Heterotrophic Potential for Amino Acid Uptake in a Naturally Eutrophic Lake

The uptake of sixteen (14)C-labeled amino acids by the indigenous heterotrophic microflora of Upper Klamath Lake, Oregon, was measured using the kinetic approach. The year-long study showed a seasonal variation in the maximum uptake velocity, V(max), of all the amino acids which was proportional to temperature. The maximum total flux of amino acids by the heterotrophic microflora ranged from 1.2 to 11.9 mumol of C per liter per day (spring to summer). Glutamate, asparagine, aspartate, and serine had the highest V(max) values and were respired to the greatest extent. The percentages of the gross (net + respired) uptake of the amino acids which were respired to CO(2) ranged from 2% for leucine to 63% for glutamate. Serine, lysine, and glycine were the most abundant amino acids found in Upper Klamath Lake surface water; at intermediate concentrations were alanine, aspartate, and threonine; and the remaining amino acids were always below 7.5 x 10(-8) M (10 mug/liter). The amino acid concentrations determined chemically appear to be the sum of free and adsorbed amino acids, since the values obtained were usually greater than the (K(t) + S(n)) values obtained by the heterotrophic uptake experiments.     

Paleolimnological evidence of change in a shallow, hypereutrophic lake: Upper Klamath Lake, Oregon, USA

Sediment cores were collected from Upper Klamath Lake in October, 1998 and analyzed for ²¹⁰Pb, ¹⁴C, ¹⁵N, N, P, C, Ti, Al, diatoms, Pediastrum, and cyanobacterial akinetes. These results were used to reconstruct changes in water quality in Upper Klamath Lake over the last 150 years. The results showed that there was substantial mixing of the upper 10 cm of sediment, representing the previous 20 to 30 years. However, below that, ²¹⁰Pb activity declined monotonically, allowing reasonable dating for the period from about 1850 to 1970. The sediment accumulation rates (SAR) showed a substantial increase in the 20th century. The increase in SAR corresponded with increases in erosional input from the watershed as represented by the increases in sediment concentrations of Ti and Al. The upper 20 cm of sediment, representing the last 150 years, also showed increases in C, N, P, and ¹⁵N. The increases in nutrient concentrations may be affected to various degrees by diagenetic reactions within the sediments, although the changes in concentrations also were marked by changes in the N:P ratio and in a qualitative change in the source of N as reflected in increasing δ¹⁵N. The diatoms showed modest changes in the 20th century, with increases in Asterionella formosa, Stephanodiscus hantzschii, and S. parvus. Pediastrum, a green alga, was well-preserved in the sediments and exhibited a sharp decline in relative abundance in the upper sediments. Total cyanobacteria, as represented by preserved akinetes, exhibited only minor changes in the last 1000 years. However, Aphanizomenon flos-aquae, a taxon which was formerly not present in the lake 150 years ago, but that now dominates the summer phytoplankton, has shown major increases over the past 100 years. The changes in sediment composition are consistent with activities including timber harvest, drainage of wetlands, and agricultural activities associated with livestock grazing, irrigated cropland, and hydrologic modifications.     

Application of the fluorescent-antibody technique to the study of a methanogenic bacterium in lake sediments.

Fluorescent antibody (FA) was prepared for a methanogenic bacterium isolated from Wintergreen Lake pelagic sediment. The isolate resembles Methanobacterium formicicum. The FA did not cross-react with 9 other methanogens, including M. formicicum strains, or 24 heterotrophs, 18 of which had been isolated from Wintergreen Lake sediment. FA-reacting methanogens were detected in heat-fixed smears of several different lake sediments and anaerobic sewage sludge. Pretreatment of all samples with either rhodamine-conjugated geletin or bovine serum albumin adequately controlled nonspecific absorption of the FA. Autofluorescent particles were observed in the sediment samples but, with experience, they could easily be distinguished from FA-reacting bacteria. FA direct counts of the specific methanogen in Wintergreen Lake sediments were made on four different sampling dates and compared with five-tube most-probable-number estimates of the total methanogenic population that was present in the same samples. The FA counts ranged from 3.1 X 10(6) to 1.4 X 10(7)/g of dry sediment. The highest most-probable-number estimates were at least an order ofmagnitude lower.     

Application of the fluorescent-antibody technique to the study of a methanogenic bacterium in lake sediments.

