Nitrogen limitation and particulate elemental ratios of seston in hypersaline Mono Lake, California, U.S.A.

Particulate elemental ratios (C:N, N:P and C:Chl a) of seston in hypersaline (70–90 g kg^–1) Mono Lake, California, were examined over an 11-year period (1990–2000) which included the onset and persistence of a 5-year period of persistent chemical stratification. Following the onset of meromixis in mid-1995, phytoplankton and dissolved inorganic nitrogen were substantially reduced with the absence of a winter period of holomixis. C:N, N:P and C:Chl a ratios ranged from 5 to 18 mol mol^–1, 2 to 19 mol mol^–1 and 25 to 150 g g^–1, respectively, and had regular seasonal patterns. Deviations from those expected of nutrient-replete phytoplankton indicated strong nutrient limitation in the summer and roughly balanced growth during the winter prior to the onset of meromixis. Following the onset of meromixis, winter ratios were also indicative of modest nutrient limitation. A 3-year trend in C:N and N:P ratios toward more balanced growth beginning in 1998 suggest the impacts of meromixis weakened due to increased upward fluxes of ammonium associated with weakening stratification and entrainment of ammonium-rich monimolimnetic water. A series of nutrient enrichment experiments with natural assemblages of Mono Lake phytoplankton conducted during the onset of a previous episode of meromixis (1982–1986) confirm the nitrogen will limit phytoplankton before phosphorus or other micronutrients. Particulate ratios of a summer natural assemblage of phytoplankton collected under nitrogen-depleted conditions measured initially, following enrichment, and then after return to a nitrogen-depleted condition followed those expected based on Redfield ratios and laboratory studies.     

Artemia monica cyst production and recruitment in Mono Lake,California, USA

Annual egg production was determined for Artemia monica in Mono Lake, California, from 1983 to 1987. Annual oviparous (overwintering cyst) production was 3 and 7 million cysts m^–2 yr^–1 in 1986 and 1987, respectively, as measured by in situ sediment traps. Cyst production for the entire five year period was calculated using Artemia census data and inter-brood duration derived from mixolimnetic temperature. These estimates ranged from 2 to 5 million cysts m^–2 yr^–1. This method underestimated annual production by 30%, when compared to estimates using sediment traps. Cyst production was similar during 1983–1986 and showed a significant increase in 1987, which was due primarily to a larger reproductive population later in the year. Recruitment into the adult populations of the following spring ranged between 1.4 to 3.2%. Overall abundance of this generation reflected the patterns in annual cyst production. Compensatory effects must operate on the second generation of each year, since summer populations were similar in all years despite differences in cyst production.     

Analysis of fae and fhcD Genes in Mono Lake, California

Genes for two enzymes of the tetrahydromethanopterin-linked C₁ transfer pathway (fae and fhcD) were detected in hypersaline, hyperalkaline Mono Lake (California), via PCR amplification and analysis. Low diversity for fae and fhcD was noted, in contrast to the diversity previously detected in a freshwater lake, Lake Washington (Washington).     

Analysis of fae and fhcD genes in Mono Lake, California

Genes for two enzymes of the tetrahydromethanopterin-linked C(1) transfer pathway (fae and fhcD) were detected in hypersaline, hyperalkaline Mono Lake (California), via PCR amplification and analysis. Low diversity for fae and fhcD was noted, in contrast to the diversity previously detected in a freshwater lake, Lake Washington (Washington).     

