Search

The genus Halomonas possesses bacteria that are halophilic or halotolerant and exhibit a wide range of pH tolerance. The genome of Halomonas sp. Soap Lake #7 was sequenced to provide a better understanding of the mechanisms for salt and pH tolerance in this genus. The bacterium’s genome was found to possess two complete multiple resistance and pH antiporter systems, Group 1 and Group 2. This is the first report of both multiple resistance and pH antiporter Groups 1 and 2 in the genome of a haloalkaliphilic bacterium.

Aims Development of biomineralization technologies has largely focused on microbially induced carbonate precipitation (MICP) via Sporosarcina pasteurii ureolysis; however, as an obligate aerobe, the general utility of this organism is limited. Here, facultative and anaerobic haloalkaliphiles capable of ureolysis were enriched, identified and then compared to S. pasteurii regarding biomineralization activities. Methods and results Anaerobic and facultative enrichments for haloalkaliphilic and ureolytic micro-organisms were established from sediment slurries collected at Soap Lake (WA). Optimal pH, temperature and salinity were determined for highly ureolytic enrichments, with dominant populations identified via a combination of high-throughput SSU rRNA gene sequencing, clone libraries and Sanger sequencing of isolates. The enrichment cultures consisted primarily of Sporosarcina- and Clostridium-like organisms. Ureolysis rates and direct cell counts in the enrichment cultures were comparable to the S. pasteurii (strain ATCC 11859) type strain. Conclusions Ureolysis rates from both facultatively and anaerobically enriched haloalkaliphiles were either not statistically significantly different to, or statistically significantly higher than, the S. pasteurii (strain ATCC 11859) rates. Work here concludes that extreme environments can harbour highly ureolytic active bacteria with potential advantages for large scale applications, such as environments devoid of oxygen. Significance and impact of the study The bacterial consortia and isolates obtained add to the possible suite of organisms available for MICP implementation, therefore potentially improving the economics and efficiency of commercial biomineralization.

Soap Lake, located in Washington State, is a meromictic soda lake that was the subject of a prior National Science Foundation funded Microbial Observatory. Several organisms inhabiting this lake have been identified as producers of siderophores that are unique in structure. Two isolates found to be of the species Halomonas, SL01 and SL28, were found to produce suites of amphiphilic siderophores consisting of a peptidic head-group, which binds iron appended to fatty acid moieties of various lengths. The ability for siderophores to self-assemble into vesicles was determined for three suites of amphiphilic siderophores of unique structure (two from SL01 and one from SL28). These siderophores resemble the amphiphilic aquachelin siderophores produced by Halomonas aquamarina strain DS40M3, a marine bacterium. Vesicle self-assembly studies were performed by dynamic light scattering and epifluorescence microscopy. The addition of ferric iron (Fe3+) at different equivalents, where an equivalence of iron is defined as equal to the molarity of the siderophore, demonstrated vesicle formation. This was suggested by both dynamic light scattering and epifluorescence microscopy. Bacteria thriving under saline and alkaline conditions are capable of producing unique siderophores that self-assemble in micelles and vesicles due to ferric iron chelation.

Thioalkalimicrobium cyclicum Sorokin et al. 2002 is a member of the family Piscirickettsiaceae in the order Thiotrichales. The γ-proteobacterium belongs to the colourless sulfur-oxidizing bacteria isolated from saline soda lakes with stable alkaline pH, such as Lake Mono (California) and Soap Lake (Washington State). Strain ALM 1(T) is characterized by its adaptation to life in the oxic/anoxic interface towards the less saline aerobic waters (mixolimnion) of the stable stratified alkaline salt lakes. Strain ALM 1(T) is the first representative of the genus Thioalkalimicrobium whose genome sequence has been deciphered and the fourth genome sequence of a type strain of the Piscirickettsiaceae to be published. The 1,932,455bp long chromosome with its 1,684 protein-coding and 50 RNA genes was sequenced as part of the DOE Joint Genome Institute Community Sequencing Program (CSP) 2008.

Two novel taxa of heliobacteria, Heliorestis acidaminivorans sp. nov. strain HR10B(T) and 'Candidatus Heliomonas lunata' strain SLH, were cultured from shoreline sediments/soil of Lake El Hamra (Egypt) and lake water/benthic sediments of Soap Lake (USA), respectively; both are highly alkaline soda lakes. Cells of strain HR10B were straight rods, while cells of strain SLH were curved rods. Both organisms were obligate anaerobes, produced bacteriochlorophyll g, and lacked intracytoplasmic photosynthetic membrane systems. Although the absorption spectrum of strain HR10B was typical of other heliobacteria, that of strain SLH showed unusually strong absorbance of the OH-chlorophyll a component. Major carotenoids of both organisms were OH-diaponeurosporene glucosyl esters, as in other alkaliphilic heliobacteria, and both displayed an alkaliphilic and mesophilic phenotype. Strain HR10B was remarkable among heliobacteria in its capacity to photoassimilate a number of carbon sources, including several amino acids. Nitrogenase activity was observed in strain HR10B, but not in strain SLH. The 16S ribosomal RNA gene tree placed strain HR10B within the genus Heliorestis, but distinct from other described species. By contrast, strain SLH was phylogenetically more closely related to neutrophilic heliobacteria and is the first alkaliphilic heliobacterium known outside of the genus Heliorestis.

