-85 1-Jan-86 1-Jan-87 1-Jan-88 1-Jan-89 1-Jan-90 1-Jan-91 1-Jan-92 1-Jan-93 1-Jan-94 1-Jan-95 1-Jan-96 1-Jan-97 1-Jan-98 1-Jan-99 1-Jan-00 1-Jan-01 1-Jan-02
Figure A2.50. pH at site 3 (Salford Quays St Francis Basin) since impoundment
The sites upstream of Mode Wheel do not appear to have shown elevated pH (Figure A2.49) during this time. However, the site upstream of Barton Locks had two measurements in excess of pH 12 in April 2002 (from EA data). It is possible that these high pH measurements were associated with spring algal blooms removing carbon dioxide during photosynthesis and altering the carboxyl cycle. As discussed later these high pH values occur only occasionally but are particularly problematic for fish since they encourage the dissociation of ammonia into the un-ionised form which is highly toxic to fish.
2.9 Conductivity
Conductivity is often considered an indicator of gross pollution in rivers and can be described fundamentally as an expression of the water’s ability to conduct an electric current. This property is related to the ionic content of the sample, which is in turn a function of the dissolved (ionisable) solids concentration.
The conductivity of water in the MSC upstream of Mode Wheel Lock (APEM Site 1) has remained largely similar over the years and has ranged between 131 and 1000 μS/cm (Figure A2.51). It is highly variable, which can be mostly attributable to rainfall causing either dilution or the washing in of pollutants. Effluents from sewage treatment works as well as weather conditions can also influence water conductivity. 48
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Brief rainfall can have a diluting effect (reducing conductivity) while prolonged rainfall can increase conductivity since storm sewage overflows discharge into rivers feeding the MSC. Furthermore, rainfall following winter road gritting can cause chloride ion rich runoff water, which would subsequently increase conductivity in the waterbody. Elevated conductivity could also occur due to anoxic bottom waters causing metal and nutrient release from sediments during dry summer months.
Monitoring at sites downstream of Mode Wheel Locks commenced in June 20006. Similar conductivities were measured within all pounds, ranging from 222 to 928μS/cm. The mean conductivities were 513μS/cm in the Mode Wheel to Barton pound, 600μS/cm in the Barton to Irlam pound and 559μS/cm in the Irlam to Latchford pound. These concentrations are therefore similar to that observed upstream of Mode Wheel Lock, where the mean conductivity was 506μS/cm (from 2000-2006).
1000 APEM Site 1 900
800
700
600
500
400
Conductivity S(uS/cm) Conductivity 300
200
100
0
7 5 8 6 8 9 9 0 9 9 9 0 1985 1986 1 1988 1989 1990 1991 1992 1993 1994 1 1996 1997 1 1999 2000 2001 2002 2003 2004 2005 2
Figure A2.51. Conductivity at the surface in the MSC above Mode Wheel Locks at APEM Site 1.
2.10 Total residual chlorine
No measurements of total residual chlorine are known to have been taken previously within the MSC at either APEM or EA monitoring sites.
6 EA conductivity was reported at 25oC from June 2000 January 2003 and at 20oC from February 2003 onwards. 49
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2.11 Bacteriology
2.11.1 Upstream Mode Wheel Locks
The EC Bathing Waters Directive (76/160/EEC) was implemented in 1976 and became one of the first pieces of European environmental legislation. In order to provide management data for water sports activity for Salford City Council, APEM has been monitoring bacteriology at Salford Quays since 1993. The Quays have shown a considerable improvement in bacteriology since isolation from the MSC. Isolation of these dock basins from the MSC has prevented the ingress of sewage effluent and standards have now reached such a high level that an application is in progress to designate the Quays as a Bathing Water under the Directive.
Monitoring of bacteriology in the MSC is undertaken by APEM at monitoring Site 10 on a fortnightly basis. Samples are collected for the determination of cell counts for faecal and total coliforms. The total coliform cell counts have repeatedly exceeded the mandatory standard for the EC Bathing Waters Directive (10,000 cells/100ml) and on the majority of sampling occasions values have exceeded the limit of detection (20,000 cells/100ml). Faecal coliform cell counts in the MSC were also usually in excess of the mandatory levels (2,000 cells/100ml) stipulated by the directive.
Total coliform values 400,000 greater than upper limit of detection 350,000 (20,000 cells/100ml)
300,000 Total coliforms Faecal coliforms
250,000
200,000
150,000
100,000
EC mandatory levels Total and faecal coliforms (counts/100ml) 50,000
0 05-Jul-99 24-Jul-00 01-Jul-02 28-Jul-03 15-Jul-96 28-Apr-93 25-Oct-93 02-Oct-06 07-Apr-98 19-Jan-00 29-Jan-01 16-Jan-02 19-Jan-04 26-Jun-95 02-Jan-96 27-Mar-06 03-Feb-03 28-Feb-05 19-Feb-97 30-Nov-94 13-Aug-01 02-Aug-04 12-Sep-05 15-Sep-97 15-Dec-98 12-May-94 Figure A2.52 Total and faecal cell counts upstream of Mode Wheel Locks at APEM site 10.
In addition to microbiological parameters, there are also other measures made in the MSC and Salford Quays to coply with provisions within the EC Bathing Waters Directive covering physicochemical parameters, pesticides and heavy metals. Biannual sampling in the quays includes a site at APEM Site 10 in the MSC for analysis of phenols, pesticides and heavy metals (including arsenic, mercury,
50
Final Report – September 2007 APEM Scientific Report 410039 cadmium, chromium and lead) was undertaken in January and July 2006. Most of the extensive list of parameters tested for were measured below the limits of detection.
2.11.2 Downstream of Mode Wheel Locks
No monitoring of microbiology is known to have been undertaken at any of the EA monitoring sites in the pounds downstream of Mode Wheel Locks.
2.12 Influence of sediment on water quality
The interaction between bottom sediments and overlying water is particularly important in assessing water quality in the MSC. Inputs from industry and WwTWs since the industrial period combined with the slow flowing nature of the MSC has led to the settling out and accumulation of polluted organic-rich sediments throughout the upper MSC. The high organic content of the sediments is thought to contribute to water-column anoxia, sediment rafting, noxious gas generation and metal mobilisation (White et al., 1993; Boult & Hendry, 1995) as well as providing a continual source of nutrients for algal growth.
Sediment rafting and noxious gas generation was a major problem for the MSC in the late 1980s and investigated by APEM in a 1989-1990 study (Webb 1993). At that time around 0.5m of sewage derived organic sediments were thought to be deposited in the Turning Basin each year over the winter period. As the water warmed up in spring, microbial and fungal fibres grew through the sediment layer binding it together. Due to the highly labile, organic nature of the sediments microbial activity generated gases (predominantly methane but also nitrogen and on occasion hydrogen sulphide). These gases would accumulate within the cohesive sediment layer, making it buoyant, eventually causing it to slough off and erupt at the water’s surface. During the late 1980s, sediment rafts were so prolific that on occasion they could cover the entire surface of the 70 acre Turning Basin giving the impression of solid ground. During one week alone, three dogs were reported as having drowned after jumping onto the raft’s surface assuming it was solid.
One of the key recommendations from the 1989/90 study (Webb 1993) was that oxygen injection alone would not prevent the eruption of sediment rafts, as it was unlikely that oxygen enriched water would be able to penetrate the 0.5m deep sewage derived sediment layer. Hence as part of the solution identified, dredging was promoted in conjunction with oxygen injection. However, as the 1990s progressed the eruption of sediment rafts became less and less common, ceasing altogether by the late 1990s. Hence dredging was no longer required as part of the solution to aesthetic water quality amelioration in the Turning Basin and oxygen injection alone was progressed as the means to reduce excessive bubbling and foul odours. Nevertheless as part of these studies various investigations into sediment quality were undertaken.
In terms of metals, the input from industrial pollutants including copper, zinc, chromium, lead and cadmium, have led to severe contamination (NWW 1987b) within the sediments of the MSC. This has been a long term issue in the MSC, although some improvements have been observed. In the late 1980s the reduction of
51
Final Report – September 2007 APEM Scientific Report 410039 metal contamination within the closed basins of the Quays compared with the MSC was recorded and attributed to the associated reduction of inputs due to isolation.
Metal contamination presents significant problems, because under conditions of severe anoxia that regularly occur in the water column of the Ship Canal, leaching of metals into the overlying water is likely to occur and may have implications for overall water quality as well as biota in the Canal. This presents a potential problem for aquatic biota through direct toxicity and bioaccumulation of heavy metals. This was initially discussed in APEM (1989b) in relation to the effects upon zooplankton and several species of stocked fish within Salford Quays. The investigation found that zooplankton and chironomid larvae may have bioaccumulated zinc and lead which was subsequently bioaccumulated by stickleback (which graze on zooplankton and chironomids). However, metal contamination was not found to be a cause for concern for the majority of fish species, as stocked fish thrived in the Quays. The only other potential fishery problem highlighted by this investigation was that bream were found to have undergone stress in the Quays causing a high mortality rate. However, subsequent investigations found that this problem was short lived and the Quays now support a healthy population of bream. More recent investigations in the MSC above Mode Wheel Locks found bioaccumulation of heavy metals to be a problem for invertebrate species (Bassett 2005) and clearly still raises concern for ecology. However, it should be stressed that leached contaminants do not appear to be restricting ecological recovery where oxygenation is taking place. This suggests that if an oxidised surface sediment layer is maintained then contamination is effectively ‘locked away’ from the overlying water and ceases to be available to the biota.