Separation of DNA restriction fragments by ion-exchange chromatography on FPLC columns Mono P and Mono Q

Separation of DNA restriction fragments by FPLC ion-exchange chromatography on Mono Q and Mono P columns was investigated. The columns were found to be particularly suitable for the separation of fragments up to 500–600 bp long. Larger fragments can also be separated although less effectively. We found the following practical working ranges for the parameters investigated: pH, 4 to 11; flow rate, 0.05 to 0.6 ml/min corresponding to separation times between 2 and 20 h. (better resolution is achieved at lower flow rates); gradient slope; between 0.5 mm eluting salt/ml buffer and over 5 mm/ml (better resolution is achieved at lower gradient slopes; eluting ionic strength was found to be independent of gradient slope); gradient composition, chloride salts of smaller monovalent cations eluted the DNA at lower ionic strengths but separations obtained were similar; additives, substances such as urea, formamide, and EDTA can be added without chromatographic effects; sample amount: amounts from 2.5 to 200 μg were applied, corresponding to single peak content of from 42 ng to 74μg DNA. Yields were generally over 90% and the chromatographed DNA was fully accessible to restriction enzyme cleavage. Separations occurred predominantly according to DNA size, but AT-rich fragments were retarded in a predictable way.     

Nearshore and pelagic abundances of Artemia monica in Mono Lake,California

The spatial distribution and abundance of the brine shrimp, Artemia monica, in Mono Lake, California were determined during 1982 and 1983. Peak abundances of shrimp occur in midsummer and reach densities of 15–17 individuals l^-1 in the nearshore regions and 6–8 individuals 1^-1 in the pelagic region. The brine shrimp were non-uniformly distributed both vertically and horizontally. The coefficient of variation in shrimp abundance among stations within the nearshore region was similar to that found in the pelagic region. On two of the nine dates, nearshore densities were 3 to 4 times greater than those in the pelagic zone, and on average the brine shrimp appear to be slightly over-dispersed to the nearshore region. However, including nearshore abundances in lakewide estimates will usually result in a change of less than a 10%.     

Abundance,Distribution, and Diversity of Viruses in Alkaline,Hypersaline Mono Lake,California

Mono Lake is a large (180 km²), alkaline (pH ~10), moderately hypersaline (70–85 g kg^–1) lake lying at the western edge of the Great Basin. An episode of persistent chemical stratification (meromixis) was initiated in 1995 and has resulted in depletion of oxygen and accumulation of ammonia and sulfide beneath the chemocline. Although previous studies have documented high bacterial abundances and marked seasonal changes in phytoplankton abundance and community composition, there have been no previous reports on the occurrence of viruses in this unique lake. Based on the high concentrations and diversity of microbial life in this lake, we hypothesized that planktonic viruses are also abundant and diverse. To examine the abundance and distribution of viruses and bacteria, water samples were collected from four stations along 5 to 15 vertical depths at each station. Viral abundance ranged from 1 × 10⁸ to 1 × 10⁹ mL^–1, among the highest observed in any natural aquatic system examined so far. Increases (p < 0.1) in viral densities were observed in the anoxic bottom water at multiple stations. However, regression analysis indicated that viral abundance could not be predicted by any single environmental parameter. Pulsed field gel electrophoresis revealed a diverse viral community in Mono Lake with genome sizes ranging from ~14 to >400 kb with most of the DNA in the 30 to 60 kb size range. Cluster analysis grouped the anoxic bottom-water viral community into a unique cluster differentiating it from surface and mid-water viral communities. A hybridization study using an indigenous viral isolate as a probe revealed an episodic pattern of temporal phage distribution with strong niche stratification between oxic and anoxic waters.     

