2014

Tolonen, Kimmo; Hämäläinen, Heikki; Lensu, Anssi; Meriläinen, Jarmo J.; Palomäki, Arja; Karjalainen, Juha

Environmental conventions aim to protect ecosystem structures and functions to provide goods and services for mankind. The degree of aquatic ecosystem naturalness, or ecological status as it is defined in the Water Framework Directive (WFD) of the European Union, is notionally linked to supplies of ecosystem services. In practice, these links have rarely been documented or even investigated, and to justify conservation and management objectives based on the status indicators, it is essential to demonstrate their relationships to ecosystem functions and services. The WFD requires member states to classify their surface waters aiming to achieve good ecological status of water bodies. However, an implicit assumption of the WFD, that the ecosystem functions and services targeted to be protected and maintained are related to the measured status, remains uncertain. Using a time‐series data set covering almost 50 years, we examined the development of ecological status of eight sub‐basins of a large boreal lake in response to improved wastewater management and decreasing pollution. We particularly evaluated whether the observed descriptors of biodiversity, ecosystem functions and services were associated with the judgements of ecological status, and hence whether the ecological status is a relevant proxy for ecosystem values to be protected. The ecological status of the polluted sub‐basins responded consistently to the decreased nutrient and organic loading. Temporal trends in the biological quality elements and water quality were mostly parallel and showed good status roughly simultaneously. Combined ecological status also appeared to predict some features of taxon diversity (profundal macroinvertebrate and phytoplankton richness), ecosystem functions (primary and bacterial production) and ecosystem services (fish catch and reproductive potential of coregonids). Synthesis and applications. We observed that some ecosystem service supplies and taxon diversity increased with increasing ecological status of the lake. Therefore, our results suggest that ecological status estimates based on simple structural characters are relevant to the ultimate management goals of maintaining biodiversity, ecosystem functions and services and hence might suffice for extensive assessment and monitoring of lake ecosystems.