The Incidence of R Factors in Bordetella bronchiseptica Isolated from Pigs

Bordetella bronchiseptica strains isolated from the nasal cavities of young pigs in Japan from 1969 to 1972 were surveyed for drug resistance and distribution of R factors. Of 304 strains examined, 71 (23%) were resistant to either one or more of following three drugs, streptomycin (SM), sulfadimethoxine (SA), and aminobenzyl penicillin (APC). Triple (SM.SA.APC)-resistance was most frequent among these resistant strains. Strains of double (SM. SA)- or single (SM)- and (SA)-resistance were also isolated, but were very few in numbers. Of the 71 drug-resistant strains, 61 (86%) were found to carry R factors which were capable of conjugal transfer. All of these R factors had the triple (SM.SA.APC)-resistant markers and were identified as fi^– (no fertility inhibition) type. The (SM.SA.APC)-resistant strains carrying R factors had been isolated from pigs reared on various farms in different districts, and consequently the prevalence of B. bronchiseptica strains carrying R factors was considered to be relatively wide-spread in young pigs.     

Drug Resistance of Enteric Bacteria

Drug resistance of 3,000 Shigella strains isolated in 1965 were investigated. These strains originated from 10 City Hospitals and 4 Prefectural Health Centers, which are located in different parts of Japan. One hundred and seventy strains which were resistant to 4 drugs, chloramphenicol (CM), tetracycline (TC), dihydrostreptomycin (SM), and sulfanilamide (SA), were selected at random from these stock cultures in this laboratory and the distribution of R factors in these isolates was examined. It was found that the strains all harbored R factors which were capable of transferring drug resistance by usual conjugal process. Among the strains carrying R factors, 85 per cent harbored a single type of R factor and 15 per cent carried two types of R factor in a cell. The latter is called the hetero-R state. Among the strains in the hetero-R state, isolation of strains harboring both R (SM.SA) and R (TC.CM.SM.SA) factors was most frequent. It was found that 25 R (SM.SA) factors isolated from strains in hetero-R had the genetic determinant iR^?, while most of the R (TC.CM.SM.SA) factors isolated from natural sources were iR⁺. When two types of R factor, R (SM.SA) and R (TC.CM.SM.SA) derived from the same host cells, were brought together in a host cell by superinfection with both factors, they were found to exist stably in a host bacterium. These results confirmed the stable existence of both factors in Shigella strains isolated from dysenteric patients.     

Effects of Chemotherapeutics on Bacterial Ecology in the Water of Ponds and the Intestinal Tracts of Cultured Fish,Ayu (Plecoglossus altivelis)

Drug-resistant gram-negative bacilli conferred with R factors were isolated with high frequencies from the intestinal tracts of ayu (Plecoglossus altivelis) cultured in ponds, in which chemotherapeutics had often been used, and with relatively low frequencies from ayu which received no administration of chemotherapeutics. Drug-resistant bacteria were also isolated at low frequencies from the intestinal tracts of wild ayu in rivers, as well as from the water of ayu-culturing ponds and some of them carried R factors. The drug-resistant bacteria carrying R factors were Aeromonas liquefaciens, Citrobacter, Enterobacter cloacae, Escherichia coli, Hafnia and unidentified strains. All the R factors were classified as the Fi^–(F) type, except the two R factors detected in an E. coli strain and in an unidentified strain.     

Carotenoids of land-locked and sea-run types of masu salmon Oncorhynchus masou ishikawae inhabiting in the Nagara River,Japan, from the perspective of chemical ecological study

Carotenoids of the land-locked type (Amago) and sea-run type (Satsukimasu) of masu salmon Oncorhynchus masou ishikawae inhabiting the Nagara River, Gifu Prefecture, Japan were investigated from the perspective of the chemical ecological point of view. Yellow xanthophylls, 3′-epilutein, lutein, zeaxanthin, and diatoxanthin were major carotenoids in wild Amago. They were also present in the flesh of wild Amago. These carotenoids originated from aquatic insects, which wild Amago fed on. On the other hand, tunaxanthin, zeaxanthin, and salmoxanthin were major carotenoids in the integument of Satsukimasu, which migrated from the Ise Bay to the Nagara River. Astaxanthin was a major carotenoid in the flesh of Satsukimasu. These carotenoids accumulated from marine fish and crustaceans, which Satsukimasu fed on during migration in the sea. Carotenoids of Amago and Satukimasu well-reflect their ecological life history.     

