Fishing for diatoms: fish gut analysis reveals water quality changes over a 75-year period |
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Authors: | Isabelle Lavoie Stéphane Campeau |
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Institution: | 1.Département de Géographie,Université du Québec à,Trois-Rivières,Canada |
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Abstract: | Defining the reference state of some perturbed streams and rivers is challenging since their non-altered state is undocumented.
Despite the near-absence of pristine sites in highly anthropogenic areas, information about aquatic communities that existed
prior to human disturbance can be obtained from historic sources. Sediment coring is commonly used in paleolimnology to estimate
past environmental conditions of lakes, but this technique is often not appropriate for studies of lotic systems. An alternative
is to use diatom assemblages present in the guts of fish that were captured in the streams prior to significant human disturbance.
The purpose of the present study was to evaluate the biological integrity of several streams in Ontario and Québec during
the early twentieth century based on “paleo” diatom assemblages extracted from the guts of fish stored in museums. The Eastern
Canadian diatom index (IDEC: Indice Diatomées de l’Est du Canada) was used to evaluate the biological status of “paleo” and
“modern” diatom assemblages. The IDEC shows the position of diatom assemblages on a general pollution gradient. The comparison
of IDEC values calculated for the 1925–1948 and the 2003–2007 periods showed that several streams were severely polluted in
the early 1900s. In general, present water quality has declined compared to the early 1900s. The biological integrity of only
three of the 22 sites has increased. IDEC values were not influenced by the species of fish studied. |
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