1. Northern GIG Intercalibration of lake macrophytes Seppo Hellsten, Nigel Willby, Geoff Phillips, Frauke Ecke, Marit Mjelde, Deirdre Tierney

2. Approach Dataset originates from first intercalibration Methods updated – Final Finnish method – Revised UK method – New common ICCM Challenges – UK uses similar class boundaries in CBGIG and NGIG – Small fertility gradients for some types – Large variation from atlantic sites (IE, UK, NO) to continental ones (SE, FI). Also S-N gradient

3. Basis of exercise Five MS (FI, IE, NO, S, UK) testing comparability of classifications of four common lake types (low and moderate alkalinity, clear and humic lakes) Three MS (IE, NO and UK) comparing classification of high alkalinity clear and humic lakes. Eutrophication is primary pressure being assessed All methods assess composition Methods of FI, IE and UK multimetric and require data on specific abundance scale, max depth colonisation or cover of algae or helophytes. => Option 2 comparison

4. Data basis Biology: full presence-absence floristic data on submerged and floating-leaved taxa Environmental data: alkalinity, area, depth, altitude, colour Pressures: TP, chl a, secchi depth, (catchment land cover)

5. Methods FIN (National macrophyte classification (FINMAC) IE (Free Macrophyte Index) NO (National macrophyte index (Trophic Index – TIc) SE Trophic Macrophyte Index (TMI) UK (Improved LEAFPAC macrophyte lake classification tool)

6. MS Pressure-response relationships R 2 = 0.15-0.65; All significant at p = 0.0001

7. Common metric Cross GIG database of 1600 lake macrophyte surveys in 15 MS in NW and central Europe. Calculated arithmetic mean [TP] for each taxa based on lakes occupied. 174 scoring taxa. TP values log transformed and rescaled to continuous gradient from 1 (ultraoligotrophic ) to 10 (hypertrophic). ICM value per lake based on unweighted average scores of all taxa present Converted to EQR using a GLM of national reference sites with alkalinity, colour and altitude to predict expected values EQR = (Obs ICM-10)/(Exp ICM-10)

8. ICM v TP relationship

9. Benchmarking Initial basis of benchmark sites was national reference sites submitted to GIG dataset. Genuine reference lakes available in this GIG Reference sites then screened at GIG level to exclude outliers and potentially impacted sites Pressures considered: [TP], [chl a ], secchi depth and (catchment land cover). Started with 450 putative reference sites, reduced to 432 in Phase 1, subsequently to 394 and finally to 330 in Phase 2 (partly due to method revisions etc). Sites screened at global and within-country level based on ICM EQR v pressure relationships

10. Sources of benchmark differences Methodological – Whole lake – Transects – Rakes - Aquascope/Videos Typological – Geology influences Biogeographical – Latitude – Post glacial recovery – Continental species pool

11. Benchmarking – way forward MS has highly significant fixed effect in TP v alkalinity relationship  rule-based screening or continuous benchmarking is NOT valid……methodological or typological reasons

12. Benchmark standardisation GLM with ICM as dependent variable, colour and MS as fixed effects and alkalinity and altitude as covariates, based on population of 330 benchmark sites Provides site specific expected ICM for any lake in any MS EQR = (Obs ICM-10)/(Exp ICM-10)

13. Benchmark sites

14. Benchmark site valuesModeled ICM EQR for benchmark sites Applying ICCM

15. MS EQR v ICM EQR relationships R 2 = 0.39 – 0.82 P = <0.0001

16. Boundary comparison – low and moderate alkalinity lakes NOUKIESFI HG-0.100.09-0.130.39-0.03 GM-0.22-0.16-0.150.330.22 Boundary bias as class equivalents Since benchmarking considers all types together it is logical to consider the average bias across the four IC lake types. However NO and S also have lake type-specific class boundaries At type specific level bias at GM in type 201 v low for NO (-0.7) NOUKIESFI HG-0.060.09-0.130.39-0.03 GM-0.12-0.16-0.150.330.22

17. High alkalinity lakes Failed IC of HA lakes at GIG level but bilateral comparison of UK and IE successful, NO very precautionary IE and UK closely comparable, UK boundaries for HA lakes already intercalibrated in CB-GIG (where precautionary). Reference sites comparable in all three MS. NO unwilling to adjust boundaries. NOUKIE HG0.69-0.11-0.34 GM0.69-0.35-0.33 NOUKIE HG 0.09-0.08 GM -0.060.08

18. Characterisation

19. Biological characterisation Low alkalinity, humic lakes Low alkalinity, clear lakes

20. Final boundaries ClassificationEcological Quality Ratios MethodHigh-good boundaryGood-moderate boundary Common metric0.955 0.855 FIFinnmac 0.8 (all types) 0.6 (all types) IE Free Macrophyte Index 0.9 (all types) 0.68 (all types) NO National macrophyte index (Trophic Index – TIc) Type 101: 0.98 Type 102: 0.96 Type 201: 0.95 Type 202: 0.99 Type 101: 0.85 Type 102: 0.87 Type 201: 0.75 Type 202: 0.77 SE Trophic Macrophyte Index (TMI) Type 101: 0.93 Type 102: 0.93 Type 201: 0.89 Type 202: 0.91 Type 101: 0.80 Type 102: 0.83 Type 201: 0.78 Type 202: 0.78 UK LEAFPACS lake macrophyte classification tool 0.8 (all types) 0.66 (all types)