Effects of algal and terrestrial carbon on methane production rates and methanogen community structure in a temperate lake sediment

1. Sources of atmospheric CH₄ are both naturally occurring and anthropogenic. In fact, some anthropogenic activities may influence the production of CH₄ from natural sources, such as lakes. 2. Ongoing changes in the catchment of lakes, including eutrophication and increased terrestrial organic carbon export, may affect CH₄ production rates as well as shape methanogen abundance and community structure. Therefore, inputs from catchments to lakes should be examined for their effects on CH₄ production. 3. We added algal and terrestrial carbon separately to lake sediment cores and measured CH₄ production. We also used quantitative polymerase chain reaction and terminal restriction fragment length polymorphism to determine the effects of these carbon additions on methanogen abundance and community composition. 4. Our results indicate that CH₄ production rates were significantly elevated following the addition of algal biomass. Terrestrial carbon addition also appeared to increase methanogenesis rates; however, the observed increase was not statistically significant. 5. Interestingly, increased CH₄ production rates resulted from increases in per‐cell activity rather than an increase in methanogen abundance or community compositional shifts, as indicated by our molecular analyses. 6. Overall, anthropogenic impacts on aquatic ecosystems can influence methanogenesis rates and should be considered in models of global methane cycling and climate.     

Mechanism of silicate elution by hydrogen sulfide from bottom sediment in a brackish lake

Limnology - Highly concentrated dissolved silicate was detected in pore water from anoxic-reducing sediment in Lake Nakaumi, a brackish lake. Silicate concentration also simultaneously increased...     

Microbial activity and community structure in a lake sediment used for psychrophilic anaerobic wastewater treatment

Aims: The aim of the study was to investigate the feasibility of a continuous reactor for psychrophilic anaerobic wastewater treatment by using the sludge from cold natural environment. Methods and Results: Six sludge samples (S1–S6) were collected from different cold natural locations to select sludge with high anaerobic microbial activity under low temperatures. After a 225‐day incubation, the maximum specific methane production rate of a waterfowl lake sediment (S1) at 15°C (70·5 mLCH₄ gVSS^?1 day^?1) was much higher than all other samples. S1 was thus chosen as the seed sludge for the reactor treating synthetic brewery wastewater at 15°C, by immobilizing the micro‐organisms on polyurethane foam carriers. The chemical oxygen demand (COD) removal efficiency reached over 80% after 240‐day operation at an organic loading rate of 5·3 kg m^?3 day^?1, and significant enrichment of biomass was observed. Clone libraries of the microbial communities in the inoculum had high diversities for both archaea and bacteria. Along with a decrease in microbial community diversities, the dominant bacteria (79·5%) at the end of the operation represented the phylum Firmicutes, while the dominant archaeon (41·5%) showed a similarity of 98% with the psychrotolerant methanogen Methanosarcina lacustris. Conclusions: The possibility of using anaerobic micro‐organisms from cold environments in anaerobic wastewater treatment under psychrophilic conditions is supported by these findings. Significance and Impact of the Study: This study enriches the theory on microbial community and the application on anaerobic treatment of sludge from cold natural environments.     

Microbial sulfate reduction in a brackish meromictic steppe lake

Patterns of sulfate reduction were studied in water and sediments of Lake Shira, South Siberia, Russia. The lake was characterized by a high level of sulfate (91-116 mM). The concentration of hydrogen sulfide in the anoxic waters of the lake reached 0.6 mM. In summer the sulfate reduction rate in the water column, measured by radiometric technique, varied from 0.25 to 9.81 mol sulfate l^-1 d^-1. There were two peaks of sulfate reduction activity: just below the chemocline and near the sediment surface. Sulfate reduction rate in the profundal silts ranged from 4.1 to 90.6 mol l^-1 d^-1. The zone of the most active sulfate reduction was restricted to the surface sediment layers. The acceleration of sulfate reduction rate (up to 236 mol l^-1 d^-1) and the increase of density of viable sulfate reducers (up to 2 x 10⁵ cells ml^-1) were recorded in the littoral sediments adjacent to the mouth of the Son River and sewage discharge. It was apparently caused by the input of allochthonous organic substrates and also by a high environmental temperature. On an areal basis, sulfate reduction rate in the water was approximately 8 times higher than that in the profundal sediments. Sulfate reduction was the most important process of anaerobic oxidation of organic carbon in Lake Shira. In summer in the profundal zone of the lake, sulfate reducers were able to mineralize about 67% of the daily integrated primary production of phototrophic and chemotrophic organisms.     

