Environmental predictors of benthic consumers and autotrophic communities along a recovery gradient

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Abstract:

Ecological theory predicts that biological factors replace abiotic regulation of community structure during recovery from ecosystem stress. We examined relationships between benthic autotroph (epilithic periphyton) and consumer communities, and environmental variables, along a gradient of six recovering acidified lakes to identify the best explanatory variables of community structure. Dissolved organic carbon, pH, and total dissolved phosphorus were important predictors of autotrophic biomass, while total dissolved phosphorus was the only significant factor explaining variation in consumer biomass. Abiotic factors (e.g., dissolved organic carbon, pH) were also significant predictors of autotrophic and consumer community composition. Autotrophic biomass was significantly greater in recovering lakes owing to an increased abundance of attached filamentous green algae. However, consumer biomass did not differ significantly between severely stressed and recovering lakes because of a compensatory shift from numerous small tolerant omnivores to fewer large-bodied sensitive grazers. Lack of a significant relationship between autotrophic and consumer biomass along with stable isotopic evidence of few primary consumers suggested that grazing pressure was weak, especially in the stressed lakes. The persistent importance of abiotic factors to autotrophic and consumer communities suggested that ecosystem recovery remained incomplete in these lakes.

La théorie écologique prédit que les facteurs biologiques remplacent les facteurs abiotiques dans le contrôle de la structure de la communauté lorsque l’écosystème récupère d’un stress. Nous avons examiné les relations entre les communautés benthiques d’autotrophes (périphyton épilithique) et de consommateurs et les variables du milieu sur un gradient formé de six lacs acidifiés en récupération pour déceler les meilleures variables explicatives de la structure de communauté. Le carbone organique dissous, le pH et le phosphore dissous total sont des variables prédictives importantes de la biomasse des autotrophes, alors que seul le phosphore dissous total est un facteur explicatif significatif de la variation de la biomasse des consommateurs. Les facteurs abiotiques, tels que le carbone organique dissous et le pH, sont aussi des variables prédictives significatives de la composition des communautés d’autotrophes et de consommateurs. La biomasse des autotrophes est significativement plus importante dans les lacs en récupération à cause de l’abondance accrue des algues vertes filamenteuses attachées. Cependant, la biomasse des consommateurs ne diffère pas significativement entre les lacs fortement stressés et les lacs en récupération à cause d’un remplacement compensatoire des nombreux petits omnivores tolérants par un nombre moindre de brouteurs sensibles de grande taille. L’absence de relation significative entre la biomasse des autotrophes et celle des consommateurs, de même que le petit nombre de consommateurs primaires (confirmé par l’analyse des isotopes stables), laissent croire que la pression de broutage est faible, particulièrement dans les lacs stressés. L’importance persistante des facteurs abiotiques pour les communautés d’autotrophes et de consommateurs semble indiquer que la récupération est encore incomplète dans ces lacs.

Document Type: Research Article

Publication date: October 1, 2005

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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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