Mojave Applied Ecology Notes Fall 2009

USDA working to manage invasive annual grasses, effects of heat and smoke on red brome soil seed bank, how burial depth and substrate affect germination of Sahara mustard and red brome, environmental effects of the southern Nevada groundwater projec

Final report on interrelationships between chemical, physical and biological conditions of the waters of Las Vegas Bay of Lake Mead

This program was a status study of the interaction between Las Vegas Wash, an enriched stream, and Las Vegas Bay, a wedge shaped arm of one of the world\u27s deeper reservoirs. The program centered primarily on identification and counting of planktonic algae from several points in Las Vegas Bay. Additional work on nutrient enrichment of water samples was conducted to aid in interpretation of algal distribution related to nutrient input. Examination of a variety of physical, chemical, and biological parameters, both at many surface points in the bay, as well as in vertical profile, was also accomplished and further aided interpretation of nutrient cycling, sources of nutrient input and other limnological events commonly associated with the process of eutrophication. One copy of data is provided as an appendix to this report. Other copies are available on request. An intensive sampling program has been the core of the project. Fifteen stations were located to provide an early warning network for detection of directed movement of water bodies or strata in the bay, reliability in evaluation of surface plankton distributions, and reference points for exploitation of unanticipated opportunities. These stations were visited approximately weekly during the contract period for plankton samples to evaluate biologically-induced or biologically - responsive changes as cumulative indices of the chemical status of the system. Evaluation of results was aided by determinations of depth profiles of the standard limnological parameters: temperature, a measure of the degree of stratification or mixing of a lake, oxygen, pH and oxidation-reduction potential. Conductivity, to identify isothermal yet saline discontinuities and especially the location of the flow from Las Vegas Wash, was also measured. Colonies or unicellular plankton were counted to determine distribution versus time over the bay surface. Distribution and density, rather than productivity, was of primary interest; although evidence for growth or accumulation at given points was also obtained. Chemical analyses for principal anions and cations (such as sulfate, chloride, sodium and potassium) and major nutrients (such as phosphate) were performed in cooperation with Desert Research Institute and Environmental Protection Agency. Counts of total and coliform bacteria were made on samples from vertical profiles at various times to establish the reason for the pattern of oxygen depletion found

Final report: Lake Mead monitoring program

The Lake Mead Monitoring Program has continued to develop information on the limnological condition of Lake Mead. We have significantly increased our analytical capabilities this year by developing a cooperative project with the U.S. Bureau of Reclamation and continuing our cooperative program with E.P.A. We also were able to derive significant benefit from the reviews of the Pollution Abatement Project written by Clair Sawyer and Charles Goldman. Partially as a result of these reviews we have had the opportunity to interpret and more fully explain the significance of our work to a wider public audience than would otherwise have been possible. Among the important issues that have been of primary interest this year are: 1. The significance, extent and effect on nutrient distribution of a density current from Las Vegas Wash. 2. The significance of lake level on algal abundance and productivity in Las Vegas Bay. 3. The probably effects of the AWT plant on algal abundance and productivity in Las Vegas Bay. This report more fully explains the data available on the density current and shows that the current becomes completely dissipated and mixed with waters of Las Vegas Bay, usually within the middle portion of the Bay. The influence of lake level on algal abundance is also examined with evidence supporting a hypothesis that higher lake levels result in lower algal populations. While we do not have accurate data on water volumes in Las Vegas Bay at various lake levels, rough calculations suggest that rising lake levels since 1972 have in fact resulted in a greater dilution of the inflowing nutrients from Las Vegas Wash. In effect the higher water levels have probably resulted in improved conditions in the lake because the nutrient inflows have actually become increasingly diluted in Las Vegas Bay since 1972. This is basically the same effect that would result by removing nutrients from an inflowing stream if lake level remained stable. A series of bioassays were performed to attempt a reasonable prediction of the probable effects of phosphorous removal on algal growth in Las Vegas Bay. Because of a number of variables, we did not obtain a quantitative estimate of the effect of phosphorous removal on algal growth in the bay. We did demonstrate however that reduction in phosphorous inflow will result in reduction of algal growth in Las Vegas Bay, if the bioassay procedures have approximately simulated conditions in Las Vegas Bay. Additional experimentation is necessary to approach a quantitative model of the effects of phosphorous removal on algal production in Lake Mead. Again we believe the value of the monitoring program has been demonstrated. Without the long-term data base provided by the Lake Mead Monitoring Program, the public discussion that has resulted from the interest created by AWT construction would have been forced to rely on short-term investigations, interpretation by interested and concerned laymen or emotional argument by individuals or organizations with special interests

