Depleted dissolved organic carbon and distinct bacterial communities in the water column of a rapid-flushing coral reef ecosystem

Coral reefs are highly productive ecosystems bathed in unproductive, low-nutrient oceanic waters, where microbially dominated food webs are supported largely by bacterioplankton recycling of dissolved compounds. Despite evidence that benthic reef organisms efficiently scavenge particulate organic matter and inorganic nutrients from advected oceanic waters, our understanding of the role of bacterioplankton and dissolved organic matter (DOM) in the interaction between reefs and the surrounding ocean remains limited. In this study, we present the results of a 4-year study conducted in a well-characterized coral reef ecosystem (Paopao Bay, Moorea, French Polynesia) where changes in bacterioplankton abundance and dissolved organic carbon (DOC) concentrations were quantified and bacterial community structure variation was examined along spatial gradients of the reef:ocean interface. Our results illustrate that the reef is consistently depleted in concentrations of both DOC and bacterioplankton relative to offshore waters (averaging 79 μmol l⁻¹ DOC and 5.5 × 10⁸ cells l⁻¹ offshore and 68 μmol l⁻¹ DOC and 3.1 × 10⁸ cells l⁻¹ over the reef, respectively) across a 4-year time period. In addition, using a suite of culture-independent measures of bacterial community structure, we found consistent differentiation of reef bacterioplankton communities from those offshore or in a nearby embayment across all taxonomic levels. Reef habitats were enriched in Gamma-, Delta-, and Betaproteobacteria, Bacteriodetes, Actinobacteria and Firmicutes. Specific bacterial phylotypes, including members of the SAR11, SAR116, Flavobacteria, and Synechococcus clades, exhibited clear gradients in relative abundance among nearshore habitats. Our observations indicate that this reef system removes oceanic DOC and exerts selective pressures on bacterioplankton community structure on timescales approximating reef water residence times, observations which are notable both because fringing reefs do not exhibit long residence times (unlike those characteristic of atoll lagoons) and because oceanic DOC is generally recalcitrant to degradation by ambient microbial assemblages. Our findings thus have interesting implications for the role of oceanic DOM and bacterioplankton in the ecology and metabolism of reef ecosystems.     

Linking the composition of bacterioplankton to rapid turnover of dissolved dimethylsulphoniopropionate in an algal bloom in the North Sea

The algal osmolyte, dimethylsulphoniopropionate (DMSP), is abundant in the surface oceans and is the major precursor of dimethyl sulphide (DMS), a gas involved in global climate regulation. Here, we report results from an in situ Lagrangian study that suggests a link between the microbially driven fluxes of dissolved DMSP (DMSPd) and specific members of the bacterioplankton community in a North Sea coccolithophore bloom. The bacterial population in the bloom was dominated by a single species related to the genus Roseobacter , which accounted for 24% of the bacterioplankton numbers and up to 50% of the biomass. The abundance of the Roseobacter cells showed significant paired correlation with DMSPd consumption and bacterioplankton production, whereas abundances of other bacteria did not. Consumed DMSPd (28 nM day⁻¹) contributed 95% of the sulphur and up to 15% of the carbon demand of the total bacterial populations, suggesting the importance of DMSP as a substrate for the Roseobacter -dominated bacterioplankton. In dominating DMSPd flux, the Roseobacter species may exert a major control on DMS production. DMSPd turnover rate was 10 times that of DMS (2.7 nM day⁻¹), indicating that DMSPd was probably the major source of DMS, but that most of the DMSPd was metabolized without DMS production. Our study suggests that single species of bacterioplankton may at times be important in metabolizing DMSP and regulating the generation of DMS in the sea.     

High similarity between bacterioneuston and airborne bacterial community compositions in a high mountain lake area

The bacterioneuston (bacteria inhabiting the air–water interface) is poorly characterized and possibly forms a unique community in the aquatic environment. In high mountain lakes, the surface film is subjected to extreme conditions of life, suggesting the development of a specific and adapted bacterioneuston community. We have studied the surface film of a remote high mountain lake in the Pyrenees by cloning the PCR-amplified 16S rRNA gene and comparing with bacteria present in underlying waters (UW), and airborne bacteria from the dust deposited on the top of the snow pack. We did not detect unusual taxa in the neuston but rather very common and widespread bacterial groups. Betaproteobacteria and Actinobacteria accounted for >75% of the community composition. Other minor groups were Gammaproteobacteria (between 8% and 12%), Alphaproteobacteria (between 1% and 5%), and Firmicutes (1%). However, we observed segregated populations in neuston and UW for the different clades within each of the main phylogenetic groups. The soil bacterium Acinetobacter sp. was only detected in the snow–dust sample. Overall, higher similarities were found between bacterioneuston and airborne bacteria than between the former and bacterioplankton. The surface film in high mountain lakes appears as a direct interceptor of airborne bacteria useful for monitoring long-range bacterial dispersion.     