Detection of R+ Bacteria in Cultured Marine Fish,Yellowtails (Seriola quinqueradiata)

Many drug-resistant gram-negative bacilli were isolated from the intestinal tracts of yellowtails (Seriola quinqueradiata) cultured on farms in various parts of Kochi and Ehime Prefectures, Shikoku Island. They were Vibrio, Pseudomonas, Proteus, Citrobacter and some unidentified Enterobacteriaceae. Of these drug-resistant strains, Vibrio and Pseudomonas were found to carry R factors in high frequencies. These R factors had four types of resistance markers, SA, SA. CM, SM. CM. ABP. and SA. SM. CM. TC. All R factors were found to belong to the fi^– type. In contrast, only one drug-resistant gram-negative bacillus was detected in a cultured yellowtail on farms near Numazu City, Shizuoka Prefecture.     

Unstable Mutants of R Factor

Thirty mutants sensitive to tetracycline were obtained from an R100 factor capable of conferring resistance to tetracycline (TC), chloramphenicol (CM), streptomycin (SM) and sulfanilamide (SA). Among the TC sensitive mutants, three showed a high frequency of spontaneous loss from host strains. The genetic loci governing the stability of R factor in host bacteria were denoted as stb. The stb^– R factors have lost many of the properties of a wild type R factor, such as, the capability to sexually transfer drug resistance and host chromosome, to confer superinfection immunity and to inhibit F function. All of these properties did not revert to a wild type phenotype, suggesting that these mutations are deletions including genetic determinants governing both TC resistance and stability of R factor. Recombinational analysis between stb^– and stb⁺ R factors indicated that crossovers between the stb loci and those governing CM (or SM.SA) resistance took place at high frequency. No crossovers were detected between stb loci and those governing TC resistance, indicating that the stb loci are linked closely to the loci governing TC resistance.     

Application of <Emphasis Type="Italic">Gracilaria lichenoides</Emphasis> (Rhodophyta) for alleviating excess nutrients in aquaculture

A study was conducted in Xiangshan Bay, Ningbo, China, using red alga Gracilaria lichenoides to alleviate nutrient pollution in shrimp (Litopenaeus vannamei) and fish (Epinephelus awoara) culture ponds. Our results showed that G. lichenoides was efficient at absorbing inorganic nitrogen (IN) and inorganic phosphate (IP), and maintained a more stable dissolved oxygen (DO) level. A total of 506.5 kg (1,013 kg ha⁻¹) of shrimp and 210.5 kg (421 kg ha⁻¹) of fish were harvested from the shrimp/algae (SA) and fish/algae (FA) ponds, respectively. Only 53.5 kg shrimp were harvested from the shrimp pond without Gracilaria (S) due to anoxic asphyxia, and 163 kg fish were harvested from the fish culture pond without Gracilaria (F). Compared with using microalgae, bioremediation by macroalgae has no risk of harmful algal blooms (HABs), and it is easy to control seaweed biomass. During the experiment, there was a better environmental condition (lower chemical oxygen demand, IN, IP and chlorophyll a concentrations) in the ponds with Gracilaria. Furthermore, Gracilaria spp. can be used as food for abalone or other aquacultured animals and thus enhance economic return.     