闽江河口区淡水和半咸水潮汐沼泽湿地土壤产甲烷菌多样性

为认识盐度对河口潮汐沼泽湿地土壤产甲烷菌的影响,应用PCR-RFLP技术及测序分析对闽江河口区淡水-半咸水盐度梯度上分布的4个短叶茳芏潮汐沼泽湿地土壤产甲烷菌群落结构进行研究。闽江河口区短叶茳芏潮汐沼泽湿地土壤产甲烷菌群落结构受盐度影响明显,位于下洋洲和塔礁洲的短叶茳芏潮汐淡水沼泽湿地土壤产甲烷菌的香农-威纳多样性指数值分别为2.81和2.65,位于蝙蝠洲和鳝鱼滩的短叶茳芏潮汐半咸水沼泽湿地土壤产甲烷菌香农-威纳多样性指数值分别仅为2.33和2.27。系统发育分析表明:短叶茳芏沼泽湿地土壤产甲烷菌类群主要有甲烷杆菌目(Methanobacteriales),包括Methanobacterium、Methanobrevibacter和Methanobacteriaceae;甲烷微菌目(Methanomicrobiales),主要有Methanoregula,以及甲烷八叠球菌目(Methanosarcinales),主要有Methanosarcina和Methanococcoides。闽江河口区短叶茳芏潮汐淡水沼泽湿地土壤主要的优势产甲烷菌有Methanoregula、Methanosarcina和Methanobacterium,而短叶茳芏潮汐半咸水沼泽湿地土壤主要的优势产甲烷菌则转化为仅以Methanoregula为主。     

Investigation of methanogen population structure in biogas reactor by molecular characterization of methyl-coenzyme M reductase A (mcrA) genes

The methanogen community in biogas reactor running on cattle dung was investigated in two different seasons; summer (April, 36 °C) and winter (December, 24 °C), in the year 2004 by a culture-independent approach. Community structure was determined by phylogenetic analyses of 343 and 278 mcrA clones belonging to summer and winter month libraries, respectively. In summer month’s library, 41.7% clones were affiliated to Methanomicrobiales, 30% to Methanosarcinales, 19% to Methanobacteriales, 5% to Methanococcales and a total of 4.3% clones belonged to unclassified euryarchaeotal lineages. In winter month’s library, Methanomicrobiales encompassed 98.6% clones, and Methanobacteriales included 1.4% of total clone diversity. Biogas plant performance data collected during the winter month indicated significant reduction in daily biogas produced as compared to summer month because of lowering in ambient temperature and associated shift in microbial community. Results from this molecular study showed the existence of highly diverse and complex methanogens communities present in biogas plant.     

Changes in water and sediment bacterial community structure in a lake receiving acid mine drainage

Water and sediment bacterial communities in a freshwater impoundment were studied over a 13-month period for stress-related responses to a point source of acid mine drainage (AMD). Comparisons of community structure were made on collections taken at the mouth of the acid stream, at a point 2 km downstream, and at the mouth of an uncontaminated stream. Monthly measurements of pH and specific conductance indicated the expected decrease in the AMD pollution with increasing distance from the source. Acridine orange direct counts did not differ significantly among the sites; however significantly fewer viable heterotrophs were observed by plate counts at the acid impacted station relative to the uncontaminated site. The diversity of the communities was significantly lower at the sites receiving mine drainage as compared with the unaffected station, and comparisons of community similarity showed that collections from the impacted sites were more like each other than like the control site. The assemblage at the latter site contained many bacterial guilds not found at the contaminated sites. The guilds unique to the control site showed a reduced in vitro ability to tolerate heavy metals as compared with the general community.     

