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?

minimum flows during periods of stress (severe drought)

reproduction (spawning, nesting, nursery habitats)

movement between critical habitats (e.g., longitudinal & lateral connectivity)

prolonged high flows during periods critical for …

high flow pulses that create key habitat features

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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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.

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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 –