Fluorescent antibody (FA) was prepared for a methanogenic bacterium isolated from Wintergreen Lake pelagic sediment. The isolate resembles Methanobacterium formicicum. The FA did not cross-react with 9 other methanogens, including M. formicicum strains, or 24 heterotrophs, 18 of which had been isolated from Wintergreen Lake sediment. FA-reacting methanogens were detected in heat-fixed smears of several different lake sediments and anaerobic sewage sludge. Pretreatment of all samples with either rhodamine-conjugated geletin or bovine serum albumin adequately controlled nonspecific absorption of the FA. Autofluorescent particles were observed in the sediment samples but, with experience, they could easily be distinguished from FA-reacting bacteria. FA direct counts of the specific methanogen in Wintergreen Lake sediments were made on four different sampling dates and compared with five-tube most-probable-number estimates of the total methanogenic population that was present in the same samples. The FA counts ranged from 3.1 X 10(6) to 1.4 X 10(7)/g of dry sediment. The highest most-probable-number estimates were at least an order ofmagnitude lower.     

广东大亚湾甲藻孢囊及其与锥状斯氏藻赤潮的关系

1999年12月至2001年1月,在大亚湾澳头海域用沉积物捕捉器(Sediment trap)及TFO重力采泥器对甲藻孢囊进行每月一次的周年监测,并同时研究了浮游植物的季节变化.结果显示,晚秋孢囊形成率最高(3.48105 cysts/m2d),冬季形成率较低,年平均为1.28105 cysts/m2d.锥状斯氏藻(Scrippsiella trochoidea)是大亚湾沉积物孢囊中的绝对优势种,除个别季节外,其形成率一般占孢囊总形成率的50%以上.2000年8月至9月,该海域发生了一次较大规模的锥状斯氏藻赤潮,最高细胞密度达4.0104 cells/mL.赤潮中后期,锥状斯氏藻孢囊包括暂时性孢囊和休眠孢囊大量形成,孢囊的形成减少了水体中营养细胞数量,是赤潮消退原因之一.       

Brevetoxin persistence in sediments and seagrass epiphytes of east Florida coastal waters

A bloom of Karenia brevis Davis developed in September 2007 near Jacksonville, Florida and subsequently progressed south through east Florida coastal waters and the Atlantic Intracoastal Waterway (ICW). Maximum cell abundances exceeded 10⁶ cells L⁻¹ through October in the northern ICW between Jacksonville and the Indian River Lagoon. The bloom progressed further south during November, and terminated in December 2007 at densities of 10⁴ cells L⁻¹ in the ICW south of Jupiter Inlet, Florida. Brevetoxins were subsequently sampled in sediments and seagrass epiphytes in July and August 2008 in the ICW. Sediment brevetoxins occurred at concentrations of 11–15 ng PbTx-3 equivalents (g dry wt sediment)⁻¹ in three of five basins in the northern ICW during summer 2008. Seagrass beds occur south of the Mosquito Lagoon in the ICW. Brevetoxins were detected in six of the nine seagrass beds sampled between the Mosquito Lagoon and Jupiter Inlet at concentrations of 6–18 ng (g dry wt epiphytes)⁻¹. The highest brevetoxins concentrations were found in sediments near Patrick Air Force Base at 89 ng (g dry wt sediment)⁻¹. In general, brevetoxins occurred in either seagrass epiphytes or sediments. Blades of the resident seagrass species have a maximum life span of less than six months, so it is postulated that brevetoxins could be transferred between epibenthic communities of individual blades in seagrass beds. The occurrence of brevetoxins in east Florida coast sediments and seagrass epiphytes up to eight months after bloom termination supports observations from the Florida west coast that brevetoxins can persist in marine ecosystems in the absence of sustained blooms. Furthermore, our observations show that brevetoxins can persist in sediments where seagrass communities are absent.     