Summary Culture-based and culture-independent methods were used to explore the diversity of phototrophic purple bacteria in Soap Lake, a small meromictic soda lake in the western USA. Among soda lakes, Soap Lake is unusual because it consists of distinct upper and lower water bodies of vastly different salinities, and its deep waters contain up to 175 mM sulfide. From Soap Lake water new alkaliphilic purple sulfur bacteria of the families Chromatiaceae and Ectothiorhodospiraceae were cultured, and one purple non-sulfur bacterium was isolated. Comparative sequence analysis of pufM, a gene that encodes a key photosynthetic reaction centre protein universally found in purple bacteria, was used to measure the diversity of purple bacteria in Soap Lake. Denaturing gradient gel electrophoresis and subsequent phylogenetic analyses of pufMs amplified from Soap Lake water revealed that a significant diversity of purple bacteria inhabit this soda lake. Although close relatives of several of the pufM phylotypes obtained from cultured species could also be detected in Soap Lake water, several other more divergent pufM phylotypes were also detected. It is possible that Soap Lake purple bacteria are major contributors of organic matter into the ecosystem of this lake, especially in its extensive anoxic and sulfidic deep waters.

Kallis, Jahn, Leo Bodensteiner, and Anthony Gabriel, 2010. Hydrological Controls and Freshening in Meromictic Soap Lake, Washington, 1939-2002. Journal of the American Water Resources Association (JAWRA) 46(4): 744-756. DOI: 10.1111/j.1752-1688.2010.00446.x Abstract: The chemically stratified layer of naturally formed meromictic lakes exhibits unusual and often extreme physical and chemical conditions that have resulted in the evolution of uniquely adapted species. The Columbia Basin Irrigation Project appears to have had a marked effect on the hydrology of Soap Lake, a meromictic lake in the Grand Coulee of central Washington. The relation of hydrology to salinity was assessed by analyzing water budgets before and after the introduction of the irrigation project. Before irrigation, water gains were balanced by losses; after irrigation began groundwater gains approximately doubled. To manage lake levels and reduce groundwater influx, wells were installed to intercept groundwater. Although the hydrological cycle has been restored to pre-irrigation conditions, the meromictic character of the lake continues to change. Interception wells remove 10 to 16 Mm3 of groundwater annually, but influx continues based on change in the monimolimnion. From 1958 to 2003 the chemocline descended 1.1 m and the volume of the monimolimnion from 698,000 m3 to 114,000 m3. Annual loss of volume is occurring at a rate of 1.9% since 1958. Although groundwater interception wells are maintaining the volume of the entire lake, the recession of the chemocline indicates that conditions that have maintained meromixis at Soap Lake are currently not in equilibrium.

Hexavalent chromium is one of the most widely distributed environmental contaminants. Given the carcinogenic and mutagenic consequences of Cr(VI) exposure, the release of Cr(VI) into the environment has long been a major concern. While many reports of microbial Cr(VI) reduction are in circulation, very few have demonstrated Cr(VI) reduction under alkaline conditions. Since Cr(VI) exhibits higher mobility in alkaline soils relative to pH neutral soils, and since Cr contamination of alkaline soils is associated with a number of industrial activities, microbial Cr(VI) reduction under alkaline conditions requires attention.Soda lakes are the most stable alkaline environments on earth, and contain a wide diversity of alkaliphilic organisms. In this study, a bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State. The ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor. Metal reduction rates were quantified using Monod kinetics. In addition, Cr(VI) reduction experiments were carried out in the presence of Fe(III) to evaluate the possible enhancement of Cr(VI) reduction rates through electron shuttling mechanisms. While Fe(III) reduction rates were slow compared to previously reported rates, Cr(VI) reduction rates fell within range of previously reported rates.

