Isolation and description ofHaloanaerobium praevalens gen. nov. and sp. nov., an obligately anaerobic halophile common to Great Salt Lake sediments

A new halophilic species is described that was isolated from the hypersaline (>20%) surface sediments of Great Salt Lake, Utah, via transfer from MPN end-dilution tubes that contained a complex organic medium. The organism was an obligate anaerobe that proliferated optimally at approximately 13% salt, but did not grow significantly at <2% or ≥30% salt. It stained Gram-negative, was nonmotile, nonsporing, and contained an outer-wall membranous layer. The complex lipids of the organism were fatty acid esters that did not change dramatically during growth at 5% or 25% NaCl. The DNA base composition was 27.0±1 mol% guanosine plus cytosine. The temperature range for growth was >5°C and <60°C, the pH range was between 6.0 and 9.0. The doubling time for growth in complex medium with 25% NaCl was 7 h. The organism utilized carbohydrates, peptides, and amino acids. Butyrate, acetate, propionate. H₂, and CO₂ were the major fermentation end products formed. Glucose, mannose, fructose,n-acetyl glucosamine, and pectin were used as energy sources for growth. Methylmercaptan was produced from methionine degradation. The nameHaloanaerobium praevalens gen. nov. sp. nov. is proposed for the type strain GSL which has been deposited as DSM 2228. The taxonomic relationships ofH. praevalens to other obligate halophiles and anaerobes, as well as its biological role in the Great Salt Lake microbial ecosystem, are discussed.     

Sediment formation in Lake Baikal

The following stages in the formation of sediments in Lake Baikal have been distinguished. In the Middle Miocene lacustrine deposits accumulated in the southern depression. In Early and Middle Pliocene, as well as in Early-Middle Pleistocene the bottom of the southern and middle Baikal depressions was occupied by large lakes, but the northern basin was mainly dry with a system of small lakes, streams and rivers. This accounts for the great facies variety and the genetic heterogeneity of sediments in the northern depression. At the end of Middle and in the Late Pleistocene an abrupt warping of the depression took place, and a shore-line similar to the present one was formed. Sands in the upper part of the sediments are considered to be the product of intensive erosion which probably occurred in the pluvial epoch in the Late Pleistocene period.     

Feeding habits of the clupeid Limnothrissa miodon (Boulenger), in Lake Kivu

A limnological sampling programme implemented during 1980 in Lake Kivu, Rwanda, confirmed a seasonal increase of the pelagic plankton biomass at the end of the dry season during the windy period of August/September. From plankton samples taken in the littoral and pelagic zones of the Lake it was concluded that a successful introduction of the freshwater clupeid Limnothrissa miodon Boulenger, during 1958–1960, had not obviously influenced the species composition of the Copepoda in the Lake. Examination of stomach contents of different length classes of Limnothrissa proved that the Kivu clupeid is not a strict planktonphagic species. Its diet is adapted to its life cycle and inshore/offshore migration patterns. In pelagic waters of the lake it is an exclusive plankton feeder, while in littoral waters it has more littoral bound feeding habits. Cannibalism was observed among individuals larger than 100 mm, near the margins of the lake. Echosoundings and periodic observations on stomach contents support the hypothesis that Limnothrissa feeds in the late afternoon and digests its food during the night, while a second feeding/digestion cycle starts in the early morning, at sunrise.     

In situ predatory behavior ofMysis relicta in Lake Michigan

Selectivity coefficients (W) and predation rates on Lake Michigan zooplankton were determined forMysis relicta during spring through fall using anin situ method. W values indicated the following ranked order of prey preference: Cladocera > copepod copepodites and copepod nauplii > adult diaptomids and cyclopoids. With few exceptions, W values for different prey categories remained fairly constant despite greatly changing relative abundances of prey. Predation rates and prey selectivity were similar in most cases to those determined in laboratory studies. Ingestion rates (percent dry body weight · day^–1) were correlated to total prey biomass (r = 0.38) and to effective prey biomass (r = 0.85), where the weighting factors were overall mean selectivity coefficients for the different prey categories. This result suggested that seasonally varying composition of prey caused much of the variation in ingestion rates among experiments. Feeding trials performed at the same depth with daytime and nighttime assemblages of zooplankton indicated that Cladocera may escape heavyMysis predation at night by migrating from the metalimnetic-hypolimnetic interface into the epilimnion.Contribution 333 from the Great Lakes Research Division, The University of Michigan and contribution 287 from the Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration.Contribution 333 from the Great Lakes Research Division, The University of Michigan and contribution 287 from the Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration.     