While metal leaching represents a potentially severe issue for the MSC’s water quality under poor oxygen conditions, a potentially far greater impact upon the overall ecology of the Canal comes from the sediment demand for oxygen. The severely organically enriched sediment of the upper MSC can exert a huge sediment oxygen demand (SOD) on the overlying water, stripping it of oxygen. SOD in the MSC is known to be spatially variable and will change according to sediment mobilisation during high flows and dredging activities, but peak values of SOD have been recorded at over 1000mg/m2/hr (HR Wallingford 1999, APEM R&D). This value is far in excess of what would be expected in un-impacted sites and is representative of heavily organically polluted sediments. Such high SOD levels become particularly problematic when combined with high water column BOD levels and further exacerbated during hot, still conditions. With little flow through the locks and minimal aeration from wind driven mixing, anoxic conditions can occur throughout the water column.
In the Manchester Ship Canal, sediment oxygen demand (SOD) has, in general, followed a trend of reduction since 1989 (APEM, 1999; APEM, 2000) upstream of Mode Wheel Locks. This trend may be related to remediation via oxygenation equipment aiming to increase the dissolved oxygen concentration in the water column (Teesdale, 2002). However, extremely high peak values of SOD are still known to occur within the MSC and are clearly continuing to contribute significantly to the overall oxygen demand of the Canal.
In addition to the oxygen stripping potential of the sediment during static conditions near to the bed, the sediment also has the potential to become extremely problematic 52
Final Report – September 2007 APEM Scientific Report 410039 when agitated and resuspended in the water column, caused either by high flows or dredging activities. Under such conditions the resuspended sediment can significantly elevate the BOD of water by introducing an increased proportion of organically rich material to the water. This redistribution of material during high flow and dredging activities is discussed in APEM (1991) and has resulted in the bottom sediment being well mixed and unstratified. As a result the SOD and metal contaminants are homogenous throughout the sediment’s depth.
The potential for organically enriched and polluted sediments to cause water quality problems is therefore evident. Effectively dealing with such problems can be difficult, but proved successful in the isolated basins of Salford Quays. Salford Quays has undergone 20 years of remediation focused on the water column, but which has impacted on the physical and chemical nature of sedimentation (see Taylor et al., 2003 for further explanation of the processes occurring during remediation). As a result of this remediation, water quality and subsequently sedimentology and biology in Salford Quays have markedly improved over recent years (White et al., 1993; Boult & Rebbeck, 1999; APEM 2006).
In Salford Quays, cores taken from the sediment displayed a vertical grading in concentrations of sulphate, nitrate, ammonium, iron, manganese and silicon (Taylor et al., 2003). Metal concentrations displayed a significant variability down the sediment column with the sediment layers from 10 – 15 cm below the sediment-water-interface exhibiting markedly higher metal concentrations than in the upper layers. This pattern has also been observed in relation to petrography and mineralogy, where the sediment displayed unusually large amounts of authigenic minerals and detrital grain assemblage in the same depth range. This sediment layer therefore represents heavily anthropogenically impacted sediment. However, the topmost layers, representing sediment deposited since isolation in the late 1980s (1 cm year-1), corroborate water column quality improvements since that time (Taylor et al., 2003). This is also reflected in much reduced detrital mineral concentrations and abundant siliceous algal remains. Presently, sedimentation takes places at a rate of about 20 g m-2 day-1 averaged over the year and mainly at the end of the summer (September; algal die off) (Taylor et al., 2003). Algal populations increased following isolation (Bellinger et al., 1993), which would have subsequently affected sedimentation processes in the Quays.
In addition to the benefit of isolation, the Quays have had the continued benefit of an artificial mixing system (Helixors) since 1987 that have help oxidise the surface sediments and lock away much of the polluted material. Clearly isolation is not an option for the upper MSC and it is not known what effect the oxygen injection system (upstream of Mode Wheel Locks) will have on SOD over the long term. It is debatable weather any significant reduction will be apparent due to the continual ‘rain’ of organic material and the anoxic nature of the interstitial waters within the sediment itself.
2.13 Fish Kill in May 2006
A fish kill event was reported in the MSC on the 15th May 2006. Between Mode Wheel and Barton Locks approximately 1,500 dead fish were recovered, although it is likely that many more were killed. Measurements of DO upstream of Mode Wheel on 53
Final Report – September 2007 APEM Scientific Report 410039 this day ranged from 5.5 mg/l at Trafford Road bridge, 2.61 mg/l immediately upstream of Mode Wheel locks and down to 0.48 mg/l at North Bay (adjacent to Huron Basin between APEM Site 10 and Mode Wheel locks). Additional measurements of dissolved oxygen were taken in the pound between Mode Wheel and Barton locks in response to the fish kill. A repeat survey was undertaken throughout the length of the Mode Wheel to Barton pound on 9th June and 7th July 2006, approximately one and two months respectively after the fish kill event. During the first survey a clear increase in surface water oxygen saturation and a corresponding decrease in bottom water oxygen concentration was apparent downstream of monitoring Site 12 (Figure A2.54 and Figure A2.55). The data from 9th June reveal relatively stable oxygen concentrations in the bottom water, around 5 mg/l, which towards the downstream end of the pound begins to decrease, approaching 2-3 mg/l. However, at approximately the same point in the pound, surface oxygen concentrations begin to increase, reaching over 20 mg/l. At 13°C this represents oxygen supersaturation of around 190%. This level of supersaturation can only occur naturally as a by-product of algal photosynthesis. A considerable algal bloom must have been present to achieve this level of supersaturation. At high biomass, algal respiration and hence oxygen demand at night is likely to cause a severe oxygen sag, potentially resulting in complete anoxia. Oxygen sags of this magnitude have detrimental effects on the aquatic ecology and can be fatal for fish.
However, data from the EA continuous monitoring sondes (Figure A2.27) shows that around the time of the fish kill, day time dissolved oxygen concentrations day were not considerably higher than those at night. If a large algal bloom had been present at the time of the fish kill then day time dissolved oxygen levels would have been massively elevated.
400 25 DO (%) satn. Temperature 350 Spot samples 20 300
250 15 C) o
200
10 Temperature ( 150 Fish kill reported between Mode Wheel and Barton Locks Dissolved oxygen % saturation
100 5
50
0 0 08 Apr 18 Apr 28 Apr 07 Jun 17 Jun 27 Jun 29 Mar 08 May 18 May 28 May Figure A2.53. Dissolved oxygen (%) and temperature measurements from the continuous monitoring sonde located upstream of Barton Locks (SPT 88020291).
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Title: MSC Water Quality Monitoring Sites (Manchester to Irlam) Version: 1.03 Date produced: 12/03/2007 Legend (! fish kill sites1
WY Direct WwTW input ! EA Marine team monitoring sites
11 10 9 W (! (! 8 o 12 (! r s (! 7 l (! e
y (! 6 13 B
r (! o (! 5
o M a k WY (! nc 14 he (! st 4 er (! S h (! ip 15 3 C an (! 2(! al 1 ! (! 16 k (! roo e B ltey Sa Mode Wheel Locks B ri dg WY ew a te 17 r C an (!! al
WY Barton Locks ±
0310 620 1,240 Meters
Figure A2.54 Map of monitoring sites for repeat survey on 9th June and 7th July 2006, after fish kill event on 15th May.
25
Surface dissolved oxygen (mg/l) Bottom water dissolved oxygen (mg/l)
20
15
10 Dissolved oxygen (mg/l)
5
0 1234567891011121314151617
Figure A2.55. Surface and bottom water DO (mg/l) between Mode Wheel and Barton Locks on 9th June 2006 following the fish kill on 15th May 2006.
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3 RIVER INPUTS
The review of water quality data has shown that the Manchester Ship Canal (MSC) fails to comply with the EC Freshwater Fish Directive (EC FFD 78/659/EEC) standards for ammonia and biological oxygen demand (BOD). The Canal’s feeder rivers contribute both direct inputs (e.g. treated sewage effluent and storm sewage discharges) to the MSC as well as resuspension of organic rich sediment (Rees and White, 1993). In order to understand the compliance failure of the MSC it is useful to examine the mass flux entering the MSC from these feeder rivers.
Three rivers combine at the upstream limit of the canal. These are the Irwell, Irk and Medlock. All three rivers drain heavily urbanised catchments in the Greater Manchester area. Two other major rivers enter the MSC further downstream; these are the Mersey and the Bollin. The combined flow received by the MSC in 2006 from these large riverine inputs was 1,209,713 Ml (Table A3.1). The percentage contribution of each river to the annual flow in the MSC is also shown.