Soap Lake, located in Washington State, is a naturally occurring saline and alkaline lake. Several organisms inhabiting this lake have been identified as producers of siderophores that are unique in structure. Bacterial isolates, enriched from Soap Lake sediment and water samples, were screened for siderophore production using both the chrome azurol S (CAS) agar plate and liquid methods. Bacterial isolate Halomonas sp. SL01 was found to produce relatively high concentrations of siderophores in liquid medium (up to 40 µM). Siderophores from the isolate were separated from the culture supernatant using solid phase extraction and purified by high-performance liquid chromatography (HPLC). Siderophore structure was determined using LC/MS/MS (liquid chromatography/mass spectrometry/mass spectrometry) and fatty acid methyl ester (FAME) GC. Two distinct new families of amphiphilic siderophores were produced by isolate SL01. All siderophores ranged in size from 989 to 1096 atomic mass units and consisted of a conserved peptidic head group (per family), which coordinates iron, coupled to fatty acid moieties. The fatty acyl moieties were C10–C14 in length and some with hydroxyl substitutions at the third α position. These siderophores resembled amphiphilic aquachelin siderophores produced by Halomonas aquamarina strain DS40M3, a marine bacterium as well as siderophores from isolate Halomonas sp. SL28 that was found to produce amphiphilic siderophores. Bacteria thriving under saline and alkaline conditions are capable of producing unique siderophores resembling those produced by microbes inhabiting marine environments.

A variety of anaerobic bacteria have been shown to transfer electrons obtained from organic compound oxidation to the surface of electrodes in microbial fuel cells (MFCs) to produce current. Initial enrichments for iron (III) reducing bacteria were set up with sediments from the haloalkaline environment of Soap Lake, Washington, in batch cultures and subsequent transfers resulted in a culture that grew optimally at 7.0% salinity and pH 11.0. The culture was used to inoculate the anode chamber of a MFC with formate as the electron source. Current densities up to 12.5 mA/m2 were achieved by this bacterium. Cyclic voltammetry experiments demonstrated that an electron mediator, methylene blue, was required to transfer electrons to the anode. Scanning electron microscopic imaging of the electrode surface did not reveal heavy colonization of bacteria, providing evidence that the bacterium may be using an indirect mode of electron transfer to generate current. Molecular characterization of the 16S rRNA gene and restriction fragment length profiles (RFLP) analysis showed that the MFC enriched for a single bacterial species with a 99% similarity to the 16S rRNA gene of Halanaerobium hydrogeniformans. Though modest, electricity production was achieved by a haloalkaliphilic bacterium at pH 11.0 and 7.0% salinity.

Soap Lake is a small saline lake in central eastern Washington that is sharply stratified into two layers. In addition to being highly alkaline (~pH 10), Soap Lake also contains high concentrations of sulfide. Here, we report the community profile of the prokaryotic microbiota associated with Soap Lake surface water.

Soda lakes are highly alkaline extreme environments that form in closed drainage basins exposed to high evaporation rates. Because of the scarcity of Mg2+ and Ca2+ in the water chemistry, the lakes become enriched in CO3 2− and Cl−, with pHs in the range 8 to >12. Although there is a clear difference in prokaryotic communities between the hypersaline lakes where NaCl concentrations are >15% w/v and more dilute waters, i.e., NaCl concentrations about 5% w/v, photosynthetic primary production appears to be the basis of all nutrient recycling. In both the aerobic and anaerobic microbial communities the major trophic groups responsible for cycling of carbon and sulfur have in general been identified. Systematic studies have shown that the microbes are alkaliphilic and many represent separate lineages within accepted taxa, while others show no strong relationship to known prokaryotes. Although alkaliphiles are widespread it seems probable that these organisms, especially those unique to the hypersaline lakes, evolved separately within an alkaline environment. Although present-day soda lakes are geologically quite recent, they have probably existed since archaean times, permitting the evolution of independent communities of alkaliphiles since an early period in the Earth's history.

A Gram-positive, obligately anaerobic, motile, slender, flexible rod, designated SC/BZ-SP2T, was isolated from mixed alkaline water and sediment of Soap Lake, Washington State, USA. Strain SC/BZ-SP2T formed salmon to pink colonies and was alkaliphilic. The isolate grew at pH35 °C 7.5–10.5 (optimum pH35 °C 9.7), at 8–40 °C (optimum 35–37 °C) and with 0.35–1.38 M Na+ (optimum 0.44–0.69 M Na+). The isolate utilized l-arabinose, d-ribose, d-xylose, d-fructose, d-mannose, d-galactose, cellobiose, maltose, sucrose, trehalose, sorbitol, xylan, malate and yeast extract as carbon and energy sources; best growth was observed with l-arabinose, cellobiose, maltose and trehalose. The major fermentation products from beechwood xylan were propionate and acetate. The dominant fatty acids were iso-C15 : 0, anteiso-C15 : 0, iso-C17 : 0 3-OH, C17 : 0 3-OH and C15 : 0 3-OH. The cell-wall sugars were ribose, xylose, galactose and glucose. Thiosulfate and sulfite could be reduced to sulfide. The genomic DNA G+C content was 39.5±0.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SC/BZ-SP2T belonged to the family Marinilabiliaceae of the order Bacteroidales , class Bacteroidia . The most closely related strains were Alkaliflexus imshenetskii Z-7010T (91.8 % 16S rRNA gene sequence similarity), Marinilabilia salmonicolor Cy s1T (91.0 %) and Anaerophaga thermohalophila Fru22T (90.4 %). On the basis of phenotypic, chemotaxonomic and phylogenetic features, strain SC/BZ-SP2T represents a novel species in a new genus of the family Marinilabiliaceae , for which the name Alkalitalea saponilacus gen. nov., sp. nov. is proposed. The type strain of Alkalitalea saponilacus is SC/BZ-SP2T ( = ATCC BAA-2172T = DSM 24412T).

