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
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.
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
• 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
How are these characteristics achieved?
reproduction (spawning, nesting, nursery habitats)
movement between critical habitats (e.g., longitudinal & lateral connectivity)
prolonged high flows during periods critical for …
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)
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.)
• 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
• 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
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evident changes in structure,
minimal changes in function
Human Disturbance GradientLOW HIGH
3
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evident changes in
structure & function
Aquatic Life Conceptual Model, Biological TiersSusan Jackson, US EPA
natural
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.
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).
Holistic ecological indicators:
Effects of regional factors must be recognizedand 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
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.
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)
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
How to study specific indicator taxa? Issues of scale:
Spatial scale – how large of an area? how many areas?
Habitat
Microhabitat
Reach
Segment
River
Drainage
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.
0
200
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CM
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6/93 6/94 6/95 6/96
Oxbow 1 connects
Oxbow 2 connects
Oxbow 3 connects
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
• 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)
Seeking a Sound Ecological Environment– conclusions –
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