Guidance on establishing nutrient concentrations to support good ecological status Introduction and overview Martyn Kelly

Purpose What it is not: a step towards international nutrient standards that will be enforced by the European Commission What it is: guidance to help Member States understand concentrations necessary to support GES At GES “nutrient concentrations [should] not exceed the levels established so as to ensure the functioning of the ecosystem and the achievement of the values specified for the biological quality elements (Annex V, Section 1.2) Who for? Everyone, in theory, to check their current standards; more specifically, for MS developing or revising standards

Key principles What fractions are measured? What is the temporal resolution of data? N and/or P? Do we understand ecological processes? What about multiple stressors? A causal relationship between nutrient(s) (“pressure”) and a biological variable (“response”) can be expressed in a statistically meaningful manner which can inform decisions for managing water bodies Several facets: Ecological Chemical Statistical Regulatory How do we deal with noisy datasets, non-linearity, short gradients and associated issues? How much does the regulatory regime influence the approach to setting nutrient standards?

Historical roots: Vollenweider and the OECD models Several principles emerge: Need for international co-operation Use of regression analysis Need to incorporate statistical uncertainty Recognition that different types of lake need different standards.

Ecological principles Early methods developed for phytoplankton in deep lakes Linear regression models less powerful in many other ecosystems Shallow lakes (“alternative stable states”) Rivers Coastal and transitional waters Multiple stressors N versus P When is a bivariate cause-effect relationship appropriate? How do other stressors interact with variable of interest? How do MARS outputs help us?

Chemical principles “Pressure” = excess supply of limiting nutrient Do we know what this is? How? N:P ratio? Bioassay? Does it vary through the year? How representative is the measure used? Annual / seasonal average versus spot samples? Sampling frequency? Does fraction equate to “available”? TP in lakes: the “pressure” is also the “response” Units Different in freshwaters and marine/transitional waters

Statistical principles To be covered by Geoff

Regulatory issues Objective is to minimise mismatch between classifications based on biology and nutrients Therefore increase likelihood that interventions will lead to change in biology Biology  GES < GES Chemistry GES No problem Mismatch! Left: use of line of best fit. Some rivers wrongly downgraded

How is nutrient standard used? Action triggered as soon as boundary is exceeded? Use upper confidence interval to minimise “false positives” (i.e. action where biology  GES) Exceedance of nutrient boundary is one of several strands of evidence that needs to be considered Lower boundary may be appropriate

Feasibility checks Intercalibrated BQE known to be sensitive to nutrients in the water bodies under consideration? Dataset spans at least four status classes? Linear response across range of interest? H/G and G/M boundaries Predictive power? (regression v categorical approach) Can national types be merged? Can you work with neighbouring MS?

Overview of process (“Road map”) Do you have nutrient thresholds at present If so ... Check via Tables If not ... Use flow charts

Other approaches Establish historical baselines (DE) Modelling approaches (SE) Multivariate analyses Site-specific predictions (UK) Use lake standards to derive river standards (NO) Scope for more to be added ...

Validation Check standards using independent data / variables Arctic charr to check thresholds in deep lakes Chara to check thresholds in shallow lakes Cyanobacteria abundance Palaeoecology Other ideas ?

Comments received Who is the document for? Clarify when categorical approaches should be used Multiple pressures identified … but what are the solutions? Nutrient combination rule? Identify role of nutrient history / internal loading Protecting downstream water bodies Validation should be developed Big document … move toolkit and broad type thresholds to annex?