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Assessing Stream Substrate Quality: Metrics, Types, and Impacts on Aquatic Life

This document outlines the evaluation of stream substrate types and metrics critical for aquatic ecosystems. It details various substrate categories such as boulders, cobbles, gravel, sand, silt, and muck, including their identification, origin, and impact on fish and macroinvertebrate populations. Methodologies for pebble counting, such as the Wolman and Zig-Zag counts, are also discussed. The relationship between substrate quality, embeddedness, and the Index of Biotic Integrity (IBI) highlights the importance of maintaining diverse substrate types for healthy aquatic communities.

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Assessing Stream Substrate Quality: Metrics, Types, and Impacts on Aquatic Life

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  1. QHEI Header Standard River Code & RM Stream Name New Station ID Location Description Date Scorer Lat/Long

  2. Substrate Metric

  3. Substrate Metric • Identify Two Predominant Substrate Types • By Amount or Function • Two boxes in case one type is only dominant type (e.g., bedrock) • Lines after boxes for checking or estimating % of all substrate types present • Pebble count procedure provides good training for assessment of substrate

  4. Substrate Size Categories Boulder: > 10” Boulders as slabs: flat rather than round pieces Cobble: 2.5” to 10” Gravel: 1/12” to 2.5” (note wide range) Sand: gritty texture Silt: greasy texture, inorganic Muck: decayed organic material Detritus: leaves, sticks, wood Hardpan: usually clay, hard gummy surface

  5. Boulder-Cobble

  6. Clean Gravel Substrates

  7. Substrate Metric • Substrate Diversity • Number of substrate types • More substrate types = more “niches” • Many fish and macroinvertebrate species are associate with specific substrate types • Substrate Origin • Informational • From where did the substrates originate? • Bedrock, tills, alluvial sediments, colluvial sediments?

  8. Substrate Origin • Limestone: Often contains fossils, easily scratched with knife, usually bedrock or flat boulders and cobbles • Tills: Sediments deposited by glaciers; particles often rounded. Can be carried into non-glaciated areas • Wetlands: Usually organic muck and detritus • Hardpan: Clay – smooth, usually slippery • Sandstone: Contains rounded fragment of sand “cemented” together • Rip/Rap: Artificial boulders • Lacustrine: Old lake bed sediments • Shale: “Claystone,” sedimentary rock made of silt/clay, soft and cleaves easily • Coal Fines: Black fragments of coal, generally SE Ohio only

  9. Pebble Count Methodologies • Wolman Pebble Count • Zig-Zag Pebble Count • Riffle Stability Index • Others

  10. Pebble Count

  11. Pebble Count - Trends

  12. Silt Cover & Embeddedness • Pervuasiveness of silt cover & embeddedness • Smother habitats • Reduce oxygen penetration • Fines fill interstitial spaces

  13. Silt Cover

  14. Embeddedness – Side View

  15. Embeddedness • Sands, other fines cover larger substrates • “Dunes” indicate high bedload • Can often dig down to larger substrates

  16. Embeddedness - Aggradation • Import of fines > export • Results in “aggradation of sediments in riffles and pools • Symptom can be “spongy” deposits of sands and fine gravels that smother larger riffle particles

  17. Low Embeddedness: “Fish-eye View”

  18. High Embeddedness: “Fish-eye View”

  19. Substrate Embeddedness

  20. Fish IBI

  21. Substrate Metrics Strongly Correlated with IBI, Metrics • Affects overall community structure • Decrease substrate quality leads to loss of sensitive species • Decreasing substrate quality leads to increase in omnivores • Decrease substrate quality leads to decrease in many sport fish species (e.g., smallmouth bass).

  22. Substrate Score vs IBI

  23. TIVs for Substrate Score

  24. Substrate Effects: Strong on Individual Species: QHEI Substrate Score

  25. Smallmouth Bass vs QHEI Substrate

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