How stressor specific are trait-based ecological indices for ecosystem management?

Area of Science:

• Ecology
• Environmental Science
• Bioindicators

Background:

• Macroinvertebrates are traditional ecological indicators for various stressors.
• Correlations between macroinvertebrate indices in field data can stem from correlated stressors or inherent taxon sensitivities.
• Ignoring correlation sources leads to ambiguous conclusions on stressor impacts.

Purpose of the Study:

• To demonstrate a method using Monte Carlo simulations to differentiate correlation causes.
• To assess the stressor specificity of trait-based indices and its dependence on taxon pool and resolution.
• To analyze inherent correlations versus actual correlations in field samples.

Main Methods:

• Monte Carlo simulations to distinguish correlation sources.
• Analysis of sensitive/insensitive taxa frequencies for index combinations.
• Comparison of inherent correlations from random taxon pools with actual field sample correlations.
• Application to existing (SPEARpesticides, Saprobic Index) and new indices (temperature, flow, pH).

Main Results:

• Strong correlations were observed between several indices in the Swiss Plateau study area.
• The probability of correlations being solely due to inherent taxon sensitivities was low (max 0.34).
• Inherent correlation issues are more pronounced with smaller taxon pools and lower taxonomic resolution.

Conclusions:

• Correlation in taxon sensitivities creates inherent correlations in trait-based indices, reducing their explanatory power.
• Correlation analyses are crucial when using trait-based indices for ecosystem management.
• This is particularly important in regions with reduced biodiversity.