Changes in the limnology of two saline lakes, Lake Lenore and Soap Lake, in the lower Grand Coulee, Washington, between 1949 and the present are described.

The microbial community diversity and composition of meromictic Soap Lake were studied using culture-dependent and culture-independent approaches. The water column and sediments were sampled monthly for a year. Denaturing gradient gel electrophoresis of bacterial and archaeal 16S rRNA genes showed an increase in diversity with depth for both groups. Late-summer samples harbored the highest prokaryotic diversity, and the bacteria exhibited less seasonal variability than the archaea. Most-probable-number assays targeting anaerobic microbial guilds were performed to compare summer and fall samples. In both seasons, the anoxic samples appeared to be dominated by lactate-oxidizing sulfate-reducing prokaryotes. High numbers of lactate- and acetate-oxidizing iron-reducing bacteria, as well as fermentative microorganisms, were also found, whereas the numbers of methanogens were low or methanogens were undetectable. The bacterial community composition of summer and fall samples was also assessed by constructing 16S rRNA gene clone libraries. A total of 508 sequences represented an estimated >1,100 unique operational taxonomic units, most of which were from the monimolimnion, and the summer samples were more diverse than the fall samples (Chao1 = 530 and Chao1 = 295, respectively). For both seasons, the mixolimnion sequences were dominated by Gammaproteobacteria , and the chemocline and monimolimnion libraries were dominated by members of the low-G+C-content group, followed by the Cytophaga-Flexibacter-Bacteroides (CFB) group; the mixolimnion sediments contained sequences related to uncultured members of the Chloroflexi and the CFB group. Community overlap and phylogenetic analyses, however, not only demonstrated that there was a high degree of spatial turnover but also suggested that there was a degree of temporal variability due to differences in the members and structures of the communities.

Soap Lake is a hypersaline, alkaline lake in Central Washington State (USA). For the past five years the lake has been the site of an NSF Microbial Observatory project devoted to identifying critical geochemical and microbial characteristics of the monimolimnion sediment and water column, and has demonstrated rich multispecies communities occupy all areas of the lake. Soap Lake and similar soda lakes are subject to repeated transient periods of extreme evaporation characterized by significant repetitive alterations in salinity, pH, and total water volume, yet maintain high genetic and metabolic diversity. It has been argued that this repetitive cycle for salinity, alkalinity, and sulfur concentration has been a major driver for prokaryote evolution and diversity. The rapidity of wet-dry cycling places special demands on genome evolution, requirements that are beyond the relatively conservative eukaryotic evolutionary strategy of serial alteration of existing gene sequences in a relatively stable genome. Although HGT is most likely responsible for adding a significant amount of noise to the genetic record, analysis of HGT activity can also provide us with a much-needed probe for exploration of prokaryotic genome evolution and the origin of diversity. Packaging of genetic information within the protective protein capsid of a bacteriophage would seem preferable to exposing naked DNA to the highly alkaline conditions in the lake. In this study, we present preliminary data demonstrating the presence of a diverse group of phage integrases in Soap Lake. Integrase is the viral enzyme responsible for the insertion of phage DNA into the bacterial host's chromosome. The presence of the integrase sequence in bacterial chromosomes is evidence of lysogeny, and the diversity of integrase sequences reported here suggests a wide variety of temperate phage exist in this system, and are especially active in transition zones.

A halotolerant, alkaliphilic dissimilatory Fe(III)-reducing bacterium, strain SFB, was isolated from salt flat sediments collected from Soap Lake, WA. 16S ribosomal ribonucleic acid gene sequence analysis identified strain SFB as a novel Bacillus sp. most similar to Bacillus agaradhaerens (96.7% similarity). Strain SFB, a fermentative, facultative anaerobe, fermented various hexoses including glucose and fructose. The fructose fermentation products were lactate, acetate, and formate. Under fructose-fermenting conditions in a medium amended with Fe(III), Fe(II) accumulated concomitant with a stoichiometric decrease in lactate and an increase in acetate and CO(2). Strain SFB was also capable of respiratory Fe(III) reduction with some unidentified component(s) of Luria broth as an electron donor. In addition to Fe(III), strain SFB could also utilize nitrate, fumarate, or O(2) as alternative electron acceptors. Optimum growth was observed at 30 degrees C and pH 9. Although the optimal salinity for growth was 0%, strain SFB could grow in a medium with up to 15% NaCl by mass. These studies describe a novel alkaliphilic, halotolerant organism capable of dissimilatory Fe(III) reduction under extreme conditions and demonstrate that Bacillus species can contribute to the microbial reduction of Fe(III) in environments at elevated pH and salinity, such as soda lakes.

