Defining Reference Conditions Setting Class Boundaries & Setting Class Boundaries

A number of definitions: The condition that is representative of a group of minimally disturbed sites organized by selected physical, chemical, and biological characteristics (Reynoldson et al. 1997). Representing important aspects of 'natural' or pre-Columbian conditions and at the same time, politically palatable and reasonable (Hughes 1995).

WFD’s definition Expected background (i.e. reference) conditions with no or minimal anthropogenic stress and satisfying the following criteria: (i) they should reflect totally, or nearly, undisturbed conditions for hydromorphological elements, general physico-chemical elements, and biological quality elements, (ii) concentrations of specific synthetic pollutants should be close to zero or below the limit of detection of the most advanced analytical techniques in general use, and (iii) concentrations of specific non-synthetic pollutants, should remain within the range normally associated with background levels (European Commission 2000). 75 words in Eus definition or 4xs the number of words of the previous 2 definitions.

A number of approaches: Best judgement (e.g. theoretical) Historical Spatial (regional) reference sites Predictive modelling Paleoecological reconstruction Curve fitting (stress trajectories) Extrapolation of lab to field

Best professional judgement convening expert panels to determine reference conditions BUT... judgement is a function of scientists’ expertise and quality of data supplied may be biased “it was always better then…” static measure

Historical may work for general statements about conditions BUT... useful if sites have been periodically resampled BUT... data often incomplete methods may not be comparable frequency/timing of sampling may confound analysis usually limited to a single community

Spatial reference sites acceptable levels of disturbance must be ascertained community variability represents the range of acceptable conditions BUT... ecoregions may not apply universally habitat (ecotype) classification often needed availability?

Predictive modelling allows for natural environmental gradients (continua) applicable to many metrics site-specific resolution BUT... high initial costs requires data, calibration and validation

Paleoecological reconstruction often restricted to lakes use of diatoms, pollen & chironomids BUT... high initial costs indicators may (only) reflect changes in water quality restricted to only a few organism groups

Curve fitting plotting metric or index values against disturbance or natural variables to determine reference conditions through curve fitting BUT... outliers, uneven data and absence of data from minimally disturbed sites can distort models

Extrapolating lab results to field relationships between test species and some stressors are known BUT... data not applicable to entire communities unsuitable for systems disturbed by other stressors

Do different approaches differ? What is the expected variability among methods commonly used to establish reference?

Lake Härsvatten size = 0.19 km2 Zmean =5.7m & Zmax = 26m altitude = 130 m a.s.l. catchment = 68% coniferous forest, 13% mire & 9% other water oligotrophic, mean TP = 7 µg/L

What is the reference ”pH” of lake Härsvatten?

pH - expert opinion

pH - regional variability

pH - site-specific modelling

pH - paleoreconstruction

pH - paleoreconstruction

So, what is the reference ”pH” of lake Härsvatten?

What is the reference ”TP” of lake Mälaren?

What is the reference ”TP” of lake Mälaren?

Setting Class Boundaries

WFD - the normative classification can be summarized as: high ≈ no or only minor deviations; good ≈ low levels of disturbance, but deviate only slightly; moderate ≈ moderate deviations and significant effects; poor ≈ major biological alterations and substantial deviation; bad ≈ severe biological alterations and large deviation.

WFD - stipulates 3 types of monitoring Surveillance - status & long-term changes Operational - systems at risk & ameliorative effects Investigative - ascertain causes of systems failing to meet environmental objectives

Factors to be considered in setting class boundaries number of classes - scientific or political stressor - response relationship symmetry or asymmetry of classes upper and lower limits or anchors variance within and among classes errors…errors…errors...

Errors associated with classification - sample collection & processing sampling variability (natural spatial heterogeneity and interoperator) sample processing (sort & identification) natural temporal variability asymmetrical pollution effects

Example of stressor - response relationship

Distribution reference values & selection of upper and lower anchors

Choice of upper anchor 95% CI may result in higher frequency of type 1 errors 10th percentile may result in higher frequency of type 2 errors

Choice of lower anchor zero value may result in higher frequency of type 2 errors minimum value may result in higher frequency of type 1 errors

Probability of misbanding (PM)† misclassification error increases markedly with band-width error! †Taken from Clarke 2000

The WFD is only the first footprint, we still need to find the path!