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Assessments 2:
What the biota can tell us about watershed condition
K.E. Limburg lecture notes
26 March, 2002
Outline
1. Intro: a brief glimpse at a defining moment for KL
2. What we mean by “watershed health”
3. Biotic assessments – common methods
Biotic assessments – an introduction through a study by KL and colleagues in the Hudson River watershed
Research project:
“Larval fish use of tributaries of the Hudson” – R.E. Schmidt and K.E. Limburg
Goal: to quantify “larval fish flux” from tributaries to the mainstem – connecting the system pieces
Initial hypotheses:
1. Spawning would proceed from south to north (temperature effect)
2. More production in smaller streams
3. Anthropogenic effects might be important
Studied 16 tribs, in 4 “reaches” of the estuary: 1st to 9th order
• sampled weekly for 15 weeks in spring
• 4 teams sampled during same 48 hr period – synoptic survey
• collected fish larvae, measured flow, DO, pH
Some streams were sublime
Some had obvious problems!
Some streams were just mysterious at the time!
Methods
Dusk sampling…
“proto-GIS”
Method of quantifying land use
Results
Ln(1
+(#
fish/
m3 )
)
Strong spatial patterns
Tribs warmed up more or less simultaneously – we did not see a south-to-north trend in fish production
Size of stream did not appear to matter in this study
Land use type, in particular, land in urban and suburban uses, did!!
Main points:
Verified by other studies in other places
Watershed Health• How does land use change affect the ecological structure and function of a watershed?
• How can environmental change be linked to land use and economic change?
• What is/should be the role of watershed health and monitoring in designing policy?
• How does tributary health affect the larger ecosystem?
Ecosystem (and hence, watershed) health, qu’est-ce que c’est? - a concept that’s been around a long time, currently enjoying a comeback
• maintenance of “biotic integrity”
• resistance and/or resilience of systems in the face of disturbance
• absence of factors that degrade ecological population, community, and ecosystem structure and function
Waterways and water bodies are often good sites for assessing “watershed health”
-- why?
Low Human influence High
Met
ric B
Met
ric A
Ecosystem indicators of anthropogenic disturbance should ideally be sensitive to these factors, and not confounded by natural ones
(or at least possible to tease out the differences)
Federal, state, local agencies have really espoused this concept
So have many non-profit organizations
Possible to enlist the help of many volunteers (e.g., FL-LOWPA, Hudson R. Basin Watch)
US EPA
EPA Bioindicators homepage:
http://www.epa.gov/bioindicators/index.html
US EPA
US EPA
US EPA
US EPA
Assessing watershed health with biotic indicators:
The idea: organisms and ecosystems integrate and reflect the insults (or lack thereof) resulting from watershed-level processes
Some techniques have proven robust after 25+ years of testing; others in development
Indicators of ecosystem health can (should?) evaluate changes at levels of
•Population•Community/habitat•Whole-system
Metrics may not all be additive, although many schemes designed that way
1. Taxonomic soundness and easily recognized2. Cosmopolitan distribution3. Numerical abundance4. Low genetic and ecological variability5. Large body size6. Limited mobility and relatively long-life history7. Ecological characteristics are well known8. Suitable for use in laboratory studies
Ideal indicator species characteristics
(Resh and Rosenberg, 1993)
Uses fish community characteristics to assess aquatic health: includes for example
• Species richness & abundance• Total biomass (and distribution)• Ratio of native spp to introduced• Functional role ID (generalists vs specialists, detritivores, piscivores, etc)• Condition & health indices
Example: Index of Biotic Integrity (IBI)
IBI’s originally worked out for Ohio streams (James Karr and colleagues)
- in general, these are region-specific
- therefore, IBI’s must be calibrated to a given region
- for northern Mid-Atlantic drainages, a calibration study for a regional IBI will soon be published (Daniels et al., Transactions of the American Fisheries Society)
Other taxonomic can also be used as indicators of watershed condition – most, but not all, work is done in streams:
• benthic macroinvertebrates
• periphyton
• macrophytes (aquatic and wetland)
• birds (some work in PA and Southeast)
NY State biotic assessment website:
http://www.dec.state.ny.us/website/dow/stream/index.htm
This site is specifically for rapid bio-assessments using stream macroinvertebrates – contains a pictorial key and verbal descriptions
Pro’s and con’s of indicators