An alkaliphilic purple sulfur bacterium, strain SC5, was isolated from Soap Lake, a soda lake located in east central Washington state (USA). Cells of strain SC5 were gram-negative, non-motile, and non-gas vesiculate cocci, often observed in pairs or tetrads. In the presence of sulfide, elemental sulfur was deposited internally. Liquid cultures were pink to rose red in color. Cells contained bacteriochlorophyll a and spirilloxanthin as major photosynthetic pigments. Internal photosynthetic membranes were of the vesicular type. Optimal growth of strain SC5 occurred in the absence of NaCl (range 0–4%), pH 8.5 (range pH 7.5–9.5), and 32°C. Photoheterotrophic growth occurred in the presence of sulfide or thiosulfate with only a limited number of organic carbon sources. Growth factors were not required, and cells could fix N2. Dark, microaerobic growth occurred in the presence of both an organic carbon source and thiosulfate. Sulfide and thiosulfate served as electron donors for photoautotrophy, which required elevated levels of CO2. Phylogenetic analysis placed strain SC5 basal to the clade of the genus Thiocapsa in the family Chromatiaceae with a 96.7% sequence similarity to its closest relative, Thiocapsa roseopersicina strain 1711T (DSM217T). The unique assemblage of physiological and phylogenetic properties of strain SC5 defines it as a new species of the genus Thiocapsa, and we describe strain SC5 herein as Tca. imhoffii, sp. nov.

Culture-dependent and -independent techniques were used to study the diversity of chemolithoautotrophic sulfur-oxidizing bacteria in Soap Lake (Washington State), a meromictic, haloalkaline lake containing an unprecedentedly high sulfide concentration in the anoxic monimolimnion. Both approaches revealed the dominance of bacteria belonging to the genus Thioalkalimicrobium , which are common inhabitants of soda lakes. A dense population of Thioalkalimicrobium (up to 10 7 cells/ml) was found at the chemocline, which is characterized by a steep oxygen-sulfide gradient. Twelve Thioalkalimicrobium strains exhibiting three different phenotypes were isolated in pure culture from various locations in Soap Lake. The isolates fell into two groups according to 16S rRNA gene sequence analysis. One of the groups was closely related to T. cyclicum , which was isolated from Mono Lake (California), a transiently meromictic, haloalkaline lake. The second group, consisting of four isolates, was phylogenetically and phenotypically distinct from known Thioalkalimicrobium species and unique to Soap Lake. It represented a new species, for which we suggest the name Thioalkalimicrobium microaerophilum sp. nov.

Soap Lake is a haloalkaline lake located in central Washington. This lake is a remnant of the Missoula flood events that created the landscape of western Montana, the southeastern portion of Washington state, and much of Oregon. It is 15,000 - 20,000 years old, and has maintained a stable meromixis for the last 10,000 years. This carbonate lake is characterized by a brackish mixolimnion, and a monimolimnion with a salinity of ~14%. The pH of both layers of the lake is approximately 10. Both layers also have a high concentration of dissolved sulfate, with the mineral mirabilite (Na 2 SO 4 •10H 2 O) found in the monimolimnion sediments. Sulfide concentrations in the monimolimnion exceed 100 mM. As part of the mission of the NSF Soap Lake Microbial Observatory, microorganisms involved in the sulfur cycle in this lake were studied in terms of their diversity and function. High rates of sulfate reduction were measured in both layers of the lake, with new species of sulfate-reducing bacteria seen in both areas. A particularly novel psychrophilic sulfur oxidizer was isolated from the monimolimnion. This organism has the ability to induce the formation of mirabilite, which was assumed to be an abiotically deposited evaporite mineral. This is the first evidence for a biogenic origin of this mineral. This leads to the possibility that related sulfate minerals, such as those reported on the Mars surface, may have a biogenic origin.

In many arid regions, lakes often lose significant amounts of water through evaporation, leading to alkaline and saline aquatic systems. The water in terminal lakes (i.e. lakes with no outlet) may contain from 0.3–30% NaCl and higher (Williams 1998). Saline lakes are globally distributed and account for approximately half of the total volume of all inland surface water in the world (Williams 1998). The alkaline-saline lakes are a special class of saline lakes, with a pH from 9 to almost 12 in addition to high salinity (Duckworth et al. 1996). Lake Magadi (Kenya), Mono Lake (California, USA) and Soap Lake (Washington, USA) are examples of such lakes.

