Seeking a Sound Ecological Environment: Biotic Responses to Instream Flow Variation

1. Seeking a Sound Ecological Environment:Biotic Responses to Instream Flow Variation Kirk O. Winemiller Section of Ecology, Evolution and Systematic Biology Dept. of Wildlife and Fisheries Sciences Texas A&M University, College Station

2. The state of Texas has requested studies that identify flow conditions in the state’s rivers and streams necessary to support a sound ecological environment (Texas Water Code 16.059) The challenge is to make this concept operational.

3. A sound ecological environment: ________________ 1. sustains the full complement of native species in perpetuity 2. sustains key habitat features required by species 3. retains key features of the natural flow regime required by species to complete their life cycles 4. sustains key ecosystem processes & services, such as elemental cycling & productivity of important plant & animal populations

4. How are these characteristics achieved? • minimum flows during periods of stress (severe drought) • prolonged high flows during periods critical for … reproduction (spawning, nesting, nursery habitats) movement between critical habitats (e.g., longitudinal & lateral connectivity) • high flow pulses that create key habitat features

5. minimum flows during periods of stress (severe drought)

6. prolonged high flows during periods critical for … reproduction (spawning, nesting, nursery habitats) movement between critical habitats (e.g., longitudinal & lateral connectivity)

7. high flow pulses that create key habitat features

8. Maintenance of a sound ecological environment requires: • knowledge of biotic responses to flow variation (not for every element, but some important elements) • adoption of ecological indicators that permit assessment of success or failure (We need hydro-biological analogues of the water quality indicators used for TCEQ’s aquatic life use standards.) Maintenance of a sound ecological environment requires: • knowledge of biotic responses to flow variation (not for every element, but some important elements) • adoption of ecological indicators that permit assessment of success or failure (we need an analogue of the TCEQ aquatic life use standards) 

9. • knowledge of biotic responses to flow variation we have this for certain elements– generally - fluvial geomorphology, instream & riparian habitats - fish spawning periods, nursery habitats we have this for certain systems/species– specifically - blue suckers in lower Colorado River - fountain darters in San Marcos River • adoption of ecological indicators that permit assessment of success or failure

10. • knowledge of biotic responses to flow variation • adoption of ecological indicators that permit assessment of success or failure holistic– involving flow-sensitive elements of instream habitat fish assemblages riparian trees specific– fish species mollusk species riparian tree species

11. Aquatic Life Conceptual Model, Biological Tiers Susan Jackson, US EPA 1 natural 2 evident changes in structure, minimal changes in function 3 Condition of the Biotic Community (Specific to Ecotype) 4 5 evident changes in structure & function 6 LOW Human Disturbance Gradient HIGH

12. Ecological indicators: The number of elements comprising holistic indicators & the number of specific indicators … should be kept to a minimum… for ease of implementation and consistency, but, more importantly, for validity.

13. Ecological indicators … must be sensitive to changes in flow more than other environmental impacts such as degradation of water quality (pollution) or physical habitat (channelization, siltation).

14. Holistic ecological indicators: Effects of regional factors must be recognized and controlled. • Climate • Geology • Historical biogeography Linam, G.W., L.J. Kleinsasser & K.B. Mayes. 2002. Regionalization of the index of biotic integrity for Texas streams. TPWD, River Studies Report No. 17 • Southern deserts • Western high plains and southwestern tablelands • Subhumid agricultural plains • Central Texas plateau • Southern Texas plains • South central and southern humid, mixed land use region • Western Gulf coastal plain

15. Hoeinghaus, D.J., K.O. Winemiller & J.S. Birnbaum. Local vs. regional influences on the structure of fish assemblages in Texas streams. Submitted to Journal of Biogeography • Methods • • species assemblage & environmental data for 157 sites in 10 streams from 5 basins • • species grouped into functional groups based on trophic & life-history characteristics • • 19 local & 14 regional environmental variables • • analysis with similarity indices, null models of co-occurrence & ordination techniques • Findings • Taxonomic analyses reveal prominent role of regional-scale environmental factors & historic biogeography on fish assemblage structure. • Analysis of functional groups indicated equal roles of local & regional environmental factors, with assemblages distinguished by a habitat template irrespective of biogeographic province.

16. Specific ecological indicators: Flow sensitive, but also species of special concern– • Threatened species (but not too rare) (e.g. blue sucker) • Recreationally important species (e.g. Guadalupe bas) • “Keystone” species (e.g. bald cypress)

17. How to study indicator taxa? Issues of scale: Taxonomic scale – species vs. environmental guilds Welcomme, R.L., K.O. Winemiller & I.G. Cowx. 2005. Ecological guilds as a tool for environmental impact assessment in rivers. River Research and Applications, in press. Rithronic– riffle pool Potamonic– pleisiopotamonic paleopotamonic annual eupotamonic pelagophilic eupotamonic lithophilic eupotamonic phytophilic parapotamonic eupotamonic benthic eupotamonic riparian Estuarine– freshwater brackishwater semi-anadromous amphidromous catadromous marine

18. How to study specific indicator taxa? Issues of scale: Spatial scale – how large of an area? how many areas? Drainage River Segment Reach Habitat Microhabitat

19. Oxbow 1 connects Oxbow 2 connects Oxbow 3 connects 6/93 6/94 6/95 6/96 How to study specific indicator taxa? Issues of scale: Temporal scale – when to sample? how often? Zeug, S.C., Winemiller, K.O. & S. Tarim. 2005. Response of Brazos River oxbow fish assemblages to patterns of hydrologic connectivity and environmental variability. Transactions of the American Fisheries Society 134:1389-1399. Fish assemblage structure in both the Brazos River & oxbow lakes is influenced by flows that connect channel & off-channel habitats.

20. How to study specific indicator taxa? Issues of scale: Level of mechanistic detail – How much? Simple: Linear regression abundance = a(flow) + b Intermediate: Hydraulic-habitat discharge relationships • IFIM–PHabSim, etc. Complex: Individual-based simulation models • mechanistic bio-environmental relationships are modeled explicitly • information (data) hungry • computationally intensive

21. Seeking a Sound Ecological Environment – conclusions – • requires consensus for an operational definition of a sound ecological environment • adoption of ecological indicators that permit assessment of success or failure holistic– aq. life use indicators w/ flow-sensitive elements specific– indicator fish, mollusk, riparian tree taxa • establish relationships of indicators to streamflow characteristics (subsistence, base, high, pulse, flood)