Table A3.1.Gross annual input of flow from the five major rivers entering the MSC in 2006. River Total flow (Ml) Contribution to total river input (%) Irwell 514,857 42.6 Irk 71,793 5.9 Medlock 19,071 1.6 Mersey 423,744 35.0 Bollin 180,249 14.9 Total river input 1,209,713 100
The largest total flow enters the MSC in the upper reaches from the River Irwell. Hence, this river is likely to have the greatest significance on water quality in the upper MSC. In contrast the Irk and the Medlock are comparatively small rivers, contributing 5.9% (Irk) and just 1.6% (Medlock). Therefore the rivers would be expected to impact on water quality in the MSC to a lesser extent. All three catchments are heavily urbanised and therefore receive a large quantity of industrial and WwTW inputs. In fact, the Irwell drains a catchment area of 559 km2, approximately 26 % of which is urbanised. In comparison, 51 % of the Medlock catchment is urbanised, although, this only accounts for 29 km2 of the catchment. Further downstream the River Mersey contributed the second largest flow input of 423,744 Ml to the MSC in 2006. The Canal has increased in size by the time the Mersey enters it’s mid-reaches, as the MSC has received a number of addition flow inputs from minor tributaries, industrial and WwTW inputs. Some of these, such as the discharge from Daveyhulme WwTW, are major input flows, akin to a moderate river.
Mass Flux Calculation
A greater understanding of the relative contribution of these rivers to the ammonia, BOD and dissolved oxygen load are important to help identify the sources / causes of compliance failure. Previously an assessment of the mass flux identifying the individual river loads entering the MSC was undertaken as part of the earlier APEM review (1990a, 1990b). Although in the intervening years a number of changes to gauging stations and Environment Agency (EA) water quality sampling sites have 56
Final Report – September 2007 APEM Scientific Report 410039 occurred, these are sufficiently close to the original sites to allow comparison. The flow gauging station and water quality monitoring sites closest to the downstream limit of each feeder limit have been selected for the mass flux calculations. No significant major flow inputs are known to enter downstream of these sites, although it is acknowledged that some flow accretion is likely to occur. The sites used to calculate the mass flux are detailed in Table A3.2.
Table A3.2. Locations of EA flow gauging stations and routine river input monitoring sites used for mass flux calculations. EA Flow Gauging Station EA River Input Monitoring Site River Site Name EA Easting Northing Sample EA Ref. Easting Northing Ref. Point No. NGR NGR No. Irwell Adelphi 690511 382420 398740 River 88002348 382258 399020 Weir Irwell Foot Bridge at Salford University Irk Colleyhurst 690611 384850 399690 River Irk 88002380 384199 399171 Weir at Red Bank above Scotland Weir Medlock London 690713 384900 397520 River 88002413 385700 397750 Road Medlock at Pinmill Brow Mersey Ashton 692726 377230 393560 River 88002065 374213 393762 Weir Mersey at Flixton Road Bridge Bollin Dunham 693536 372670 387530 River 88002605 370250 388753 Massey Bollin Warburton Bridge Healey
The mass flux (load in kg per year) for each river was calculated using the ammonia, BOD or DO concentration and the mean flow on the date each sample was collected (Equation 1). In 2006 approximately twelve samples were analysed from each site to form the basis of the mass flux. The mean daily load was scaled to estimate the annual load.
Equation 1 Mass Flux = BOD or Ammonia or DO (mg/l) x Mean Flow (l/day)
It should be recognised that this approach provides an approximation based on the data available. Furthermore, it should be noted that the routine sampling of the MSC by the EA on an approximately monthly basis is likely to miss extreme high and low flow events. Episodic events may result in a deterioration in water quality due to
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Final Report – September 2007 APEM Scientific Report 410039 inputs from combined sewage overflows (CSO’s) as well as the release of pollutants from resuspended sediments (Rees and White, 1993).
River loads entering the MSC
Ammonia, BOD and DO annual loads entering the MSC from the five major river inputs were calculated for 2006. The River Irwell contributed the largest ammonia and dissolved oxygen load, whereas, the BOD load was greatest from the Mersey (Table A3.3).
Table A3.3. Ammonia, BOD and DO (concentration) load entering the Rivers Irwell, Irk, Medlock, Mersey and Bollin in 2006. Values are reported in kg/year.
River Ammonia BOD DO kg/year kg/year kg/year Irwell 797,567 1,472,502 5,609,374 Irk 23,680 210,434 530,714 Medlock 3,951 72,648 233,810 Mersey 480,770 2,202,510 4,466,893 Bollin 50,001 930,372 2,679,065 Total 1,355,970 4,888,466 13,519,856
The ammonia load is likely to be mainly derived from WwTW inputs, although a significant industrial discharge is known to be present in the Irwell (Magnesium Electron Ltd). The Irwell receives effluent from the Rossendale, Bury and Bolton WwTW, all of which are expected to receive investment during AMP4 to reduce ammonia output. On a positive note, despite this ammonia load, the annual DO load from the Irwell entering the MSC was higher than the other major river inputs. Similar improvements are scheduled for Stockport WwTW (on the Mersey) over the next few years. The River Mersey accounted for the highest annual BOD load of 2.2 million kg/year (45%) in 2006, which represents almost half the total riverine input of BOD to the MSC. The contributions from Rivers Irk and Medlock are relatively minor in comparison to the Irwell and Mersey, with the Irk contributing 1.7% ammonia and 4.3% BOD and the Medlock contributing 0.3% ammonia and 1.5% BOD. The River Bollin contributes 3.6% of ammonia and 19% of the total BOD entering the MSC. This BOD load is almost half that of the Mersey, which flows into the MSC 7km up stream of the Bollin. The oxygen input from the Bollin is also significant, representing almost 20% of the total input.
As mentioned above the mean daily load was calculated during the previous APEM review (1990a; 1990b) for the rivers Irwell, Irk and Medlock. The recent data from Table A3.3 have been converted to mean daily loads for comparison. This review was based on data gathered between 1983 and 1987 (Table A3.4). Over the twenty year period a considerable reduction in the ammonia load entering the MSC has been seen in all three rivers. A halving of the ammonia load has been observed in the River Irwell, whereas the mean daily load in the Medlock in 2006 was 5% of that measured between 1983 and 1987 (Table A3.4). These substantial decreases in ammonia load have resulted from considerable investment in WwTW by UU during the AMP process. It is expected that similar reductions will have been observed in the River Mersey and Bollin, although the calculations were not undertaken in the original 58
Final Report – September 2007 APEM Scientific Report 410039 review (APEM, 1990a; 1990b). Despite these improvements to the ammonia load, the MSC continues to fail the FFD standard and hence tighter consent conditions have been set by the EA. Since the largest ammonia load is received from the River Irwell, an improvement in ammonia load in this river would be expected to have the greatest effect on ammonia in the MSC.
Table A3.4.Contribution of the Rivers Irwell, Irk, Medlock, Mersey and Bollin to the mean daily load (kg/day) entering the MSC. Ammonia BOD DO River Previous Current % Previous Current % Previous Current % review 1 review2 Change review 1 review 2 Change review 1 review 2 Change Irwell 4,256 2,185 -48.7 10,488 4,034 -61.5 12,623 15,368 +21.7 Irk 443 65 -85.3 1,605 577 -64.0 1,460 1,454 -0.4 Medlock 247 11 -95.5 783 199 -74.6 494 641 +29.8 Mersey n/a 1,317 n/a n/a 6,034 n/a n/a 12,238 n/a Bollin n/a 137 n/a n/a 2,549 n/a n/a 7,340 n/a 1 Based on mean daily mass flux between 1983 and 1987 (APEM, 1990b) 2 Current study based on 2006 data n/a = Results were not available
The decrease in BOD load since the 1990 review (APEM, 1990a; 1990b) in all three feeder rivers indicates a substantial reduction in the organic matter entering them. The load entering the MSC from the Medlock in 2006 was about a quarter of that seen previously. As with the ammonia load, the BOD input from the Irwell has halved in recent years reflecting considerable investment in WwTW bringing about water quality improvements. However, despite this progress the MSC continues to fail the FFD for BOD. Somewhat surprisingly, given the lower ammonia load from the Mersey compared to the Irwell, the BOD load entering the MSC from Mersey is greater than that entering from the three rivers at the head of the canal combined.
Increases in DO in the MSC have been observed over a number of years (Section 2.3). Improvements to the DO are particularly important in the canalised MSC where anoxia in bottom waters results in the release of noxious odours, nutrients and metals from the sediments. DO in Irwell and Medlock have gradually improved, again as a result of tighter standards for effluent inputs from WwTW’s. However, the DO input from the Irk in 2006 was largely similar to that observed between 1983 and 1987 (APEM 1990a; 1990b).
