Aquatic insect larvae as geomorphic agents in travertine-building: a case study from the Barely Karst, Australia

Abstract

Louie Creek (18° 49'S, 138° 29'E) is a karst spring-fed creek that drains the northeastern Barkly Karst, northern Australia. The stream deposits travertine along a reach of approximately 1.5 km. Although physico-chemical processes dominate the downstream evolution of the bulk solution, aquatic insect larvae play both a direct and an indirect geomorphological role in travertine deposition at the microenvironment level. The most conspicuous roles are played by simulids and chironomids (Order: Diptera), pyralids (Order: Lepidoptera) and hydropsychids (Order: Trichoptera). The latter are by far the most important fauna. The dominant genus (Cheumatopsyche) constructs cylindrical cases and silk nets on the travertine surfaces, especially where strong currents prevail. Cases consist of local materials, including travertine quarried from the stream bed. The nets are usually erected between cases or constructed over the case openings. They serve to trap food carried downstream in suspension. Both nets and retreats are important substrata for calcium carbonate deposition and interrupt stream flow due to their considerable microrelief.