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。     

Dinoflagellate cyst records in recent sediments from Daya Bay, South China Sea

Nine sediment cores of 8–26 cm in length were collected from two basins of Daya Bay, the South China Sea, by Tokyo University Fisheries Oceanography Laboratory core sampler in August 2001 to investigate the distribution of dinoflagellate resting cysts. In the present study, 51 different cyst morphotypes representing 22 genera were identified from 65 sediment samples. Among them, there were 21 autotrophic species and 30 heterotrophic ones. Cyst species richness in each sample varied from 12 to 29, while the values of Shannon‐Weaver diversity index (H′) were between 0.15 and 4.13. There were an obvious increase in both species richness and values of H′in 2–6 cm sediments. Cyst concentrations varied from 154 to 113 483 cysts per gram dry weight sediment, and were much higher in upper sediments. Scrippsiella trochoidea was the most dominant cyst type, which took up over 90% of cyst assemblages in the upper sediments. The abrupt increase of S. trochoidea cysts in the surface sediments reflected the bloom of this species in Daya Bay in 2000. The results from cyst assemblages showed some trend of changes in water quality in this area, and indicated a typical type of pollution caused by cultural eutrophication, which started in the 1980s and greatly accelerated in the middle of 1990s. Cysts of Alexandrium, mainly those of Alexandrium catenella and Alexandrium tamarense complex, occurred frequently and abundantly in this area, with the highest concentration and relative frequency of 503 cysts per gram dry weight sediment and 22.3%, respectively. The high abundance of Alexandrium cysts provided rich ‘seed bed’ for Alexandrium blooms and was also an important source of paralytic shellfish poisoning toxins, especially in winter.     

Life-history traits of a tube-dwelling corophioid amphipod, Paracorophium excavatum, exposed to sediment copper

This is the first demonstration that sediment contaminants can influence the reproduction of amphipods. Groups of Paracorophium excavatum from a slightly contaminated estuarine site were held within laboratory mesocosms containing four copper-spiked estuarine sediments (Cu 14-46 μg g⁻¹ dry weight) and a control sediment (Cu 5 μg g⁻¹ dry weight) at 15 °C for 28 days. Copper sediment concentration did not affect the amphipod sex ratio. Female maturation was inhibited within copper-spiked sediments but female length was similar. Juvenile recruitment occurred only in sediments containing less than 20 μg g⁻¹. Males were significantly larger than females in the control sediment (Cu 5 μg g⁻¹ dry weight) and male length decreased linearly with increasing copper concentration. The copper concentration within whole body tissues increased with dry body dry weight in all sediments except the highest copper concentration. Following 28 days of exposure, none of the female amphipods from the copper-dosed sediments was brooding embryos. In contrast, brood size of females in the control sediment (Cu 5 μg g⁻¹) was similar to field samples. Because low concentrations of sediment copper affect the maturation and growth rates of male and female amphipods differently, these life-history traits could affect the population structure of amphipods exposed to copper contaminated sediments.     

Spatial distribution and historical deposition behaviors of perfluoroalkyl substances (PFASs) in sediments of Lake Chaohu,a shallow eutrophic lake in Eastern China

Sediment samples were collected from the Chaohu Lake basin to investigate the spatial distribution and historical deposition behaviors of 17 perfluoroalkyl substances (PFASs). Concentrations of the total PFASs (∑PFASs) in limnetic sediments ranged from 0.719 to 2.429 ng/g dry weight (dw), with an average of 1.449 ng/g dw. A clear gradient in the spatial distribution was observed from west to east in surface sediments of Lake Chaohu. Perfluorooctane sulfonic acid and perfluorooctanoic acid were predominant in limnetic sediments, with an average of 0.383 and 0.275 ng/g dw, respectively. The ∑PFASs concentrations in riverine sediments were the highest in the Shiwuli River, followed by the Nanfei River. PFASs in riverine sediments indicated that industrial discharge and urban runoff played key roles in PFAS distribution and pollution levels. In vertical profiles, concentrations of the ∑PFASs and PFAS congeners in three sediment cores generally increased with decreasing depths, indicating that the input history of the ∑PFASs could be attributed to the development of industrialization and urbanization in the Chaohu Lake basin. The correlations between PFASs and sedimentary characteristics, organic carbon, nutrients and inorganic salts suggested that both hydrophobic and electrostatic effects played important roles in PFAS distribution and pollution levels in sediments of Lake Chaohu.     

Distribution and habitat characteristics of Manayunkia speciosa and infection prevalence with the parasite Ceratomyxa shasta in the Klamath River, Oregon-California

A survey for Manayunkia speciosa, the freshwater polychaete host for the myxozoan parasite Ceratomyxa shasta, was conducted from 2003 to 2005 as part of an integrated study of the epizootiology of ceratomyxosis in Klamath River salmonids. Substrata samples (n = 257) were collected in a variety of habitats from Klamath Lake to the mouth of the Klamath River to document occurrence and relative abundance of the polychaete by habitat type and to estimate the prevalence of C. shasta within selected polychaete populations. Populations of M. specios a were identified throughout the Klamath River within pools (51.6%), eddy-pools (47.0%), and runs (40.0%). Large populations of M. speciosa were consistently found at the inflow to the main-stem reservoirs where densities were correlated with distance from the inflow into the reservoir. Using polymerase chain reaction assay and composite samples, 12 of 71 populations identified were tested for C. shasta, revealing a mean infection prevalence of 0.27%. An area of elevated infection prevalence (4.9 and 8.3%) was identified with 2 populations below a barrier to salmonid migration, which explains the high infectious spore densities demonstrated in concurrent studies and observations of C. shasta-induced mortality in Klamath River fall Chinook salmon (Oncorhynchus tshawytscha).     