Photosynthetic activity and population dynamics of Amoebobacter purpureus in a meromictic saline lake

Abstract A dense population of the purple sulfur bacterium Amoebobacter purpureus in the chemocline of meromictic Mahoney Lake (British Columbia, Canada) underwent consistent changes in biomass over a two year study period. The integrated amount of bacteriochlorophyll reached maxima in August and declined markedly during early fall. Bacteriochlorophyll was only weakly correlated with the light intensity and water temperature in the chemocline. In the summer, bacterial photosynthesis was limited by sulfide availability. During this period the intracellular sulfur concentration of A. purpureus cells decreased. A minimum concentration was measured at the top of the bacterial layer in August, when specific photosynthetic rates of A. purpureus indicated that only 14% of the cells were photosynthetically active. With the exception of a time period between August and September, the specific growth rates calculated from CO₂ fixation rates of A. purpureus were similar to growth rates calculated from actual biomass changes in the bacterial layer. Between August and September 86% of the A. purpureus biomass disappeared from the chemocline and were deposited on the littoral sediment of Mahoney Lake or degraded within the mixolimnion. This rise of cells to the lake surface was not mediated by an increase in the specific gas vesicle content which remained constant between April and November. The upwelling phenomenon was related to the low sulfur content of A. purpureus cells and a low resistance of surface water layers against vertical mixing by wind.     

Nitrogen dynamics in a eutrophic lake sediment

Nitrogen flux from sediment of a shallow lake and subsequent utilization by water hyacinth (Eichhornia crassipes [Mart] Solms) present in the water column were evaluated using an outdoor microcosm sediment-water column. Sediment N was enriched with ¹⁵N to quantitatively determine the movement of NH₄-N from the sediment to the overlying water column. During the first 30 days. 48% of the total N uptake by water hyacinth was derived from sediment ¹⁵NH₄-N. This had decreased to 14% after 183 days. Mass balance of N indicates that about 25% sediment NH₄-N was released into the overlying water, but only 17% was assimilated by water hyacinth. NH₄-N levels in the water column were very low, with very little or no concentration gradients. NH₄-N levels in the interstitial water of the sediment were in the range of 30–35 mg L^–1 for the lower depths (> 35 cm), while in the surface 5 cm of depth NH₄-N levels decreased to 3.2 mg L^–1. Simulated results also showed similar trends for the interstitial NH₄-N concentration of the sediment. The overall estimated NH₄-N flux from the sediment to the overlying water was 4.8 µg cm^–2 day^–1, and the soluble organic N flux was 5.8 µg N cm^–2 day^–1. Total N flux was 10.6 µg N cm^–2 day^–1.     

Ecological consequences of food partitioning for the fish population structure in a eutrophic lake

In the highly eutrophic lake, Frederiksborg Slotssø, the diet composition of the bream (Abramis brama L.) and roach (Rutilus rutilus L.) populations was examined during three periods with different food availability. The length range of bream and roach was 9–34 cm (TL) and 5–18 cm (TL), respectively. The relative food composition was examined for 2 cm and 1 cm length intervals of bream and roach, respectively. During all three periods, bream shifted from benthic cladocerans (Alona sp.) to zooplankton and chironomids within a transitional length of 15.0–20.0 cm. These foodshifts were coupled with a change in feeding behaviour from particulate to filter feeding. The biomass of chironomids was too low to sustain the consumption of larger bream (>20.0 cm) which initiated feeding in the pelagic zone even in periods when the mean length and biomass of the preferred zooplankton, Daphnia cucullata, were low. In contrast to bream, roach fed mainly on zooplankton. With increasing size, roach progressively shifted to larger zooplankton species due to the increasing mesh size of their branchial system. The importance of benthic animals in the diet of roach was minor due to low feeding efficiency on prey buried in the sediment. Detritus appeared in the diet of bream and roach in periods of low availability of animal food items. Feeding on detritus may provide an energetic advantage to bream and roach and increase the carrying capacity for these species in lakes, where detritus is highly abundant. Especially for the larger fish due to the decrease in their relative metabolic demands. However, the ability of bream to filter feed and with increasing size to retain food items smaller than those retained by roach may be the main mechanism for the dominance of bream over roach in highly eutrophic lakes.     

