Life Sciences Commons^™

Light And Temperature Mediate Algal Simulation Of Heterotrophic Activity On Decomposing Leaf Litter, Cody A. Pope, Halvor M. Halvorson, Robert H. Findlay, Steven N. Francoeur, Kevin A. Kuehn

Faculty Publications

1. Recent evidence suggests that periphytic algae stimulate plant litter heterotrophs (fungi and bacteria) in the presence of light, but few studies have tested whether this stimulation varies across gradients of light, which may covary with temperature.
2. We exposed field‐conditioned Typha domingensis litter to fully‐crossed, short‐term gradients of temperature (15, 20, 25, and 30°C) and light (0, 25, 53, 123, and 388 µmol quanta m⁻² s⁻¹) and measured responses of litter‐associated algal, fungal, and bacterial production rates and β‐glucosidase, β‐xylosidase, and phenol oxidase enzyme activities in the laboratory.
3. Increased light stimulated algal production rates, from immeasurable production under …

The Effects Of Light On The Bacterial Biomass Of Decomposing Leaf Litter In Freshwater, Savannah L. Underwood

Honors Theses

Recent evidence has suggested that the presence of light (and in conjuction, periphytic algae) stimulates the growth and production of bacteria on decaying plant litter. However, the current method of measuring bacterial biomass, flow cytometry, drastically underestimates the bacterial biomass levels associated with litter samples. To determine and correct for this underestimation, the present study determined conversion factors using direct counting methods via epifluorescence microscopy. These conversion factors were then applied to flow cytometry counts for seven different studies. The studies analyzed the effects of light and other covarying factors on the bacterial biomass associated with various samples of leaf …

Algal-Mediated Priming Effects On The Ecological Stoichiometry Of Leaf Litter Decomposition: A Meta-Analysis, Halvor M. Halvorson, Steven N. Francoeur, Robert H. Findlay, Kevin A. Kuehn

Faculty Publications

In aquatic settings, periphytic algae exude labile carbon (C) that can significantly suppress or stimulate heterotrophic decomposition of recalcitrant C via priming effects. The magnitude and direction of priming effects may depend on the availability and stoichiometry of nutrients like nitrogen (N) and phosphorus (P), which can constrain algal and heterotrophic activity; in turn, priming may affect heterotrophic acquisition not only of recalcitrant C, but also N and P. In this study, we conducted a meta-analysis of algal-mediated priming across leaf litter decomposition experiments to investigate (1) bottom-up controls on priming intensity by dissolved N and P concentrations, and (2) …

The Role Of Temperature In Affecting Carry-Over Effects And Larval Competition In The Globally Invasive Mosquito Aedes Albopictus, Nnaemeka F. Ezeakacha, Donald Yee

Faculty Publications

Background

Ectotherms, like mosquitoes, have evolved specific responses to variation in environmental conditions like temperature, and these responses could confer a fitness benefit or cost when carried-over to different life stages. However, effects of temperature on animals with complex life-cycles often only focus on part of their life-cycle, or only consider how single aspects of life-history may carry over to new stages. Herein we investigated how temperature affects intraspecific larval competition and carry-over effects from larval to adult stages in the widespread invasive Asian tiger mosquito Aedes albopictus.

Methods

For larval competition, larvae were reared at three densities (10, …

Periphytic Algae Decouple Fungal Activity From Leaf Litter Decomposition Via Negative Priming, Halvor M. Halvorson, Jacob R. Barry, Matthew B. Lodato, Robert H. Findlay, Steven N. Francoeur, Kevin A. Kuehn

Faculty Publications

1. Well‐documented in terrestrial settings, priming effects describe stimulated heterotrophic microbial activity and decomposition of recalcitrant carbon by additions of labile carbon. In aquatic settings, algae produce labile exudates which may elicit priming during organic matter decomposition, yet the directions and mechanisms of aquatic priming effects remain poorly tested.

2. We tested algal‐induced priming during decomposition of two leaf species of contrasting recalcitrance, Liriodendron tulipifera and Quercus nigra, in experimental streams under light or dark conditions. We measured litter‐associated algal, bacterial, and fungal biomass and activity, stoichiometry, and litter decomposition rates over 43 days.