The relative contribution of the Irwell, Irk and Medlock to the upper reaches of the MSC was assessed as part of the initial APEM water quality review (1990a; 1990b). Table A3.5 shows that some changes have occurred to the relative loads from the three rivers, not withstanding the overall reduction in mass flux identified earlier. The River Irwell contributes a substantial proportion of the flow to the upper reaches of the MSC (Table A3.1) and is thus responsible for a significant part of the ammonia, BOD and DO load. A halving of the River Irwell ammonia load has been observed over the last twenty years, which is of great significance since it is the dominant load entering the upper MSC. However, substantial improvements have also been observed in the Irk and Medlock and have resulted in a smaller proportion of ammonia entering from these rivers, resulting in a corresponding increase in the percentage of the ammonium load from the Irwell. The BOD and DO load entering the upper MSC has shown considerable improvement over the last few years. A substantial reduction in the BOD and a gradual increase in DO have been seen. The relative proportion of 59
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BOD and DO load entering the MSC from each river has remained largely unchanged.
Table A3.5. Percentage contribution of the Rivers Irwell, Irk and Medlock to the overall mean daily load entering the MSC. Ammonia BOD DO River Previous Current Previous Current Previous Current review 1 review2 review 1 review 2 review 1 review 2 Irwell 86 97 81 84 87 88 Irk 9 3 12 12 10 8 Medlock 5 <1 6 4 3 4 Total 100 100 100 100 100 100 1 Based on mean daily mass flux between 1983 and 1987 (APEM, 1990b) 2 Current study based on 2006 data
Conclusions
Overall, the Irwell contributes the largest riverine flow input to the MSC. The flow exceeds that from the Medlock and Irk in the upper reaches of the Canal and also that of the Mersey in the mid-reaches. This has resulted in the Irwell being of greatest significance in terms of the ammonia and DO load entering the MSC. Considerable improvements to water quality in the Irwell have contributed to substantial progress in MSC water quality. A halving in the ammonia load entering the MSC from the Irwell has resulted from considerable investment as part of the AMP process. Further improvements are scheduled to the WwTW on the Irwell, as well as the other rivers feeding into the MSC, as part of AMP4. Substantial reductions have been seen in the organic pollution inputs to the Irk and Medlock although these rivers, in mass flux terms, have comparatively little influence on the loads to the MSC by virtue of the relatively minor contribution to flow. The Mersey enters in the mid reaches of the MSC and contributes the second largest flow of all rivers in the system. However, the BOD load from the Mersey exceeds that entering from all the other rivers combined prior to the entry of the Bollin.
Marked improvements in the ammonia, BOD and DO load have been observed since the previous APEM water quality review (1990a, 1990b). These have largely occurred as a result of tighter standards being set by the regulator, resulting in investment to improve industrial, WwTW and storm sewage inputs in the area. Further investment is scheduled with the aim of reducing the current ammonia and BOD load. It remains to be seen whether the continued investment will result in further improvements to water quality in the MSC.
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4 REVIEW OF MSC BIOLOGICAL DATA
4.1 Historical macro-invertebrate data: MSC
Macro-invertebrates are important indicators of the ecological status within aquatic systems, with the presence or absence of certain species being a function of the biological condition in a given waterbody. Within the MSC invertebrates are typically collected using colonisers, left within the Canal for invertebrates to populate. In the laboratory the collected macro-invertebrates are sorted, identified to at least family level and enumerated. The BMWP (Biological Monitoring Working Party) score and ASPT (Average Score Per Taxon) is then calculated for each sample. The BMWP system has been the accepted index for assessing pollution stress in rivers using macro-invertebrates in the United Kingdom since the early 1980s. Although it will detect a wide range of aquatic stressors, the index is primarily based on organisms’ sensitivity to organic pollution.
Invertebrates are assigned a score from 1 – 10 according to their perceived tolerance/sensitivity to organic pollution; higher scores denoting less tolerance/greater sensitivity. The BMWP score is the sum of the values of the BMWP families recorded in a sample (the ASPT is a mean of these scores). The number of scoring taxa (NST) are also recorded and is simply the number of scoring families in a sample. BMWP scores can be in excess of 150 for pristine sites, and less than 10 for polluted sites. Occasionally, particularly poor sites have been known to score 0.
Data in the MSC have been collected by APEM in the Turning Basin, initially as a control site to compare improvements arising from the water quality improvements at Salford Quays and more recently to examine the ecological effects of the oxygenation scheme.
For many years the macro-invertebrate diversity of the upper MSC has been very low, characterised by four or five pollution tolerant species typical of poor water environments. These included worms (Oligochaeta), leeches (Erpobdella sp.), midge larvae (Chironomidae) and the water hog-louse (Asellus aquaticus). Whilst these species remain present, they are accompanied by an annually increasing number of species representative of cleaner water. Taxa now found include the caddis fly (Phryganea sp.), the freshwater shrimp (Crangonyx pseudogracilis), the river limpet (Ancylus fluviatilus) and flatworms (e.g. Dugesia sp. and Dendrocoelum lacteum). Particular increases in species diversity have been recorded during years when the oxygenation system has been in operation (Figure A4.1). In 2006, a total of 39 macro- invertebrate taxa were identified in the MSC.
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Number of Invertebrate Taxa in the Upper Manchester Ship Canal
45 Oxygenation
40
35
30 Oxygenation trials 25
20
Number of Taxa 15
10
5
0
1990-1991 1991-1992 1992-1993 1993-1994 1994-1995 1995-1996 1996-1997 1997-1998 1998-1999 1999-2000 2000-2001 2001-2002 2002-2003 2003-2004 2004-2005 2005-2006 Figure A4.1. Total number of macro-invertebrate taxa recorded in the MSC from 1990 to 2006.
Gradual changes in the invertebrate community composition are well illustrated by examining the switch in relative abundance of Asellus aquaticus and Crangonyx pseudogracilis (Figure A4.2). Although A. aquaticus continues to be the most abundant species within the MSC system, the total number of individuals recorded has generally decreased since 1998 (commencement of oxygenation trials). The reduction in Asellus and increase in Crangonyx in 2001 coincided with the oxygenation system commissioning and initial operational phase.
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10,000 250 Asellus aquaticus 9,000 Crangonyx pseudogracilis
8,000 200
7,000
6,000 150
5,000
4,000 100
3,000 Average Asellus numbers Average Crangonyx numbers 2,000 50
1,000
0 0 30-Apr-05 30-Apr-04 30-Apr-03 30-Apr-02 30-Apr-01 30-Apr-00 30-Apr-99 30-Apr-98 30-Aug-05 30-Aug-04 30-Aug-03 30-Aug-02 30-Aug-01 30-Aug-00 30-Aug-99 30-Aug-98 30-Dec-05 30-Dec-04 30-Dec-03 30-Dec-02 30-Dec-01 30-Dec-00 30-Dec-99 30-Dec-98 Figure A4.2. Average numbers of Asellus aquaticus and Crangonyx pseodogracilis in the MSC from 1998 to 2006
Macroinvertebrate data from the MSC also comes from a number of degree and masters theses (Fan, 1996; Litton, 1996; Govan, 2003 and Bassett, 2005). In 1996 Litton and Ming Fan both reported that the invertebrate community in the upper reaches of the MSC was composed of only pollution tolerant species i.e. Asellus sp., supporting the findings of Hendry et al. (1997).
After the installation of the oxygen units into the upper reaches of the MSC in 2001 Govan (2003) reported a noticeable increase in invertebrate diversity at some sites with a decrease in the abundance of the pollution tolerant species found previously.
In 2005 Bassett investigated the concentrations of manganese, zinc, copper and lead in the sediment and also the tissues of two genera of invertebrate (Asellus and Erpobdella) and gudgeon (Gobio gobio) from five sites on the upper reaches of the MSC and the lower reaches of the River Irwell. Bassett (2005) found that at Site 2, situated within the Turning Basin of MSC, higher concentrations of lead, zinc and copper were found within the sediment and invertebrates compared to the other sites.
The increase in macroinvertebrate species richness and change in community composition in the Turning Basin since 1998 is therefore clear, and can partly be attributed to artificial oxygenation. It would therefore be useful to examine what would have happened to the macroinvertebrate community, without the benefit of this oxygenation. Whilst data exists upstream of the oxygenation system these sites in the lower Irwell/Upper MSC are subject to improved oxygen conditions arising from WwTW improvements in the Irwell catchment. They do not represent true control as the physical habitat is more riverine in terms of velocities, without the tendency to stratify and stagnate as seen the MSC ‘proper’ and the Turning Basin. Hence data from Pomona Dock, upstream of the Turning Basin but without oxygen injection offers a better control to compare the improvements against. 63
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Such data comes from APEM’s surveys on behalf of the Mersey Basin Campaign (MBC)/ Healthy Waterways Trust (HWT). Sampling had been undertaken by APEM since 2001. Standard colonising units (SCUs) were used to sample the macro- invertebrate community within eight sites in the Turning Basin (oxygenated zone) and three upstream of the area of oxygenation (Figure A4.3). The upstream sites include the site at Pomona (Site 2), mentioned above and useful as a control to compare the influence of the oxygenation units against.