Structure of planktonic microbial food web in a brackish stratified Siberian lake

The distribution of primary components of the microbial community (autotrophic pico- and nanoplankton, phototrophic bacteria, heterotrophic bacteria, microscopic fungi, heterotrophic flagellates, ciliates and heliozoa) in the water column of Lake Shira, a steppe brackish-water, stratified lake in Khakasia, Siberia (Russia), were assessed in midsummer. Bacterioplankton was the main component of the planktonic microbial community, accounting for 65.3 to 75.7% of the total microbial biomass. The maximum concentration of heterotrophic bacteria were recorded in the monimolimnion of the lake. Autotrophic microorganisms contributed more significantly to the total microbial biomass in the pelagic zone (20.2–26.5%) than in the littoral zone of the lake (8.7–14.9%). First of all, it is caused by development of phototrophic sulphur bacteria at the oxic-anoxic boundary. The concentrations of most aerobic phototrophic and heterotrophic microorganisms were maximal in the upper mixolimnion. Heterotrophic flagellates dominated the protozoan populations. Ciliates were minor component of the planktonic microbial community of the lake. Heterotrophic flagellates were the most diverse group of planktonic eucaryotes in the lake, which represented by 36 species. Facultative and obligate anaerobic flagellates were revealed in the monimolimnion. There were four species of Heliozoa and only three of ciliates in the lake.     

Community structure of Archaea and Bacteria in a profundal lake sediment Lake Kinneret (Israel)

The microbial community structure of an anoxic profundal lake sediment, i.e., subtropical Lake Kinneret, was analysed with respect to its composition by culture-independent molecular methods including terminal restriction fragment length polymorphism (T-RFLP) analysis, comparative sequence analysis, and quantitative real-time PCR. In particular we were interested in the structure, species composition, and relative abundance of the overall microbial community in the methanogenic sediment layer (0-10 cm depth). Pairwise comparison of archaeal and bacterial 16S rRNA gene T-RFLP profiles obtained from three independent samplings indicated stability of the microbial community. The numbers of Archaea and Bacteria, quantified by real-time PCR, amounted to about 10(8) and 10(10) 16S rRNA gene copies cm(-3) sediment, respectively, suggesting that Archaea may account for only a minor fraction (approximately 1%) of the total prokaryotic community. Hydrogenotrophic Methanomicrobiales and acetoclastic Methanosaeta spp. dominated T-RFLP profiles of the archaeal community. T-RFLP profiles of the bacterial community were dominated by Deltaproteobacteria, sulphate reducers and syntrophs in particular. The second most abundant group was assigned to the Bacteroidetes-Chlorobi-group. Only one bacterial group, which was affiliated with halorespiring bacteria of subphylum II of the Chloroflexi, showed variation in abundance within the sediment samples investigated. Our study gives a comprehensive insight into the structure of the bacterial and archaeal community of a profundal lake sediment, indicating that sulphate reducers, syntrophs, bacteroidetes, halorespirers and methanogens are of particular importance in Lake Kinneret sediment.     

Comparative plankton investigations in a brackish lake (L. Veere) and a brackish tidal estuary (Westerschelde) in the SW Netherlands

Summary As the data, presented in this lecture, have been published elsewhere (see references), only a summary is given here.A comparison was made between the plankton assemblages of the mesoand polyhaline ranges of Lake Veere and the Westerschelde estuary. Species composition, densities and seasonal distributions of the predominant planktonic organisms of the investigated brackish water ecosystems were quite different, depending on several other environmental factors than salinity.     