Mapping andfi character determination of R factors ofEnterobacter cloacae DF13

In conjugation experiments betweenEnterobacter cloacae DF13 andEscherichia coli K12, resistances against tetracycline, sulfanilamide, streptomycin, and chloramphenicol were nearly always transferred simultaneously. These properties could be transferred fromE. coli exconjugants by transduction to a drug-sensitiveE. coli K12 strain with bacteriophage P1kc. It may be inferred thatEnt. cloacae DF 13 harbours a multiple R factor, which promotes its own transfer. This R factor was found to be of thefi ⁺ type. The molecular nature of this R factor was studied by labelling the DNA of an exconjugant with³H-thymidine, careful lysis, sedimentation of the chromosomal DNA, and characterization of the circular DNA by sucrose-gradient centrifugation, equilibriumdensity centrifugation in CsCl containing ethidium bromide and by electron microscopy. By these methods the multiple R factor was identified as a circular DNA molecule with a contour length of 22.6 Μm, corresponding to a molecular weight of 45 × 10⁶ daltons. A segregant R factor harbouring resistance against tetracycline only, was found to have a contour length of 16.0 Μm and a sedimentation constant of 58 S. In addition to the multiple R factor, the wild-type strain harboured a plasmid with a sedimentation constant of 38 S, corresponding to a molecular weight of 16 × 10⁶ daltons. The function of this plasmid is unknown. After many transfers on agar slants spontaneous segregation of the R factor was observed and several types of segregants were obtained. In most segregants, resistance against streptomycin could not be transferred by conjugation and could not be mobilized by other sex factors. Some of these segregants had acquired a requirement for methionine; in these, the streptomycin-resistance determinant may be integrated into the chromosome. The resistance pattern of the various types of segregants and exconjugants allowed to draw a circular map of the R factor. The order of markers is ---tet---rtf---sul---str---cml-. After short-term conjugation experiments most exconjugants were found to have received resistance against sulfanilamides only. This resistance determinant does not promote its own transfer by conjugation but could be mobilized by other sex factors. An exconjugant become resistant against tetracycline and sulfanilamide, was found to harbour two independent plasmids of which only that carrying resistance against tetracycline promoted its own transfer. Consequently a second R factor, determining resistance against sulfanilamide alone must be present inEnt. cloacae DF13. This R factor was identified as a circular DNA molecule with a sedimentation constant of 26 S, a contour length of 2.6 Μm and a buoyant density of 1.709. From a strain harbouring the independent R(SA) plasmid and an R(TC) fragment of the multiple R factor, transductants resistant against sulfanilamide were obtained. These were found to harbour an R(SA) plasmid with properties of a defective Rfi ⁺ transfer factor. Most probably these plasmids resulted from recombination between the R(SA) plasmid and the Rtf region of the R(TC) fragment. The author published previously under the name of “G. A. Tieze”. The technical assistance of Miss J.T.M.P.A. Havermans, Mrs. A. Mak-Zuidervaart, and Mr. M. V. M. Lafleur is gratefully acknowledged. The authors thank Dr. E. F. J. van Bruggen and Dr. D. Ellens for the electronmicroscopical measurements.     

三种海水生态养殖池塘细菌数量特征及其与环境因子的相关性

为阐明不同生态养殖池塘浮游细菌数量变化规律及其与环境因子间的相关性,以期为多元立体综合养殖模式中的水质安全与生物疾病防控提供科学依据。利用荧光显微镜细菌计数法(Acridine Orange Direct Counting),研究了“参-虾”“蟹-蛏”和“蜇-蛏”三种海水生态养殖池塘的细菌数量特征,使用典范对应分析(Canonical Correspondence Analysis, CCA)探讨细菌数量与环境因子的相互关系。结果表明,“参-虾”“蟹-蛏”和“蜇-蛏”池塘的细菌平均密度分别为(0.49～3.32)×10⁵ cell/mL、(0.52～2.98)×10⁵ cell/mL和(0.47～2.55)×10⁵ cell/mL,细菌数量有明显的时间差异,夏季密度大于春秋季。三种海水生态养殖池塘的水温、溶解氧和pH变化均不明显,且相差不大,而硝态氮均发生显著变化;其中“蟹-蛏”和“蜇-蛏”池塘的硝态氮、亚硝态氮、活性磷、总氮和总磷均高于“参-虾”池塘,透明度、叶绿素a和化学耗氧量则均低于“参-虾”池塘。典范对应分析(C...     