Encystment of Peridinium gatunense: occurrence, favourable environmental conditions and its role in the dinoflagellate life cycle in a subtropical lake

1. The abundance of cysts of the bloom‐forming dinoflagellate Peridinium gatunense in the sediments of Lake Kinneret and the effects of environmental conditions on encystment were studied in relation to bloom dynamics. Peak cyst formation coincided with the highest growth rate of the population, prior to bloom peak. 2. Peridinium cysts were counted in water and sediment corer samples from 2000 to 2003 and in archived sediment trap samples collected during 1993–94. The cyst data were examined in relation to ambient temperature and nutrient records, and revealed no direct correlation. 3. In laboratory encystment experiments with Peridinium cells collected from the lake, 0.2–3% of the vegetative cells encysted. Temperature, light and cell density had no significant effect on the percentage of encystment. 4. Cysts were always present in the lake sediments but their abundance in ‘non Peridinium’ years was much lower than after a massive bloom. Vegetative cells were always present in the water column after the collapse of the annual dinoflagellate bloom, potentially serving as the inoculum for the next bloom. We propose that the hardy cysts serve as an emergency ‘gene bank’ to initiate population build up following catastrophic die outs.     

Microbial diversity in lake sediments detected by PCR-DGGE

In this study, PCR-denaturing gradient gel electrophoresis (DGGE) was applied to analyze the microbial communities in lake sediments from Lake Xuanwu, Lake Mochou in Nanjing and Lake Taihu in Wuxi. Sediment samples from seven locations in three lakes were collected and their genomic DNAs were extracted. The DNA yields of the sediments of Lake Xuanwu and Lake Mochou were high (10 μg/g), while that of sediments in Lake Taihu was relatively low. After DNA purification, the 16S rDNA genes (V3 to V5 region) were amplified and the amplified DNA fragments were separated by parallel DGGE. The DGGE profiles showed that there were five common bands in all the lake sediment samples indicating that there were similarities among the populations of microorganisms in all the lake sediments. The DGGE profiles of Lake Xuanwu and Lake Mochou were similar and about 20 types of microorganisms were identified in the sediment samples of both lakes. These results suggest that the sediment samples of these two city lakes (Xuanwu, Mochou) have similar microbial communities. However, the DGGE profiles of sediment samples in Lake Taihu were significantly different from these two lakes. Furthermore, the DGGE profiles of sediment samples in different locations in Lake Taihu were also different, suggesting that the microbial communities in Lake Taihu are more diversified than those in Lake Xuanwu and Lake Mochou. The differences in microbial diversity may be caused by the different environmental conditions, such as redox potential, pH, and the concentrations of organic matters. Seven major bands of 16S rDNA genes fragments from the DGGE profiles of sediment samples were further re-amplified and sequenced. The results of sequencing analysis indicate that five sequences shared 99%–100% homology with known sequences (Bacillus and Brevibacillus, uncultured bacteria), while the other two sequences shared 93%–96% homology with known sequences (Acinetobacter, and Bacillus). The study shows that the PCR-DGGE technique combined with sequence analysis is a feasible and efficient method for the determination of microbial communities in sediment samples. __________ Translated from Acta Ecologica Sinica, 2006, 26(11): 3610–3616 [译自: 生态学报]     

Mercury accumulation in the muscles and feathers of pheasants, Phasianus colchicus (L. 1758)

Mercury concentrations were determined in muscles and feathers of 58 cock pheasants. Birds were collected from seven different polluted sites in southern Poland in 1987. The mercury concentrations in the muscle ranged from 0.010 to 0.026 mug g dry mass. The significantly highest values were found in muscle samples from Przylasek and Przemysl. The levels found in the flight feathers were higher than in breast feathers. Average concentrations in flight feathers ranged from 0.050 mug g (Przemysl) to 0.240 mug g dry mass (Przylasek). © Rapid Science 1998     