Sea Ice Microbial Communities: Distribution, Abundance, and Diversity of Ice Bacteria in McMurdo Sound, Antarctica, in 1980

An abundant and diverse bacterial community was found within brine channels of annual sea ice and at the ice-seawater interface in McMurdo Sound, Antarctica, in 1980. The mean bacterial standing crop was 1.4 × 10¹¹ cells m⁻² (9.8 mg of C m⁻²); bacterial concentrations as high as 1.02 × 10¹² cells m⁻³ were observed in ice core melt water. Vertical profiles of ice cores 1.3 to 2.5 m long showed that 47% of the bacterial numbers and 93% of the bacterial biomass were located in the bottom 20 cm of sea ice. Ice bacterial biomass concentration was more than 10 times higher than bacterioplankton from the water column. Scanning electron micrographs showed a variety of morphologically distinct cell types, including coccoid, rod, fusiform, filamentous, and prosthecate forms; dividing cells were commonly observed. Approximately 70% of the ice bacteria were free-living, whereas 30% were attached to either living algal cells or detritus. Interactions between ice bacteria and microalgae were suggested by a positive correlation between bacterial numbers and chlorophyll a content of the ice. Scanning and transmission electron microscopy revealed a close physical association between epibacteria and a dominant ice alga of the genus Amphiprora. We propose that sea ice microbial communities are not only sources of primary production but also sources of secondary microbial production in polar ecosystems. Furthermore, we propose that a detrital food web may be associated with polar sea ice.     

Coral reefs modify their seawater carbon chemistry – implications for impacts of ocean acidification

Reviews suggest that that the biogeochemical threshold for sustained coral reef growth will be reached during this century due to ocean acidification caused by increased uptake of atmospheric CO₂. Projections of ocean acidification, however, are based on air‐sea fluxes in the open ocean, and not for shallow‐water systems such as coral reefs. Like the open ocean, reef waters are subject to the chemical forcing of increasing atmospheric pCO₂. However, for reefs with long water residence times, we illustrate that benthic carbon fluxes can drive spatial variation in pH, pCO₂ and aragonite saturation state (Ω_a) that can mask the effects of ocean acidification in some downstream habitats. We use a carbon flux model for photosynthesis, respiration, calcification and dissolution coupled with Lagrangian transport to examine how key groups of calcifiers (zooxanthellate corals) and primary producers (macroalgae) on coral reefs contribute to changes in the seawater carbonate system as a function of water residence time. Analyses based on flume data showed that the carbon fluxes of corals and macroalgae drive Ω_ain opposing directions. Areas dominated by corals elevate pCO₂ and reduce Ω_a, thereby compounding ocean acidification effects in downstream habitats, whereas algal beds draw CO₂ down and elevate Ω_a, potentially offsetting ocean acidification impacts at the local scale. Simulations for two CO₂ scenarios (600 and 900 ppm CO₂) suggested that a potential shift from coral to algal abundance under ocean acidification can lead to improved conditions for calcification in downstream habitats, depending on reef size, water residence time and circulation patterns. Although the carbon fluxes of benthic reef communities cannot significantly counter changes in carbon chemistry at the scale of oceans, they provide a significant mechanism of buffering ocean acidification impacts at the scale of habitat to reef.     

Fluxes of bacterioplankton between a tidal estuary and the sea: returning to the “Outwelling Hypothesis”

The tidal dynamics of bacterioplankton communities at the outer part ofa shallow estuary (Ria de Aveiro, Portugal) were studied during 6 tidal cyclesat a fixed sampling site. Bacterial numbers (0.2–8.1 ×10⁹ cells l^–1), aminopeptidase activity(189–1662 nmol l^–1 h^–1),-glucosidase activity (1.7–67.0 nmoll^–1 h^–1) and potential glucoseincorporation (0.48–3.99 nmoll^–1 h^–1) followed a consistent patternof increase during ebb and decrease during flood.Fluxes of bacterioplankton populations and associated heterotrophic activitiesbetween the estuary and the coastal area during a tidal cycle were estimatedfrom the water flux as derived from a two-dimensional vertically-integratednumerical model. The net fluxes estimated for a tidal cycle ranged from–26.0 to –2.5 to × 10¹⁶ bacterial cells. The nettidal fluxes of potential heterotrophic activities ranged from –10 to–80 mol h^–1 for aminopeptidase, –0.33to –1.10 mol h^–1 for -glucosidase and–0.18 to +0.03 mol h^–1 for glucoseincorporation. Net fluxes were generally negative in sign indicating thetransfer of phyto- and bacterioplankton, as well as potential capacities for thedegradation and recycling of organic matter, from the outer estuarinecompartment to the sea.     

