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Changes in Stream Primary Producer Communities Resulting from Large-Scale Catastrophic Amphibian Declines: Can Small-Scale Experiments Predict Effects of Tadpole Loss?
Journal article   Peer reviewed

Changes in Stream Primary Producer Communities Resulting from Large-Scale Catastrophic Amphibian Declines: Can Small-Scale Experiments Predict Effects of Tadpole Loss?

Scott Connelly, Catherine M. Pringle, Rebecca J. Bixby, Roberto Brenes, Matt R. Whiles, Karen R. Lips, Susan Kilham and Alexander D. Huryn
Ecosystems (New York), v 11(8), pp 1262-1276
01 Dec 2008
DOI: https://doi.org/10.1007/s10021-008-9191-7
Featured in Collection :   UN Sustainable Development Goals @ Drexel

Abstract

Ecology Environmental Sciences & Ecology Life Sciences & Biomedicine Science & Technology
Global declines of amphibian populations are well documented, yet effects of these declines on freshwater ecosystem structure and function are poorly understood. Here we examine responses of algal primary producers to tadpole extirpation over differing spatial and temporal scales. We experimentally excluded tadpoles from artificial substrata within localized areas (0.25 m(2)) of two streams. One stream had an intact community of frogs (frog stream), and the other had recently experienced a catastrophic decline (frogless stream), leaving virtually no tadpoles. In the frog stream, there were significantly greater levels of chlorophyll a (+111%, P = 0.009), ash-free dry mass (AFDM) (+163%, P = 0.02), inorganic sediments (+114%, P = 0.001), and higher mean algal cell biovolume in tadpole exclusion treatments than in the tadpole access treatments. Correspondingly, overall AFDM-specific net primary production (NPP) increased by 38% (P = 0.001) and chlorophyll a-specific NPP increased by 29% (P = 0.001) in tadpole access treatments compared to tadpole exclusion treatments. Areal-specific NPP did not differ between treatments. There were no significant differences in chlorophyll a, AFDM, inorganic sediments, algal cell biovolume, or biomass-specific NPP between treatments in the frogless stream. Fifteen months after our experiments, a massive amphibian decline associated with a fungal pathogen occurred in the frog stream, resulting in the extirpation of over 90% of tadpoles. This extirpation was followed by significant increases in levels of chlorophyll a (269%, P = 0.001), AFDM (+220%, P < 0.001), and inorganic sediments (+140%, P = 0.001). Reach-scale NPP increased from -1587 to -810 mg DO m(-2) d(-1). Additionally, algal community composition shifted from a dominance of small adnate diatoms (predecline) to a dominance of large upright algal species (post-decline). Our experimental results, combined with algal monitoring at the reach scale, indicate that over the course of our study catastrophic amphibian losses have significant effects on stream ecosystem structure and function. Ecosystem-level impacts of tadpole extirpations were more dramatic than results from our small-scale, short-term experiments, which predicted the direction of change in response variables but underestimated the magnitude. However, the long-term stream ecosystem responses remain unknown.

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65 citations in Web of Science
71 citations in Scopus

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#15 Life on Land

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Collaboration types
Domestic collaboration
Web of Science research areas
Ecology
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