Bonytail (Gila elegans) may enhance survival of Razorback Suckers (Xyrauchen texanus) in rearing ponds by preying on exotic crayfish

This study examined the potential of bonytail (Gila elegans) to enhance survival of young razorback sucker (Xyrauchen texanus) in rearing ponds by serving as a biological control agent for young stages of Red Swamp Crayfish (Procambarus clarki). Large populations of crayfish in rearing ponds negatively affect the survival of razorback suckers, through predation and competition for food. Traps made with 6.34 mm (0.25 inch) mesh have been used in an effort to reduce crayfish populations, however crayfish less than 17 mm carapace length (CPL) are able to escape. Juvenile bonytail in experimental trials ate young crayfish ranging in size from 3 to 15 mm CPL. Crayfish consumption was not reduced in the presence of an alternative food source, but was reduced slightly by the presence of cover. These results suggest that juvenile bonytail may reduce numbers of crayfish smaller than 15 mm CPL in ponds used to rear razorback suckers. If so, integration of rearing programs for endangered razorback sucker and bonytail could have beneficial effects for both species

Thermal tolerances and preferences of fishes of the Virgin River system (Utah, Arizona, Nevada)

Critical thermal maxima (CTM) and thermal preferenda of the common fishes of the Virgin River were examined. Differences in final temperature preferenda and CTM for species with low thermal lability (speckled dace, spinedace, roundtail chub) correspond well with differences in their distribution and abundance in the river. These species shifted their acute thermal preferences relatively little as acclimation temperature increased. For thermally labile species (woundfin, red shiner, desert sucker, and fiannehnouth sucker), the final preferendum is a less precise indicator of probable distribution. The woundfin, an endangered fish, has a high CTM (39.5 C at 25 C acclimation) and a labile acute preferendum (slope nearest 1) compared to other species in the system. The introduced red shiner likewise has a high CTM and a labile acute preferendum. In cooler temperatures, its acute preferendum shifts more rapidly than does that of the woundfin. At higher temperatures (above 15 C), the red shiner does not shift its acute preferendum as rapidly as does the woundfin. The red shiner, however, has a higher final preferendum. For thermally labile species, influence of acclimation temperature on mean preferendum, together with CTM, provides a better insight into distributional relationships within the system

Phytoplankton successions and lake dynamics in Las Vegas Bay, Lake Mead, Nevada

Phytoplankton successions, applications of the general growth equation, and physical measurements have been employed to investigate events occurring at the interface between industrial and sewage effluent contained in Las Vegas Wash and the waters of Lake Mead, Nevada. The data indicate that the entering waters tend to form a density current interrupted at intervals by dynamic effects generated in the lake. The dynamic relationships described here for the spring months suggest that a much more thorough understanding of physical, chemical and biological interactions is necessary to permit solution of the numerous problems of Las Vegas Bay discussed or alluded to by Hoffman et al

Distribution of stream pollution in lake water

Wastewater effluent-laden waters from Las Vegas Wash (LVW) form a density current that may be detected in Boulder Basin of Lake Mead at considerable distances from the wash estuary. This led to the suspicion that water from the inflowing stream [40 mgd (1.5 X 105 cu m/day)] might not be rapidly diluted in the enormous volume of the lake [19 mil acre-ft (2.3 X 1010 cu m)], but might persist as a recognizable entity to the vicinity of the intake of a major water source for populous Clark County, Nev. Because of the detection sensitivity implicit in the use of bacteria as tracers, the signal amplification factor inherent in their growth on media, and precedent in work on streams and air, it was decided to investigate the possibility that they might be used to study the practical problem under consideration. Ideally, certain thermophilic spore-forming bacteria may be deliberately added as tracers. The next best choice would be a rnesophilic spore former (such as Bacillus subtilis var. niger), and a third alternative would be naturally occurring populations of bacteria indigenous to LVW. The last alternative was adopted because of the health hazards (though slight) inherent in adding large numbers of spores to the envirqnrnent under investigation

