Macroinvertebrate (“Bug”) Monitoring
Biological monitoring using macroinvertebrates indicates water quality based on what organisms (insect larvae, aquatic worms, snails, leeches, crayfish) are living in the stream. As most spend a large part of their life cycle in the water, macroinvertebrates can give a longer-term feel for water quality where chemistry provides a “snapshot”.
Some macroinvertebrates are pollution intolerant while others are more tolerant. The results of a macroinvertebrate survey are dependent to a large extent on habitat. Some species simply prefer one habitat type (riffle vs. pool) and are not expected to be found at another habitat type regardless of water quality. Biological indices based on macroinvertebrates use knowledge of tolerance of different insect larvae specifically to dissolved oxygen concentration (for example, Hilsenhoff’s work in Wisconsin rivers). It may not be appropriate to compare data between an upstream cold rocky reach and a downstream slough because of differences in physical habitat. We continue to tackle this project with borrowed equipment through the University of Wisconsin Extension office and the cooperation of Andy Goyke at Northland College for the use of microscopes.
Macroinvertebrate sites mirror current or desired water chemistry monitoring sites, with some annual fluctuations in partipants. We are using Hilsenhoff’s Family-Level Index to “score” water quality at each site, determined by the identification of macroinvertebrates to family level. Through training from SRWA staff, our volunteers may complete identification of their 125 “bug” sample. We continue to work with UW-Superior to double-check all identifications and determine other appropriate indices for interpreting our data.