Rapid decomposition of fish bones in Lake Erie sediments

In an effort to explain the rarity of fish bones in the Great Lakes sediments, the degradation of ground fresh fish bones in microcosms containing Lake Erie sediments has been studied. The rapid build-up of phosphorus in the aqueous phase points to the great instability of the bone mineral in these sediments, while the actual analysis of the sediments shows that 10–50% of the added bone was degraded in three weeks. The decomposition rate was independent of the redox conditions of the microcosm, and was biologically mediated. Also, the incongruent dissolution of the bone apatite entailed the secondary formation of vivianite (ferrous phosphate) and other calcium and aluminocalcium phosphates. Calculations suggest that fish debris account for well over 10–20% of the P flux to the sediments in some nearshore areas. Since most of this P is quickly remineralized, the contribution of carrion to the differences in the quality of nearshore and offshore waters of the Lower Great Lakes must remain an intriguing question.     

Factors influencing densities and distributions of Pontoporeia hoyi in Lake Ontario

The physical and chemical characteristics of the sediment-water interface greatly influence distributions of the bottom-feeding amphipod Pontoporeia hoyi which is a major component of the Great Lakes aquatic food-webs. Sediment-water interface samples from the Great Lakes indicate that Pontoporeia densities are positively correlated with sediment concentrations of organic carbon, particularly in the upper depth range of the species. Pontoporeia is not found in anoxic sediments. Growth rates and production of Pontoporeia are influenced by the quality of food supplies and there appears to be a seasonal response to the down-flux of plankton detritus. Comparisons of numerations and distribution patterns also revealed an apparent positive relationship between Pontoporeia and sediment-associated bacteria. Interlake comparisons of population densities provide no clear evidence of any large scale impact by contaminated sediment on this species. Depending upon the extent to which organic carbon (OC) is assimilated in the water column, bottom sediments may store and buffer the quantity of OC available to Pontoporeia. Thus, if the annual down-flux of OC remains generally constant, populations of Pontoporeia should also remain constant unless influenced by changes in predation intensity.Numerations of Pontoporeia revealed that populations of this amphipod are much larger in Lake Michigan than in Lake Ontario. We suggest that much of this difference can be accounted for by different forms of predator-prey interaction near the base of the benthic food-web. Commercial fisheries data tend to support this idea. We also speculate that differences in the concentration of dissolved silica may figure prominantly among factors that affect Pontoporeia population densities.Under proposed new taxonomy (Bousfield, 1989), Pontoporeia hoyi is now classified as Diporeia hoyi. However, for convenience, we have retained the commonly used genus Pontoporeia throughout this text.     

Index to plants collected on Howard Stansbury’s expedition to the Great Salt Lake, 1849–1850

Presented here is a synonymized list, including a list of types, of the plants collected on Howard Stansbury’s expedition to the Great Salt Lake, 1849–1850.     

The release of dissolved organic carbon as a result of diatom fragmentation during feeding byMysis relicta

The release of dissolved organic carbon (DOC) byMysis relicta that occurs while feeding may be an important pathway in the recycling of nutrients in Lake Michigan. Laboratory experiments were conducted to determine the levels of DOC released byM. relicta from Lake Michigan while grazing on laboratory-cultured diatoms. Increasing filtering rates were observed at progressively lower chlorophyll concentrations. Higher filtering rates were accompanied by higher fragmentation of diatoms and a higher concomitant release of DOC from broken cells. While the amount of DOC release is small (0.02–3.30 g C · 1^–1· h^–1), it nonetheless is of importance to bacteria and possibly some algae. After assimilation by bacteria and algae, the organic carbon is then available to consumers.Contribution No. 239, Center for Great Lakes Studies, The University of Wisconsin-Milwaukee, Milwaukee, WI 53201, U.S.A.Contribution No. 239, Center for Great Lakes Studies, The University of Wisconsin-Milwaukee, Milwaukee, WI 53201, U.S.A.     

