1. Intercalibration of lake phytoplankton – Northern GIG
Milestone 6 report results
Ecostat
NGIG lead Anne Lyche Solheim, Norwegian Institute for Water Research (NIVA), Oslo, Norway
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2. Outline Countries involved Dataset available
National methods compliance check, incl. BSP
IC feasibility check
Pressure-response relationships
Benchmark standardisation
Relationships with common metric and IC results
Description of phytoplankton at boundaries
Remaining issues
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3. Countries and experts involved
Norway Anne Lyche Solheim, NIVA, GIG lead
Sweden Stina Drakare, SLU
Finland Marko Järvinen (Ansa Pilke), SYKE
UK Geoff Phillips, EA, major role in comparability calculations)
Ireland Gary Free (W. Trodd & D. Tierney), EPA
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4. Dataset available Ref. lakes
183 Reference lakes, validated with pressure criteria:
Natural land-use > 80%
Intensive agric land-use < 10%
Pop.dens. < 10 p.e./km2
Artificial land-use < 1%
TP < 20 µg/l
Chla < HG boundary from IC phase 1
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5. Description of phytoplankton at reference
Clearwater lakes (L-N1, L-N2a, b, L-N5):
Tax. comp.: Proportion of reference taxa exceeds the proportion of impact taxa. Dominance of reference taxa, such as chrysophytes, whereas impact taxa, such as harmful Cyanobacteria, are in very low abundance. Typical taxa found in the LN2a lake type at reference conditions are: Kephyrion, Chroomonas, Chrysolykos, Pseudokephyrion, Uroglena, Stichogloea, Merismopedia.
Biomass: Concentration of chlorophyll and biovolume is low. Typical chla ref.value is 2,0 ±0,5 µg/l and a biovolume of ca. 0,2 mg/l. (Appendix 4 and 7).
Blooms: Nuisance blooms never or rarely reported. If present, only short lived (only seen on calm days) and minor in extent. Biovolume of Cyanobacteria are rarely exceeding 0,05 mg/l (90th %ile)
Equivalent description has been given for the humic lakes (L-N3a, L-N6a, L-N8a) in the M6 report
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6. Dataset available – All lakes
Numbers are lake-years
All taxa are harmonised according to REBECCA/WISER code
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7. National methods compliance
All countries provided methods
Ref.values and boundaries for single metrics provided for all countries and types (Appendix 2 to M6 report)
Documentation (Appendix 1) will be completed in November (GIG leads ran out of time !)
All methods
all relevant parameters included: biomass, taxonomic composition and are able to detect “algal blooms”
specify combination rules
sampling differences: SE, FI, IE: low frequency, UK: Littoral/outflow sampling
boundary setting based on relationships between single metrics with sensitive and tolerant taxa, or equidistant division of classes using the max and min values in dataset
Problems with SE method (next slide)
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8. Problems with Swedish method:
Non-compliance with WFD:
Too low sampling frequency (1 /year)
SE equidistant division of classes not documented to be compliant with normative definitions
Non-compliance with IC phase 1 results:
Too lax biovolume boundaries for lowland lakes, (not consistent with chla) (existing GM boundaries more relevant for LCB1?)
