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2022_Kowarik_et_al_STOTEN.pdf (3.42 MB)

Stream degradation affects aquatic resource subsidies to riparian ground-dwelling spiders

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posted on 2022-10-04, 09:07 authored by Carmen Kowarik, Dominik Martin-Creuzburg, Kate MathersKate Mathers, Christine Weber, Christopher T Robinson

Freshwater systems have undergone drastic alterations during the last century, potentially affecting cross-boundary resource transfers between aquatic and terrestrial ecosystems. One important connection is the export of biomass by emergent aquatic insects containing omega-3 polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA), that is scarce in terrestrial systems. Because of taxon-specific differences in PUFA content and functional traits, the contribution of different insect groups should be considered, in addition to total biomass export. In this context, one important trait is the emergence mode. Stoneflies, in contrast to other aquatic insects, crawl to land to emerge instead of flying directly from the water surface, making them accessible to ground-dwelling predators. Because stoneflies are especially susceptible to environmental change, stream degradation might cause a mismatch of available and required nutrients, particularly for ground-dwelling predators. In this study, we estimated emergent biomass and EPA export along two streams with different levels of habitat degradation. The EPA content in aquatic insects did not differ with different degrees of habitat degradation and total biomass export in spring was with 7.9 ± 9.6 mg m−2 day−1 in the degraded and 7.3 ± 8.5 mg m−2 day−1 in the natural system, also unaffected. However, habitat degradation substantially altered the contribution of crawling emergence to the total export in spring, with no biomass export by stoneflies at the most degraded sites. The EPA content in ground-dwelling spiders was correlated with emergent stonefly biomass, making up only 16.0 ± 6.2 % of total fatty acids at sites with no stonefly emergence, but 27.3 ± 3.0 % at sites with highest stonefly emergence. Because immune function in ground-dwelling spiders has been connected to EPA levels, reduced crawling emergence might impact spider fitness. Functional traits, like emergence mode as well as nutritional quality, should be considered when assessing the effects of stream degradation on adjacent terrestrial ecosystems.

Funding

Federal office of the environment (FOEN) as part of the research program “Hydraulic Engineering and Ecology”

History

School

  • Social Sciences and Humanities

Department

  • Geography and Environment

Published in

Science of The Total Environment

Volume

855

Publisher

Elsevier

Version

  • VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/

Acceptance date

2022-09-06

Publication date

2022-09-14

Copyright date

2022

ISSN

0048-9697

Language

  • en

Depositor

Dr Kate Mathers. Deposit date: 3 October 2022

Article number

158658

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