Leaf breakdown rates as a functional indicator were influenced by an invasive non-native invertebrate in urban ponds

Thornhill, I, Friberg, N, Batty, L, Thamia, V and Ledger, M.E (2021) 'Leaf breakdown rates as a functional indicator were influenced by an invasive non-native invertebrate in urban ponds.' Ecological Indicators. ISSN 1470-160X (Forthcoming)

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Abstract

Impacts on biodiversity and the functioning of ecosystems are often overlooked in small waterbodies as they are not regularly monitored as part of the Water Framework Directive (WFD). These small systems are, however, often essential for freshwater biodiversity and are frequently characterized by high beta-diversity. In this study we examined shredder diversity and ecosystem functioning (leaf litter breakdown) as indicators of environmental stress along a gradient of urbanisation. The native isopod Asellus aquaticus and the non-native shrimp Crangonyx pseudogracilis (Amphipoda) were dominant species of the shredder communities in 26 study ponds. Variation in shredder community composition among ponds was ex-plained by pond surface area (P < 0.05) and the coverage of impermeable surface within 500m (P <0.05), indicative of urban impact, which was strongly, and negatively correlated with shredder richness. Site mean total leaf breakdown were 0.0020 k d-1 (range 0.0003 - 0.0053), whilst breakdown rates owing to mi-crobial and fungal activity were lower and averaged 0.0010 k d-1 (range 6.72-5 - 0.0036). Both total and microbial activity driven breakdown rates showed relatively weak relationships with the environmental gradient reflecting degrees of urbanization. A model-averaging procedure suggested that total litter break-down rates could be attributed to activity of shredders with A. aquaticus and C. pseudogracilis contributing most, explaining 65% of the variance (R2 = 0.65, F = 13.7, P < 0.001), which significantly and similarly predicted total leaf breakdown rates (P < 0.05). Total leaf breakdown rates were significantly correlated with the densities of both C. pseudogracilis (P < 0.001) and A. aquaticus (P < 0.001), however partial correlations indicated that the former showed the strongest association.

Item Type: Article
Keywords: biodiversity and ecosystem functioning (BEF), shredders, ecosystem functioning, freshwater, functional replacement, functional indicators
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QH Natural history
Q Science > QH Natural history > QH301 Biology
Divisions: School of Sciences
Date Deposited: 08 Jan 2021 18:10
Last Modified: 04 Feb 2021 17:43
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