Investigation of physicochemical form of uranium in sediment of brackish Lake Obuchi using sequential extraction procedure

The physicochemical form of uranium (²³⁸U) in the sediment of brackish Lake Obuchi was investigated using the standard procedures of sequential extraction. Approximately 60% to 70% of ²³⁸U was composed of the form bound to carbonates and iron (Fe)-manganese (Mn) oxides in silty sediments, whereas more than 50% of ²³⁸U existed in the minerals of sandy sediments. The proportions of ²³⁸U bound to carbonates in the sediments of brackish Lake Obuchi were larger than those in fresh-water lake sediments. Most of the uranium in the brackish lake sediment was considered to be mainly influenced by UO₂(CO₃)₃ ⁴⁻ in seawater, judging from the fact that the ²³⁴U/ ²³⁸U activity ratios (1.13 to 1.16) of silty sediments were very close to that of seawater (1.14). The high correlation found between the ²³⁸U concentration in the sediment and the amount of organic matter demonstrated that organic matter acts as a scavenger for ²³⁸U accumulation on the lake bottom. Received: July 2, 1999 / Accepted: May 25, 2000     

Fish-induced sediment resuspension: effects on phytoplankton biomass and community structure in a shallow hypereutrophic lake

An in situ mesocosm experiment was performed at Old Woman CreekEstuary, OH, to assess the importance of fish-induced sedimentresuspension in regulating phytoplankton biomass and communitystructure Six polyethylene tubes (1 m diameter x 2 m long) wereplaced into the lake, enclosing portions of the water columnand sediments Three duplicated treatments were established:(i) control, no fish, (ii) fish, stocked with small fish fromthe lake; and (iii) fish/net, stocked with fish, but into tubeswith coarse nets suspended above the sediments to prevent resuspension.Total P concentrations and algal biomass in the fish tubes becamemarkedly higher than the fish/net and control tubes. Centricdiatoms and small cryptomonads were the initial dominants. Inthe lake and fish tubes, this community was replaced by nanochlorophytes.In the fish/ net and control tubes, a very different successionoccurred, where large cryptomonads became dominant These resultsindicate that sediment nutrient resuspensions by fish activitiescan maintain a phytoplankton community in an immature state,with small r-selected dominants. When sediment nutrient resuspensionwas prevented (in the fish/net and control tubes), larger algalspecies increased in relative biovolume, regardless of whetherfish were present.     

The nature of a shield lake sediment

The nature of the sediment of Drinking Lake in the Churchill River Basin in Canada was studied with special reference to its chemical and colloidal composition. Crystalline minerals present in the colloidal fractions of the sediment are quartz, cristobalite, feldspars, micas, amphiboles, vermiculite, chlorite and kaolinite. Sesquioxidic components and the extractable Ca and Mg are present not only in the colloidal fractions but also in the non-colloidal fractions of the sediment. Over 99% of the nitrogen in the sediment is organic and about 60% of the sediment phosphorus is inorganic. The importance of the crystalline and non-crystalline mineral components of the sediment studied in the exchange of nutrients between the sediment and its overlying water is discussed. In view of the important roles of these mineral components in affecting the transfer of nutrients, possible significant modifications of the quality of the lake water after impoundment, if a dam were constructed in the basin for a hydro-electric development, deserve close attention.     

Microbial population structure in a stratified,acidic pit lake in the Iberian Pyrite Belt

Abstract

We examined the geochemistry and bacterial and archaeal community structure in the acidic (pH < 2.4) pit lake at Peña de Hierro, near the headwaters of the Río Tinto. The lake has strong vertical gradients in light, O₂, pH, conductivity, and dissolved ions. Bacterial and archaeal communities between 0 and 32?m displayed low species richness and evenness. Relatives of iron cycling taxa accounted for 60-90% of the operational taxonomic units (OTUs) throughout the water column. Relatives of heterotrophic, facultative Fe(III)-reducing species made up more than a third of the bacterial and archaeal community in the photic zone. Taxa related to Fe(II) oxidizers Ferrithrix thermotolerans and Acidithix ferrooxidans were also abundant in the photic zone. Below the photic zone, relatives of the lithoautotrophic Fe(II) oxidizers Leptospirillum ferrooxidans and Ferrovum myxofaciens bloomed at different depths within or just below the oxycline. Thermoplasmatales predominated in the deep, microoxic zone of the lake. The microbial population structure of the lake appears to be influenced by the production of oxygen and organic matter by phototrophs in a narrow zone at the lake surface and by strong geochemical gradients present in the water column that create distinct niches for separate Fe(II) oxidizers.