Schmidt’s stability concept is used in a comparison of profiles of temperature and salinity for six meromictic lakes in 1953–4958 and 1972. The dual control of density in these lakes is emphasized by distinguishing “thermal” from “chemical” (or “meromictic”) stability. A slight modification of the Schmidt equation is made to yield a plot with depth of the minimum work required for destratification. Significant erosion of the salinity stratification has occurred in nearly all those lakes investigated, with consequent decreases in stability. Soap Lake, in the Lower Grand Coulee, has been considerably modified by dilution; one effect has been to prolong the existence of meromixis by at least 20 years.

The profiles of soluble fallout plutonium in two partially anoxic waters revealed minimum concentrations at the 02-H2S interface, indicating Pu removal onto particulate phases of Fe and other oxidized species that form during the redox cycle. In Saanich Inlet, an intermittently anoxic fjord in Vancouver Island, Canada, the concentration of soluble Pu in the anoxic zone was slightly less than in the oxygenated surface layer. In Soap Lake, a saline meromictic lake in eastern Washington State, Pu concentrations in the permanently anoxic zone were at least an order of magnitude higher than at the surface. Differences in the chemical characteristics of these two waters suggest important chemical species that influenced the observed Pu distribution. In the permanently anoxic zone of Soap Lake, high values of total alkalinity ranging from 940 to 1,500 meq liter-‘, sulfide species from 38 to 128 FM, dissolved organic carbon from 163 to 237 mg liter-‘, and total dissolved solids from 80 to 140 ppt, all correlated with the observed high concentration of Pu. In Saanich Inlet, where total alkalinity ranged from 2.1 to 2.4 meq liter-’ and salinity from 25 to 32%~ and H,S concentration in May 198 1 showed a maximum of 8 PM, the observed Pu concentrations were significantly lower than for the Soap Lake monimolimnion.

Soap Lake and Lake Lenore occupy adjacent basins in the Lower Grand Coulce, Washington, but show several strong limnological contrasts despite correspondence in rates and trends of heat storage. Seasonal events in the dynamics of phytoplankton and zooplankton populations generally coincide with different phases in thermal behavior of the lakes. Both lakes show a dramatic summer decline in phytoplankton population density, with spring and fall periods of more intense activity. In Soap Lake, which stratifies thermally in summer, a dense algal population is established in the metalimnion. The summer phytoplankton minima in both lakes coincide with maximum development of zooplankton populations, although there is no conclusive evidence that zooplankton grazing actually limits phytoplankton growth. The seasonal phytoplankton cycles may be more closely dependent on nutrient depletion in surface waters, and oxygen inhibition of photosynthesis might also be implicated. Close agreement was evident in 14C productivity measurements for both lakes, but these may have been affected by oxygen inhibition in light and dark bottles. Both lakes, however, are highly productive, and productivity estimates are comparable with those obtained for soda lakes elsewhere.

In the Lower Grand Coulee, Washington, Diaptomus nevadensis in Soap Lake contains larger amounts of the carotenoid astaxanthin than in Lake Lenore. During winter, Diaptomus sicilis contains larger amounts of pigment in both lakes, but in summer individuals from Lake Lenore are much reduced in pigment while those from Soap Lake are unchanged. The amount of astaxanthin might be a reflection of the amount of pigment in the copepods’ diet or might reflect the relative importance of selective forces acting for and against pigmentation, Seasonal variations in copepod carotenoid content did not correspond with variations in total lipid content. Algal abundance was measured by chlorophyll a and plant carotenoids correlated with copepod carotenoids only in the case of D. neuadensis in Soap Lake. The percent of D. nevadensis guts containing algae was correlated with their pigment content in both lakes. Visually oriented predators, such as damselfly nymphs from both lakes and salamander larvae from Lake Lenore, selected red copepods, but few predators from Lake Lenore contained D. nevadensis. Since members of this species were rare, the probability of finding a predator that had consumed one was low. When fed identical diets, copepods from Lake Lenore were a fifth to a thirtieth as efficient at assimilating carotenoid as those from Soap Lake. This supports the hypothesis that the pigment differences are the result of natural selection. Selective predation is implicated as the explanation for the small amounts of pigment in Lake Lenore copepods.

Elevated activities of dissolved Th have been found in Soap Lake, an alkaline lake in Eastern Washington. Dissolved 232Th ranges from less than 0.001 to 4.9 dpm/L compared to about 1.3 × 10−5 dpm/ L in sea water. The enhanced activity in the lake coincides with an increase in carbonate alkalinity. Experiments were conducted to evaluate the effect of pH, ionic strength and carbonate alkalinity on Th adsorption on goethite. Thorium (10−13 M total) in the presence of 5.22 mg/L α-FeOOH and 0.1 M NaNO3 has an adsorption edge from pH 2–5. At pH 9.0 ± 0.6 the percent Th absorbed on the solid began to decrease from 100% at 100 meq/L carbonate alkalinity and exhibited no adsorption above 300 meq/L. The experimental data were modeled to obtain the intrinsic adsorption equilibrium constants for Th hydrolysis species. These adsorption constants were incorporated in the model to interpret the observed effect of carbonate alkalinity on Th adsorption. There are two main effects of the alkalinity. To a significant degree the decrease in Th adsorption is due to competition of HCO−3 and CO2−3 ions for surface sites. Dissolved Th carbonate complexes also contribute to the increase of Th in solution.

