When assessing ecological status, do we use the best indicators?

All that are working with the EU Water Framework Directive (WFD) are familiar with the quality elements used as indicators to assess the ecological status of water bodies. But does that mean that we know what the best indicators are? In a new paper, Finnish BIOWATER colleagues have tested the use of fungi as indicators of ecological status. Fungi are a key component in stream ecosystem functioning, but they are rarely used in contemporary monitoring.

The authors compared how fungi and two traditional biological quality elements reflected ecological status in rivers:

  • Leaf-associated fungal decomposers, which are, quite simply, fungi that decompose leaves.
  • Benthic macroinvertebrates, which are small animals living at the bed of a river, such as insects, molluscs, and worms.
  • Diatoms, which are single-celled algae with a cell wall made of silica.

Whereas the two latter indicators are widely used, the potential use of fungi has been much less studied. Using data from 113 Finnish streams, the authors built models for prediction of reference conditions for fungi, macroinvertebrate, and diatom taxa.

From the experiements, with fungi leaf-pack assay in a Finnish stream. Photo: Jukka Aroviita.

Interestingly, the fungi proved the most sensitive parameter to assess impacts in streams disturbed by multiple anthropogenic stressors (nutrient enrichment, sedimentation, and acidification).

The outcome clearly suggests that using fungi could make an important contribution to ecological assessment. Moreover, the rapid progress of global microbial databases and declining costs of high-throughput sequencing will facilitate the use of fungal communities in bioassessment.

Jyväsjärvi J, Lehosmaa K, Aroviita J, Turunen J, Rajakallio M, Marttila H, Tolkkinen M, Mykrä H, Muotka T 2021. Fungal assemblages in predictive stream bioassessment: A cross-taxon comparison along multiple stressor gradients. Ecological Indicators 121: 106986. https://doi.org/10.1016/j.ecolind.2020.106986

(Feature photo: Eva Skarbøvik)