Flux of aquatic insect productivity to land: comparison of lentic and lotic ecosystems

• Published in: Ecology
• Main Authors: Gratton, Claudio, Zanden, M. Jake Vander
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Tundra
• Online Access: http://dx.doi.org/10.1890/08-1546.1; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1890%2F08-1546.1; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/08-1546.1

Recently, food web studies have started exploring how resources from one habitat or ecosystem influence trophic interactions in a recipient ecosystem. Benthic production in lakes and streams can be exported to terrestrial habitats via emerging aquatic insects and can therefore link aquatic and terrestrial ecosystems. In this study, we develop a general conceptual model that highlights zoobenthic production, insect emergence, and ecosystem geometry (driven principally by area‐to‐edge ratio) as important factors modulating the flux of aquatic production across the ecosystem boundary. Emerging insect flux, defined as total insect production emerging per meter of shoreline (g C·m −1 ·yr −1 ) is then distributed inland using decay functions and is used to estimate insect deposition rate to terrestrial habitats (g C·m −2 ·yr −1 ). Using empirical data from the literature, we simulate insect fluxes across the water–land ecosystem boundary to estimate the distribution of fluxes and insect deposition inland for lakes and streams. In general, zoobenthos in streams are more productive than in lakes (6.67 vs. 1.46 g C·m −2 ·yr −1 ) but have lower insect emergence to aquatic production ratios (0.19 vs. 0.30). However, as stream width is on average smaller than lake radius, this results in flux ( F ) estimates 2½ times greater for lakes than for streams. Ultimately, insect deposition onto land (within 100 m of shore) adjacent to average‐sized lakes (10‐ha lakes, 0.021 g C·m −2 ·yr −1 ) is greater than for average‐sized streams (4 m width, 0.002 g C·m −2 ·yr −1 ) used in our comparisons. For the average lake (both in size and productivity), insect deposition rate approaches estimates of terrestrial secondary production in low‐productivity ecosystems (e.g., deserts and tundra, ≈0.07 g C·m −2 ·yr −1 ). However, larger lakes (1300 ha) and streams (16 m) can have average insect deposition rates (≈0.01–2.4 g C·m −2 ·yr −1 ) comparable to estimates of secondary production of more productive ecosystems such as grasslands. Because of ...