DIRECTORATE GENERAL JRC
JOINT RESEARCH CENTRE
Institute of Environment and Sustainability
Milestone 6 Report – Lake GIGs
Please send your responses before 9th of June 2006 by e-mail to with copy to
GIG / AGIGInformation provided by / DEIRDRE TIERNEY
PHYTOPLANKTON- FINAL TECHNICAL REPORT FOR CHLOROPHYLL Updated March 22nd 2007
A – General approach1. Describe the common intercalibration types, specifying the countries participating for each type and the biological quality elements/ pressures that are intercalibrated (update ‘types manual’ tables
Table 1. Summary details of country participation and the lake types being intercalibrated for phytoplankton (chlorophyll) and the pressure eutrophication.
Amalgamation of types
L–-A1 and L-A2 datasets were amalgamated - L-A1/A2 - to create a larger and more useful database on the assumption that lake size is not a critical type factor for setting the phytoplankton boundaries. It had been shown using macrophyte data that there was no difference attributable to size differences (see Annex A, Part I).
D 2. Describe the general intercalibration approach (which intercalibration option -1,2, 3 or hybrid was used)
Chlorophyll A only as a surrogate for biomass was intercalibrated using option 1.
The approach used was to identify relationships between increased chlorophyll a concentrations and changes in other quality elements that would be influenced by secondary effects due to changes in phytoplankton biomass. Due to the limited size of the available data set and the similarity in the UK of the CGIG and AGIG intercalibrated lake type (lowland, shallow, calcareous), the relationships developed by the CGIG for a similar lake type (L-CB1) were also taken into consideration.
Taxonomic composition will be continued in the next round. Statistical analyses showed differences in phytoplankton composition between countries that were probably not due to geographical differences (Annex A Part II). This precluded the use of the data in this round. Additional samples have been collected. The majority of samples were identified by the same taxonomist. Samples that have been processed by another taxonomist will be quality assured.
3. Specify which data was used to set the boundaries applying the BSP (e.g. common GIG dataset [option 2], separate MS data sets [option 3]
Common GIG dataset [option 2] and included reference to conclusions drawn from the analysis of data from other GIGs.
4. Identify the national classification methods that were intercalibrated (for all countries, if available); provide detailed description in Annex A
Only chlorophyll a was intercalibrated for reasons already outlined. Member states field and laboratory methodologies are supplied in Annex A Part III.
B – Setting of Reference conditions
1. Summarize the common approach for setting of reference conditions. Give a more detailed description of procedure and criteria, and identify reference sites for each country and type according to those criteria in Annex B
Provide reference conditions for each type and metrics
All reference sites were from the Republic of Ireland as no reference sites of this type were available from UK. Reference sites were identified based on existing chemical and biological data, the absence of deleterious impact or landuse and expert judgement but also included paleaolimnological data – confirmation – which was considered an overriding factor (See Annex B parts 1 and II) .
Nine lakes were identified as reference sites based on their palaeolimnology. Reference site analyses included data from all nine lakes. A conservative approach was also adopted. Six lakes were excluded because they required further evaluation and / or had a mean TP exceeding 10ug l-1. This left three lakes. This was considered to be too few for statistical analysis to provide a robust estimate of reference conditions. The median value was considered to give a reasonable estimate of a type Reference value, but the upper percentiles would be much less reliable. The results obtained from this analysis were thus compared with results from a similar lake type in CGIG.
C – Setting of Boundaries
- Summarize how boundaries were set following the framework of the BSP , demonstrating that this was done in accordance to WFD Annex V, normative definitions:
- For High/Good boundary
- For Good/Moderate boundary
(a) Reference and High/Good boundary values
Reference and HG boundary values were determined from the distribution of chlorophyll a concentrations from reference lakes confirmed by palaeolimnology (Annex C, Part 1). The median value was taken as an estimate of the reference value and the 75th percentile as an estimate of the HG boundary. The 75th percentile was selected because lake years were used with some lakes possibly deviating from reference. It is noted that the data set i.e. number of lakes is too small to be statistically valid. The results were compared with similar analysis carried out for CGIG lakes for a similar type (L-CB1). The results - reference and HG boundary values - were similar and thus validated or supported each other.
