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The Effects of Substrate Size on Stream Macroinvertebrate Population Size and Structure

The Effects of Substrate Size on Stream Macroinvertebrate Population Size and Structure. K.M.Livengood A.M.Fusco M.R.Hogan. Objectives. Introduction - Background - Previous Studies - Hypothesis Methods Results Conclusion. Background.

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The Effects of Substrate Size on Stream Macroinvertebrate Population Size and Structure

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  1. The Effects of Substrate Size on Stream Macroinvertebrate Population Size and Structure K.M.Livengood A.M.Fusco M.R.Hogan

  2. Objectives Introduction - Background - Previous Studies - Hypothesis Methods Results Conclusion

  3. Background • Substrate size and type determines the type of macroinvertebrates which will live in a specific habitat • Large size substrate = more interstitial habitat and reduced current = species abundance and diversity?

  4. Previous Studies • Evaluating the Effectiveness of Five Mineral Artificial Substrates for the Sampling of Benthic Macroinvertebratesby Alonso and Camargo • No affect of substrate size on species richness • Substrate size affects the density of macroinvertebrates

  5. Hypothesis • More abundant macroinvertebrates in large substrate habitats • Increased macroinvertebrate diversity in large substrate habitats

  6. Study Site • Sinking Creek • Giles County, Virginia • Hardness= 141.6 ppm • High buffering capacity • pH= 8.5 • Diverse macroinvertebrate population

  7. Gravelometer • Substrate measured at two sites • Gravelometer measures b-axis of stones • Site one, small substrate= 2-11.6 mm • Site two, large substrate= 16-180 mm

  8. Experiment • Mesh bags were filled with stones • Four bags of large stones, four bags of small stones, and four bags of mixed stones • Tied closed • Mesh large enough for macroinvertebrates to come and go

  9. Experiment • Two bags of each substrate size (small, large, mixed) were placed at each site • Bags were left in stream for colonization for three weeks • Identified macroinvertebrates to family

  10. Downstream Site

  11. Upstream Site

  12. Analysis of Data: Shannon-Weiner • Two-way ANOVA test • The P value was > 0.05

  13. Total Abundance and EPT Abundance • Two-Way ANOVA results for total abundance showed there was not a great enough difference in location or treatment to rule out chance • Two-Way ANOVA results for EPT abundance showed that there was not enough difference in treatments to rule out chance • However, there was a significant difference in location – the Upstream site had a greater EPT abundance than the Downstream site

  14. EPT • a group of three orders of insects (Ephemeropter [mayflies], Plecoptera [stoneflies], and Trichoptera [caddisflies]) generally considered as sensitive to pollution and used in some cases as primary indicators of stream aquatic integrity.

  15. Ephemeroptera FIGURE 2 Trichoptera FIGURE 4 Plecoptera FIGURE 3 EPT

  16. Discussion • Our results did not support our hypothesis • EPT abundance was greater in the upstream section, where there were larger substrates originally • We believe that on a larger scale our hypothesis would be true

  17. Conclusions • Treatments did not lead to results that are statistically significant • Our hypotheses was not supported, future studies could be done differently • More reps could rule out chance and nets may be left in the stream longer for colonization • Our hypotheses may be wrong and the substrate size may not have as great an effect on macroinvertebrate population as other environmental factors

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