We compared benthic community structure among stands of Typha angustifolia (narrow-leaf cattail) and herbicide-treated (Glypro) and untreated Phragmites australis (common reed) over two summers in a Lake Erie coastal wetland (i.e., drowned river mouth). Both macrophytes are invasives, but only Phragmites is currently controlled by herbicides because of its reputed “undesirable” effects on wetland community structure and function. Macroinvertebrate diversity was similar among stand types and relatively high (Shannon-Weaver indices ∼2.6–4.2), probably because of high system primary productivity and a mix of lentic and riverine species. Proportions of macroinvertebrate functional feeding groups were also similar, but Jaccard's similarity indices were relatively low (29%–57%), suggesting macroinvertebrate compositional differences among stand types. Coleopterans particularly affected species presence/absence patterns, but their presence was associated with low water level rather than hydrophyte type per se. Moreover, total macroinvertebrate densities were greater in both Phragmites treatments than in Typha; a pattern generated mostly by gastropods (≥ 95% Gyraulus deflectus and Physella gyrina) and chironomids. Microalgal food supply likely plays a part in explaining these density differences, given diatom-dominated epiphyton was denser on submerged shoots of Phragmites than on Typha. Common diatom assemblages were similar among stand types, but species richness was significantly greater on untreated-Phragmites than on herbicide-treated, early senescent Phragmites and untreated-Typha. However, advanced senescence from herbicide application (∼3 months) did not apparently affect macroscale habitat suitability and structure above and below the waterline, given counts of ovipositing odonates (mostly Ischnura and Enallagma) and captures of juvenile fishes (> 90% Lepomis spp.) were similar among stand types. Overall, our results suggest that benthic community structure is comparable between similarly-aged stands (∼4 yrs old) of invading reed and cattail and is not directly or indirectly affected by Glypro application.
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Vol. 28 • No. 1