The Type Reference value was taken as the median value 3.2 ug/L as a growing season mean.
The Type H/G boundary value was taken as 6 ug/L as a growing season mean with an EQR of 0.53.
The GIG notes that the proposed CGIG values for the same type are 3.2 ug/L and 5.8 ug/L which gives an EQR of 0.55. The chlorophyll values are not significantly different but the resulting EQR is. It is recommended that when harmonising results JRC should consider the possibility of rounding chlorophyll values to the nearest 0.5 prior to the calculation of the EQRs. This would avoid spurious accuracy and simplify application in MS where the same lake type can occur in more than one GIG region.
In the interest of harmonization, the AGIG has subsequently agreed to adopt the CGIG HG boundary and EQR.
(b) Good Moderate Boundary
IRL had preliminary views of a lower GM boundary derived by using total phosphorus to determine points of ecological changes for macrophytes among others- compatible with the normative definitions- along the pressure gradient eutrophication (Annex C, Part II). The total phosphorus value at the GM boundary was subsequently used to determine the corresponding chlorophyll a by a regression equation from the N American literature. This was further supported by a chlorophyll a vs TP relationship from the MS dataset (Annex C, Part III).
The UK propose – and the GIG has agreed - that as the reference and HG boundaries values for L-A1/2 lakes are similar to L-CB1 lakes, the analysis of these lakes (which included lakes from AGIG) and the resulting boundaries can be applied to L-A1/2 lakes (CGIG Milestone 6 Report Annex C).
The GIG have been able to agree a GM boundary based on the intermediate between the UK proposal and the IRL proposal harmonised with the CGIG. The type GM boundary value was taken as 10 ug/L as a growing season mean.
IRL had preliminary views of a lower GM boundary derived by using total phosphorus to determine points of ecological changes for macrophytes among others- compatible with the normative definitions- along the pressure gradient eutrophication (Annex C, Part II). The total phosphorus value at the GM boundary was subsequently used to determine the corresponding chlorophyll a by a regression equation from the N American literature. This was further supported by the chl a vs TP relationship from the MS dataset (Annex C, Part III).
The UK propose that as the reference and HG boundaries values for L-A1/2 lakes are similar to L-CB1 lakes, the analysis of these lakes (which included lakes from AGIG) and the resulting boundaries can be applied to L-A1/2 lakes (Annex C, Part IV).
3. Provide the data underlying the analysis in Annex D
It will be oOn CIRCA by the 8th September. The reference dataset is attached.
D – Final outcome of the Intercalibration
1. Provide HG and GM boundary numerical values and EQR values for each type and metrics
Ref: 3.2 ug/L mean growing season
HG: 5.8 ug/L mean growing season, EQR 0.55
GM: 10 ug/L mean growing season EQR 0.32
The AGIG supports the approach proposed by both NGIG and CGIG of proposing a small range of reference values and a fixed type specific EQR. This would enable sufficient flexibility for each MS to apply the GIG typology.
The AGIG would thus propose to adopt the same range of Reference conditions as CGIG (2.56-3.84 ug/L) with a range for the HG boundaries of 4.6-7 ug/L and for the GM boundary of 8-12 ug/L.
Ref: 3 ug/L mean growing season
HG: 6 ug/L mean growing season, EQR 0.5
GM: 10 ug/L EQR 0.33 – midways between the proposed boundaries
2. Present how common intercalibration types and common boundaries will be transformed into the national typologies/assessment systems (if applicable)
UK: The UK propose to use a lake specific model to predict reference chlorophyll a concentration based on a regression between reference TP and Chl a using equations published by REBECCA. These values will be compared with the range established for the IC lake type and truncated to ensure that the values remain within the range agreed by the GIGs. The HG and GM boundaries will be determined for each lake using the agreed type specific EQRs agreed by the GIGs. The UK also propose to calculate an annual, rather than a growing season average as several lakes in the UK have significant phytoplankton populations during the winter months. The majority of GIGs used growing season data - April to September - to establish boundaries. Annual values will be compared using a conversion factor of 1.27 (statistically significant relationship between Annual and April - September means). To facilitate the calculation of confidence of classification as required by the directive, data will be log transformed prior to determination of the mean. An adjustment will be made to convert arithmetic boundaries determined by GIGs to the Geometric equivalents that UK propose to use. It is anticipated that additional metrics will be available to assess taxonomic composition and bloom frequency of phytoplankton, but the overall method of combining each metric has still to be determined.