The central part of the State of Washington has an arid climate and contains a number of saline lakes. Several are meromictic and show a variety of vertical gradients of salinity and temperature. The mixolimnion of Soap Lake has been diluted by increased entry of freshwater from 39.4 g/liter in 1946 to 18.0 in 1964 while the monimolimnion has been maintained at more than 130 g/liter. The stability of the chemocline was studied by an injection of radioactive rubidium. The radioactivity spread laterally in all directions, mostly in a layer less than 2 m thick, to a maximum observed mean radius of 53 m in 13 days. The corresponding eddy diffusion coefficient is 3.2 cm2/sec.

The lakes that occupy the abandoned gorge of the Columbia River below Dry Falls, Washington, were formerly fed by groundwater and precipitation, and they lost water solely by evaporation. As a result the lower lakes became saline. Since 1951 an inflow of irrigation water from the development of the Columbia Basin Irrigation Project has caused the lakes to freshen. The lake levels are now controlled by pumping excess water directly from Lake Lenore and from protective wells drilled around the perimeter of Soap Lake. Data on the distribution of deuterium and chloride in the system, on measurements of the flow of water between two of the lakes, and on measurements of the pumpage have been used to develop models of the system for preirrigation and postirrigation periods. The models indicate the quantities of water that entered each lake from natural sources and from the irrigation system and that left by evaporation and by flow or seepage between the lakes, e.g., the quantities required to maintain the balance of water and chloride in the several lakes and in the system as a whole and to reproduce the distribution of deuterium and chloride in the lake waters. Annually prior to irrigation about 14 × 106 m3 of water entered the system and escaped by evaporation. About 20% of this amount was precipitated on the lake surfaces. The remainder was groundwater that entered in about equal quantities two areas separated by, the Park and Blue lakes; the groundwater seepage into these two lakes appears to have been negligible. Precipitation and groundwater have introduced 93 tons of chloride annually, and chloride has accumulated in Soap Lake at the same rate. At this rate 2350 years would have been required for the accumulation of the preirrigation chloride in Soap Lake. At present 20 × 106 m3 of irrigation water enters the system annually. The accessions of irrigation water, like those of natural groundwater, are limited to two areas separated by the Park, Blue, and Alkali lakes. The protective wells intercept much of the irrigation water and natural groundwater that would otherwise enter Soap Lake. The flow of water through the lakes is 1.7 of that prior to irrigation. The wells remove from the lakes 2550 tons of chloride annually, which is 25 times the annual inflow; this removal is rapidly reducing the chlorinity of Lake Lenore and Soap Lake. The history of the lake system in relation to changing climate is discussed.

