Transcript Desperately Seeking a Sound Ecological Environment: Biotic

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
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
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
Maintenance of a sound ecological environment requires:
Maintenance of a sound ecological environment requires:

• knowledge of biotic responses to flow variation
• knowledge of biotic responses to flow variation
(not for every element, but some important elements)
(not for every element, but some important elements)
• adoption of ecological indicators that permit assessment
of success
failure indicators that permit assessment
• adoption
of or
ecological
of
success
or failure
(We
need hydro-biological
analogues of the water quality
indicators used for TCEQ’s aquatic life use standards.)
(we need an analogue of the TCEQ 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
Condition of the Biotic Community
(Specific to Ecotype)
Aquatic Life Conceptual Model, Biological Tiers
Susan Jackson, US EPA
1
natural
2
evident changes in structure,
3
minimal changes in function
4
5
evident changes in
structure & function
LOW
Human Disturbance Gradient
6
HIGH
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 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
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)
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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?
Drainage
River
Segment
Reach
Habitat
Microhabitat
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.
1400
1200
Oxbow 1 connects
CMS
1000
800
Oxbow 2 connects
600
Oxbow 3 connects
400
200
0
6/93
6/94
6/95
6/96
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
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)