Diatom taxonomic and morphological changes as indicators of metal pollution and recovery in Lac Dufault (Québec, Canada)

• Published in: Journal of paleolimnology Vol. 32; no. 2; pp. 163 - 175
• Main Authors: Cattaneo, Antonella, Couillard, Yves, Wunsam, Sybille, Courcelles, Michel
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.08.2004
• Subjects: Achnanthes minutissima; Acid mine drainage; Acidification; Asterionella formosa; Brachysira vitrea; Chaetoceros muelleri; Chemical recovery; Contamination; Environmental indicators; Fragilaria; Freshwater; Metals; Plankton; Sediments; Tabellaria flocculosa; Water chemistry; Canada, Quebec; Canada, Quebec, Abitibi
• ISSN: 0921-2728; 1573-0417
• DOI: 10.1023/B:JOPL.0000029430.78278.a5

We studied diatom taxonomic composition and the presence of morphological alterations (size and deformations) along a sediment core collected in Lac Dufault, Abitibi, whose watershed has a long history of mining pollution presently undergoing mitigation. According to sediment dating with ^sup 210^Pb and metal profiles along the core, we could identify four periods in the contamination history of the lake, which were characterized by different diatoms. Tabellaria flocculosa was dominant in the pre-mining period but was drastically reduced at the onset of pollution when Fragilaria cf. tenera became important. This diatom, together with other Fragilaria species and cysts of Chaetoceros muelleri, typified the transition period in which Cu reached its maximum value and other metals started to increase. During the period of maximum contamination with Zn, Cd, and Fe accompanied by acid mine drainage, Achnanthes minutissima and Brachysira vitrea were dominant. These taxa started to wane in the most recent sediments representing a partial chemical recovery. Asterionella formosa, which almost vanished at mining onset, reappeared with high abundance in these superficial sections. Beside these taxonomical shifts, we observed during the contamination period significant reduction in valve length together with increased percentages of valve deformations. Because available data on water chemistry and a diatom-based pH reconstruction suggest that Lac Dufault escaped severe acidification, diatom patterns observed in the core can be mostly ascribed to metal contamination. Individual diatom abundance and valve length had strong statistical relationships with the different metals identified in the core. Diatom changes both taxonomic and morphological can be excellent specific indicator of metal contamination and early recovery.[PUBLICATION ABSTRACT]