Sediments from Soap Lake, an alkaline-saline lake on the arid Columbia Plateau, demonstrate postdepositional changes in response to a measured osmotic potential gradient through the sediment. The primary mechanism for osmotic readjustment is redistribution of water and dissolved ions through the sediment, altering scdimcnt water content and pore water salinity. This redistribution provides a mechanism for mobilizing ions from exchange sites and from minerals to form pore waters of altered composition, The historical record of aquatic ecosystems preserved in lake sediments provides information about the evolution of ecosystems and their reaction to environmental change. Microfossils are commonly used as indicators of a lake’s history, but in saline lakes, the biota is often limited, its members may exhibit a wide range of tolerance, and their preservation may be poor. In very saline lakes, a wealth of authigenic minerals can be used for environmental interpretation. In some lakes, however, the water is too saline to use microfossils, yet too dilute to exhibit many authigenic minerals; in such lakes the major record is in the salinity of the pore water. Sediments are multiphase systems; redistribution of ions can occur not only among the phases present in a sediment stratum but also between strata. Because of the likelihood of these postdepositional alterations, direct paleolimnological interpretation based on chemical and mineralogical characteristics of the sediment is difficult. The purpose of this study was to evaluate the usefulness of chemical characteristics of saline sediment for paleolimnological interpretation as well as the diagenetic mechanisms altering the saline sediment after deposition. l Supported by National Research Council of Canada Fellowships and National Science Foundation Grant GB 3567, 2 Present address: Division of Life Sciences, Scarborough College, University of Toronto, West Hill, Ontario. In saline sediments, an important diagenetic mechanism is the movement of water and dissolved ions up and down the sediment column. Because the rates are too slow to measure in the field, this movement has to be inferred indirectly. One approach is to measure sediment water potential. Sediment water potential ( @kACd) is defined as the difference between the chemical potential of water in the sediment ( JLC~) and the chemical potential of pure free water at the same temperature and pressure ( ~~0)) divided by the partial molal volume of water (V*,) to convert !Pksed to units of pressure (Kramer 1969) : !a scd = (j-b /-ho> /En. Since the chemical potential of a system is a measure of its capacity to do work, the sediment water potential gradient defines the direction in which water can move spontaneously: water will move from sediment with a high sediment water potential to sediment with a lower potential. The sediment water potential expression can be written as !I! scd RTln ’ =v*W& [ 1 ,o where e is the vapor pressure of water in the sediment and e” the vapor pressure of pure free water at the same temperature and pressure ( Kramer 1969). Thus, .by measuring the vapor pressure of water in the sediment, we can measure the water potential of the sediment and define the LIMNOLOGY AND OCEANOGRAPHY 403 MAY 1973, V. H(3) 404 MARK A. MANTUANI potential gradients that control the direction of movement of water in the sediment, This concept has been used to study the dynamics of salt and water movement in the soil-plant system, and it seems natural to apply it to readjusting wet, unconsolidated saline sediment. It emphasizes the colligative properties of the system rather than simply focusing on the vertical distribution of a few ions, Finally, sediment water potential allows integration of the various mechanisms that can cause water movement, i. e. !?? sea = *k,n + $I + *k, + *k,, where ek,, is matric or capillary potential, *, is pressure potential, !lXk, is osmotic or solute potential, and 9, is gravitational potential. Since many of these components are most easily expressed in terms of pressure units, it is useful to have +\ksed also expressed as pressure, rather than as the activity of water. Soap Lake, an alkaline-saline lake in the Lower Grand Coulee, Washington, lies in the Columbia Basin, in the rainshadow of the Cascade Mountains. Annual rainfall is less than 25 cm per year, and the potential evaporation is greater than the precipitation throughout the year ( Gilkeson 1962). The Grand Coulee was formed by the Columbia River when it was diverted from its regular channel by ice dams formed during the Wisconsin glaciation; upon retreat of the glacier at the end of the Pinedale glaciation, the last substage of the Wisconsin, the Columbia river reoccupied its old channel, leaving a series of lakes in the coulee (Richmond et al. 1965). The level of Soap Lake, the southernmost lake in the series, dropped below its outlet 11,000 years ago, and the lake rapidly became saline. In the last 20 years alteration of the hydrology of this basin by the Columbia Irrigation Project has significantly diluted Soap Lake (Friedman and Redfield 1971). I chose the sediments of Soap Lake for this study because they should record both its evolution from a dilute periglacial lake to an alkaline-saline lake and the recent dilution.

Previously I reported a color difference between populations of Diaptomus nevadensis found in two athalassic salt lakes of the Lower Grand Coulee, Washington State, USA (Hairston 1979a). In Soap Lake, which has a salinity ranging between 16 and 17‰, the copepods were bright red, while in Lake Lenore (1.5 to 1.9‰) they were for the most part pale blue or only slightly red. The red color was due to the presence of the carotenoid astaxanthin and its esters (Hairston 1976) and the blue resulted from this pigment forming an association with a protein (Zagalsky 1976). During a year-long study of this phenomenon, the color of D. nevadensis was recorded in two ways. First, extractions made from groups of whole adult copepods documented a nearly 10 fold difference in weight specific pigment content between the populations from the two lakes (Hairston 1979a).

The somewhat unique problems associated with the interception, control, or removal of water from the Soap Lake area are of considerable interest from the standpoint of irrigation and drainage engineering. This paper will discuss only the technical engineering or scientific aspects of the problem, with only brief mention of the admittedly controversial matters that lie more properly within the field of the administrator, public relations specialist, attorney, and medical practitioner.

included in the Columbia Basin Project, the largest single irrigation plan ever conceived. Grant County is large, almost a hundred miles long and fifty miles wide. Within the area has been one of the sparsest populations of the state, yet few agricultural regions have had greater changes resulting from war conditions. What the future will bring when the Columbia Basin Project has been completed and thousands of farms are developed in the region, it is difficult to conjecture. Physically, the county is a southsloping, semi-arid plateau with elevation varying between 1000 and 2000 feet. The county is divided into five parts on the basis of its soils and topography: the Channeled Scablands, the Waterville Plateau, the Quincy Flats, the Folded Ridges, and the Sand Hills. The Channeled Scablands is largest of the five parts occupying the northern and eastern half of the county to the north and east of Soap Lake, Ephrata, and Moses Lake (see map). The scablands are glacial channels left by meltwater of the ice sheet which covered