Osmoregulation in nestling California gulls at Mono Lake,California

• 1.1. Hematocrit (Hct), plasma sodium ([Na]_pl), chloride ([Cl]_pl) and osmotic concentration (Osm_pl); volume and concentration of 1.0MNaCl induced salt gland secretion (SGS); and weights of osmoregulatory organs: kidneys, adrenal glands, and salt glands and nonosmoregulatory organs (liver and heart) were determined in nestling California gulls, Larus californiens (CG), on Krakatoa Islet, Mono Lake, California.
• 2.2. The mean Hct was 40.0% + 1.0%, the mean [Na]_pl and [Cl]_pl were 153.9 ± 0.9 and 110.1 ± 0.5 mM (n = 22); and the mean Osm_pl was 323.6 ± 1.3 mOsm/kg (n = 18).
• 3.3. In CG nestlings with a mean age of 10 days (n = 7), the mean SGS [Na] was 719 ± 19 mM and the birds secreted 81 ± 18% of the injected fluid containing 59 ± 13% of the injected Na. By the mean age of 23 days (n = 7), mean SGS [Na] was slightly higher (790 ± 30 mM than in younger birds (P < 0.05), but the percentage of secreted fluid (54 ± 10%) and Na (42 ± 6%) tended to be less.
• 4.4. In 18 CG nestlings mean organ weights (% body weight) were: kidneys 1.52 ±0.06%; salt glands, 0.13 ±0.01%, and adrenal glands 0.07 ±0.01%.
• 5.5. Nestling CG had significantly greater Hct (P < 0.001), [Na]_pl and [ci]_pl (P < 0.001), Osm_pl, (P < 0.005), and adrenal gland weight (P < 0.01), compared to nestling glaucous-winged Gulls (GWG), L. glaucescens (Hughes, 1984), which nest under cooler, moister conditions. CG kidney weight was smaller (P < 0.001); salt gland weight and salt excretion were the same as GWG.

     

Mono and diterpene production in Escherichia coli

Mono- and diterpenoids are of great industrial and medical value as specialty chemicals and pharmaceuticals. Production of these compounds in microbial hosts, such as Escherichia coli, can be limited by intracellular levels of the polyprenyl diphosphate precursors, geranyl diphosphate (GPP), and geranylgeranyl diphosphate (GGPP). To alleviate this limitation, we constructed synthetic operons that express three key enzymes for biosynthesis of these precursors: (1). DXS,1-deoxy-d-xylulose-5-phosphate synthase; (2). IPPHp, IPP isomerase from Haematococcus pluvialis; and (3). one of two variants of IspA, FPP synthase that produces either GPP or GGPP. The reporter plasmids pAC-LYC and pACYC-IB, which encode enzymes that convert either FPP or GGPP, respectively, to the pigment lycopene, were used to demonstrate that at full induction, the operon encoding the wild-type FPP synthase and mutant GGPP synthase produced similar levels of lycopene. To synthesize di- or monoterpenes in E. coli using the GGPP and GPP encoding operons either a diterpene cyclase [casbene cyclase (Ricinus communis L) and ent-kaurene cyclase (Phaeosphaeria sp. L487)] or a monoterpene cyclase [3-carene cyclase (Picea abies)] was coexpressed with their respective precursor production operon. Analysis of culture extracts or headspace by gas chromatography-mass spectrometry confirmed the in vivo production of the diterpenes casbene, kaur-15-ene, and kaur-16-ene and the monoterpenes alpha-pinene, myrcene, sabinene, 3-carene, alpha-terpinene, limonene, beta-phellandrene, alpha-terpinene, and terpinolene. Construction and functional expression of GGPP and GPP operons provides an in vivo precursor platform host for the future engineering of di- and monoterpene cyclases and the overproduction of terpenes in bacteria.     

Bayesian estimation of genetic parameters for growth,stem straightness,and survival in Eucalyptus globulus on an Andean Foothill site

