Identifying good indicators of disturbance

Posted on July 20, 2015

Because freshwater communities are vulnerable to many types of disturbance, such as changing land use, the removal of riparian vegetation, chemical contamination, and invasions by alien animals and plants, it’s useful to identify sensitive species, environmental parameters and freshwater systems that can be used as early indicators of disturbance. In a recent large-scale study, physical and biological data from 66 stream and 51 lake sites across northern Europe were analysed to compare the responses of different types of biota to nutrient enrichment. Data on phytoplankton, macrophytes and fish were available for lakes, and information on benthic diatoms, benthic invertebrates and fish were available for streams. For each taxonomic group, multispecies analysis was used to generate an index of community composition for each site. After the influence of system size (i.e, lake area or stream order) was factored out, the relationship between each community index and nutrient (total phosphorus) concentration was examined. All such correlations, but especially those involving the diatom and invertebrate indices, were significant. The curved shape of the relationships showed that diatom communities shifted strongly as nutrient levels rose to about 50 µg/L, while invertebrate communities changed at higher phosphorus concentrations (>1 mg/L). All the various community indices were significantly correlated with one another in both stream and lake habitats. However, because macrophytes were involved in the strongest of these correlations it seems that they were the best indicators of overall system biodiversity.

Reference: Johnson, R.K. et al. 2014. Cross-taxon responses to elevated nutrients in European streams and lakes. Aquatic Sciences 76, 51–60.