Figure A4.3. Approximate locations of the macro-invertebrate survey sites
At Pomona (Site 2), the data shows a generally improving trend in BMWP scores since 2002, as is the case for Sites 4, 5 and 8 within the oxygenated zone (Figure A4.4). In 2004 particularly high BMWP scores were recorded at Site 2, although this was attributed to cold conditions resulting in less oxygen stress on biota.
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45 1993 1994 40 2001 2002 35 2003 2004 30 2005 2006 25
20 BMWP score 15
10
5
0 12345678 Sites upstream oxygenation Sites within oxygenated region
Figure A4.4 Summer BMWP scores derived from Standard colonising unit data from 1993 to 2006 (N.B. discontinuous years)
It is clear that continual improvements are occurring even in the area upstream of artificial oxygenation, mirroring the long term improvements in BOD and ammonia (APEM, 2006). Nevertheless temporal intra-site differences (i.e. within individual sites over time) can sometimes be difficult to interpret and thus using averaged scores over the oxygenated zone may give a better illustration of the changes. It is apparent from these scores that artificial oxygenation has allowed improvements to occur. This is demonstrated in Figure A4.5, which shows an increasing BMWP score trend since 1993. In the control site, similar improvements have been made although at a slightly slower rate than the oxygenated region.
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40 Oxygenated region Site 2 (Control Site) Atypically high 35 BMWP score thought due to cold conditions 30
25
20
15 AverageScore BMWP
10 Oxygenation system shutdown 5
0 1993 1994 2001 2002 2003 2004 2005 2006
Figure A4.5. Average BMWP scores over time within the oxygenated region and at the comparison Site 2 upstream.
4.2 Historical macro-invertebrate data: A comparison between the MSC and Salford Quays
Along side the data collected in the MSC, data from the enclosed basins of Salford Quays can be used to observe the beneficial effect of removing the input of organic pollution upon invertebrates.
Historical data pertaining to macro-invertebrates available for comparison between the MSC and Salford Quays comes from two main sources: APEM and North West Water Authority (1988). The latter was responsible for monitoring prior to APEM’s sampling commencing in 1989. Table A4.1 gives the location of each of the sampling sites within the MSC and Salford Quays discussed in this section.
Table A4.1. Sampling sites within the MSC and Salford Quays Basin Sampling site Open or Date of APEM MSC (APEM) closed from separation sampling site MSC from MSC 9a Huron 8 Closed 1989 - 9b Erie 9 Closed 1989 - Central Bay 10 Open - After separation still part of the MSC 8 Ontario 6,7 Closed 1987 - 6 South Bay 1,2 Open 1987 Site 1. Site 2 no longer part of APEM monitoring. 7a St Francis 5 Closed 1987 - 7b St Louis 4 Closed 1987 - 7c St Peters 3 Closed 1987 -
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When sampling first commenced in Salford Quays in 1986 (between July and November; NWW, 1987a) the diversity and abundance of macro-invertebrates was poor at all sites. However, slightly better conditions were seen in the basins still open to the MSC at that time (Huron, Erie and South Bay). This was attributed to high pH levels in the closed basins caused by leaching from construction materials used during dam construction (see Section 2.8). Among the species found were red and green chironomid midge larvae (Sites 2, 5, 7, 8, 9), croxids-water boatmen (Sites 5, 7), ceratopogonid midge larva (Site 8), tubificid worms (Sites 2, 8, 9), asellus-water louse (Site 9), erpobdella-leech (Site 8), daphnia (Sites 5, 8), copepod (Site 1), Lymnaea peregra – snail (Site 7) and nematode worms (Site 1).
The differences observed between the open and closed basins between July and November 1986 became less pronounced between December 1986 and May 1987 but similar species were found (NWW, 1987b). Diversity and abundance were still very low with a high proportion of samples recording the absence of any macro- invertebrates. Chironomids were present in large numbers during this sampling period, which was a clear indication of an unstable biological community within the Quays at this time.
Towards the end of 1988 snails (Lymnaea) were becoming well established in the closed Basins 7 (St Francis, St Louis and St Peters) and 8 (Ontario) and various midge larvae (Chironomids and Certopogonids) were common throughout the system (North West Water Authority, 1988; NWW, 1989). Closure of Basin 9 (Huron and Erie) in 1989, reportedly resulted in an ‘explosion’ in the population of micro-crustaceans. However, the presence of Chironomids in high densities continued to suggest the biological community within the Quays was still unstable at this time.
For the first few years after implementation of the water management strategy in the enclosed basins at Salford Quays (1987, i.e. isolation and aeration), no significant improvements were seen in invertebrate species diversity and only nine species were found in the closed basins (Table A4.2) (Hendry et al., 1997). After two years there was no difference between the invertebrate fauna in the open and closed basins and both were still dominated by taxa characteristic of polluted waters. The main difference observed during this time was a reduction in the number of Erpobdella octoculata (leech) and an increase in the abundance of the mollusc Lymnaea peregra (Hendry et al., 1997). The slow rate of colonisation was linked to a lack of immigration routes into the Quays and to the homogeneity of the habitats available (Hendry et al., 1997). Artificial reefs and macrophytes were introduced to provide an increased number of niches for invertebrates to colonise which proved to be successful. An increase in diversity was seen and within two years taxa less tolerant of organic pollution were found [waterboatmen (Corixae), mayflies (Baetis rhodani), damselflies (Ischnura elegans) and caddisflies (Ecnomus tenellus and Cyrnus trimaculatus)] (Struthers, 1995; Hendry et al., 1997). Two years later a further 10 taxa were found and in 1997 the enclosed basins were found to support 29 invertebrate taxa, many of which were species indicative of improving water quality (Hendry et al., 1997).
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Table A4.2. Invertebrates in the MSC and the enclosed basins at Salford Quays., 0, absent: +, present; ++, common. Data from colonisation samplers. Modified from White et al., (1993) in Hendry et al., (1997)
Taxa Ship Enclosed Enclosed Enclosed Canal Basins Basins Basins 1989 1991 1993 COELENTERATA 0 0 + +
ANNELIDA Oligochaeta + + + + Erpobdella octoculata ++ + + + Glossiphonia complanata ++ + + + Helobdella stagnalis ++ + + +
MOLLUSCA Lymnaea peregra + ++ ++ ++ Physa fontinalis + ++ ++ + Physa acuta 0 0 0 ++ Planorbis complanatus 0 0 + ++
CRUSTACEA Asellus aquaticus ++ ++ ++ ++ Crangonyx pseudogracilis 0 0 + ++ Gammarus pulex 0 0 0 +
ARACHNIDA Hydracarina (water mites) 0 0 0 ++
INSECTA Chironomidae (midge + + + ++ larvae) Muscidae (housefly + 0 0 + larvae) Limnephilidae 0 0 0 + Corixidae 0 0 + ++ Dytiscidae 0 0 0 + Haliplidae 0 0 0 + Baetis rhodani 0 0 + + Phryganea bipunctata 0 0 + ++ Ecnomus tenellus 0 0 0 + Cyrnus trimaculatus 0 0 0 ++ Ischnura elegans 0 0 + + Agraylea mutlipunctata 0 + + +
4.3 Historical macro-invertebrate data: River Inputs
Macro-invertebrate sampling has been carried out by the Environment Agency on six sites in tributaries of the Manchester Ship Canal (MSC) from as early 1985. Three minute kick samples were taken and invertebrates were identified to family level to allow for the calculation of BMWP score and Average Score Per Taxon (ASPT). The Number of Scoring Taxa (NST) were also given.
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The early records from each site showed the macro-invertebrate diversity to be very poor. BMWP scores as low as 2, a sample in which only non-biting midges (Chironomidae) were found, were recorded on one occasion in the Salteye Brook downstream of Eccles treatment works. At all sites the fauna was commonly restricted to a few specimens of Oligochaete worms, Chironomidae, and freshwater hog-louse (Asellidae), all of which are tolerant to highly organic conditions and associated low oxygen concentrations.
The universally poor BMWP and ASPT scores recorded in these watercourses in the 1980s were seen to improve during the early 1990s. The biotic scores of samples in Salteye Brook and Red Brook appear to improve after 1991, albeit only briefly in the former, with ASPT scores regularly exceeding 3 for the first time since records began. A second improvement was recorded in 1997 in the Salteye Brook.
Samples taken in the River Medlock, River Glaze and River Mersey at Flixton Bridge show an increase in BMWP and ASPT scores after 1992 (Figure A4.6). Initial communities dominated by leeches (Hirudinea), hog-lice (Asellidae), midges (Chironomidae) and worms (Oligochaeta), were diversified with less pollution tolerant taxa such as the freshwater shrimp (Gammaridae), blackfly larvae (Simuliidae), and even highly sensitive members of mayfly (Leptophlebiidae) being recorded. However, the samples taken from the River Mersey at Bollin Point were only seen to improve in late 1999 (Figure A4.7), after which specimens of damselfly (Calyopterygidae) and caddisfly (Limnephilidae) were recorded along with the several families of flatworm (Planariidae, Dugesiidae and Dendrocoelidae).
