Levels of Ecological Organizationin Freshwater Systems
Population
Community
Ecosystem
Freshwater Ecosystems andAquatic-Terrestrial Linkages
•To describe the “ecosystem concept”.
•To review recent advances in our understanding ofthe ecosystem ecology of freshwater systems,focusing on linkages between freshwater andterrestrial systems.
•To expand this discussion of freshwater-terrestriallinkages by examining the community-levelimplications of these linkages.
The Ecosystem Concept
• Ecosystem = natural unit of the landscape with a “critical”level of homogeneity.
• Nutrients and energy cycle within ecosystems and moveamong ecosystems by abiotic process and biotic processes.
> Individuals / populations / communities are differentways of packaging energy and nutrients, and offerdifferent perspectives on how energy and nutrients movewithin and among ecosystems.
• By tracking the input, internal cycling, and output of energyand nutrients, we can understand the fundamental role of anecosystem in the larger landscape.
We have seen the influence ofthe ecosystem concept already:
What else can an ecosystem approachtell us about the connection betweenfreshwater and terrestrial systems?
• Are streams just plumbing thelandscape?
• Where does the C that supportslake productivity come from?
• Are streams just plumbing thelandscape?
N
What else can an ecosystem approachtell us about the connection betweenfreshwater and terrestrial systems?
The N problem
“Rivers deliverN to coastalecosystems”
“Streams andrivers are notN-limited”
The LINXproject
Spiraling Length
How far does the average N atom traveldownstream before taken up by the biota?
N
• S Low = Retentive
• S High = Leaky
(Peterson et al. 2001)
LINXResults
(Peterson et al. 2001)
LINX Implications
Streams help to prevent terrestrial N fromreaching coastal ecosystems…
…especially headwater streams.
What else can an ecosystem approachtell us about the connection betweenfreshwater and terrestrial systems?
• Where does the C that supportslake productivity come from?
Where does the C that supports lakecommunities come from?
Autochthonous
Allochthonous
Where does the C that supports lakeproductivity come from?
CO2
Respiration > Photosynthesis
TheExperiment
13C
(Pace et al. 2004)
• Corrected for 13C thatcould have come fromphotosynthesis.
• Allochthonous Caccounted for 40-55%of POC and 22-50% ofzooplankton.
The Results
(Pace et al. 2004)
Conclusions
•Lakes themselves don’t produce enough C tosupport the animals that live in them.
•Input of organic matter from the watershedallows for more secondary productivity than iflakes were isolated microcosms.
(Pace et al. 2004)
birds, bugs, and fishvs.N and C
Population
Community
Ecosystem
How connected are stream andterrestrial communities?
The Experiment
• Plots in and along a headwater stream onHokkaido Island, Japan
• Forest is deciduous
(Nakano and Murakami 2001)
Predator Communities
Forest
Stream
• Physical conditions in stream and riparian zone:
Temperature
Light input
• Biological conditions in stream and riparian zone:
Availability of aquatic and terrestrial invertebrate“prey”
Flux of invertebrate prey from stream-to-forestand from forest-to-stream
Proportion of “allochthonous” prey in fish andbirds (i.e., prey from where the predators aren’t)
(Nakano and Murakami 2001)
Temperature Results
(Nakano and Murakami 2001)
: Leaves on
: Leaves off
Daily mean temperature (ºC)
Terrestrial Predator Diet Results
(Nakano and Murakami 2001)
: Leaves on
: Leaves off
Aquatic Predator Diet Results
(Nakano and Murakami 2001)
: Leaves on
: Leaves off
PredatorDietResults
(Nakano andMurakami 2001)
Conclusions
• Both stream AND terrestrial predatorsuse prey inputs from the other systems.
Maybe “freshwater” and “terrestrial”distinctions are less useful than wethought…
*The views expressed here are those of theperson doing the talking.
Editorial*
“It does appear that on many, many differenthuman attributes-height, weight, propensity forcriminality, overall IQ, mathematical ability,scientific ability - there is relatively clearevidence that whatever the difference inmeans-which can be debated - there is adifference in the standard deviation, andvariability of a male and a female population.”
- Lawrence H. Summers President of Harvard January 14, 2005
Editorial*
• Mary E. Power, UC Berkeley
• Bobbi L. Peckarsky, Cornell and University of Wisconsin
• Margaret A. Palmer, University of Maryland
• Kate H. Macneale, NOAA
• Margaret A. Palmer, University of Maryland
• Emily S. Bernhardt, Duke University
• Judy L. Meyer, University of Georgia
• Carol L. Folt, Dartmouth College
• Nancy B. Grimm, Arizona State University
• Margaret B. Davis, University of Minnesota
• Jane M. Hughes, Center for Riverine Landscapes, Australia
*The views expressed here are those of theperson doing the talking.
Editorial*
“It does appear that on many, many differenthuman attributes-height, weight, propensity forcriminality, overall IQ, mathematical ability,scientific ability-there is relatively clearevidence that whatever the difference inmeans-which can be debated-there is adifference in the standard deviation, andvariability of a male and a female population.”
- Lawrence H. Summers Former President of Harvard January 14, 2005
WRONG