Insights into Human Impacts on Streams from Tolerance Profiles of Macroinvertebrate Assemblages

Abstract

We present the concept of assemblage tolerance profiles (ATPs) as an aid to freshwater bioassessment, and illustrate it with a practical example. An ATP describes the proportion of taxa in an observed assemblage that is estimated to tolerate each level of a specific stressor within a defined range. We used an extensive compilation of biomonitoring field data to estimate the lower tolerances for pH and dissolved oxygen (DO) of common families of macroinvertebrates in rivers of south-eastern Australia. These limits were then used to establish ATPs for macroinvertebrate assemblages at 30 sites across six river systems with varying levels of exposure to drainage from disused mines and discharges from sewage treatment plants. We hypothesised that sites with more exposure to mine drainage would have ATPs indicating greater tolerance of low pH, whereas sites with more exposure to sewage discharges would have ATPs indicating greater tolerance of low DO, and found that these hypotheses were confirmed for five of the six river systems. We suggest that stressor-specific ATPs, based on tolerances derived from either field distributions or laboratory tests, can help to verify or eliminate candidate causes of inferred human impacts on aquatic ecosystems.

Relationships between lotic macroinvertebrate traits and responses to extreme drought

“…Use of atmospheric respiration was characterised as the percentage of all respiratory modes of aquatic life‐cycle stages of each family that involved access to atmospheric oxygen (possible modes being aerial, branchial, cutaneous, plastron and pulmonary). An estimate of minimum dissolved oxygen (DO) concentration tolerated by aquatic stages of each family was obtained from calculations made by Chessman & McEvoy ().…”