70 BMWP 5.0 ASPT 4.5 60 4.0
50 3.5
3.0 40 2.5 ASPT BMWP 30 2.0
20 1.5 1.0 10 0.5
0 0.0
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Figure A4.6. BMWP and ASPT scores from EA data for the River Mersey at Flixton Bridge.
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40 4.0 BMWP ASPT 35 3.5
30 3.0
25 2.5
20 2.0 ASPT BMWP 15 1.5
10 1.0
5 0.5
0 0.0 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Figure A4.7. BMWP and ASPT scores from EA data for the River Mersey at Bollin Point.
While there appears to be an improvement in the communities at each site, even those samples taken most recently would be considered to be poor in terms of biodiversity, and are comprised largely of pollution tolerant taxa. These results would suggest that the sites are highly organically enriched and are likely to suffer from periodic low levels of dissolved oxygen. In other words, despite the improvements in water quality described earlier, there is still considerable scope for improvement in stream ecology with respect to invertebrates.
The Riverine InVertebrate Prediction And Classification System (RIVPACS) is used to compare the macro-invertebrate communities in a site to those that might be expected if it were in pristine condition. Using the RIVPACS methodology, the macro-invertebrate communities are compared to those that might be found, given the habitat, in an unpolluted system. The ratios generated are used by the Environment Agency to determine the biological General Quality Assessment (GQA). These GQA grades range from ‘a’ (very good) to ‘f ‘(bad).
Table A4.3 shows the biological GQA grades for the six sites upstream of the MSC. It can be seen that recent improvements were recorded over the 17 year period in all but one of the six watercourses. The greatest improvements were recorded in Red Brook and the River Medlock, however all were graded either bad (f), poor (e), or fair (d) at best. Salteye Brook, having improved in 2000, was actually considered to have deteriorated in 2002-4. Unfortunately the latest GQA has not been calculated for three of the sites (Salteye Brook being one of them) and further improvement might be expected. Nevertheless, as stated above, the RIVPACS predictions support the view that the Mersey and it’s tributaries should be capable of supporting a much higher level of diversity in ecological terms, with more varied invertebrates indicative of ‘clean’ environments.
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Table A4.3. Historical Biological General Quality Assessment (GQA) Grades
Site 1990 1995 2000 2002-4 2005-7 River Mersey, Bollin Point f f f f e Salteye Brook downstream of Eccles f f e f No ETW, ptc MSC data Red Brook upstream Partington road f e f d No bridge data River Medlock upstream Dawson f e e d No Street data River Glaze ptc MSC, downstream of f e e e e the A57 River Mersey, Flixton Bridge f e e f e
The increasing macro-invertebrate diversity and abundance within the upper MSC can be attributed to the improvements in water quality experienced over time. Increased dissolved oxygen concentrations from the oxygen injection system and reduced levels of pollutants from improvements in waste water treatment have allowed increasing numbers of pollution intolerant species to survive within the MSC. Detailed analysis of the relationships between the macro-invertebrate community and water quality will be undertaken later in the project.
4.4 Historical review of algal data
Sampling of algal populations within the MSC and Salford Quays was first carried out as part of the water quality monitoring between 1986 and 1988 (NWW, 1987a & b, 1989; NWW, 1988a & b). A summary of the key findings of these reports is given in Section 4.4.1. Following this early study APEM have conducted regular monitoring of Salford Quays, including two sites within the MSC (Sites 1 and 10) from 1987 to present. APEM collect water samples at monthly intervals from each site for the identification of phytoplankton and the analysis of chlorophyll a concentrations. The EA do not currently monitor phytoplankton within the MSC.
4.4.1 Monitoring from 1986 to 1988 (NWW)
Throughout the sampling period species diversity was highest in the basins open to the MSC (Figure A4.8 and Table A4.4). The diatom taxa Melosira, Meridion and Dinobryon are indicators of clean water and were found on very few occasions whereas Nitzschia was observed frequently, which is an indicator of polluted water. Biological growth on the dock walls was poor throughout the sampling period with only a narrow band of diatoms, algae, rotifers and microcrustacea being found below the water line. Diatometers (glass microscope slides) were used as artificial substrata for colonisation from which indices of pollutional stress and biological diversity calculated. These results showed poor water quality at all sites, but particularly in the closed basins.
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Table A4.4. Number of algal species detected during surveys conducted in 1986. * not sampled (Modified from NWW, 1987a). Sites highlighted in red are those open to the MSC. Site 09/07/86 29/07/86 19/08/86 10/09/86 10/10/86 05/11/86 Average 1 12 9 14 8 8 6 9.5 2 7 6 12 9 7 4 7.5 3 4 0 4 * * * 1.3 4 1 1 1 * * * 1 5 3 1 1 * * * 0.3 6 6 5 3 * * * 2.3 7 5 4 1 * * * 1.7 8 7 8 7 9 10 4 7.5 9 9 12 7 10 9 5 9 10 7 13 9 7 6 4 7.7 Total 61 59 59 43 40 23 Average 6.1 5.9 5.9 8.6 8 4.6
10 9 8 Closed basin 7 Open 6 basin 5 4 3 Number of species Number of 2 1 0 12345678910 Site Number
Figure A4.8. Average number of algal species detected between July and November 1986 in Salford Quays and the MSC (Modified from NWW, 1987a).
During the next sampling period (December 1986 to May 1987) water quality monitoring was carried out in Salford Quays, and at three sites in the MSC, (NWW, 1987b). Low temperatures between December and April resulted in a lack of algal growth throughout the basins of Salford Quays (Table A4.5) but with the onset of warm and sunny periods at the end of April, conditions become more favourable for algae and resulted in the formation of a green algal bloom in Basin 7c (St. Louis). By contrast these conditions were not seen in the open basins or in the MSC with low chlorophyll a concentrations being recorded (Figure A4.9). Species diversity in the closed basins had also increased during the survey period to a level similar to the open basins (Table A4.5) although with a different species composition. This would be expected due to the differences in water quality between the two bodies of water.
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Table A4.5. Number of algal species detected during sampling conducted between December 1986 and May 1987 (Modified from NWW, 1987b) (- not measured). Sites highlighted in red are those open to the MSC.
Site 09-Dec-86 06-Jan-87 04-Feb-87 03-Mar-87 08-Apr-87 05-May-87 1 3 6 2 2 5 3 - 6 4 - 6 5 - 6 6 - 7 7 - 8 8 3 3 9 6 5 10 6 5 NB: it is not clear as to whether samples collected from 06 January to 08 April 1987 contained no algal species or whether no sampling was actually conducted.
Growth of periphyton during the survey period was again limited and diatometers (glass microscope slides) were used to provide an artificial substrata for colonisation.
At Site 1, within the MSC, the diatom species Synedra and Surirella, the chlorophytes Chlorella and Chlamydomonas and some rotifers were found. This diversity was very different to the other sites sampled within Salford Quays in terms of the species present, which again would be expected because of the differences in water quality.
The Total Palmer index was used to assess the surrounding water quality, based on the different pollution tolerances of the various species recorded. Values were found to be high at all sites, including the closed basins, indicating poor water quality.
The results of water quality monitoring carried out between November 1987 and April 1988 were interpreted in a report produced by North West Water Authority in 1988 (1988a). Comparatively high concentrations of chlorophyll a were recorded in November, February and March indicating the presence of high algal activity throughout the system.
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40
35
30 Closed basin
concentration concentration 25 Open basin a 20 MSC sites (ug/l) 15
10
5
Average chlorophyll chlorophyll Average 0 12345678910111213 Site Number
Figure A4.9. Average surface chlorophyll a concentrations from December 1986 to May 1987 in Salford Quays and the MSC (Modified from NWW, 1987b).
In a later report covering sampling conducted in Salford Quays between May and September 1988 (North West Water Authority, 1988b) the biology of the Quays was reported to be clearly influenced by the MSC. This was particularly true in Basin 6 (South Bay) and to a lesser extent in Basin 9 (split to form Huron and Erie Basins), which at the time had only recently been closed off from the Canal. Basins 7 and 8 (completely closed from the ship canal) had developed their own characteristics but had yet to reach stability. Throughout the summer high chlorophyll a concentrations were observed indicating increased algal growth within the whole of the Quays enclosed basins.
Between May and September 1988 (sampling conducted by North West Water, 1989) algal growth remained poor in Basin 6 (South Bay, Site 1) with chlorophyll a at lower levels than other basins. Within the closed basins algal biomass was high with a substantial increase observed in August in Basins 7a, b and c. In Basin 9 a steady growth in biomass was observed and reached a peak in July, after which chlorophyll a levels declined sharply to become similar to those levels observed in the open canal. Following on from the findings of the previous sampling period (December 1986 – May 1987) species diversity remained similar in the open (MSC) and closed (Quays) basins with increased diversity observed in all basins (apart from Basin 9).
