Authors: De Sousa, Simon; Pinel-Alloul, Bernadette; Cattaneo, Antonia

Source: Canadian Journal of Fisheries and Aquatic Sciences, Volume 65, Number 6, June 2008 , pp. 1206-1216(11)

Publisher: NRC Research Press

Abstract:

Previously pristine lakes of the Laurentian region of Quebec, Canada, have faced increasing residential development of their watershed since the 1970s. We tested whether littoral invertebrates respond to this perturbation, even though open-water nutrients and chlorophyll are not yet altered. We examined changes in biomass, size structure, and taxonomic composition of macroinvertebrates living on rocks and sediments in 13 lakes representing a gradient of lakeshore residential development and watershed clearing. Littoral invertebrates provided early indication of lake perturbation, but their response varied according to the substratum. On rocks, total invertebrate biomass increased along the perturbation gradient and size structure shifted towards large organisms. These changes were likely mediated by a concomitant increase in epilithon biomass, suggesting a bottom-up control. No significant change in total biomass and size structure was observed for invertebrates in sediments. In contrast, taxonomic composition changed with lake development in sediments, but not on rocks. Taxonomic shifts were likely related to changes in sediment heterogeneity due to a decline of woody litter and increased fine particle deposition. Oligochaetes were positively associated to perturbation, whereas mayflies were negatively associated; these taxa could be used as indicators. Sediments were a better sentinel substratum than rocks for biomonitoring the impact of lake residential development.

Les lacs de la région des Laurentides au Québec, Canada, jusqu'alors peu perturbés, font face à une augmentation du développement résidentiel dans leur bassin versant depuis 1970. Nous avons testé si les invertébrés littoraux répondaient à ces perturbations alors que la concentration en nutriments et en chlorophylle dans la colonne d'eau demeure peu changée. Nous avons analysé la biomasse et la structure en taille des macroinvertébrés sur les roches et les sédiments dans 13 lacs représentant un gradient de développement résidentiel et de déboisement des rives. Les invertébrés littoraux sont des indicateurs précoces de ces perturbations mais leur réponse varie selon le substrat. Sur les roches, la biomasse totale et la taille des invertébrés augmentent le long du gradient de perturbation. Ces changements sont associés à une hausse de la biomasse d'épilithon, suggérant un effet ascendant des ressources. La biomasse des invertébrés sur les sédiments ne change pas, contrairement aux roches, mais la composition taxinomique des invertébrés change avec le niveau de perturbation, probablement suite à la baisse de l'hétérogénéité des sédiments (moins de litière ligneuse et plus de particules fines). Les oligochètes sont positivement associés aux perturbations, alors que les éphémères y sont négativement associés. Ces taxons pourraient être utilisés comme indicateurs. Les sédiments sont considérés comme le meilleur substrat à échantillonner pour les programmes de surveillance des effets du développement résidentiel des lacs.

Document Type: Research article

Publication date: 2008-06-01

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• Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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