Method partly non-validated:
Poor correlation of %Cyano metric vs. Pressure (r2 = 0,02 for LN6a)
Poor regression with Common Metric, also due to truncation of EQR values at 1.0
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9. Actions recommended by GIG lead to improve Swedish method
Correct biovolume boundaries for lowland lake types to be consistent with chla phase 1 results, recommended values suggested by GIG lead
Demonstrate that boundary setting are compliant with normative definitions
Correct the % Cyano metric by excluding non-impact taxa (e.g. Merismopedia, Anabaena lemmermanni, other Croococcales) to improve regression with pressure (e.g. adopting the FI metric: % Impact Cyanobacteria)
Allow EQRs to exceed 1.0 (so no truncation)
Increase monitoring frequency to at 6 samples /year (monthly in growing season)
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10. Example of BSP (NO)
Tax. comp. metric boundaries based on GAM regressions with proportions of sensitive and tolerant taxa
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11. Ref.values and boundaries for single metrics, example
Norway absolute values and EQRs
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12. IC feasibility check Typology OK,
but some types missing for some countries
SE and FI typology diverging from NGIG types
Pressure: all methods respond to Eutrophication
Assessment concept: Comparable in terms of habitats, but UK samples littoral/outflow
Relationship with pressure
All countries have good relationship with pressure (when applying national methods to NGIG data for each type)
SE method have the weakest relationship, esp. for LN2a
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13. Relationships with pressure
NO: average of chla, biovolume, max cyano biomass and PTIno adj R2 = 0.47***
UK: average of chla, median cyano biomass and PTIuk adj R2 =0.50***
FI: median of chla, biovolume, % impact cyanobacteria and TPI adj R2 = 0.42***
SE: mean of biovolume, % all cyanobacteria and TPI adj R2 = 0.18***
IE: mean of chlorophyll and taxonomic metric adj R2 = 0.42***
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14. Benchmark standardisation
Significant country effects found in relationships between national EQR data vs pressure (TP), due to climatic differences and methodological differences
Continuous benchmarking was applied to remove country effects by using linear mixed models to estimate differences across the pressure gradient
The differences estimated are called country offset values
The standardisation was done by subtracting country offset values prior to calculation of the EQRs for each national method before doing the IC comparisons
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15. Common metric
Common metric = average of EQRn for chla + tax.comp.metric (PTIwiser)
Common metric shows good relationship with pressure (TP) (r2 = 0.52) (grey line in figure)
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16. Relationships with common metric, LN2a example
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17. IC results, all NGIG types
after adjustments of national boundaries and combination rules for NO, FI and UK (considerable work requiring many iterations of comparability calculations):
NGIG is passing all the IC criteria for all countries and types
CM vs. National EQRs, slope
CM vs. National EQRs, r > 0.5
CM vs. National EQRs, min. r2 > ½ max r2
HG and GM boundaries above the lower bias band
Absolute average class difference < 1 class
But problems with SE method cause failure of SE for one lowland lake type, and also close to failing for other types due to method problems
Bloom metric combination rule for UK and NO also needs adjustment to avoid too good classification of lakes without blooms
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18. IC results, example for LN2a
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19. IC results all countries & types
National EQRn (not very informative)
HG = 0.8
GM = 0.6
Common metric boundaries (so far):
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20. Description of phytoplankton at GM boundary
Clearwater lakes (L-N1, L-N2a, b, L-N5):
Tax. comp.: The phytoplankton community close to the GM boundary is highly diverse, representing the highly dynamic nature of such communities. Many taxa from many different algae classes are typical, some representing the sensitive taxa dominating in reference lakes and others representing early warning indicators of eutrophication, e.g. pennate diatoms.
The following taxa are typical for the phytoplankton community close to the GM boundary: chrysophytes (e.g. Dinobryon, Mallomonas, Spiniferomonas, Ochromonas), chlorophytes incl. desmids (e.g. Dictyosphaerium, Elakatothrix, Monomastix, Monoraphidium, Quadrigula, Synura, Staurodesmus), cryptophytes (e.g. Cryptomonas, Plagioselmis), dinophytes (e.g. Gymnodinium), pennate diatoms (e.g. Aulacoseira, Fragilaria, Tabellaria), cyanobacteria (e.g. Snowella), as well as Chrysochromulina and the harmful alga Gonyostomum semen.
Equivalent description has been given for the humic lakes (L-N3a, L-N6a, L-N8a) in the M6 report
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21. Description of phytoplankton at reference and boundaries
Based on indicator value analyses and all lakes classified to ±0.25 of proposed common metric class boundaries. Shaded areas are 95% C.I. for comparing medians.
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22. Description of phytoplankton in different classes (H, G, M, P, B)
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23. Description of phytoplankton communities – NGIG Clear-water lakes
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24. Description of phytoplankton communities – NGIG Humic lakes
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25. Remaining issues
Final discussions with SE concerning need to change national method before ( )
Revised application of combination rule with Cyano bloom metric for NO and UK, testing for at least one type before
NGIG videomeeting to discuss revised results
Attend validation workshop
Complete Appendix on National Methods in Nov.
Complete Appendix on Common Metric in Nov.
Get formal approval from all MSs for the final boundaries
Incorporate all final changes to a revised M6 report by end of 2011
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26. Future activities in NGIG
Apply IC results to set TP standards linked to phytoplankton GM boundaries
Intercalibrate other NGIG types:
mountain lakes,
very large, very deep lakes,
small polyhumic lakes (colour > 90 mg Pt/l),
very shallow moderate alkalinity lakes,
high alkalinity lakes
Harmonise national methods towards a common assessment system using a new NGIG Metric for phytoplankton??
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