Impact of Invertebrate Herbivory on Native Aquatic Macrophytes
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS
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This technical note quantifies the impact that invertebrate herbivores have on native aquatic plants by comparing dry biomass of five macrophyte species between two treatments an insecticide treatment to remove invertebrate herbivores, and a control where the herbivore complex was left to develop naturally. There is little information available that quantifies the impact of invertebrate herbivores on native macrophyte biomass in the United States. Early research indicated that while macrophytes were useful as substrates for invertebrates and epiphytic growth, they provided little if any nutritive value Shelford 1918. However, additional studies have shown the importance of macrophytes as a nutritive source for invertebrates. Soszka 1975 found that Potamogetoit species can lose 50 to 90 percent oftheir leaf area through insect herbivory and non-consumptive destruction mostly from lepidopterans, trichopterans, and dipterans. Sand-Jensen and Madsen 1989 found leaf area damage to be between 2 and 56 percent for Potamogeton species, depending on locality. This damage was primarily attributed to trichopterans and dipterans. Lodge 1991 stated that macrophytes are engaged in aquatic food webs, sometimes to the extent that biomass, productivity, and relative species abundance are dramatically changed by grazers. Finally, Cronin et al. 1998 found that freshwater macrophytes exhibited herbivory similar to that reported for terrestrial plants. These findings countered the conventional idea that aquatic plants offered only surface substrates Shelford 1918. However, due to the paucity of published accounts of invertebrate herbivory, more research is warranted.
- Biological Oceanography