Still to be determined, depending on refinement of AGIG type as above.
IE: Chlorophyll will be part of an overall assessment system because using it alone is not WFD compliant. It will used in conjunction with or directly incorporated into the phytoplankton assessment/classification tool. and The boundary values will be translated unmodified - unless there is good reason to do otherwise i.e. harmonizing EQRs across MS types where types overlap with more than one GIG type- for use on MS lake types that fit the GIG typology.
E – Workplan for the continuation of the intercalibration
Indicate plans and appropriate timing for continuation of the intercalibration for types and quality elements not currently included
Workplan for the continuation of the intercalibration
BQE Pressure
Phytoplankton taxonomic composition**Eutrophication by Summer 2007 within and in co-operation with the CGIG for the Type LCB1/ LA1/2.
The following to be intercalibrated at a future date:
Invertebrates Littoral Eutrophication/organic enrichment by Summer 2007
Profundal Eutrophication/organic enrichment
CPET Eutrophication/organic enrichment by Summer 2007
** Phytoplankton taxonomic composition is dependent on the completion of the Phytoplankton classification tool being developed under a SNIFFER funded project which is due for completion in July 2007 although an early draft tool should be available during 2006.
F– Comments and remarks
Despite the popularity of chlorophyll a as a metric in intercalibration, differences in field and laboratory methodologies have been largely ignored and may in part explain the considerable variation among countries, across GIGs and in its relationship with TP.
Please see macrophyte technical report for further comments.
ANNEX A PART I
Statistical evidence supporting amalgamation of lakes types using macrophyte data.
Cluster analyses of macrophyte data(see Figure 1 and Figure 2) - square root transformation of relative frequency of occurrence for 32 lakes and 89 taxa (dataset 3 countries MACROPHYTE data-PRIMER.- xls) - supported by multidimensional scaling (Figure 3) showed that lakes did not separate by type or country. Area did not influence macrophyte taxonomic composition. Therefore- L–A1 and L-A2 datasets were amalgamated resulting in a larger and more useful database. Data analyses courtesy of Mary Gallagher, EHS, NI.
Figure 1. Cluster analysis of AGIG lake sites using macrophyte data with type distinguished by symbols.
Figure 2.Cluster analyses but with symbols representing countries.
Figure 3. Multidimensional Scaling (MDS) of the same data as used for cluster analyses with symbols = country. Note stress level 0.18 which is okay – the data becomes unreliable if stress 0.2 or more. It has been overlaid with similarities derived from the cluster analysis.
ANNEX A PART II
Statistical evidence for ‘country’ differences.
It was evident from hierarchical cluster analyses of phytoplankton genus level data (Figure 1) - log x+1 transformed counts - and multidimensional scaling (MDS) (Figure 2) that there were ‘country’ differences in taxonomic composition. It is unlikely these were due to geographical differences. The MDS stress value also indicated that the data was unstable. It was therefore considered that the data were not appropriate for intercalibration. Consequently taxonomic composition will be addressed in the next round of IC.
Figure 1: Hierarchical Cluster analyses on Phytoplankton counts only (not biovolume) on data (log x+1 transformed) sent from Sian Davies (GB), Gary Free (RoI) and NI (Robert Bailie). Identification level for this data is to Genus as some countries had identified down to species level whilst others had XX spp. Etc. Analyses courtesy of Mary Gallagher, EHS.
Figure 2: MDS on all countries –phytoplankton genus data. Note higher stress value of 0.23 indicating that it is less reliable. Analyses courtesy of Mary Gallagher, EHS.