3. Light increased algal biomass and …

Ecological Stoichiometry: What Role Does It Play In The Competition And Spatial Distribution Patterns Of Aedes Albopictus And Aedes Aegypti?, James Deerman

Master's Theses

Ecological stoichiometry is the balance of chemical substances within animal bodies through interactions and processes within their ecosystem. Though relatively underexplored, it provides a wealth of information linking interactions across different levels of organization. Detritus is the base of the food web within the small aquatic ecosystems occupied by the mosquitoes Aedes albopictus and Aedes aegypti. Nutrient content of detritus varies, but it can have a negative effect on mosquito growth and survival if nutrient thresholds are not met. I investigated nutrient environments and species abundance in cemetery vases in New Orleans, LA to assess detrital heterogeneity and its …

Influence Of Resource Levels, Organic Compounds And Laboratory Colonization On Interspecific Competition Between The Asian Tiger Mosquito Aedes Albopictus (Stegomyia Albopicta) And The Southern House Mosquito Culex Quinquefasciatus, D.W. Allgood, Donald A. Yee

Faculty Publications

The mosquitoes Aedes albopictus (Stegomyia albopicta) (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae) are common inhabitants of tyres and other artificial containers, which constitute important peridomestic mosquito breeding habitats. We tested the hypotheses that interspecific resource competition between the larvae of these species is asymmetrical, that the concentration of chemicals associated with decomposing detritus affects the competitive outcomes of these species, and that wild and colonized strains of Cx. quinquefasciatus are affected differently by competition with Ae. albopictus. We conducted two laboratory competition experiments wherein we measured survivorship and estimated population growth (λ′) in both species under …

Concurrent Effects Of Resource Pulse Amount, Type, And Frequency On Community And Population Properties Of Consumers In Detritus-Based Systems, Donald A. Yee, Steven A. Juliano

Faculty Publications

Episodic resource inputs (i.e., pulses) can affect food web properties and community dynamics, but detailed mechanistic understanding of such effects remain elusive. Natural aquatic microsystems (e.g., tree holes, human-made containers) are colonized by invertebrates that form complex food webs dependent on episodic and sometimes sizeable inputs of allochthonous detritus from adjacent terrestrial environments. We investigated how variation in pulse frequency, amount, and resource type interacted to affect richness, abundance, composition, and population sizes of colonizing invertebrates in water-filled tires and tree hole analogs in a forest habitat. Different container types were used to assess the generality of effects across two …

Stable Isotope Analysis Reveals Detrital Resource Base Sources Of The Tree Hole Mosquito, Aedes Triseriatus, Michael G. Kaufman, Kirsten S. Pelz-Stelinski, Donald A. Yee, Steven A. Juliano, Peggy H. Ostrom, Edward D. Walker

Faculty Publications

1. Detritus that forms the basis for mosquito production in tree hole ecosystems can vary in type and timing of input. We investigated the contributions of plant‐ and animal‐derived detritus to the biomass of Aedes triseriatus (Say) pupae and adults by using stable isotope (¹⁵N and ¹³C) techniques in laboratory experiments and field collections.
2. Laboratory‐reared mosquito isotope values reflected their detrital resource base, providing a clear distinction between mosquitoes reared on plant or animal detritus.
3. Isotope values from field‐collected pupae were intermediate between what would be expected if a single (either plant or animal) detrital source dominated the …

Environmental Correlates Of Abundances Of Mosquito Species And Stages In Discarded Vehicle Tires, Donald A. Yee, Jamie M. Kneitel, Steven A. Juliano

Faculty Publications

Discarded vehicle tires are a common habitat for container mosquito larvae, although the environmental factors that may control their presence or abundance within a tire are largely unknown. We sampled discarded vehicle tires in six sites located within four counties of central Illinois during the spring and summer of 2006 to determine associations between a suite of environmental factors and community composition of container mosquitoes. Our goal was to find patterns of association between environmental factors and abundances of early and late instars. We hypothesized that environmental factors correlated with early instars would be indicative of oviposition cues, whereas environmental …

Algal Regulation Of Extracellular Enzyme Activity In Stream Microbial Communities Associated With Inert Substrata And Detritus, Steven T. Rier, Kevin A. Kuehn, Steven N. Francoeur

Faculty Publications

We tested the hypothesis that algae influence the activities of extracellular enzymes involved in mineralization processes within microbial assemblages in streams. We tested the prediction that the factors that influence algal biomass and photosynthesis (i.e., diel fluctuations in photosynthetically active radiation [PAR], long-term variations in light regime, and community development stage) would have a corresponding effect on extracellular enzyme activities. We also tested the prediction that algae would influence enzyme activities on inorganic substrata and in detrital communities where they ultimately would influence plant litter decomposition rates. We allowed microbial communities to develop on inert substrata (glass-fiber filters) or on …

Amino Acid Changes During In Vitro Decomposition Of Marsh Plant Detritus, Armando A. De La Cruz, Kirit D. Chapatwala, William E. Poe

Gulf and Caribbean Research

Dead plant material was collected from a tidal marsh, ground to a uniform size (250 μm) and decomposed in vitro at 30°C in darkness for 36 days. Crude protein, total amino acids, and essential amino acids increased from 19.0 to 31.0 mg/g, 11.1 to 17.6 mg/g and 5.8 to 8.1 mg/g respectively from day 0 to day 36. The amino acid and crude protein values observed in the detritus are generally low but the increment during decomposition is considered significant in terms of the marine consumers that depend on highly decomposed detritus for food.