Mechanisms for Parasites Removal in a Waste Stabilisation Pond

A waste stabilisation pond (WSP) system formed by two anaerobic ponds, a facultative pond and a maturation pond was studied from December 2003 to September 2004 in north-western Spain in order to evaluate its efficiency in the removal of faecal indicator bacteria (total coliforms, Escherichia coli, faecal streptococci), coliphages, helminth eggs and protozoan (oo)cysts (Cryptosporidium and Giardia). Furthermore, sediment samples were collected from the bottom of the ponds to assess the settling rates and thus determine the main pathogen removal mechanisms in the WSPs system. The overall removal ranged from 1.4 log units for coliphages in the cold period to 5.0 log units for E. coli in the hot period. Cryptosporidium oocysts were reduced by an average of 96%, Giardia cysts by 98% and helminth eggs by 100%. The anaerobic ponds showed significantly higher surface removal rates (4.6, 5.2 and 3.7 log (oo)cysts/eggs removed m⁻² day⁻¹, respectively) than facultative and maturation ponds. Sunlight and water physicochemical conditions were the main factors influencing C. parvum oocysts removal both in the anaerobic and maturation ponds, whereas other factors like predation or natural mortality were more important in the facultative pond. Sedimentation, the most commonly proposed mechanism for cyst removal had, therefore, a negligible influence in the studied ponds.     

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois

Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0–761.4 g ash-free dry mass (AFDM) year⁻¹ to ponds (up to 5.5 g AFDM m⁻² year⁻¹). Larval production ranged from 0.4 to 7.4 g AFDM m⁻² year⁻¹ among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m⁻² year⁻¹ produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m⁻² and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range=2–35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0±33.9 g AFDM year⁻¹ (range=21.0–135.2 g AFDM year⁻¹) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5±140.8 g AFDM year⁻¹ into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r ² =0.94, P<0.05, n=5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Estimating hydroperiod suitability for breeding amphibians in southern Rhode Island seasonal forest ponds

In New England, seasonal forest ponds provide primary breeding habitat for several amphibian species, including Rana sylvatica (LeConte) and Ambystoma maculatum (Shaw). Because each species requires a minimum duration of inundation to complete its breeding cycle, one of the most important factors determining habitat suitability is a pond’s hydroperiod. The objective of this research was to develop a method for estimating pond hydroperiod from site characteristics such as pond morphology, geology, chemistry, and vegetation structure, and to use the estimates to assess the suitability of individual ponds for breeding amphibians. We monitored the duration of surface inundation in 65 ponds in the Pawcatuck River watershed of southern Rhode Island during 2001 and 2002. Pond hydroperiods, measured from 1 March, ranged from 19 to 44 weeks in 2001 and from 2 to 44 weeks in 2002; mean values were 30 and 21 weeks, respectively. Akaike’s Information Criterion was used to select a multivariate hydroperiod estimation model (R² = 0.59, p < 0.0001) that permitted identification of ponds with hydroperiods suitable for breeding by R. sylvatica (95.4% correct classification rate [CCR]) and A. maculatum (75.4% CCR). Canopy cover, open basin depth, and specific conductance of surface water were among the most useful site characteristics for estimating hydroperiod, while surficial geology and the texture of soil parent material made smaller contributions. The CCR using open basin depth alone was 95.4 and 73.8%, respectively. These findings indicate that it is possible to estimate the hydroperiod of seasonal ponds – and to assess their suitability for individual species of breeding amphibians – without prolonged periods of hydrologic monitoring. Such techniques could have considerable value to wetland regulatory agencies and for planning amphibian habitat management and acquisition at the landscape scale.     

The role of historic and climatic factors in the distribution of crustacean communities in Iberian Mediterranean ponds

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Differences in the growth cycle of Ruppia cirrhosa (Petagna) Grande in a Mediterranean shallow system

Ruppia cirrhosa growth cycle was analysed in a southern Mediterranean shallow system throughout 1 year. We examined the temporal variation in R. cirrhosa cover percentage, shoot density, biomass, leaf length, no. flowers m^? 2 and no. fruits m^? 2 in two groups of pond characterized by differences in some environmental parameters. Ponds were comparable for salinity and temperature but they differed for other environmental parameters such as water depth, level of suspended organic matter and chlorophyll a (CHL a). Biological parameter values were higher in B ponds, characterized by lower values of water depth, suspended organic matter and CHL a. A seasonal trend for all considered biological parameters in both typologies of ponds with maximum values in summer was also observed. Moreover, differences were observed between the two groups of ponds in relation to the reproductive strategy adopted by the plant, with populations subjected to a higher organic input and a lower water depth displaying an annual cycle. Results showed how R. cirrhosa is able to resist and to adapt to variations in environmental conditions because of the plasticity and flexibility in the growth cycle and in the reproductive effort.     

