Nutrient criteria for surface waters under the European Water Framework Directive: Current state-of-the-art, challenges and future outlook

Abstract

The aim of European water policy is to achieve good ecological status in all rivers, lakes, coastal and transitional waters by 2027. Currently, more than half of water bodies are in a degraded condition and nutrient enrichment is one of the main culprits. Therefore, there is a pressing need to establish reliable and comparable nutrient criteria that are consistent with good ecological status.This paper highlights the wide range of nutrient criteria currently in use by Member States of the European Union to support good ecological status and goes on to suggest that inappropriate criteria may be hindering the achievement of good status. Along with a comprehensive overview of nutrient criteria, we provide a critical analysis of the threshold concentrations and approaches by which these are set. We identify four essential issues: (1) Different nutrients (nitrogen and/or phosphorus) are used for different water categories in different countries. (2) The use of different nutrient fractions (total, dissolved inorganic) and statistical summary metrics (e.g., mean, percentiles, seasonal, annual) currently hampers comparability between countries, particularly for rivers, transitional and coastal waters. (3) Wide ranges in nutrient threshold values within shared water body types, in some cases showing more than a 10-fold difference in concentrations. (4) Different approaches used to set threshold nutrient concentrations to define the boundary between “good” and “moderate” ecological status. Expert judgement-based methods resulted in significantly higher (less stringent) good-moderate threshold values compared with data-driven approaches, highlighting the importance of consistent and rigorous approaches to criteria setting.We suggest that further development of nutrient criteria should be based on relationships between ecological status and nutrient concentrations, taking into account the need for comparability between different water categories, water body types within these categories, and countries.

The Globalization of Cultural Eutrophication in the Coastal Ocean: Causes and Consequences

“…However, despite numerous policy directives and conventions, the most recent assessment of trophic status of European coastal ecosystems (European Environmental Agency [EEA], 2018) shows that 40% of coastal (continental shelf) waters and 66% of transitional waters (estuaries) failed to achieve the objective of good ecological status 34 (Poikane et al, 2019). Therefore, a new Fertilizing Products Regulation was adopted in 2019, and 32 The practice of tilling sloped land along lines of consistent elevation in order to conserve rainwater and to reduce soil losses from surface erosion.…”

Nitrogen and phosphorus limitation and the management of small productive lakes

“…A Policy Forum Review in Science concluded that amelioration of the negative impacts of nutrient enrichment should be made by control and reduction of both N and P (Conley et al 2009); more recent work supports this contention (Lewis et al 2011, Wurtsbaugh et al 2019. Recent considerations on the Water Framework Directive (Poikane et al 2019) also recognise the importance of considering N as well as P reduction. Although seemingly counterintuitive, sites failing P targets (high P) might be most effectively managed by reducing N, evidenced by our finding that the phytoplankton are most likely to be N limited, and those failing N targets (high N) may be best managed by reducing P, evidenced by our finding that the phytoplankton are most likely to be P limited.…”

Comparing nutrient reference concentrations in Nordic countries with focus on lowland rivers

“…Harmonisation of Nordic methods, including nationally established RCs for nutrients, will be required to compare impacts of the land use changes across countries. As noted by Poikane et al (2019), the G/M boundaries for European rivers vary widely among the EU countries, implying variations in the associated RC levels as well.…”