A11. Macrophyte Survey - LEAFPACS 2

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1. Objectives

The LEAFPACS2 (Willby et al., 2012) was developed for the second river basin planning cycle in the UK. LEAFPACS2 is a multimeric approach which uses a suite of metrics to provide complementary sensitivity to various pressures, most notably eutrophication. Raw metric values can be evaluated by plotting them directly against a pressure, or combined to assess ecological status for the WFD.

The method is suitable for all rivers in UK, excluding canals, marsh ditch systems or strongly seasonal watercourses. For WFD assessments it should be performed on at least 5*100m stretches to be representative of the whole water body and habitat heterogeneity.

For river restoration assessments it should be applied in a BACI approach.

2. Method summary

For each survey a river length of 100m is undertaken. Within the survey area all macrophytes that are in the survey area are recorded. This includes plants that are submerged or partly submerged in the river at low flow levels and at the sides of the river and are attached or rooted to parts of the substrate that are likely to be submerged for more than 85% of the year. Plants that overhang the channel but are not rooted in the channel area are not recorded. Plants are recorded according to the taxonomic list in Appendix A (Table 1) using a nine point cover scale (made up of 9 Taxon Cover Value (TCV), Table 1).

Taxon cover Value

Surveys should be undertaken between the 1st June and 30th September avoiding periods to drought and high flows. If there is cold weather or late floods during spring sampling should start after June 30th. The number and location of the surveys depend on the driver that requires the data. Data collection for river macrophyte survey should conform to Guidance for the surveying of aquatic macrophytes in running waters and River macrophyte sampling: methodologies and variability

Calculation of metrics

From each survey parameters are calculated (the observed values) which can be compared with expected (predicted) value for a given site:

  • River Macrophyte Nutrient Index (RMNI);
  • Number of macrophyte taxa which are not helophytes (NTAXA);
  • Number of functional groups of macrophyte taxa which are not helophytes (NFG); and
  • Percentage cover of green filamentous algae (ALG)

The observed parameters can be calculated using an MS Excel spreadsheet calculator. The most recent version of the spreadsheet calculator can be found on the UKTAG website NEED LINK. Instructions for use are provided within the spreadsheet calculator.

(i) Observed RMNI (River Macrophyte Nutrient Index)

Each macrophyte taxa present is assigned the corresponding RMNI species score in column 2 of the table and combined with the cover values using the equation:

Figure 1 : Computation of Observed value of RMNI

where :

  • Rj is the river macrophyte nutrient index score for taxon j;
  • j represents a taxon listed in Appendix A, Table 1, with an RMNI score listed in column 2. j has a value of 1 to n, indicating which of all the listed taxa present in the survey (total

number = n) it represents;

  • Cj is the taxon cover value for taxon j, determined in accordance with Appendix A (Table 2).

(ii) Observed NTAXA (Number of macrophyte taxa)

The observed value for NTAXA is given by the sum of the number of taxa listed in Appendix A (Table 1) that are present in the river and identified in column 3 of the table as being truly aquatic (i.e. hydrophyes).

Note that when there are several morphologically distinct taxa present belonging to a single aggregate (e.g. Ranunculus section Batrachian), no members of which can be identified to species level, these should be recorded as separate species for the purposes of calculating this metric.

(iii) Observed NFG (Number of functional groups)

Each taxon recorded (i.e. listed in Appendix A, Table 1, and identified in Column 3 of that Table as aquatic) is assigned to the corresponding macrophyte functional group number in Column 4 of Table 1. The observed value for NFG is given by the sum of the number of different functional groups of taxa present in the survey.

(iv) Observed ALG (Percentage cover of green filamentous algae)

To calculate the observed value of ALG:

  1. use the mid-point of the percentage cover range associated with the cover score, for each recorded algal taxon, as indicated in Appendix A (Table 2).
  2. add up the individual percentage cover values of all taxa in Appendix A (Table 1) which are identified as filamentous algae in column 5.

A direct visual assessment of the overall percentage cover of green filamentous algae at the site is an acceptable alternative, but note that this cannot then be entered against the taxa in the metric calculator spreadsheet.

The observed value for the metric ALG represents the total coverage of the stream bed by green filamentous algae, and will range from 0-100.

Calculation of Ecological quality ratio (EQR) for a site

Calculate of the ecological quality ratios (EQR) based on the ration of the observed and predicted reference values. The predicted scores calculated based on the sites attributes: the alkalinity (as mg/l CaCO3) from 12 or more samples, the altitude of the water body source, the distance from the source and the slope. References values are produced by the LEAFPACS2 site specific value on the basis of references for each survey location.

The EQRs, which are ratio between these two variables are then adjusted and combined (because metrics are have different levels of precision) to produce the final class. The reference values are derived using a combination of (a) information from a network of river sites identified as being subject to no or very minor alterations likely to affect their macrophyte communities and (b) modelling.

A normalization process between the EQR is required to give the overall River LEAFPACS EQR and the assessment of macrophyte status ranking between 0 and 1 (0.2-0.4 Poor/Bad, 0.4-0.6 Moderate/poor, 0.6-0.8 Good/ Moderate, 0.8-1 High/Good). Individuals metrics shouldn’t be used in isolation their value have to be computed together to be relevant.

Calculation of the ecological quality ratio (EQR) for each metric

This step is the next one. Equation can be found on the document: UKTAG River Assessment Method Macrophytes and Phytobenthos LEAFPACS

3. Advantages

  • Standardized protocol that can be used for the WFD classification or for wider assessment and by comparing the individual metrics.
  • Can also be used for wider assessments and by comparing the individual metrics
  • Background and references available
  • Can be done by one person, but it is recommended that surveys are undertaken in pairs for safety and to reduce operator error.

4. Disadvantages

  • Should only be undertaken between June and September as plants die back in the winter and other seasons may have high flows, which can wash away macrophytes.
  • Operator variability can contribute significantly to variability in estimates of taxonomic richness and plant cover. This can be reduced by two people undertaking surveys

5. Recommendation for method application

  • Where it is not possible to identify a macrophyte present in the river to species level, it should be recorded under its genus or other aggregate taxon level.
  • Perform the survey after been trained and tested to be consistent
  • Employ pair of operator and not only one person to compare opinions and for safety purposes.
  • Follow the guideline of the reference documents for the sampling of macrophytes.

6. Cost

Depending on the number of stream sections to monitor, ease of access and the vegetation diversity within the survey sections.

7. Data analysis

Refer to the reference documents to calculate the score of the river. Descriptive data (richness, diversity) and related indices can be calculated.

8. Protocol

9. References

  • The British Standards Institution 2014. Water quality — Guidance for the surveying of aquatic macrophytes in running waters. 24p.
  • DAVEY, A., GARROW, D., 2009. Variability components for macrophyte communities in rivers: summary report. Final report. Environment Agency Report SC070051/R4.34p.
  • UKTAG, 2014, River Assessment Method Macrophytes and Phytobenthos Macrophytes (River LEAFPACS2). Water Framework Directive – United Kingdom Technical Advisory Group (WFD-UKTAG). 27p.
  • WILLBY, N.J., PITT, J.A. AND PHILLIPS, G. 2009. Development of a system for the classification of lakes and rivers in the UK using aquatic macrophytes. Part II. Rivers. Environment Agency Science Report. Collaborators: Countryside Council for Wales, Natural England, Scottish Environment Protection Agency.