Rhodospirillum salinarum sp. nov., a halophilic photosynthetic bacterium isolated from a Portuguese saltern

A new species of halophilic photosynthetic bacteria, Rhodospirillum salinarum, has been isolated and described. Its natural habitat are the terminal crystallization ponds of solar salt production plants. R. salinarum grows optimally at 42°C in the presence of 6–18% NaCl (w/v). Growth requirements are complex, yeast extract and peptone being required both for aerobic heterotrophic and for anaerobic phototrophic growth. Increasing concentrations of NaCl in the growth media did not give rise to any corresponding increase in intracellular concentrations of K⁺, Na⁺, polyalcohols or amino acids. Malate dehydrogenase from R. salinarum is not halophilic, being inhibited even at low concentrations of Na⁺ or K⁺. The GC mol % of DNA from R. salinarum is markedly higher than that for DNA from R. salexigens, the only previously described halophilic species of the genus Rhodospirillum.     

Anopheles arabiensis oviposition site selection in response to habitat persistence and associated physicochemical parameters,bacteria and volatile profiles

A better understanding of the oviposition behaviour of malaria vectors might facilitate the development of new vector control tools. However, the factors that guide the aquatic habitat selection of gravid females are poorly understood. The present study explored the relative attractiveness of similar artificial ponds (0.8 m²) aged at varying lengths prior to opening in such a way that wild Anopheles arabiensis could choose between ponds that were freshly set up, or were aged 4 or 17 days old, to lay eggs. Physicochemical parameters, bacterial profile and volatile organic compounds emitted from ponds were investigated over three experimental rounds. Fresh ponds contained on average twice as many An. arabiensis instar larvae (mean 50, 95% confidence interval (CI) = 29–85) as the ponds that had aged 4 days (mean = 24, 95% CI = 14–42) and 17 days (mean = 20, 95% CI: 12–34). Fresh ponds were associated with a significantly higher turbidity combined with higher water temperature, higher nitrite levels and a lower pH and chlorophyll level than the older ponds. Round by round analyses suggested that bacteria communities differed between age groups and also that 4‐heptanone, 2‐ethylhexanal and an isomer of octenal were exclusively detected from the fresh ponds. These characteristics may be useful with respect to developing attract and kill strategies for malaria vector control.     

Altered Kinetic Properties of Tyrosine-183 to Cysteine Mutation in Glutamine Synthetase of <Emphasis Type="Italic">Anabaena variabilis</Emphasis> Strain SA1 Is Responsible for Excretion of Ammonium Ion Produced by Nitrogenase

A L-methionine-D,L-sulfoximine-resistant mutant of the cyanobacterium Anabaena variabilis, strain SA1, excreted the ammonium ion generated from N₂ reduction. In order to determine the biochemical basis for the NH₄ ⁺-excretion phenotype, glutamine synthetase (GS) was purified from both the parent strain SA0 and from the mutant. GS from strain SA0 (SA0-GS) had a pH optimum of 7.5, while the pH optimum for GS from strain SA1 (SA1-GS) was 6.8. SA1-GS required Mn⁺² for optimum activity, while SA0-GS was Mg⁺² dependent. SA0-GS had the following apparent K _m values at pH 7.5: glutamate, 1.7 mM; NH₄ ⁺, 0.015 mM; ATP, 0.13 mM. The apparent K _m for substrates was significantly higher for SA1-GS at its optimum pH (glutamate, 9.2 mM; NH₄ ⁺, 12.4 mM; ATP, 0.17 mM). The amino acids alanine, aspartate, cystine, glycine, and serine inhibited SA1-GS less severely than the SA0-GS. The nucleotide sequences of glnA (encoding glutamine synthetase) from strains SA0 and SA1 were identical except for a single nucleotide substitution that resulted in a Y183C mutation in SA1-GS. The kinetic properties of SA1-GS isolated from E. coli or Klebsiella oxytoca glnA mutants carrying the A. variabilis SA1 glnA gene were also similar to SA1-GS isolated from A. variabilis strain SA1. These results show that the NH₄ ⁺-excretion phenotype of A. variabilis strain SA1 is a direct consequence of structural changes in SA1-GS induced by the Y183C mutation, which elevated the K _m values for NH₄ ⁺ and glutamate, and thus limited the assimilation of NH₄ ⁺ generated by N₂ reduction. These properties and the altered divalent cation-mediated stability of A. variabilis SA1-GS demonstrate the importance of Y183 for NH₄ ⁺ binding and metal ion coordination. Received: 3 July 2002 / Accepted: 29 July 2002     

