Effects of Riparian Zone Fragmentation on Primary Productivity and Fish Growth Rates

Krista Kirkham and Robert Fischer

Department of Biological Sciences, Eastern Illinois University

Introduction

Stream habitat fragmentation.

What is stream habitat fragmentation?

    A lack of connectivity between upstream and downstream populations.

What causes fragmentation?

    Human interference--agriculture, pollution, industry, forestry, erosion.

Outcome of Fragmentation

    Less than 1% of original landscape remains in Illinois

    Distinct patch formation may occur within a stream.

Effects of fragmentation.

    Abiotic effects include increased amounts of sedimentation, siltation, chemical runoff, and pollution as well as changes in dissolved oxygen, temperature, and pH.

    Biotic effects include negative effects upon diversity, richness, mortality and reproductive success as well as a disruption of habitat equilibrium.

Since stream habitat fragmentation can cause changes to an abiotic environment of a stream, one would also expect to see changes in primary productivity which may lead to changes in growth rates of fish at various trophic levels.

Objectives

1.  Determine if habitat fragmentation exists in stream environments.

2.  Discover if primary productivity is different between patches.

3.  Determine if growth rates of fish are affected by differences in primary productivity between patches.

4.  Observe the consistency of energy distribution between trophic levels in comparison to varied growth rates.

Methods

Seven sites were sampled for fish and productivity along Polecat Creek, a 4th order tributary of the Embarras River.  Reaches were 300 ft and contained at least one riffle/pool sequence when possible. 

Sampling techniques included electroshocking, collection, identification, and measurement of fish, then selection of fish for growth determination.

Results

Habitat assessment used Stream Habitat Assessment Procedure (SHAP).  SHAP Assessment is based on fifteen habitat metrics associated within the following three broad categories:

    1.  Substrate and instream cover.

    2,  Channel hydrology and morphology.

    3,  Riparian and bank features.

Productivity assessment used a biostimulation technique, testing for the growth of Selenastrum capricornutum in the presence of turbidity.

Growth rates of S. capricornutum with phosphorus (P) and nitrogen (N) treatments.

Growth rate was determined by using the back calculation technique.

Conclusions

1.  Distinct patches can be formed in stream habitats in response to land use.

2.  All sites in Polecat Creek showed limited productivity due to nutrient deficiency.

3.  Additional productivity analysis showed phosphorus to be the limiting nutrient.

4.  Growth rates of fish at different trophic levels in each patch were not affected by productivity differences.