Potential use of hydroelectric facilities for manipulating the fertility of Lake Mead

Analysis of historical nutrient data for Lake Mead indicates that the fertility of the reservoir has decreased which may be the cause for a corresponding decline in the largemouth bass population. However, it appears that fertility can be manipulated by altering the operation of the dam. The depletion of nutrients in the euphotic zone by phytoplankton and subsequent accumulation in the hypolimnion during summer and fall provide a natural nutrient gradient from which water of varying fertility can be drawn for discharge. This combined with alterations in the depth or seasonal pattern of discharge can possibly be used to enhance fertility and bass production in Lake Mead

Dynamic changes in cellular infiltrates with repeated cutaneous vaccination: a histologic and immunophenotypic analysis

<p>Abstract</p> <p>Background</p> <p>Melanoma vaccines have not been optimized. Adjuvants are added to activate dendritic cells (DCs) and to induce a favourable immunologic milieu, however, little is known about their cellular and molecular effects in human skin. We hypothesized that a vaccine in incomplete Freund's adjuvant (IFA) would increase dermal Th1 and Tc1-lymphocytes and mature DCs, but that repeated vaccination may increase regulatory cells.</p> <p>Methods</p> <p>During and after 6 weekly immunizations with a multipeptide vaccine, immunization sites were biopsied at weeks 0, 1, 3, 7, or 12. In 36 participants, we enumerated DCs and lymphocyte subsets by immunohistochemistry and characterized their location within skin compartments.</p> <p>Results</p> <p>Mature DCs aggregated with lymphocytes around superficial vessels, however, immature DCs were randomly distributed. Over time, there was no change in mature DCs. Increases in T and B-cells were noted. Th2 cells outnumbered Th1 lymphocytes after 1 vaccine 6.6:1. Eosinophils and FoxP3⁺cells accumulated, especially after 3 vaccinations, the former cell population most abundantly in deeper layers.</p> <p>Conclusions</p> <p>A multipeptide/IFA vaccine may induce a Th2-dominant microenvironment, which is reversed with repeat vaccination. However, repeat vaccination may increase FoxP3⁺T-cells and eosinophils. These data suggest multiple opportunities to optimize vaccine regimens and potential endpoints for monitoring the effects of new adjuvants.</p> <p>Trail Registration</p> <p>ClinicalTrials.gov Identifier: NCT00705640</p

Dual function of rare earth carboxylate compounds on the barrier properties and active corrosion inhibition of epoxy coatings on mild steel

In this work, two rare earth carboxylate compounds, lanthanum 4-hydroxycinnamate (La(4-OHcin)3) and yttrium 3-(4-methylbenzoyl)propanoate (Y(mbp)3), were incorporated into bisphenol-based epoxy resin to investigate their effectiveness in coating barrier properties and active corrosion inhibition. EIS results showed that the incorporation of rare earth carboxylate inhibitors significantly improved corrosion resistance compared to the inhibitor free coating, with the global impedance modulus remaining at a level higher than 1 GΩ cm2 after 219 days immersion. Following EIS experiments, cross-sectional views of the coatings exhibited a pore-plugging behavior by rare earth containing precipitates, which reinforced the coating barrier properties and delayed the electrolyte diffusion process. These effects were also reflected from the electrochemical parameters extracted from breakpoint frequency analysis and equivalent circuit modelling. Filiform corrosion experiments for artificially scratched coatings suggest that the addition of rare earth carboxylates effectively suppressed the initiation and growth of filaments as well as the development of the coating delamination front. The active corrosion inhibition is possibly related to the formation of a surface protective film consisting of bimetallic complexes and rare earth metal rich precipitates. The electrochemical measurements and surface analyses evidence the dual function of rare earth carboxylate species for enhancing coating barrier properties against electrolyte penetration and providing active corrosion inhibition for the underlying AS1020 mild steel