Lake Erie sport and boat show patrons rank Great Lakes ecosystem health issues in 1993 and 1994

In 1993 and 1994 patrons of the Mid-America Boat Show and the American-Canadian Sport, Travel and Outdoor Show, both held in Cleveland, Ohio were asked to respond to an Ohio Sea Grant survey on Great Lakes issues. In 1993 and 1994, a list of issues, identified from previous surveys and citizen advisory groups, were presented to show patrons at the Ohio Sea Grant exhibit. They were asked to rank the importance of each issue on a scale of 0 to 6. A total of 1,751 and 987 boat show and sport show patrons responded in 1993 and 1994 respectively. The four highest ranked issues and their arithmetic means and standard deviations in 1993 and 1994 respectively, were: Lake Erie water quality (5.60±0.79 and 5.53±0.81); Eliminating persistent toxic substances in the Great Lakes (5.54±0.88 and 5.49±0.89); Protecting the Great Lakes ecosystem (5.49±0.87 and 5.51±0.80); and Toxic contaminants in fish (5.49±0.97 and 5.36±1.00). A t-test was used to compare means of 1993 and 1994 responses. Significant differences (0.05) occurred in mean responses for 9 out of 14 issues common to both the surveys. Factor analysis of 1993 data suggested that patrons of the 1993 shows: (1) have a strong concern for the Great Lakes ecosystem; and (2) recognize that individual actions count. Factor analysis of the 1994 data indicated that show patrons continued to have a concern for the Great Lakes ecosystem. Boat and outdoor show patrons (recreational resource users) are a constituency that can, if politically active, validate and support efforts to protect and preserve the Great Lakes ecosystem.     

The seasonality of phytoplankton in the North American Great Lakes,a comparative synthesis

The phytoplankton and productivity of the North American Great Lakes has been studied extensively by Fisheries and Oceans Canada during the past 15 years to monitor the impact of nutrient and contaminant loading on the plankton of the ecosystem. Lakewide cruises were conducted at monthly intervals mainly during the spring to fall period. This provided extensive biomass, species, size, productivity and nutrient concentration data for the Great Lakes. These data were collected using the Utermöhl inverted microscope technique together with standardized taxonomic, productivity and data-handling procedures. These standardized methodologies were applied to all the Great Lakes which resulted in a comprehensive phycological and ecological data base for the first time. These data form the basis for the evaluation of the complex phenomenon of seasonality.The eutrophic/mesotrophic Lower Great Lakes exhibited well-developed seasonal peaks of high biomass, with inshore-offshore differentiation and spring maxima most pronounced in the inshore region. However, the oligotrophic Upper Great Lakes had low biomass and generally lacked well-developed seasonal patterns. No marked seasonal trends were observed in the ultra-oligotrophic Lake Superior. The seasonality of biomass and various taxonomic groups of phytoplankton showed differentiation between individual lakes and is discussed in detail. The seasonal succession of species provided interesting comparisons between the Lower Great Lakes, which harbour eutrophic and mesotrophic species, and the Upper Great Lakes, which harbour oligotrophic species.Due to the voluminous nature of our data, a general overview has been given for all the Great Lakes with Lake Ontario treated in detail as a case study. The Lake Ontario case study provides the state-of-the-art status ranging from the lakewide surveys of 1970 to the current research with minute organisms such as ultraplankton and picoplankton.     

Centric diatoms from Lake Frolikha (Transbaikal area) and peculiarities of distribution of some taxa in Asia

The species composition of centric diatoms from Lake Frolikha (Transbaikal area) has been studied. The lake is located on the eastern shore of Lake Baikal and connected with it by a river. Twenty-three species of Centrophyceae from 7 genera (Aulacoseira, Cyclostephanos, Cyclotella, Discostella, Handmania, Pliocaenicus, and Stephanodiscus) have been found. The most represented genus is Aulacoseira (11 species). Fifteen species and 4 genera are new for the lake record. All revealed species are known in other lakes of the Baikal region; however Baikal endemics are absent in Lake Frolikha. The flora of centric diatoms in Lake Frolikha can be divided into two groups. The first group includes taxa common in Lake Baikal, and the second group includes taxa not typical for Lake Baikal. The level of differences between flora in Lake Baikal and Lake Frolikha is high (43%) despite the close location and connection to the river. An analysis of distribution of interesting species in Asia is presented.     

