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Spatial Distribution of Benthic Macroinvertebrates in the Pithlachascotee River

This study by Dr. David L. Evans explores the spatial distribution of benthic macroinvertebrates in the Pithlachascotee River and its implications for determining minimum flows and levels (MFLs). Funded by SWFWMD, the research highlights the relationships between flow, salinity, and macroinvertebrate community structure. It provides insights into how environmental factors influence these organisms, which play a crucial role in aquatic ecosystems. The findings underscore the significance of managing water resources to maintain ecological balance, especially under changing conditions.

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Spatial Distribution of Benthic Macroinvertebrates in the Pithlachascotee River

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  1. Spatial Distribution of Benthic Macroinvertebrates in the Pithlachascotee River – Application to Minimum Flows and Levels Presented by: David L. Evans, Ph. D.

  2. Acknowledgments • Funded by SWFWMD • Douglas G. Strom • E. Lynn Mosura-Bliss • Laura A. Line • SWFWMD - Michael (Sid) Flannery

  3. Background • Florida Statute 372.042 defines MFLs as “the limit at which further withdrawals would be significantly harmful to the water resources or the ecology of the area.” • MFLs vary seasonally and spatially. • Relationships between salinity, flow, and benthic macroinvertebrate community structure.

  4. Benthic Invertebrates • Integral in establishing trophic structure of an aquatic ecosystem • Promote exchange of nutrients, oxygen and pollutants between sediments and overlying water • Limited motility - unable to escape environmental conditions • Integrate numerous environmental factors over a relatively long time span

  5. Flow and Benthos • Flow can influence biological communities • Food acquisition (filterers), physical adaptation to flow • Influence on residence time, dissolved oxygen, salinity, nutrients and substrate condition • Osmotic tolerances of species

  6. Pithlachascotee River Basin

  7. Pithlachascotee River Study Area

  8. Trend Analysis Plot for Average Flow

  9. Historical Salinity Data

  10. Top and Bottom Salinity

  11. Oyster Distribution

  12. Oyster Distribution

  13. Oyster Distribution

  14. Number of Benthic Invertebrate Taxa

  15. Shannon-Wiener Species Diversity Index

  16. Benthic Invertebrate Abundance

  17. Bray-Curtis Similarity

  18. Bray-Curtis Similarity

  19. Principal Components AnalysisMean Physicochemical Values

  20. Rank Analysis • Dominance Index • Total Abundance • Average Contribution to Dissimilarity

  21. Longitudinal distribution of Ampelisca sp.

  22. Longitudinal distribution of Mediomastusambiseta

  23. Distribution of Hobsoniaflorida

  24. Longitudinal distribution of Uromunnareynoldsi

  25. Longitudinal distribution of Americorophium sp. A

  26. Longitudinal distribution of Polypedilumhalterale

  27. Optimal Salinity at Capture

  28. Optimal Salinity at Capture (ppt) • Polypedilumhalterale 6 • Americorophium sp. A 7 • Uromunnareynoldsi 8 • Hobsoniaflorida 16 • Apocorophiumlouisianum 18 • Edotiareynoldsi 19 • Grandidieriellabonnieroides 21 From

  29. Optimal Salinity at Capture (ppt) • Laeonereisculveri 22 • Ampelisca sp. 30 • Mediomastusambiseta 30 • Fabricinudatrilobata 32

  30. Summary • Mean water column salinity 0.5 to 33 • Rapid change between RK 8 and RK 9.5 – Mesohaline zone • Oysters extend to RK 6.6 – 25ppt • 71 taxa at RK 2 to 24 taxa observed between RK 9.5 and RK 10.5

  31. Summary • Benthic infauna assemblages at RK 0 through RK 8 significantly differed from assemblages at RK 9.5 through RK 11.2 • Difference was strongly driven by the salinity gradient in mesohaline zone (8-18 ppt) between RK 8 and RK 9.5

  32. Potential Indicators • Upper limit mesohaline (8 ppt): • Americorophium sp. A • Uromunnareynoldsi • Polypedilumhalterale • Lower limit mesohaline (18 ppt) • Apocorophiumlouisianum • Edotiatriloba • Laeonereisculveri

  33. Minimum Flows and Levels • Extended periods of low flow and increased salinity: • Increase in total number of taxa • Increase in salt-tolerant taxa • Reduction or elimination of oligohaline and freshwater taxa Polypedilumhalterale Uromunnareynoldsi Gammarustigrinus

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