Knowledge of the genetic variation of key economic traits in Eucalyptus globulus under cold conditions is crucial to the genetic improvement of environmental tolerances and other economic traits. A Bayesian analysis of genetic parameters for quantitative traits was carried out in 37 E. globulus open-pollinated families under cold conditions in southern Chile. The trial is located in the Andean foothills, in the Province of Bío-Bío. The Bayesian approach was performed using Gibbs sampling algorithm. Multi-trait linear and threshold models were fitted to phenotypic data (growth traits, survival, and stem straightness). Fifteen years after planting, height, diameter at breast height, and stem volume were found to be weakly to moderately heritable with Bayesian credible intervals (probability of 90 %): $ {\widehat{h}}^2 $ ?=?0.009–0.102, $ {\widehat{h}}^2 $ ?=?0.031–0.185, and $ {\widehat{h}}^2 $ ?=?0.045–0.205, respectively. Stem straightness was found to be weakly to moderately heritable ranging from 0.032 to 0.208 (Bayesian 90 % credible interval); posterior mode $ {\widehat{h}}^2 $ ?=?0.091. Tree survival at age of 15 years was high in the trial (84.8 %) with such heritability values ranging from 0.072 to 0.157. Survival was non-significantly genetically correlated to growth and stem straightness. Stem volume had the highest predicted genetic gains ranging from 17.9 to 23.7 % (selection rate of 15.8 and 8.3 %, respectively). The results of this study confirm the potential for selective breeding of this eucalypt in areas of southern Chile where cold is a significant constraint.     

Genetic Diversity in Alpine and Foothill Populations of Campanula rotundifolia (Campanulaceae)

Climatic constraints on insects in alpine environments have important consequences for the biology of their plant mutualists; in particular, reduced insect diversity and activity in alpine plant populations can result in pollinator-limited seed set and, potentially, in low genetic diversity. However, highly effective pollination by bumblebees in alpine populations can compensate for low visitation rates. In this study we hypothesized that, because of highly effective pollination by bumblebees, alpine populations of Campanula rotundifolia would not experience more frequent cycles of pollinator limitation than low-elevation populations and would therefore exhibit comparable levels of genetic variability and inbreeding to those found in foothill populations. Enzyme electrophoresis was used to assess genetic variability at nine putative loci in alpine and foothill populations of C. rotundifolia in Colorado. Genetic variability in C. rotundifolia was found to be comparable to that reported for other long-lived herbaceous perennials. Measures of genetic variability and fixation indices did not differ between high- and low-elevation populations and were consistent with Hardy-Weinberg expectations. Nonsignificant F(ST) values indicated no genetic differentiation among all populations.     

Mono ADP-ribosylation of transducin catalyzed by rod outer segment extract.

Transducin is the retinal rod outer segment (ROS)-specific G protein coupling the photoexcited rhodopsin to cyclic GMP-phosphodiesterase. The alpha subunit of transducin is known to be ADP-ribosylated by bacterial toxins. We investigated the possibility that transducin is modified in vitro by an endogenous ADP-ribosyltransferase activity. By using either ROS, cytosolic extract of ROS or purified transducin in the presence of [alpha-32P]nicotinamide adenine dinucleotide (NAD+), the alpha and beta subunits of transducin were found to be radiolabeled. The labeling was decreased by snake venom phosphodiesterase I (PDE I). The modification was shown to be mono ADP-ribosylation by analyses on thin layer chromatography of the PDE I-hydrolyzed products which revealed only 5'AMP residues. In addition we report that sodium nitroprusside activates the ADP-ribosylation of transducin.     

Bacillus arsenicoselenatis, sp. nov., and Bacillus selenitireducens, sp. nov.: two haloalkaliphiles from Mono Lake, California that respire oxyanions of selenium and arsenic

Two gram-positive anaerobic bacteria (strains E1H and MLS10) were isolated from the anoxic muds of Mono Lake, California, an alkaline, hypersaline, arsenic-rich water body. Both grew by dissimilatory reduction of As(V) to As(III) with the concomitant oxidation of lactate to acetate plus CO₂. Bacillus arsenicoselenatis (strain E1H) is a spore-forming rod that also grew by dissimilatory reduction of Se(VI) to Se(IV). Bacillus selenitireducens (strain MLS10) is a short, non-spore-forming rod that grew by dissimilatory reduction of Se(IV) to Se(0). When the two isolates were cocultured, a complete reduction of Se(VI) to Se(0) was achieved. Both isolates are alkaliphiles and had optimal specific growth rates in the pH range of 8.5–10. Strain E1H had a salinity optimum at 60 g l^–1 NaCl, while strain MLS10 had optimal growth at lower salinities (24–60 g l^–1 NaCl). Both strains have limited abilities to grow with electron donors and acceptors other than those given above. Strain MLS10 demonstrated weak growth as a microaerophile and was also capable of fermentative growth on glucose, while strain E1H is a strict anaerobe. Comparative 16S rRNA gene sequence analysis placed the two isolates with other Bacillus spp. in the low G+C gram-positive group of bacteria. Received: 21 May 1998 / Accepted: 31 August 1998     

