Estimating Macroinvertebrate Biomass for Stream Ecosystem Assessments.

Kenneth W Cummins,Richard Merritt,Brigitte Kolouch,Margaret Wilzbach

doi:10.3390/ijerph19063240

Abstract

We propose a field procedure for estimating the dry biomass of stream macroinvertebrates. Estimates are calculated using the mean values of the a and b regression coefficients from unpublished data and an extensive review of the relevant literature. The regression equation employed for calculating dry biomass is one that has been extensively used: Y = aXb, where Y = mg dry mass of an individual macroinvertebrate; X = mm total body length of an individual macroinvertebrate; a = intercept coefficient of the Y on X regression; and b = slope coefficient Y on X. The procedure was developed for use in the field, but dry mass estimates can also be made on preserved specimens. The case is made for presenting stream macroinvertebrate dry biomass data categorized by functional feeding groups (FFGs) and their component higher level taxa. The tables summarize the FFGs and their food resources, mean regression coefficients, dry biomass estimates for FFG-taxa by size and a comparison of their numerical-to-gravimetric surrogate FFG ratios to predict the stream environmental condition. A sizing template for rapidly sorting macroinvertebrates in the field is described. Thresholds for surrogate FFG ratios that directly predict measured stream ecosystem conditions are described.

Highlights

The taxonomic composition and relative abundance of macroinvertebrates have served worldwide as major tools for evaluating the environmental condition of running water ecosystems (e.g., [1–5]).With few exceptions, stream studies have reported numerical macroinvertebrate data
When presenting macroinvertebrate biomass data, a good case can be made for categorizing them as functional feeding groups (FFGs) (e.g., [6–10])
We propose a simple procedure for estimating the dry biomass of the taxonomic components of macroinvertebrate functional feeding groups (FFGs) for use in a stream ecosystem or other analyses

Summary

Introduction

The taxonomic composition and relative abundance of macroinvertebrates have served worldwide as major tools for evaluating the environmental condition of running water ecosystems (e.g., [1–5]).With few exceptions, stream studies have reported numerical macroinvertebrate data When presenting macroinvertebrate biomass data, a good case can be made for categorizing them as functional feeding groups (FFGs) (e.g., [6–10]). The biomass ratios of the FFGs can serve as surrogates for directly measured stream ecosystem environmental attributes [7].

Results

Conclusion