4.4.2 APEM monitoring programme 1986 - present
Phytoplankton data for Site 1 in the MSC are available from 1986 to present. Up to 1988 the data comprise of a record of presence/absence of each species gathered during the surveys carried out by North West Water Authority (1988a & b) (Table A4.6). After this, samples were analysed by APEM to provide the number of colonies or cells per ml and gave a quantitative assessment of the species present. Coupled with this chlorophyll analysis shows the productivity of both the MSC and Salford Quays.
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Table A4.6. Species presence during phytoplankton surveys carried out between 1986 and 1988.
Basin 6 (Site 1) 09/07/1986 29/07/1986 19/08/1986 10/09/1986 10/10/1986 05/11/1986 09/12/1986 06/01/1987 04/02/1987 03/03/1987 08/04/1987 05/05/1987 04/05/1988 12/07/1988 07/09/1988
CYANOBACTERIA Oscillatoria sp. P P P DIATOMS Achnanthes sp. P P P Meridion sp. P P Cyclotella sp. P P P P P P P Melosira sp. P P P P Nitzschia sp. P P P Navicula P P P P P P P P P P Synedra sp. P P P P P Asterionella P P P P Diatoma sp P P P P P P P Cymbella sp. P P P P Denticula sp. P Epithemia sp. P Surirella P CRYPTOPHYTES Cryptomonas sp. P P P P P PYRROPHYTES Peridinium P DINOPHYCEA EUGLENOID FLAGELLATES Trachelmonas sp P P P P P P P CHLOROPHYTES Chlamydomonas P P Ankistrodesmus P P P Scenedesmus sp. P P P Ulothrix P Gonium sp P P P P CHRYSOPHYTA Mallomonas sp P
Species diversity at Site 1 (MSC) was relatively high at the start of the sampling period (1986) with an average of 8 different taxa being recorded. The most diverse group within samples during this time were the diatoms. Over time the number of taxa identified increased (Figure A4.10) and the maximum number of taxa recorded was 21 in June 2006. The increases and decreases observed in algal diversity during this time are a clear indication of the changing biological community at Site 1 as a result of the improvements to surrounding water quality within the Canal’s upper reaches. It is important to note that since 2000, the site has been influenced by oxygen injection from the units in the Turning Basin.
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25 Oxygen Injection
20
15
10 Maximum number of taxa recorded
5
0 Apr-89 Apr-90 Apr-91 Apr-92 Apr-93 Apr-94 Apr-95 Apr-96 Apr-97 Apr-98 Oct-89 Oct-90 Oct-91 Oct-92 Oct-93 Oct-94 Oct-95 Oct-96 Oct-97 Oct-98 23-Apr-99 28-Apr-00 27-Apr-01 24-Apr-02 25-Apr-03 22-Apr-04 27-Apr-05 20-Apr-06 13-Oct-00 31-Oct-01 31-Oct-02 31-Oct-03 28-Oct-04 27-Oct-05 01-Nov-99 01-Nov-06 Figure A4.10. Maximum number of algal taxa identified in samples from Site 1 (MSC) between 1989 and 2007.
Densities of phytoplankton were very low during the 1989 sampling period with 7 out of 9 occasions recording phytoplankton as being absent. Densities started to increase around 2001 when the peaks in cell numbers increased in frequency and duration. This coincides with the time that the oxygenation units were installed in the MSC, but also with a decrease in suspended solids (See Section 2.4).
Considerable increases in algal densities were observed in 2005 and 2006 with a peak of over 66,000 cells or colonies per ml in September 2006. This peak was caused by a bloom of cyanobacteria (blue-green algae), but overall the majority of peaks recorded throughout the reporting period have been caused by high densities of chlorophytes (Figure A4.11).
Generally, phytoplankton densities at Site 1 have not shown any clear seasonality. Chlorophytes seemed to be most prevalent during spring and summer months when increases in temperature contributed to excessive algal growth. Large increases in the number of diatoms and cyanobacteria could also be attributed to the season with peaks in the spring and autumn respectively.
Analysis of chlorophyll a in the MSC and Salford Quays enables a comparison of productivity to be carried out. Figure A4.12 and Figure A4.13 show that the MSC has had a relatively low chlorophyll a concentration compared with Salford Quays despite phosphorous concentrations being considerably higher. In the MSC various peaks in chlorophyll a occur but levels have generally remained below 30 µg/l. However, it is useful to note that during low flow periods, occasional blooms have been recorded. For example in the drought of summer 1995, chlorophyll a exceeded 200μg/l. A peak algal concentration approaching 100 μg/l was also recorded in summer 2001. Examining data from the enclosed basins at Salford Quays provides an indication as to what might be anticipated in the MSC were water clarity to improve, reaching the
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Final Report – September 2007 APEM Scientific Report 410039 transparency levels found within the Quays (up to 7m). At the Quays, following isolation, chlorophyll a displayed a generally increasing trend between 1990 to 1993 with a peak of over 800 µg/l. This substantial level of algal growth led to severe discolouration of the water but also prevented recreational use of the water due to the toxic nature of the blue-green forms of the bloom. A declining trend was since observed and since 2001 chlorophyll a has stabilised at a relatively low level (<25 μg/l).
The timeseries data since 1987 reveal that algal blooms (Figure A4.13) had a tendency to increase periodically and then crash in the Quays. The frequency and intensity of these events increased over the 5 years following isolation, with the most severe algal blooms being recorded in 1991/92. As previously explained, chlorophyll a levels are largely governed by total phosphorus concentrations, with high total phosphorus causing increased algal growth. Certain species of algae would also scavenge and fix phosphorus from the nutrient rich bottom sediments. After 1992 much of the phosphorus present in the enclosed Quays basins became gradually locked up in the sediments as a result of past algal blooms which have utilised the high orthophosphate concentrations and then crashed. The dead algal communities would then sink to the bottom of the Quays, taking with them the bound phosphate within the algal cells. The phosphorus then becomes locked up within the sediments, bound to other minerals, particularly iron oxides. Under the oxic conditions provided by the Helixors since 1987, such minerals are insoluble and remain ‘locked’ within the sediments. Any failure of the artificial mixing system would likely lead to re-entry of phosphorus into the water column, in turn resulting in the return of algal blooms.
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Density = 66,966 Cyanobacteria 96%
20000 Density = 23,652 Chlorophytes 72%
18000
16000 Diatoms 60%
14000
12000
Cryptophytes 93% 10000
8000 Chlorophytes 79% 6000 Chlorophytes 63%
4000
2000
0 Apr-89 Oct-89 Apr-90 Oct-90 Apr-91 Oct-91 Apr-92 Oct-92 Apr-93 Oct-93 Apr-94 Oct-94 Apr-95 Oct-95 Apr-96 Oct-96 Apr-97 Oct-97 Apr-98 Oct-98 23-Apr-99 28-Apr-00 13-Oct-00 27-Apr-01 31-Oct-01 24-Apr-02 31-Oct-02 25-Apr-03 31-Oct-03 22-Apr-04 28-Oct-04 27-Apr-05 27-Oct-05 20-Apr-06 01-Nov-99 01-Nov-06
Figure A4.11. Total densities of phytoplankton at Site 1 (MSC) from 1989 to 2007 with percent contribution of the dominant species within each peak.
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300
250 Stephanodiscus astraea
200
150
Surface chlorophyll a (ug/l) 100
50
0 01-Jul-86 01-Jul-87 01-Jul-88 01-Jul-89 01-Jul-90 01-Jul-91 01-Jul-92 01-Jul-93 01-Jul-94 01-Jul-95 01-Jul-96 01-Jul-97 01-Jul-98 01-Jul-99 01-Jul-00 01-Jul-01 01-Jul-02 01-Jul-03 01-Jul-04 01-Jul-05 01-Jul-06 01-Jan-86 01-Jan-87 01-Jan-88 01-Jan-89 01-Jan-90 01-Jan-91 01-Jan-92 01-Jan-93 01-Jan-94 01-Jan-95 01-Jan-96 01-Jan-97 01-Jan-98 01-Jan-99 01-Jan-00 01-Jan-01 01-Jan-02 01-Jan-03 01-Jan-04 01-Jan-05 01-Jan-06
Figure A4.12 Chlorophyll a concentration within the MSC at APEM Sites, 1986 - 2006
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800µg/L 250
200 (µg/l) a 150 Increasing algal biomass Decreasing algal
Surface chlorophyll- biomass 100
50
Low and stable biomass
0
07-Apr-89 07-Oct-89 07-Apr-90 07-Oct-90 07-Apr-91 07-Oct-91 07-Apr-92 07-Oct-92 07-Apr-93 07-Oct-93 07-Apr-94 07-Oct-94 07-Apr-95 07-Oct-95 07-Apr-96 07-Oct-96 07-Apr-97 07-Oct-97 07-Apr-98 07-Oct-98 07-Apr-99 07-Oct-99 07-Apr-00 07-Oct-00 07-Apr-01 07-Oct-01 07-Apr-02 07-Oct-02 07-Apr-03 07-Oct-03 07-Apr-04 07-Oct-04 07-Apr-05 07-Oct-05 07-Apr-06 07-Oct-06
Figure A4.13 Chlorophyll a concentration within Salford Quays, 1989 to 2006
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4.3.3 Algal Groups in MSC and Salford Quays
Cyanobacteria
The density of blue-green algae at Site 1 (MSC) has fluctuated considerably over the years (Figure A4.14). In September 2006 densities were the highest they have ever been, recorded at over 64,000 colonies/ml. The main species contributing to this peak was Chrococcus dispersus present in densities of 61,661 cells/ml. However, chlorophyll levels only reached 4 µg/l during this peak. Cyanobacteria characteristically bloom in the autumn and in 2006 September marked a peak in the number of blue-green cells, which had been increasing at Site 1 since June of that year. After this peak densities returned to an average of 46 cells/ml (November, December 2006 and January 2007), which is slightly higher than densities recorded prior to 2006 (pre-2006 average density was 23 cells/ml). There have been other notable peaks in algal densities, although none as pronounced as that seen in 2006. These included the end of 1995 where densities increasing to over 500 cells/ml, which was attributable to high densities of Oscillatoria agardhii and Microcystis sp. It is notable that no cyanobacteria were found for a long period between March 1998 and March 1999. When they were found, outside this time and before 2004, species diversity was limited to just one or two taxa and it was not until 2006 that more taxa were identified (maximum 4).
