Organisms Commons^™

Reducing Equifinality Using Isotopes In A Process-Based Stream Nitrogen Model Highlights The Flux Of Algal Nitrogen From Agricultural Streams, William I. Ford, James F. Fox, Erik Pollock

Biosystems and Agricultural Engineering Faculty Publications

The fate of bioavailable nitrogen species transported through agricultural landscapes remains highly uncertain given complexities of measuring fluxes impacting the fluvial N cycle. We present and test a new numerical model named Technology for Removable Annual Nitrogen in Streams For Ecosystem Restoration (TRANSFER), which aims to reduce model uncertainty due to erroneous parameterization, i.e., equifinality, in stream nitrogen cycle assessment and quantify the significance of transient and permanent removal pathways. TRANSFER couples nitrogen elemental and stable isotope mass‐balance equations with existing hydrologic, hydraulic, sediment transport, algal biomass, and sediment organic …

Cyanobacteria Dominance In The Oligohaline Waters Of Back Bay, Virginia, Harold G. Marshall

Biological Sciences Faculty Publications

Back Bay and its flora have historically been influenced by the interaction of freshwater flow in combination with frequent intrusion of saline water into its basin. These events have resulted in a dynamic environmental setting influencing the abundance and composition of its phytoplankton community. Dominating these oligohaline waters is a diverse representation and high abundance of freshwater filamentous and colonial cyanobacteria. These include the nonheterocystous Planktolyngbya contorta, Planktolyngbya limnetica, and Pseudanabaena limnetica, taxa implicated as bloom producers in Bay waters with N:P molar ratios ranging from 23:1 to 74:1.

Action Spectrum For Photoentrainment Of The Circadian Clock In Wild-Type Chlamydomonas Reinhardtii, Jennifer Forbes=Stovall

Masters Theses & Specialist Projects

The circadian clock is an endogenous timer that oscillates with a period of approximately 24 hours and is reset upon environmental time cues such as the daily light/ dark or temperature cycles. Chlamydomonas reinhardtii is an ideal model organism for research on the circadian clock, because it shows several well-characterized behaviors that exhibit a circadian rhythm. Its circadian rhythm of phototaxis (swimming toward light) has been automated. Former action spectrum studies using the circadian phototaxis rhythm as an indicator surprisingly found that pulses of blue light were not effective in resetting the circadian clock of dark-adapted cells. This may have …

Factors Regulating The Growth Of Algae In Continuous Culture In Diluted Secondary Sewage Treatment Plant Effluent And Subsequent Biodegradability, Edward G. Foree, Caroline P. Wade

KWRRI Research Reports

Heterogeneous algal cultures were grown in laboratory continuous culture in continuous flow, completely mixed chemostats in secondary sewage treatment plant effluent diluted to give an ammonia nitrogen concentration of 10 mg/1. Variables were lighting, pH, carbon dioxide availability, and hydraulic residence time.

Optimum growth occurred under pH 7.0, excess CO₂, and continuous lighting conditions. The availability of artificially supplied excess CO₂ greatly increased the mass (standing crop) at steady-state over that produced under otherwise identical conditions for all residence times studied. For the case of excess CO₂ availability, the nitrogen concentration in the algal cells regulated …

Algal Growth And Decomposition: Effects On Water Quality, Edward G. Foree, John S. Tapp Jr.

KWRRI Research Reports

The chemical composition of algae grown in batch culture depends mainly on environmental conditions, nutrient availability, presence of predators, cell age, and species. The effects of nutrient availability and cell age on the composition of three unialgal cultures (algae + bacteria) and one hetergeneous culture (algae + bacteria + microscopic animals) were evaluated. The cultures were grown in batch culture under both nutrient-abundant and nutrient deficient conditions and the changes in compositions were observed. Luxurious uptake where nutrients are incorporated into cellular protoplasm at levels greater than those necessary for growth, and super-luxurious uptake, where some nutrients are stored rather …