Assessing spatial deposition of aquatic subsidies by insects emerging from agricultural streams

Type Article
Date 2022-09
Language English
Author(s) Raitif Julien1, 2, Roussel Jean-Marc1, Olmos MaximeORCID1, Piscart Christophe3, Plantegenest Manuel2
Affiliation(s) 1 : DECOD (Ecosystem Dynamics and Sustainability), INRAE, Institut Agro, IFREMER, Rennes, France
2 : IGEPP, Institut de Génétique, Environnement et Protection des Plantes, Institut Agro, Rennes, France
3 : Université de Rennes, CNRS, ECOBIO - UMR 6553, Rennes, France
Source Science Of The Total Environment (0048-9697) (Elsevier BV), 2022-09 , Vol. 837 , P. 155686 (8p.)
DOI 10.1016/j.scitotenv.2022.155686
WOS© Times Cited 5
Keyword(s) Winged stream insects, Agroecosystems, Emergence, Resource pulse, Dry mass
Abstract

The role of winged aquatic insects that emerge from streams and subsidize terrestrial ecosystems has been demonstrated for natural forest landscapes, but almost no information is available for intensive agricultural landscapes. This study is the first to estimate aquatic subsidies provided by flying insects that emerge from streams and land on cropland. We investigated three major groups of aquatic insects - Trichoptera, Ephemeroptera and Chironomidae (Diptera) - that emerged from 12 third-order temperate, agricultural streams. We simultaneously monitored their emergence using floating traps and their terrestrial dispersal using passive interception traps. We estimated that the annual aquatic emerging dry mass (DM) of these groups varied from 1.4–7.5 g m−2 yr−1, depending on the stream. We used a Bayesian approach to estimate parameters of the terrestrial dispersal function of each group. We combined emerging DM and the dispersal parameters to estimate how terrestrial deposition of aquatic insect DM varied with increasing distance from streams. The results highlighted that emerging DM and dispersal to land could be higher in intensive agricultural landscapes than that previously described in natural settings. We estimated that 12.5 kg ha−1 yr−1 of winged aquatic insect DM fell to the ground 0–10 m from stream edges, composed mainly of Ephemeroptera and Trichoptera. We also estimated that 2.2 kg DM ha−1 yr−1 fell 10–50 m from the stream, especially small-bodied species of Chironomidae, throughout the year, except for the coldest weeks of winter. By influencing aquatic insect communities that emerge from streams, intensive agricultural practices change the magnitude and spatial extent of aquatic subsidy deposition on land. Implications for terrestrial food webs and ecosystem services provided to agriculture are discussed.

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