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Climate-change effects on upland stream macroinvertebrates over a 25-year period

Durance, Isabelle and Ormerod, Stephen James 2007. Climate-change effects on upland stream macroinvertebrates over a 25-year period. Global Change Biology 13 (5) , pp. 942-957. 10.1111/j.1365-2486.2007.01340.x

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Climate change effects on some ecosystems are still poorly known, particularly where they interact with other climatic phenomena or stressors. We used data spanning 25 years (1981–2005) from temperate headwaters at Llyn Brianne (UK) to test three hypotheses: (1) stream macroinvertebrates vary with winter climate; (2) ecological effects attributable to directional climate change and the North Atlantic Oscillation (NAO) are distinguishable and (3) climatic effects on macroinvertebrates depend on whether streams are impacted by acidification. Positive (i.e. warmer, wetter) NAO phases were accompanied by reduced interannual stability (=similarity) in macroinvertebrate assemblage in all streams, but associated variations in composition occurred only in acid moorland. The NAO and directional climate change together explained 70% of interannual variation in temperature, but forest and moorland streams warmed respectively by 1.4 and 1.7°C (P<0.001) between 1981 and 2005 after accounting for NAO effects. Significant responses among macroinvertebrates were confined to circumneutral streams, where future thermal projections (+1, +2, +3°C) suggested considerable change. Spring macroinvertebrate abundance might decline by 21% for every 1°C rise. Although many core species could persist if temperature gain reached 3°C, 4–10 mostly scarce taxa (5–12% of the species pool) would risk local extinction. Temperature increase in Wales approaches this magnitude by the 2050s under the Hadley HadCM3 scenarios. These results support all three hypotheses and illustrate how headwater stream ecosystems are sensitive to climate change. Altered composition and abundance could affect conservation and ecological function, with the NAO compounding climate change effects during positive phases. We suggest that acidification, in impacted streams, overrides climatic effects on macroinvertebrates by simplifying assemblages and reducing richness. Climatic processes might, nevertheless, exacerbate acidification or offset biological recovery.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Uncontrolled Keywords: Climate change ; Insects ; Models ; NAO ; Rivers ; Streams ; Temperature
Publisher: Wiley-Blackwell
ISSN: 1354-1013
Last Modified: 04 Jun 2017 01:38

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