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Stream Ecology I

Introduction

For the next six weeks, we will focus on stream ecology with particular reference to benthic macroinvertebrates. Macros include a variety of larval insects and other aquatic invertebrates. Macro diversity and abundance are important indicators of water quality stream health.

During the first of two labs introducing stream ecology, we will do a macro habitat assessment of our study stream, Middle Chillisquaque Creek at PPL’s Montour Preserve. We will determine whether the physical characteristics of this stream are sufficient for supporting benthic macroinvertebrate life.

Methods

Data collection.—Work in groups of two or three. Measure as many of the habitat characteristics that time allows. Record your data in your waterproof notebook. Methods for measuring habitat characteristics are modified from Dates and Byrne (1997).

Stream Bottom Composition—Examine a section of the stream bottom, and estimate the percent substrate in each category: boulder (>256 mm), cobble (64-256 mm), pebble (16-64 mm), gravel (2-16 mm), sand (0.06-2 mm), and silt (<0.06 mm).

Embeddedness—Embeddedness is the percent surface area of larger particles (boulder, cobble, pebble, gravel) surrounded or covered by sand or silt. Pick up a rock. Often the bottom will be a lighter color; that lighter area was embedded. Pick up six rocks and estimate the embeddedness of each one. Average the values to get an embeddedness value for the stream.

Current Velocity—Measure the current velocity in four places, two relatively fast and two relatively slow. For each velocity measurement, mark off a 3-m segment of the stream. Drop a float into the water and time how long it takes to travel 3 m. Convert your measurements to m/s and average your four values

Velocity-Depth Regimes—Record which of the following velocity-depth regimes are present in the stream: slow-deep, slow-shallow, fast-deep, fast-shallow. “Deep” is >60 cm.

Bank/Channel Alteration—Face upstream and record the percent left bank and the percent right bank that appear to be altered (by people). Also record the percent of the channel that has been artificially straightened.

Riffle Percent—Measure a 20-m segment of stream. Within that 20-m segment, measure of length of any riffles (where the water breaks the surface). Divide the sum of the riffle lengths by the total length examined (20 m) to find the percent of the segment that is riffle.

Percent Bottom Exposed—Record the percent stream bottom that is not covered by water.

Condition of Banks—Face upstream and record the percent left bank and the percent right bank that is eroding. Indicators of erosion include bare soil, crumbling or slumping bank, and exposed tree roots.

Bank Vegetation—Face upstream and record the percent left bank and the percent right bank that is covered by grasses, shrubs, or trees.

Riparian Vegetation Zone—Record the average width of the zone of trees and shrubs along the bank to the first clearing.

Overhead Canopy—Stand in the middle of the stream with arms outstretched horizontally toward each bank. Raise each arm until it points to the top of the vegetation on each bank. The percent canopy is the percent of the 180° arc that your arms traveled.

Data analysis.—In the lab, score each habitat characteristic and calculate an overall habitat assessment score.

Assignment

The data collected today will be combined with data from the next lab for the second lab report.

Literature Cited

Dates, G., and J. Byrne. 1997. Living waters: using benthic macroinvertebrates and habitat to assess your river’s health. River Watch Network, Montpelier, Vermont, USA.