Biotic assessment of water quality in the Sangamon River

Charles L. Pederson, Robert U. Fischer, Kristen M. Thomas and Shari E. Fanta

Biological Sciences Department, Eastern Illinois University, Charleston, IL

INTRODUCTION

. . . The face of the water, in time, became a wonderful book - a book that was a dead language to the uninformed passenger, but which told its mind to me without reserve, delivering its most cherished secrets as clearly as if it uttered them with a voice. And it was not a book to be read once and thrown aside, for it had a new story to tell every day.   Mark Twain, Life on the Mississippi, 1883.

The Sangamon River.

The Sangamon River drains a primarily agricultural, 14,000 km² watershed before joining the Illinois River north of Beardstown. Along its length, the river has been impounded to form several reservoirs which ensure a stable water supply as well as numerous recreational opportunities for over half a million people. Included within this watershed are urban areas such as Bloomington, Decatur, and Springfield. As a result of human demographics and the primarily agricultural land use within the watershed within, habitat quality and suitability of the river for support of aquatic life has been challenged for most of the last century. Since 1998 in conjunction with the Sanitary District of Decatur, we have been working to evaluate the ability of the Sangamon River to support a healthy stream biota.

Why Biotic Assessment?  For centuries, coal miners took canary birds down into their mines to warn of potential disaster. If a mine shaft collapsed thereby diminishing the oxygen supply or if toxic gasses such as methane began to accumulate, the canary would be the first to react. Death of the biomonitor would alert miners to trouble and enable them to take immediate action in the interest of safety. Over the years, it is rumored that this yellow songbird saved countless lives. The common example of the "canary in the coalmine" reveals the utility of biotic assessment. From such organisms (biological monitors), we can learn much about the quality of our atmosphere as well as our immediate terrestrial and aquatic environments. Such use of specific organisms in natural communities as indicators of environmental quality was proposed in the early 1900s.  Then as well as now, it is known that biological monitors provide the following benefits when compared to more routine assessment of physical or chemical conditions:

They are very sensitive to changes in environmental quality.

They may respond to environmental conditions which often are not detectable via routine analyses.

They integrate changes in environmental quality over time.

Biological Monitors Respond to Inputs Which Alter Environmental Conditions

Discharges - inputs to the river  (reservoir, sanitary)

Altered physical/chemical conditions increased sediment and nutrient loading elevated input of chemical pollutants abnormal temperature regime decreased habitat diversity.

Impact on stream biota decreased diversity through loss of sensitive species and persistence of those tolerant of degraded environmental conditions

Our Specific Objectives

1. Evaluation of physical habitat via Stream Habitat Assessment Procedure (SHAP).

2. Analysis of physical and chemical variables to describe "water quality" in the Sangamon River.

3. Evaluation of biotic indices based on fish, macroinvertebrates, and attached algal communities for biotic assessment of stream quality.

Our investigations focused on two reaches of the Sangamon River.  Sites 9, 11, and 12 are located downstream of discharge from the SDD main treatment plant. We refer to these as the DOWNSTREAM sites.  Sites 1, 3, 4, 5, 6, 7, 8 are in the reach extending upstream from the SDD discharge to the dam which impounds Lake Decatur. We refer to these as the UPSTREAM sites.  The majority of instream flow volume in the Sangamon River (upon leaving Decatur) is derived from either sanitary or reservoir discharge.

	Sangamon River sites.
	Discharge from the Main Treatment Plant of the Sanitary District of Decatur.
	Outflow from Lake Decatur into the Sangamon River.

Evaluation of Physical Habitat Using SHAP

SHAP (the Stream Habitat Assessment Procedure) was used to evaluate overall physical habitat similarity for all sites within the two stream reaches. Values for 15 individual habitat parameters (which include evaluation of substrate and instream cover, channel morphology and hydrology, and riparian and bank features) were determined using standard assessment procedures. Values for each of these metrics were then summed to provide an overall SHAP score.  Although SHAP scores for the two reaches of the Sangamon River which we studied were significantly different - values for all sites still resulted in classification of physical habitat as fair.

Physical/Chemical Characterization of Instream Flow

Routine assessment of characteristic water quality variables can aid in understanding the functioning of stream systems which are homogeneous in terms of overall physical structure.

Results

Principal Components Analysis (PCA) was used to combine measured variables into newly derived variables (PCA Factor 1, PCA Factor 2, etc.) which then may be used as "overall" measures of similarity.

Observations at sites DOWNSTREAM of the SDD are clearly distinct from those in the reach that extends UPSTREAM to the dam which impounds Lake Decatur. The only overlap identified between the UPSTREAM and DOWNSTREAM reaches was the clustering of Sites 8 and 12 into an "intermediate" group. Likely this results from the movement upstream to beyond Site 8 of discharge from SDD when reservoir flows are minimal (e.g., during July and August).

DOWNSTREAM sites are characterized by higher plant macronutrient concentrations, i.e., in the aggregate by elevated conductivity and fixed dissolved solids, but also through specific measurements of phosphorus, oxidized nitrogen, and carbon as indexed by alkalinity. In addition, discharge from SDD tends to lower the pH of the stream - although not appreciably.