64,242 5,402 3,554 600
500
400
300
200 Algal density(colonies ml) per
100
0 Apr-89 Apr-90 Apr-91 Apr-92 Apr-93 Apr-94 Apr-95 Apr-96 Apr-97 Apr-98 Oct-89 Oct-90 Oct-91 Oct-92 Oct-93 Oct-94 Oct-95 Oct-96 Oct-97 Oct-98 23-Apr-99 28-Apr-00 27-Apr-01 24-Apr-02 25-Apr-03 22-Apr-04 27-Apr-05 20-Apr-06 01-Nov-99 13-Oct-00 31-Oct-01 31-Oct-02 31-Oct-03 28-Oct-04 27-Oct-05 01-Nov-06
Figure A4.14. Blue-green densities at Site 1 (South Bay, Basin 6 open to the MSC) from 1989 to date.
Diatoms
Diatom density at Site 1 in the MSC has increased over the years with a peak in April and March 2005 of 14,500 cells/ml and of 10,200 cells/ml respectively (Figure A4.15). Diatoms tend to bloom in spring (as observed here) as the water starts to 81
Final Report – September 2007 APEM Scientific Report 410039 warm up. These blooms die back in the late spring when the silica essential for their intricate ‘skeletal’ structures becomes limited and the blooms crash. Typically fast growing green algae fill the summer gap whilst cyanobacteria start to take over with the onset of autumn. The dominant diatom species in both the April and March peaks was Navicula with large numbers of Gomphonema sp. also being recorded in March. Following this peak the number of diatoms has fallen to levels similar to those reported previously. There have been various other peaks and troughs throughout the years although none as high as these. The third highest density was recorded in May 1990 with densities of 1899 cells/ml. During this peak the dominant species was Cyclotella, although Navicula was also abundant.
10,200 14,500
2000
1500
1000 Algal density (cells/ml)
500
0 Jul-94 Apr-96 Jun-97 Jan-98 Apr-89 Jun-90 Jan-91 Oct-92 Nov-96 Nov-89 Feb-95 Mar-99 Mar-92 Dec-93 Sep-95 Aug-98 Aug-91 May-93 27-Jul-01 25-Apr-03 17-Jun-04 26-Jan-05 01-Nov-06 11-Oct-02 26-Nov-03 01-Nov-99 30-Mar-06 20-Feb-02 25-Aug-05 18-Dec-00 31-May-00
Figure A4.15. Diatom densities at Site 1 (South Bay, Basin 6) from 1989 to date.
Cryptophytes
The occurrence of cryptophytes in samples was sporadic throughout the sampling period (Figure A4.16). Densities were highest at the start of sampling in May 1989 when numbers recorded were over 5,000 cells/ml but since then no peaks of similar magnitude have been observed.
The dominant species in the May peak were Rhodomonas minuta and Cryptomonas sp.. Densities were high throughout 2001 and 2006 but there have been long periods of time when no cryptophytes were found, namely for a 6 year period from August 1993 to August 1999.
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5160
1000
900
800
700
600
500
400 Algal density (cells/ml) 300
200
100
0 Apr-89 Apr-90 Apr-91 Apr-92 Apr-93 Apr-94 Apr-95 Apr-96 Apr-97 Apr-98 Oct-89 Oct-90 Oct-91 Oct-92 Oct-93 Oct-94 Oct-95 Oct-96 Oct-97 Oct-98 23-Apr-99 28-Apr-00 27-Apr-01 24-Apr-02 25-Apr-03 22-Apr-04 27-Apr-05 20-Apr-06 01-Nov-99 13-Oct-00 31-Oct-01 31-Oct-02 31-Oct-03 28-Oct-04 27-Oct-05 01-Nov-06 Figure A4.16. Cryptophyte densities at Site 1 (South Bay, Basin 6) from 1989 to date.
Euglenoids
Euglenoids were not found at Site 1 in the MSC until March 2005 (Figure A4.17). From here onwards the number of taxa identified has been either one or two (Euglena sp. and Phacus sp.) with Phacus sp. being the most dominant. Euglenoid numbers peaked in October 2005 at 375 cells/ml, this peak being dominated by Phacus sp..
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400
350
300
250
200
150 Algal density (cells/ml)Algal
100
50
0 Apr-89 Apr-90 Apr-91 Apr-92 Apr-93 Apr-94 Apr-95 Apr-96 Apr-97 Apr-98 Oct-89 Oct-90 Oct-91 Oct-92 Oct-93 Oct-94 Oct-95 Oct-96 Oct-97 Oct-98 23-Apr-99 28-Apr-00 27-Apr-01 24-Apr-02 25-Apr-03 22-Apr-04 27-Apr-05 20-Apr-06 01-Nov-99 13-Oct-00 31-Oct-01 31-Oct-02 31-Oct-03 28-Oct-04 27-Oct-05 01-Nov-06
Figure A4.17. Euglenoid densities at Site 1 (South Bay, Basin 6) from 1989 to date.
Chlorophytes
Chlorophyte densities were consistently less than 500 cells/ml until July 2001 when a peak of 2600 cells/ml was recorded (Figure A4.18), this could well be attributed to the ‘switch on’ of the oxygenation units at this time. Densities remained high until the end of August, after which densities fell again to below 500 cells/ml. The highest peak in chlorophyte densities was observed in July 2006 when densities reached over 16,000 cells/ml. Chlorophyte densities did show some seasonality with densities generally being higher during the spring and summer months, this being the case more so in the later sampling years (2001 onwards). Abundant species included Scendesmus sp., Chlorella sp., Chlamydomonas sp. and Chlorella sp.,
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16,936
4000
3500
3000
2500
2000
1500 Algal density (cells/ml) density Algal
1000
500
0 Jul-94 Apr-89 Jun-90 Jan-91 Oct-92 Apr-96 Jun-97 Jan-98 Nov-89 Mar-92 Nov-96 Mar-99 Aug-91 Dec-93 Feb-95 Sep-95 Aug-98 May-93 18-Dec- 20-Feb- 25-Aug- 31-May- 27-Jul-01 11-Oct-02 25-Apr-03 17-Jun-04 26-Jan-05 01-Nov-99 30-Mar-06 01-Nov-06 26-Nov-03
Figure A4.18. Chlorophyte densities at Site 1 (South Bay, Basin 6) from 1989 to date.
The only other group of phytoplankton found was chrysophyta (Mallomonas sp.) but this was only recorded in November 2006 in low densities (18 cells/ml).
4.5 Conclusion
Clearly there is considerable change occurring within the algal communities observed from these long term data sets in the Turning Basin area of the MSC. Increased algal species diversity and an increased tendency for peaks in the populations of certain groups (i.e. cyanobacteria, diatoms and chlorophytes) could be related to changes in transparency observed in the MSC (Section 2.4). Reduced concentrations of suspended solids allow light to penetrate further, which in turn allows algae to photosynthesise at greater depths. Certainly phosphorus levels in the MSC are high enough to be potentially hypereutrophic, and hence further increases in transparency could allow the available phosphorus to fuel massive algal blooms. Further analysis of the relationship between the algal community and water quality will be undertaken later in the project. Nevertheless, it is clear from the water quality analysis of oxygen supersaturation and elevated pH elsewhere in this report, that intense algal blooms are highly likely to be occurring in the vast majority of the MSC, downstream of the Turning Basin. Hence it is imperative to initiate long term monitoring of algal populations and chlorophyll a to determine the extent and intensity of blooms as well as the species involved. The ramifications of excessive algal growth, fuelled by almost limitless nutrient availability, give cause for concern way beyond phytoplankton diversity and may have a profound influence on the ability of the MSC to achieve compliance with the requirements of both the Fisheries Directive and the newly adopted Water Framework Directive.
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