Proceedings - Teaching and Learning Centre - Simon Fraser ...

Fraser River Action Plan 3rd Research Workshop
Effects of Agricultural Pollutants on Amphibians in the Lower Fraser Valley
Introduction
K. Pettit
Department of Animal Science
University of British Columbia
Amphibians are among the world’s most ancient terrestrial vertebrates — the fossil record extends back more
than 350 million years. Recently, however, scientists have become alarmed by world-wide amphibian declines in
population due to habitat losses and other, unknown causes.
Amphibians, such as anurans (frogs and toads), caudata (salamanders and newts), and caecelians are cryptic and
difficult to survey successfully. Often, populations of these animals experience large temporal fluctuations.
Intensive study of amphibian populations have shown that natural populations are often fragmented and smaller
populations may be interconnected by dispersal into larger “metapopulations.” In these, some individual
populations may act as a “source” population, providing the overall population with individuals through
dispersal, and others as “sink” populations, receiving individuals from the source but not contributing to overall
population growth. In metapopulations of this type, removal of a significant source population can have impacts
beyond what may normally be expected as the sink populations normally dependent on it fail as well. Individual
population fluctuations and dynamics may be complicated by the existence of the metapopulation superstructure.
In the lower Fraser Valley, human population levels have been growing since 1862. Accompanying this growth
have been extensive changes in habitat, including the drainage in the 1920s of Lake Sumas and the extensive
wetlands associated with it. Overall a large percentage of wetlands have been drained or altered in the lower
Fraser Valley since 1862.
As natural wetlands are drained and watercourses altered, amphibian populations become more dependent on
wetland fragments adjacent to agricultural land for breeding and foraging habitat. These are susceptible to
further alterations, erosion and fertilizer and pesticide use.
Water quality testing and guidelines are often performed and written for common test organisms such as
Daphnia sp. and the fathead minnow. It is unknown whether these would be suitable for application to
amphibian species. As well, different amphibian species have different susceptibilities to pesticides and other
aquatic parameters, such as nitrogen and/or dissolved oxygen levels.
Literature Review
Objectives of Proposed Research
1. to assess reproduction of amphibians living within the Sumas watershed;
2. to assess whether habitat quality within the Sumas watershed is suitable for sustaining a diverse and
viable amphibian population; and,
3. to determine whether water quality guidelines for agricultural pollutants developed using common
indicator species will be sufficient to protect amphibians.
Hypotheses to be Tested
1. • Population density (measured as: numbers of tadpoles, froglets, and breeding and non-breeding adults
encountered per unit time) of natural populations of R. pretiosa and R. aurora living within the Sumas
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