Airborne remote sensing of chlorophyll distributions in Mono Lake, California

As part of a long-term investigation of seasonal and interannual variations of plankton in Mono Lake (California), we developed a methodology using airborne imaging spectrometry to synoptically measure chlorophyll concentrations. Images of Mono Lake were acquired with NASA's Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) and were atmospherically corrected by applying a version of the radiative transfer model MODTRAN. Using a predictive equation for calculation of chlorophyll based on a band ratio of remote sensing reflectances (R _{{ rs}}; R _{{ rs}} 490 nm/R _{{ rs}} 550 nm), spatial distributions of chlorophyll throughout the lake were determined; broad east to west gradients in chlorophyll and gyres are evident.     

Nest Site Selection by Greater Sage-Grouse in Mono County,California

ABSTRACT Loss of nesting habitat is believed to be a factor in the decline of greater sage-grouse (Centrocercus urophasianus) throughout its range. Few data are available for sage-grouse in Mono County, California, USA, in the most southwestern portion of the species’ range. We studied habitat selection of nesting sage-grouse in Mono County, California, from 2003 to 2005 by capturing and radiotracking females to identify nesting locations. We sampled vegetation at nest sites and randomly selected sites within 200 m of nests and within each of 5 subareas within Mono County. Nest sites were characterized by 42.4 ± 1.3% (x̄ ± SE) shrub canopy cover, 10.5 ± 1.0 cm residual grass height, and 2.7 ± 1.0% residual grass cover. Shrub cover was the only variable found to differentiate nest sites from randomly selected sites. Unlike some other studies, we did not find understory vegetation to be important for selecting nest sites. Mean shrub cover was 38.7 ± 1.5% at random sites within 200 m of nests and 33.6 ± 1.6% at random sites at the approximate scale of home ranges, indicating that nesting females selected nesting areas that contained denser shrubs than their home range, and nest sites that contained greater shrub cover than the vicinity immediately surrounding nests. Our results suggest that managers should consider managing for greater shrub cover in Mono County than what is currently called for in other parts of sage-grouse range and that management for sage-grouse habitat may need to be tied more closely to local conditions.     

Stratification of microbial assemblages in Mono Lake, California, and response to a mixing event

Vertical profiles of microbial assemblages from samples of Mono Lake water collected in July 1994 and in April and July 1995 were obtained by analyzing DNA via the polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal RNA (rRNA) genes. The microbial assemblage was vertically stratified and distributions of individual ribotypes were coherent with temperature, salinity, irradiance and dissolved oxygen distributions at the beginning of the study in July of 1994. The lake mixed completely during the winter of 1994–1995 and was beginning to stratify thermally by April 1995. Water column gradients were weak and oxygen was depleted at depth. The microbial assemblage was uniformly distributed throughout the water column except at 20 m, where one band dominated. The microbial assemblage was vertically stratified again by July 1995. Partial sequences (134–160 bp, except one of 83 bp) obtained from DGGE bands revealed affinities to known organisms, but only one potentially exact match was found. With a few exceptions, the same ribotypes were present on all sampling dates; there was no evidence for a marked seasonal succession in microbial community composition, despite the dramatic changes in limnological conditions that accompanied the winter overturn. A band that was ubiquitous in samples from the oxycline and hypolimnion in July of both years was found throughout the water column in April. This sequence could be attributed to the chloroplast rRNA gene of an unusual phytoplankter, the green alga Picocystis salinarum.