Long-range transport of heavy metals from the Asian continent contributes to surface sediments in Lakes Shinji and Nakaumi in western Japan

To evaluate the contribution of the long-range transport of heavy metals from the Asian continent to the enrichment of surface sediments in western Japan, heavy-metal (Cd, Cu, Pb, Sb, and Zn) concentrations were measured in sediment cores collected at three sites each in Lakes Shinji and Nakaumi. Sedimentation fluxes of these metals were calculated on the basis of their concentrations in excess of their background concentrations. Pb showed similar sedimentation fluxes in the sites, suggesting a predominant contribution of atmospheric deposition of Pb transported from the Asian continent to the input to the lakes. In contrast, the sedimentation fluxes of heavy metals other than Pb in the surface sediments were markedly high near the estuary of a principal river flowing into Lake Nakaumi. A highly positive correlation was observed between the Cd and Zn concentrations in the cores at each site (r ² = 0.84–0.97). The Cd/Zn ratios in the surface sediments (1990–2007) indicated that Lake Shinji sediments have ratios of 0.0067–0.0074, higher than those of Tokyo Bay sediments (0.0054 on average in 1990–2003), which have been polluted primarily by effluent discharges. In contrast, the ratios in Lake Nakaumi sediments (0.0053–0.0060) were close to those in Tokyo Bay sediments. Rainwater and aerosols, which were strongly affected by air pollutants from the Asian continent, have much higher Cd/Zn ratios of 0.014–0.016. This suggests that the Lake Shinji sediments with higher Cd/Zn ratios are less affected by effluent discharges. Hence, Lake Shinji sediments may be suitable for assessing the environmental impact of the long-range transport of heavy metals from the Asian continent.     

Predicted effects of increasing salinity on the crustacean zooplankton community of Pyramid Lake,Nevada

Since 1933 the salinity of Pyramid Lake, Nevada, U.S.A., has increased 32% to nearly 5.5‰. We tested the hypothesis that further increases of 1.5 to 2 times (1.5× to 2×) its present salinity would significantly reduce species richness and alter population structures of the existing crustacean zooplankton community. Three strategies were applied: in addition to monitoring zooplankton in semicontrolled indoor microcosms at 1×, 1.5× and 2× and conducting range-finding, acute, and chronic salinity bioassays, the present zooplankton community of Walker Lake (2×) was compared with that existing in Pyramid Lake (1×). Ceriodaphnia quadrangula and Diaphanosoma leuchtenbergianum, both collected from Pyramid Lake, were lacking in Walker Lake. Populations of Cyclops vernalis were significantly lower and those of Diaptomus sicilis and Moina hutchinsoni were significantly higher in Walker Lake than in Pyramid Lake. Densities of Ceriodaphnia and Cyclops were low in microcosms at salinities > 1×. Diaphanosoma could not be maintained in microcosms, regardless of salinity. Numbers of Diaptomus and Moina in microcosms were proportional to salinity level. Short-term LC50 salinities (‰) were as follows: Diaphanosoma, 6.5; Ceriodaphnia, 7.1; Diaptomus, 13.3; Cyclops, 14.8; and Moina, 17.8. Multiple-generation, chronic bioassays were run only on Cyclops and Diaptomus. Three generations of Cyclops were produced at salinities of 4.0 to 8.5‰, but not at 9.8‰ or higher. Diaptomus was unable to complete three generations at salinities ?9.6‰. We speculate that high salinity in Walker Lake may indirectly benefit Diaptomus by negatively affecting predatory Cyclops, and benefit Moina by causing extinction of competing salinity-intolerant Diaphanosoma and Ceriodaphnia. Except for the response of Diaptomus, results from bioassays were in general agreement with results from microcosms and with field data. Untested predator-prey interactions could be responsible for the apparent discrepancy.     