UPSTREAM sites tend to have higher concentrations of suspended solids, likely due to export of phytoplankton algae and fixed particles via outflow from Lake Decatur.

When taken as a whole, it may be that the UPSTREAM reach relies most heavily on allochthonous inputs of organic material to support overall community metabolism, while discharges from SDD establish a basis for autochthonous primary productivity in the DOWNSTREAM reach.

Physical and chemical water quality confirms differences between the UPSTREAM and DOWNSTREAM reaches, but qualitative judgments (good vs. bad) require an evaluation of the biotic community structure.

Fish were collected at each site using electric seining and standard boat electrofishing techniques. Fish were identified to species, counted and returned to the stream alive when possible, although voucher specimens were preserved and retained. When field identifications were not practical, specimens were preserved and returned to the laboratory. Data were used to calculate the Index of Biotic Integrity (IBI) which incorporates species richness and composition, fish abundance and condition, as well as trophic composition. IBI scores indicate categories of habitat quality as follows:

51-60 (Excellent); 41-50.9 (Good); 31-40.9 (Fair); 21-30.9 (Poor); <21(Very Poor).

Hester-Dendy sampler

Macroinvertebrates were collected using Hester-Dendy samplers. Samplers remained in the river for an exposure period of six weeks, at the end of which they were retrieved. Invertebrates were separated from the substrata and identified at least to family in the laboratory. Data on relative abundance were used to calculate the MBI (Macroinvertebrate Biotic Index) for each site. In this method, each taxon is assigned a pollution tolerance value. According to the Illinois Environmental Protection Agency, MBI values reflect water quality as follows:

< 5.0 (Excellent); 5.0-6.0 (Very good); 6.1 - 7.5 (Good/Fair); 7.6 - 10.0 (Poor) > 10.0 - Very Poor.

Floating artificial substrate

Benthic diatoms were collected on a floating artificial substrate that was placed at each site for a three week colonization period. Accumulated material was removed from the substrata, digested in acid and the resistant "shells " of the diatoms were mounted onto microscope slides. Species were identified at magnification of 1000x. Preliminary analyses have focused on qualitative observation of shifts in dominance and appearance of rare species which may indicate tolerance or sensitivity to ambient conditions in the two stream reaches.

Overall mean IBIs for data pooled from 1998, 2001 and 2002 were 32 and 35 for the UPSTREAM and DOWNSTREAM reaches, respectively.

Statistically, this difference is significant and suggests that overall habitat quality, based on the fish community, is improved in the DOWNSTREAM reach. DOWNSTREAM sites associated with the main treatment plant outfall from the Sanitary District of Decatur and may have increased IBI rating due to the predictable instream flows increased autochthonous primary production.

MBI scores averaged over the 2001 and 2002 study periods at the UPSTREAM and DOWNSTREAM sites were 7.3 and 6.1, respectively.

Although both of these scores warrant a good/fair rating, the average MBI for the DOWNSTREAM reach is significantly lower indicative of improved habitat quality. Recent MBI values for the Sangamon River associated with the Sanitary District of Decatur are lower than values reported by the Illinois Environmental Protection Agency (IEPA) in 1988, suggesting improvement of Sangamon River water quality during the past decade.

Common Dominant Species in both stream reaches included: Cyclotella meneghiniana, Nitzschia palea, Nitzschia valdestriata and Navicula vaucheriae.

Common Dominant Species specific to a given stream reach included: Achnanthes linearis, Gomphonema parvulum, Amphora ovalis, Achnanthes exigua, Navicula menisculus and Navicula protracta.

Rare Species specific to a given stream reach included: Cocconeis placentula, Gomphonema brasiliense, Cyclotella stelligera, Cymbella tumida, Pleurosira laevis, Nitzschia dissipatta, Aulacoseira italica and Caloneis hultenii.

Qualitative comparisons of shifts in community dominance currently are possible. While certain species appear to be cosmopolitan throughout the Sangamon River, both reaches are characterized by somewhat unique subordinate taxa. Additional refinement of diatom community data is necessary before relationships to stream water quality become apparent.

SUMMARY

Overall, biotic community structure and habitat characterization suggest that the Sangamon River from Lake Decatur to the Wyckle's Road overpass in Decatur, IL is a physically homogeneous system. Established biocriteria including fish and macroinvertebrate indices suggest that discharge from the SDD main treatment plant actually enhances quality of this stream resource. Although fauna may be responding positively to elevated primary production derived from nutrient inputs to the stream, biotic communities of the Sangamon River most likely benefit from the more constant instream flows resulting from discharge of treated effluent. In future years, emphasis will be placed on evaluating the presumed positive impact of the SDD on stream communities relative to what we believe might be the detrimental effect of extremely variable flows upstream of the plant resulting from the highly variable releases of water from Lake Decatur.

ACKNOWLEDGEMENTS

Major funding for this ongoing project has been provided by the Sanitary District of Decatur. Additional support has been provided by the Department of Biological Sciences, Eastern Illinois University. All of the following individuals have provided field, laboratory or other technical assistance: Chris Huggins, Scott Meiners, Nathan Badgett, Eden Rawski, Brian Metzke, Pat Enstrom, G. Matthew Groves, Ross Widinski, Scott Seeley.