Potential effects of elevated atmospheric carbon dioxide on benthic autotrophs and consumers in stream ecosystems: a test using experimental stream mesocosms

Autor: Samir K. Rosado, Kaitlen P. Gary, Chad W. Hargrave
Rok vydání: 2009
Předmět:
Zdroj: Global Change Biology. 15:2779-2790
ISSN: 1365-2486
1354-1013
DOI: 10.1111/j.1365-2486.2009.01897.x
Popis: Elevated atmospheric carbon dioxide (eCO 2 ) has been shown to have a variety of ecosystem-level effects in terrestrial systems, but few studies have examined how eCO 2 might affect aquatic habitats. This limits broad generalizations about the effects of a changing climate across biomes. To broaden this generalization, we used free air CO 2 enrichment to compare effects of eCO 2 (i.e., double ambient ∼ 720 ppm) relative to ambient CO 2 (aCO 2 ∼ 360 ppm) on several ecosystem properties and functions in large, outdoor, experimental mesocosms that mimicked shallow sand-bottom prairie streams. In general, we showed that eCO 2 had strong bottom-up effects on stream autotrophs, which moved through the food web and indirectly affected consumer trophic levels. These general effects were likely mediated by differential CO 2 limitation between the eCO 2 and aCO 2 treatments. For example, we found that eCO 2 decreased water-column pH and increased dissolved CO 2 in the mesocosms, reducing CO 2 -limitation at times of intense primary production (PP). At these times, PP of benthic algae was about two times greater in the eCO 2 treatment than aCO 2 treatment. Elevated PP enhanced the rate of carbon assimilation relative to nutrient uptake, which reduced algae quality in the eCO 2 treatment. We predicted that reduced algae quality would negatively affect benthic invertebrates. However, density, biomass and average individual size of benthic invertebrates increased in the eC0 2 treatment relative to aCO 2 treatment. This suggested that total PP was a more important regulator of secondary production than food quality in our experiment. This study broadens generalizations about ecosystem-level effects of a changing climate by providing some of the first evidence that the global increase in atmospheric CO 2 might affect autotrophs and consumers in small stream ecosystems throughout the southern Great Plains and Gulf Coastal slope of North America.
Databáze: OpenAIRE
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