OVERVIEW:
In this workshop on watersheds and pollutants students will work in pairs.
Students will use measuring skills to perform serial dilutions to simulate
the procedures used in ecotoxicology, which is “The scientific study
of how contaminants affect living organisms in their habitats.”
Students will then record data from a “pre-started” experiment
that tests the effect of salt concentrations on zooplankton survival. Students
will count the total number of living and dead zooplankton in their assigned
treatments, calculate a “proportion surviving,” and graph their
results on their data sheet. During the class summary students will compare
their results to other groups’ results.
TERMS
USED:
Process related—observation,
experiment, hypothesis, comparison, prediction, independent variable, dependent
variable, inference, data
Content related—aquifer,
concentration, condensation contaminant, ecotoxicology, effluent, evaporation,
groundwater, pollutant, proportion, runoff, serial dilution, surface water,
water table, watershed
OUTLINE
OF ACTIVITY:
After a few minutes of review from Activity 4, students will be introduced
to the science of ecotoxicology. The focus of the slide program will be the
research of two SREL scientists, Bill Hopkins and Gary Mills, who study contaminants
in wetland ecosystems. Students will be introduced to content on watersheds,
point- and non-point source pollutants, and effects of contaminants on organisms.
This will include a presentation of the “water cycle” and specifics
about their school’s watershed. The main emphasis will be that we all
live in a watershed, and the activities that occur in a watershed may affect
the water quality of all creeks, streams, and rivers in the watershed and
downstream from it.
Examples of point source pollutants and non-point source pollutants will be illustrated by a demonstration to the class using a watershed model. This activity should take about 20 minutes.
Students will then go to their science stations in groups of four, where they will work in pairs. Students will use measuring skills to perform serial dilutions to simulate the procedures used in ecotoxicology. Using salt as a “pollutant,” students will create solutions of 35 parts per thousand (PPT; the concentration of sea water), 17.5 PPT, 8.75 PPT, 4.38 PPT, and 2.19 PPT. Each pair of students will then be given a pair of beakers to which zooplankton were added prior to class—one beaker will be a control (0 PPT salt), and one beaker will be one of the salt concentrations above. Students will count the total number of living and dead zooplankton for each beaker, calculate a “proportion surviving,” and graph their results on their data sheet. During the class summary students will compare their results to those of other groups.