Seasonal changes in sediment and water chemistry of a subtropical shallow eutrophic lake

A field study was conducted (May 1981 to June 1982) to develop a data-base on seasonal changes of water and sediment chemistry of Lake Monroe (4 000 ha surface and ca. 2 m deep) located in central Florida, USA. This shallow eutrophic lake is a part of the St. Johns River. Quantitative samples of lake water and sediments were collected on a monthly basis from 16 stations and analyzed for various physico-chemical parameters. Relatively high levels of dissolved solids (mean electrical conductivity (EC) = 1832 µS cm¹) prevailed in the lake water, and seasonal changes in EC were probably associated with hydrologic flushing from external sources, such as incoming water from upstream as well as precipitation. Average monthly levels of total N and P during the study period were 1.82 and 0.21 mg l^–1, respectively. Nutrient concentrations in the water did not show any strong seasonal trends. Organic matter content of lake sediments ranged from 1 to 182 g C kg^–1 of dry sediment, reflecting considerable spatial variability. All nutrient elements in the sediments showed highly significant (P < 0.01) correlations with sediment organic C, though little or no significant relationship appeared at any sampling period between water and sediment chemistry of the lake. Temporal trends in water and sediment chemical parameters may have been concealed by periodic hydrologic flushing of the St. Johns River into Lake Monroe.Florida Agricultural Experiment Stations Journal Series No. 7836.     

Microbial biomass and utilization of dissolved organic matter in the okefenokee swamp ecosystem

The Okefenokee Swamp exhibited levels of microbial biomass and aerobic glucose uptake comparable to those of other organically rich, detritus-based aquatic ecosystems. In contrast to other peat-accumulating systems, this acidic (pH 3.7), low-nutrient environment does not show diminished water column or surface sediment microbial biomass or heterotrophic activity. The total particular ATP varied between 0.03 and 6.6 mug liter (mean, 1.6 mug liter) in water and between 1 and 28 mug g (dry weight) (mean, 10.0 mug g [dry weight] in sediments. The turnover times for dissolved d-glucose were 1.26 to 701.25 h (mean, 110.25 h) in aerobic waters and 2.4 to 72 min (mean, 10.2 min) in aerobic surface sediments. Water column bacterial secondary production, measured as the incorporation of [H]thymidine into cold-trichloroacetic acid-insoluble material, ranged from 0.06 to 1.67 nmol liter day (mean, 0.45 nmol liter day). The kinetics of d-glucose uptake by water column microflora are multiphasic and suggest the presence of a diverse microbial population capable of using labile substrates at nanomolar concentrations and at substantial rates. The presence of a large and active aerobic microbial community in the Okefenokee Swamp is indicative of an important role for microbes in swamp geochemistry and strongly suggests the existence of a detritus-based food web.     

Microbial diversity in lake sediments detected by PCR-DGGE

In this study,PCR-denaturing gradient gel electrophoresis (DGGE) was applied to analyze the microbial communities in lake sediments from Lake Xuanwu,Lake Mochou in Nanjing and Lake Taihu in Wuxi.Sediment samples from seven locations in three lakes were collected and their genomic DNAs were extracted.The DNA yields of the sediments of Lake Xuanwu and Lake Mochou were high (10 μg/g),while that of sediments in Lake Taihu was relatively low.After DNA purification,the 16S rDNA genes (V3 to V5 region) were amplified and the amplified DNA fragments were separated by parallel DGGE.The DGGE profiles showed that there were five common bands in all the lake sediment samples indicating that there were similarities among the populations of microorganisms in all the lake sediments.The DGGE profiles of Lake Xuanwu and Lake Mochou were similar and about 20 types of micro-organisms were identified in the sediment samples of both lakes.These results suggest that the sediment samples of these two city lakes (Xuanwu,Mochou) have similar microbial communities.However,the DGGE profiles of sediment samples in Lake Taihu were significantly differ-ent from these two lakes.Furthermore,the DGGE pro-files of sediment samples in different locations in Lake Taihu were also different,suggesting that the microbial communities in Lake Taihu are more diversified than those in Lake Xuanwu and Lake Mochou.The differences in microbial diversity may be caused by the different environmental conditions,such as redox potential,pH,and the concentrations of organic matters.Seven major bands of 16S rDNA genes fragments from the DGGE profiles of sediment samples were further re-amplified and sequenced.The results of sequencing analysis indicate that five sequences shared 99%-100% homology with known sequences (Bacillus and Brevibacillus,uncultured bacteria),while the other two sequences shared 93%-96% homology with known sequences (Acinetobacter,and Bacillus).The study shows that the PCR-DGGE tech-nique combined with sequence analysis is a feasible and efficient method for the determination of microbial com-munities in sediment samples.     