Introgression of Oncorhynchus masou subsp. (Biwa salmon) genome into lake-run O. m. ishikawae (Amago salmon) introduced into Lake Biwa, Japan

An investigation to determine the extent of introgression between Biwa salmon Oncorhynchus masou subsp. and lake-run Amago salmon O. m. ishikawae from Lake Biwa was conducted using mtDNA sequence and amplified fragment length polymorphism (AFLP) analysis. Hatchery-reared Amago salmon from the Samegai Trout Farm, the main source of stock released into the inflowing rivers of Lake Biwa, were also investigated. The extent of mtDNA introgression between these two subspecies was quite low: an anomalous haplotype was detected in just 1 of 55 Biwa salmon and 2 of 63 lake-run Amago salmon. Many of the mtDNA haplotypes found in lake-run Amago salmon were common to those in hatchery-reared Amago salmon. In the AFLP analysis, the nuclear genome of Amago salmon was hardly detected in Biwa salmon, but the Biwa salmon genome comprised 13.4% of the total amplified fragments from lake-run Amago salmon, being detected in different proportions in 28 of the 63 investigated individuals of the latter subspecies. These results suggest that introgression has occurred between Biwa salmon and lake-run Amago salmon descending from hatchery-reared Amago salmon from the Samegai Trout Farm.     

Landscape and local correlates with two green tree-frogs,Rhacophorus (Amphibia: Rhacophoridae) in different habitats,central Japan

Changes in land-use and local factors have strong influences on amphibian distributions. However, the effects of both combined factors on assemblages are still unclear. The green tree-frogs, Rhacophorus, are sensitive to differences in landscape fragmentation. Herein, two species of Rhacophorus schlegelii and Rhacophorus arboreus have been surveyed, along the ecological gradient ranging from paddy-dominated plains to forest-dominated mountains (located in Toyota, Okazaki, and Shinshiro, central Japan). The effects of landscape and local factors on the existence of the above frogs were investigated using generalized linear models (GLMs); the Akaike Information Criteria (AIC) were used for model selection. The lowest AIC for R. schlegelii and R. arboreus were obtained at a 250-m-radius and 500-m-radius buffers, respectively. Habitat selections of each species showed distinct results in the paddy-field vs. ponds group. Nevertheless, both species exhibited a high abundance with increasing elevation and forest cover. At the local level, R. schlegelii displayed positive relationships with the presence of trees and the proportion of embankment vegetation. Our findings demonstrate that each species responded to various landscape scale and spatial composition, habitat, and species-dependent achievements of appropriate management actions to improve restoration practices are required.

     

重庆丘陵山区池塘沉积物有机碳埋藏速率及其影响因素

池塘等小型水体在全球碳循环中发挥着重要作用,是碳排放的热区,但是对池塘碳埋藏速率认识相对匮乏,限制了全面认识池塘在流域碳传输中的功能。为探究池塘沉积物有机碳埋藏速率及其影响因素,选取重庆市北碚区柳荫镇的11个池塘为研究对象,于2022年7月对池塘沉积物进行采样,分析了池塘沉积物基本理化性质,估算出池塘沉积物有机碳埋藏量和埋藏速率,并分析了池塘因素和流域因素对池塘沉积物有机碳埋藏速率的影响。结果显示：(1)沉积物总有机碳(TOC, Total Organic Carbon)含量在1.03%—3.51%之间变化,总体呈现随深度增加而逐渐降低的趋势;(2)有机碳埋藏速率均值为194.60 g m^-2 a^-1,范围区间为142.76—293.32 g m^-2 a^-1,略高于其他池塘的类似研究结果;(3)沉积物TOC含量与总氮(TN, Total Nitrogen)含量呈显著正相关(P<0.01),与流域中林地面积占比呈显著正相关(P<0.05),与旱地面积占比呈显著负相关(P<0.05),...