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Establishing a Baseline Ecology of a Creek Ecosystem

Barbara Mannion
1991 Woodrow Wilson Biology Institute


Level:

A research study recommended for upper level high school students

GOALS OF THE STUDY:

The investigation of a baseline ecological system can be the focus of an ecology curriculum. Taking the first nine weeks for the introduction, planning, forming of student teams, building of screens and other necessary materials, the rest of the year can be used for data collection its evaluation, and discussions. Understanding the physical, chemical and biological interactions of an aquatic ecosystem is the goal of this student centered research study. As suggested by Wilhm in 1972 various organisms and communities can serve to indicate the summation of environmental conditions within that ecosystem over the duration of the life cycles of the biotic species present. Identification of these indicators and of other factors which contribute in negative or positive ways to the balance of the system are the means by which students observe and measure the various interactive relationships.

OBJECTIVES:

Students will investigate the physical, chemical and biological parameters necessary to establish an ecological baseline. Establishing an ecological baseline not only shows the ecological characteristics of a creek but makes the possible future environmental monitoring of the creek as human activities increase the stress on the system. The general problem under study may include the following null hypotheses:

HOW TO ORGANIZE THE DATA FOR STATISTICAL ANALYSIS:

(Hypotheses You Could Select Which Best Fit Your Plan)

Among six selected sample sites in your creek...

  1. there is no significant difference among mean substrate indices;
  2. there is no significant difference among mean water temperatures, among mean color values, and among mean changes in these values before and after rainfall;
  3. there is no significant difference among mean pH readings, among mean dissolved oxygen values, among mean values of dissolved carbon dioxide, alkalinity, hardness, ammonia, nitrites, nitrates and phosphates;
  4. there are no mean differences among means of other chemical components such as halogens and metals;
  5. there are no significant differences between mean rates of flow and before and after rainfall
  6. there are no significant differences among the total and the mean fecal coliform counts;
  7. there are no significant differences among the mean diversity indices of benthic macroinvertebrates associations sampled;
  8. there are no significant differences among the mean densities and mean importance values of benthic invertebrates sampled;
  9. there are no significant differences among the mean densities and and mean importance values of benthic invertebrates sampled from three types (evaluate your creek for the appropriateness of this number) of uniform substrata and from artificial Dendy-type substrata;
  10. there are no significant differences among the mean diversity indices of macroinvertebrate associations from uniform and artificial substrata;
  11. there are no significant mean differences among the densities, importance values and diversity indices of macroinvertebrates sampled from uniform and artificial substrata which have been submerged for different time periods
  12. there are no significant differences among the mean densities, mean weights, mean lengths and mean diversity indices of fish sampled by seines
    and if appropriate to your situation:
  13. there are no significant differences among the collective mean values of all parameters mentioned above from sites above and below the pollutant source (e.g. industrial effluent entering the creek site) in your area .

METHODS AND MATERIALS

To test the null hypotheses you may employ the following methods:

A. Stream substrata will be sampled by means of a uniform cylindrical sampler. Samples will be dried and shaken through a stack of standard Tyler sieves with mesh sizes of 25.4, 9, 2,1 0.4, 025, 0.105 and 0.044 mm respectively. . . Weights of residues remaining in each sieve will be measured and relative weights will be calculated and plotted on semi-logarithmic paper. A pair of substratum indices will be calculated using the 50% class size as one and the size of the 60% class divided by the 10% class size as the other.

B. Chemical tests can be caried out using a Hach direct reading portable field laboratory, following procedures provided by the company. This equipment employs colorimetric methods for most tests and is also equipped with a conductivity meter.

C. Temperature and dissolved oxygen will be measured using the YSI portable field oxygen meter.

D. Rates of flow will be estimated using readings from a digital flow meter. Discharge will be determined by using meter tapes and sticks to measure the dimensions of a cross section at each site and multiplying the resultant area by the mean rate of flow..

E. Supplies for coliform tests will be obtained from the Millipore Corp., and the procedures they recommend will be followed.

F. Resident benthic macroinvertebrates will be sampled by means of time kicked samples and dredge sampling. Four replicate samples will be taken from each site on each sample date. Diversity indices will be determined initially using the sequential comparison index (Cairns, et al., 1968) and a Shannon -Weaver index will be calculated following identification. Since many of the acquatic invertebrates of your area (especially if your location is in the southern part of the U.S.) are as yet unnamed, diversity will usually be based upon generic determinations.

G. Samples of colonizing macroinvertebrates will be collected from substrate samplers . Each substratum set-up will include replicate pairs of trays of coarse gravel, fine gravel and mixed substrata materials. Four of these units will be placed at each sample site during the first week of the study. The first set will be removed abd sorted after two days, the second after seven days, the third after 14 days and the final after 28 days. Sets of Dendy multiplate samplers will be attached to each substratum box and will be sampled according to the same time schedule.

H. Fishes will be sampled by means of seining.

I. Mean differences will be determined by means of various designs employing confidence intervals or F-tests.

A Possible Time Schedule for Sampling Your Creek

Date Activity
weeks 1-9 Begin ecology course with research in aquatic biology, concentrating on stream investigations. Take preliminary samples from the creek for the development of technique and identification of invertebrates and fishes, learn to use field equipment, and read the literature on stream ecology.
week 10 Reexamine selected sites; categorize adjacent land uses; measure stream channel dimensions measure rates of flow; determine rates of discharge; carry out substrate analysis; and construct substrate boxes.
week 11 Place artificial substrata (first day); begin the FIRST CYCLE of physical-chemical and biotic sampling. Remove first substrate set by day three.
week 12 Remove second substrate set; measure rates of flow; continue FIRST CYCLE of sampling biotic, chemical and physical parameters, and continue identifications.
week 13 Remove third substrate set; measure rates of flow; begin SECOND CYCLE of sampling biotic, chemical and physical parameters; continue identifications
week14 Continue SECOND CYCLE sampling and identification of collected samples.
week 15 Removal final substrate set; measure rates of flow; continue SECOND CYCLE sampling and identifications.
week 16 Begin THIRD CYCLE of biotic, chemical and physical sampling; continue identifications.
week 17 Measure rates of flow; continue THIRD CYCLE sampling; continue identifications.
week 18 Begin final data analysis
week 19-? Begin report writing, and evaluation and preparation for a class science symposium.


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