Organochlorine Pesticides in Sediments around Chaohu Lake: Concentration Levels and Vertical Distribution

Eighteen organochlorine pesticides (OCPs) were investigated in surface sediments from the Nanfei River and in four sediment cores from the primary estuaries of Chaohu Lake, Eastern China. The results indicate that the OCP concentrations in the surface and core sediments around Chaohu Lake were 3.48–121.08 (with a mean of 34.93) ng/g and 0.60–39.28 (7.07) ng/g, respectively. Significantly higher concentrations of ΣOCPs were observed in sediment samples from the Nanfei River and its estuary. The three important OCP contributors around Chaohu Lake were dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), and hexachlorobenzene (HCB), which originated primarily from the historical use of technical DDTs and HCHs. A principal component analysis (PCA) suggests that HCB and lindane may originate from the same sources, and DDTs were greatly influenced by organic carbon from the soil environment and the impact of urbanization processes.     

Method for enumeration of 5-cyano-2,3-ditoyl tetrazolium chloride (CTC)-active cells and cell-specific CTC activity of benthic bacteria in riverine, estuarine and coastal sediments

Bacteria are the most abundant and active organisms in marine sediments and are critical for nutrient cycling and as a food source to many benthic and pelagic organisms. Bacteria are found both as free-living cells and as particle-associated cells, which can make investigations of these communities difficult. We found that common procedures for extracting bacteria from sediments leave the bacteria clay particle-associated and the clay particles clump, which reduce the reproducibility of direct counts. We optimized a sonication/surfactant method that produces a homogeneous suspension of bacterial cells against a uniform background of clay particles, which results in reproducible samples for epifluorescence microscopy. We developed a method to estimate CTC-positive cells and cell-specific CTC content in intact cores of surficial sediment communities from riverine, estuarine and coastal sites. Benthic bacterial abundances averaged 4.9x10(8) cells/g dry wt sediments in Apalachicola River, Florida sediments, 4.9-13.8x10(9) cells/g dry wt sediments in a variety of Apalachicola Bay sediments and 3.6x10(8) cells/g dry weight in shallow, anoxic Gulf of Mexico sediments. Percent CTC-positive cells ranged from low values of 9-10% CTC-positive cells in Apalachicola River and Apalachicola Bay sediments to high values of 25% CTC-positive cells in anoxic Gulf of Mexico sediments. After correction for abiotic CTC reduction and chlorophyll interference, estimates of cell-specific CTC reduction ranged from 0.15 to 0.55 fmol CTC(red)/active cell in the Apalachicola Bay sediments to 1.6 to 3.8 fmol CTC(red)/active cell in anoxic Gulf of Mexico sediments.     

环境因素对东平湖沉积物细菌群落结构的影响

【目的】探讨环境因素对东平湖沉积物细菌群落结构的影响。【方法】应用T-RFLP(Terminal RestrictionFragment Length Polymorphism)技术分析和比较了6个不同位置的东平湖沉积物在丰水期和枯水期的细菌多样性,并结合不同样品环境因子的差异,采用主成分分析(PCA)和典型对应分析(CCA),探讨了环境因子对细菌多样性的影响。【结果】不同沉积物样品的T-RFLP图谱具有较高的相似性。除2号样品外,所有枯水期样品的细菌群落具有较高的丰富度、多样性、均匀度和较低的优势度。CCA结果表明,558bp T-RF的丰度与总磷、总氮、总有机碳、铵态氮和硝态氮含量呈负相关而与碳氮比和水深呈正相关;64.5、164、509和543bp T-RFs的丰度与总氮、总有机碳、铵态氮、硝态氮、碳氮比和水深呈正相关;而其它14种主要的T-RFs在不同样品间分布较为稳定受环境因子影响不大。90、136.5、138和488bp等T-RFs可能代表了东平湖沉积物中占优势地位的土著菌群。通过Phylogenetic Assignment Tool在线分析结果推测,东平湖沉积物中的优势菌群可能属于Firmicutes和Proteobacteria门。【结论】环境因素对东平湖沉积物的细菌多样性产生显著影响,但对其土著菌群的影响不大。