泉州西湖沉积物中硝化细菌的分布及其作用

比较研究泉州西湖沉积物中氨氧化细菌(AOB)和亚硝酸盐氧化细菌(NOB)的分布及氨氧化潜力和亚硝酸盐(NO2?)氧化潜力。结果表明: 西湖沉积物中存在高浓度的有机质(OM)、总氮(TN)和氨氮。AOB生物量为1.1×106?6.4×106 个/g干土, 显著高于NOB生物量4.2×105?7.4×105 个/g 干土(配对t-检验, P<0.05)。对于NOB, 硝化杆菌属(Nitrobacter)和硝化螺菌属(Nitrospira)同时存在于西湖沉积物中, 以Nitrobacter为优势种群。AOB和NOB生物量的差异一定程度上导致西湖沉积物中氨氧化潜力显著高于NO2?氧化潜力(配对t-检验, P<0.05), NO2?氧化过程成为硝化作用的限制步骤。另外, 西湖沉积物中存在的较高浓度氨氮, 一方面促进了AOB的生长和活性, 导致较高速率的氨氧化过程, 另一方面却对亚硝酸盐氧化过程产生选择性抑制, 这也是导致NO2?氧化潜力较低的主要原因之一。     

Microbial biogeochemistry of Boiling Springs Lake: a physically dynamic,oligotrophic, low‐pH geothermal ecosystem

Boiling Springs Lake (BSL) in Lassen Volcanic National Park, California, is North America's largest hot spring, but little is known about the physical, chemical, and biological features of the system. Using a remotely operated vessel, we characterized the bathymetry and near‐surface temperatures at sub‐meter resolution. The majority of the 1.2 ha, pH 2.2 lake is 10 m deep and 50–52 °C, but temperatures reach 93 °C locally. We extracted DNA from water and sediments collected from warm (52 °C) and hot (73–83 °C) sites separated by 180 m. Gene clone libraries and functional gene microarray (GeoChip 3.0) were used to investigate the BSL community, and uptake of radiolabeled carbon sources was used to assess the relative importance of heterotrophic vs. autotrophic production. Microbial assemblages are similar in both sites despite the strong temperature differential, supporting observations of a dynamic, convectively mixed system. Bacteria in the Actinobacteria and Aquificales phyla are abundant in the water column, and Archaea distantly related to known taxa are abundant in sediments. The functional potential appears similar across a 5‐year time span, indicating a stable community with little inter‐annual variation, despite the documented seasonal temperature cycle. BSL water‐derived DNA contains genes for complete C, N, and S cycles, and low hybridization to probes for N and S oxidation suggests that reductive processes dominate. Many of the detected genes for these processes were from uncultivated bacteria, suggesting novel organisms are responsible for key ecosystem services. Selection imposed by low nutrients, low pH, and high temperature appear to result in low diversity and evenness of genes for key functions involved in C, N, and S cycling. Conversely, organic degradation genes appear to be functionally redundant, and the rapid assimilation of radiolabeled organic carbon into BSL cells suggests the importance of allochthonous C fueling heterotrophic production in the BSL C cycle.     

Continued feeding on <Emphasis Type="Italic">Diporeia</Emphasis> by deepwater sculpin in Lake Huron

Monitoring changes in diets of fish is essential to understanding how food web dynamics respond to changes in native prey abundances. In the Great Lakes, Diporeia, a benthic macroinvertebrate and primary food of native benthivores, declined following the introduction of invasive Dreissena mussels and these changes were reflected in fish diets. We examined the diets of deepwater sculpin Myoxocephalus thompsonii collected in bottom trawls during 2010–2014 in the main basin of Lake Huron, and compared these results to an earlier diet study (2003–2005) to assess if their diets have continued to change after a prolonged period of Dreissena mussel invasion and declined Diporeia densities. Diporeia, Mysis, Bythotrephes, and Chironomidae were consumed regularly and other diet items included ostracods, copepods, sphaerid clams, and fish eggs. The prey-specific index of relative importance calculated for each prey group indicated that Mysis importance increased at shallow (≤55 m) and mid (64–73 m) depths, while Diporeia importance increased offshore (≥82 m). The average number of Diporeia consumed per fish increased by 10.0% and Mysis decreased by 7.5%, while the frequency of occurrence of Diporeia and Mysis remained comparable between time periods. The weight of adult deepwater sculpin (80 mm and 100 mm TL bins) increased between time periods; however, the change in weight was only significant for the 80 mm TL group (p?<?0.01). Given the historical importance of Diporeia in the Great Lakes, the examination of deepwater sculpin diets provides unique insight into the trophic dynamics of the benthic community in Lake Huron.     

