Levels of Ecological Organization in Freshwater Systems Population Community Ecosystem

Freshwater Ecosystems and Aquatic-Terrestrial Linkages To describe the “ecosystem concept”. To review recent advances in our understanding of the ecosystem ecology of freshwater systems, focusing on linkages between freshwater and terrestrial systems. To expand this discussion of freshwater-terrestrial linkages by examining the community-level implications 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 move among ecosystems by abiotic process and biotic processes. > Individuals / populations / communities are different ways of packaging energy and nutrients, and offer different perspectives on how energy and nutrients move within and among ecosystems. By tracking the input, internal cycling, and output of energy and nutrients, we can understand the fundamental role of an ecosystem in the larger landscape.

We have seen the influence of the ecosystem concept already:

What else can an ecosystem approach tell us about the connection between freshwater and terrestrial systems? Are streams just plumbing the landscape? Where does the C that supports lake productivity come from?

Are streams just plumbing the landscape? N What else can an ecosystem approach tell us about the connection between freshwater and terrestrial systems?

The N problem

“Rivers deliver N to coastal ecosystems” “Streams and rivers are not N-limited”

The LINX project

Spiraling Length How far does the average N atom travel downstream before taken up by the biota? N S Low = Retentive S High = Leaky (Peterson et al. 2001)

LINX Results (Peterson et al. 2001)

LINX Implications Streams help to prevent terrestrial N from reaching coastal ecosystems… …especially headwater streams.

What else can an ecosystem approach tell us about the connection between freshwater and terrestrial systems? Where does the C that supports lake productivity come from?

Where does the C that supports lake communities come from? Autochthonous Allochthonous

Where does the C that supports lake productivity come from? CO 2 Respiration > Photosynthesis

The Experiment 13 C (Pace et al. 2004)

Corrected for 13 C that could have come from photosynthesis. Allochthonous C accounted for 40-55% of POC and 22-50% of zooplankton. The Results (Pace et al. 2004)

Conclusions Lakes themselves don’t produce enough C to support the animals that live in them. Input of organic matter from the watershed allows for more secondary productivity than if lakes were isolated microcosms. (Pace et al. 2004)

birds, bugs, and fish vs. N and C Population Community Ecosystem

How connected are stream and terrestrial communities?

The Experiment Plots in and along a headwater stream on Hokkaido 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-forest and from forest-to-stream  Proportion of “allochthonous” prey in fish and birds (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

Predator Diet Results (Nakano and Murakami 2001)

Conclusions Both stream AND terrestrial predators use prey inputs from the other systems.

Maybe “freshwater” and “terrestrial” distinctions are less useful than we thought…

*The views expressed here are those of the person doing the talking. Editorial* “It does appear that on many, many different human attributes-height, weight, propensity for criminality, overall IQ, mathematical ability, scientific ability - there is relatively clear evidence that whatever the difference in means-which can be debated - there is a difference in the standard deviation, and variability 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 the person doing the talking. Editorial* “It does appear that on many, many different human attributes-height, weight, propensity for criminality, overall IQ, mathematical ability, scientific ability-there is relatively clear evidence that whatever the difference in means-which can be debated-there is a difference in the standard deviation, and variability of a male and a female population.” - Lawrence H. Summers Former President of Harvard January 14, 2005 WRONG