Soluble nutrient effects on microbial communities and mosquito production in Ochlerotatus triseriatus habitats

Abstract

We investigated the effects of soluble nutrient inputs into larval habitats of Ochlerotatus triseriatus (Diptera: Culicidae) on microbial components and mosquito production using laboratory and field microcosm experiments. Labile carbon, added as glucose, was the most consistent stimulus of bacterial production as measured by leucine incorporation rates. In laboratory experiments, glucose, but not nitrate or phosphate, stimulated bacterial production in natural treehole water samples; however, glucose in combination with nitrate and phosphate was necessary to stimulate bacterial production on laboratory microcosm leaf surfaces. Field microcosm experiments were then conducted in which the nutrient combination was added periodically during larval development. In the first experiment, nutrients were added weekly or not at all in a 2 × 2 factorial design with larval presence or absence. Larval grazing effects on bacterial abundance and production, protozoan and rotifer abundance and biovolume, protozoan cyst abundance, and leaf fungal biomass as measured by ergosterol content, were much more pronounced than any nutrient effects. However, nutrient additions enhanced mosquito survival and affected leaf surface bacterial production. In separate experiments, weekly additions of nutrients at twice the initial concentrations enhanced mosquito production compared to 1 ⁄ 2 initial nutrient concentrations. Additionally, supplementation of nutrients at initial levels, but on successive days during the second week of larval development, enhanced mosquito production relative to additions during the first and third weeks of larval development. Our results show that microbial communities in larval habitats are more likely to be limited by top-down larval feeding effects than bottom-up soluble nutrient inputs; however, mosquito production can be enhanced through soluble nutrient stimulation of microbial growth and the timing of that stimulation.

Larval mosquito communities in discarded vehicle tires in a forested and unforested site: detritus type, amount, and water nutrient differences

“…The relatively high levels of TP relative to TN encountered in these tires suggests nitrogen limitation. Addition of detritus-derived nitrogen has been shown to be important for mosquito growth (Carpenter 1982,Walker et al 1991,Kaufman et al 2002,Yee and Juliano 2006. Besides nitrogen, labile carbon is much more likely to limit production of basal microbial food resources than is phosphorous in some mosquito systems (Kaufman et al 2002,Kaufman and.…”

“…Organic detritus, particularly leaves, is thought to be the major organic carbon source for communities of container mosquito larvae (Merritt et al 1992, Kaufman et al 2002 as most forms of primary productivity are absent (Carpenter 1983). Growth and survival of container mosquitoes are affected by detritus type and dissolved nutrients (e.g., Walker et al 1997, Léonard and Juliano 1995, Paradise and Dunson 1997, Yee and Juliano 2006.…”

Richness–productivity relationships between trophic levels in a detritus-based system: significance of abundance and trophic linkage

“…Our results are consistent with those of Kneitel and Miller (2002), who found that in pitcher plant communities, richness of a higher trophic level (protozoans) was positively affected by initial resources (dead ants), but richness of a lower trophic level (bacteria) was unrelated to similar increases in resources. Biomass of protozoa in the water column is negatively affected by the presence of filter-feeding mosquito larvae (Kneitel and Chase 2004;Kaufman et al 2002;Eisenberg et al 2000;CochranStafira and von Ende 1998;Paradise and Dunson 1998). Moreover, protozoan community composition (Kneitel and Chase 2004) varies with the intensity of predation by mosquito larvae.…”

“…As our study was designed to describe relationships of productivity and richness, we cannot determine the mechanisms by which productivity affects different species, although aquatic microorganisms appear to be limited by availability of carbon, nitrogen, and phosphorous (Wetzel 1995;Pace and Cole 1996;Sterner and Elser 2002), and some of these nutrients are correlated with primary productivity in other aquatic systems (Leibold 1999;Chase and Ryberg 2004). For tree holes, carbon is thought to be the primary limiting nutrient (Kaufman et al 2002), as most carbon in these systems is in a refractory form (e.g., tannins, cellulose, and lignins). Future studies investigating the effects of productivity in detritus-based aquatic systems should make use of multiple measures of productivity, which may act in concert to affect richness and have different effects on separate trophic levels.…”

“…In constructing trophic levels, we acknowledge that all protozoans may not be equally edible to invertebrates, although none of the invertebrates is susceptible to predation by protozoans. Protozoan populations are negatively affected by mosquitoes (the dominant group in tree holes, Kneitel and Chase 2004;Kaufman et al 2002;Eisenberg et al 2000;Cochran-Stafira and von Ende 1998;Paradise and Dunson 1998). We further recognize that additional trophic levels (e.g., omnivorous protozoans) are likely present within some tree holes.…”