Abundance and community composition of ammonia-oxidizing archaea and bacteria in two different zones of Lake Taihu

The abundance and community composition of ammonia-oxidizing archaea and ammonia-oxidizing bacteria in the surface sediments of 2 different zones (Meiliang Bay and Eastern Lake Taihu) of Lake Taihu were investigated using real-time quantitative polymerase chain reaction and clone libraries. The amoA gene copy numbers in the surface sediment of Meiliang Bay ranged from 4.91?× 10(5) to 8.65?× 10(6) copies/g dry sediment for the archaeal amoA gene and from 3.74?× 10(4) to 3.86?× 10(5) copies/g dry sediment for the bacterial amoA gene, which were significantly higher than those of Eastern Lake Taihu (P?< 0.05). Concentrations of ammonia (NH(4)(+)), total nitrogen, organic matter, and pH of the sediments exhibited significantly negative correlations with the abundance of ammonia-oxidizing archaea or ammonia-oxidizing bacteria (P?< 0.05 or P?< 0.01, respectively). The potential nitrification rates show remarkable correlations with the copy numbers of the archaeal amoA gene. Diversity of the archaeal amoA gene in Eastern Lake Taihu was significantly higher than that of Meiliang Bay, whereas the bacterial amoA gene diversity was comparable for the 2 lake zones. The data obtained in this study would be useful to elucidate the role of ammonia-oxidizing archaea and ammonia-oxidizing bacteria in the nitrogen cycle of freshwater ecosystems.     

A microcosm study of nitrogen utilization in the Great Salt Lake,Utah

Microcosms were used to study the effects of two inorganic nitrogen sources (ammonia and nitrate) and two organic nitrogen sources (urea and glutamic acid) on the growth of algae and bacteria found in the Great Salt Lake, Utah. Ammonia, nitrate and urea stimulated bacterial growth indirectly through increased algal production of unknown organic substances. Glutamic acid, representing readily available organic carbon and nitrogen, stimulated the bacteria directly. No nitrification was observed in the microcosms although nitrite was found when the microcosms were supplemented with nitrate. Lake sediment contained a number of anaerobic bacteria producing hydrogen sulfide, methane and other gases. Production of these gases was stimulated in the columns with high algal and bacterial activity.     

Evolution and diversity of two cisco forms in an outlet of glacial Lake Algonquin

The diversity of Laurentian Great Lakes ciscoes (Coregonus artedi, sensu lato) arose via repeated local adaptive divergence including deepwater ciscoes that are now extirpated or threatened. The nigripinnis form, or Blackfin Cisco, is extirpated from the Great Lakes and remains only in Lake Nipigon. Putative nigripinnis populations were recently discovered in sympatry with artedi in a historical drainage system of glacial Lake Algonquin, the precursor of lakes Michigan and Huron. Given the apparent convergence on Great Lakes form, we labeled this form blackfin. Here, we test the hypothesis that nigripinnis may have colonized this area from the Great Lakes as a distinct lineage. It would then represent a relict occurrence of the historical diversity of Great Lakes ciscoes. Alternatively, blackfin could have evolved in situ in several lakes. We captured more than 600 individuals in the benthic or pelagic habitat in 14 lakes in or near Algonquin Provincial Park (Ontario, Canada). Fish were compared based on habitat, morphology, and genetic variation at 6,676 SNPs. Contrary to our expectations, both cisco and blackfin belonged to an Atlantic lineage that colonized the area from the east, not from the Great Lakes. Sympatric cisco and blackfin were closely related while fish from different lakes were genetically differentiated, strongly suggesting the repeated in situ origin of each form. Across lakes, there was a continuum of ecological, morphological, and genetic differentiation that could be associated with alternative resources and lake characteristics. This study uncovers a new component of cisco diversity in inland lakes of Canada that evolved independently from ciscoes of the Laurentian Great lakes. The diversity of cisco revealed in this study and across their Canadian range presents a challenge for designating conservation units at the intraspecific level within the framework of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).