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Dryad

Benthic macroinvertebrates of 63 northern Finnish streams along a dissolved organic carbon gradient

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Nov 18, 2022 version files 34.61 KB

Abstract

Concentrations of dissolved organic carbon (DOC) have increased over the past few decades, causing freshwater browning. The impacts of browning on biodiversity have been little studied, despite many of the individual stressors associated with browning being known to control freshwater communities. We explored the responses of benthic invertebrates along a wide gradient of DOC concentrations (3.6 mg to 27 mg L-1) in 63 boreal streams variously impacted by peatland drainage or peat production. DOC was a prime determinant of macroinvertebrate diversity and abundance, with the strongest negative response in algal scrapers. Threshold indicator taxa analysis indicated a community change at 12-13 mg DOC L-1, with only four taxa increasing, while 13 taxa decreased along the DOC gradient. Our findings of both a gradual loss and an abrupt change of biodiversity along a browning gradient provide a benchmark against which changes to stream biodiversity relative to the predicted browning trend can be gauged.