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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.

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seeking a sound ecological environment biotic responses to instream flow variation
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

slide2

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.

slide3

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

slide4

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

slide6

prolonged high flows during periods critical for …

reproduction (spawning, nesting, nursery habitats)

movement between critical habitats

(e.g., longitudinal & lateral connectivity)

slide7

high flow pulses that create

key habitat features

slide8

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)

slide9

• 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

slide10

• 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

slide11

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

slide12

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.

slide13

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).

slide14

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

slide15

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.

slide16

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)

slide17

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

slide18

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

slide19

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.

slide20

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

slide21

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)