Fluctuating deposition of ocean water drives plant function on coastal sand dunes

Sea‐level rise will alter the hydrology of terrestrial coastal ecosystems. As such, it becomes increasingly important to decipher the present role of ocean water in coastal ecosystems in order to assess the coming effects of sea‐level rise scenarios. Sand dunes occur at the interface of land and sea. Traditionally, they are conceived as freshwater environments with rain and ground water as the only water sources available to vegetation. This study investigates the possibility of ocean water influx to dune soils and its effect on the physiology of sand dune vegetation. Stable isotopes are used to trace the path of ocean water from the soil to the vegetation. Soil salinity, water content and δ¹⁸O values are measured concurrently with stem water and leaf tissue of eight species during the wet and dry season and from areas proximal and distal to the ocean. Our results indicate the dune ecosystem is a mixed freshwater and marine water system characterized by oceanic influence on dune hydrology that is spatially heterogeneous and fluctuates temporally. Ocean water influx to soil occurs via salt spray in areas 5–12 m from the ocean during dry season. Accordingly, vegetation nearest to the sea demonstrate a plastic response to ocean water deposition including elevated integrated water use efficiency (δ¹³C_leaf) and uptake of ocean water that comprised up to 52% of xylem water. We suggest physiological plasticity in response to periodic ocean water influx may be a functional characteristic common to species on the leading edge of diverse coastal habitats and an important feature that should be included in modeling coastal ecosystems. Rising sea level would likely cause a repercussive landward shift of dune species in response to encroaching maritime influences. However, human development would restrict this process, potentially causing the demise of dune systems and the protection from land erosion they provide.     

Influence of the bacterioplankton community of a tropical eutrophic lagoon on the bacterial community of its neighbouring ocean

The Rodrigo de Freitas lagoon (RFL) is a tropical eutrophic coastal ecosystem located in the urban area of Rio de Janeiro, Brazil. This environment consists of freshwater but has communication with the ocean through a channel (Jardim de Alah’s Channel). The aim of this study was to evaluate the influence of lagoon water on the nearby ocean using molecular and traditional microbiological methods. We hypothesised that due to the eutrophic low-salinity environment, the bacterioplankton community from the RFL would have a native “brackish” composition influenced by both freshwater and marine phylotypes, and that bacterial phylotypes of this community would be detected in oceanic samples closer to the channel between the lagoon and the ocean. The cultivation and microscopy experiments clearly showed this influence. Bacterial cell counts revealed that the greater amounts of bacterial cells present in the lagoon increased the observed values seen at oceanic stations near the channel. The Denaturing gradient gel eletrophoresis community profiles also showed a clear influence of Rodrigo de Freitas lagoon waters on the adjacent beaches. The band patterns found for the stations near the channel showed that these communities were mixtures of the communities of the lagoon and sea, and as the distance from the channel increased, the samples became more similar to ocean bacterial communities. A 16S rRNA gene clone library was constructed using a sample acquired from the connection point between the lagoon and the ocean. Around 52% of the sequences in the library showed similarity to the genus Proteobacteria (1% Alpha, 21% Beta, 19% Gamma and 29% unclassified Proteobacteria), and the second most abundant genus was Bacteroidetes, with 15% of the total clones. The results showed that the structure of the bacterial community had both freshwater and marine characteristics.     

Activity and Phylogenetic Diversity of Bacterial Cells with High and Low Nucleic Acid Content and Electron Transport System Activity in an Upwelling Ecosystem

We evaluated whether bacteria with higher cell-specific nucleic acid content (HNA) or an active electron transport system, i.e., positive for reduction of 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), were responsible for the bulk of bacterioplankton metabolic activity. We also examined whether the phylogenetic diversity of HNA and CTC-positive cells differed from the diversity of Bacteria with low nucleic acid content (LNA). Bacterial assemblages were sampled both in eutrophic shelf waters and in mesotrophic offshore waters in the Oregon coastal upwelling region. Cytometrically sorted HNA, LNA, and CTC-positive cells were assayed for their cell-specific [³H]leucine incorporation rates. Phylogenetic diversity in sorted non-radioactively labeled samples was assayed using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes. Cell-specific rates of leucine incorporation of HNA and CTC-positive cells were on average only slightly greater than the cell-specific rates of LNA cells. HNA cells accounted for most bacterioplankton substrate incorporation due to high abundances, while the low abundances of CTC-positive cells resulted in only a small contribution by these cells to total bacterial activity. The proportion of the total bacterial leucine incorporation attributable to LNA cells was higher in offshore regions than in shelf waters. Sequence data obtained from DGGE bands showed broadly similar phylogenetic diversity across HNA, LNA, and CTC-positive cells, with between-sample and between-region variability in the distribution of phylotypes. Our results suggest that LNA bacteria are not substantially different from HNA bacteria in either cell-specific rates of substrate incorporation or phylogenetic composition and that they can be significant contributors to bacterial metabolism in the sea.     

需钠弧菌(Vibrio natriegens)合成聚羟基丁酸的研究

研究结果表明,V.natriegens可以利用葡萄糖,果糖,以及糖蜜为碳源合成聚羟基丁酸[Poly(3HB)] ,当以糖蜜为碳源时,积累的Poly(3HB)达到细胞干重的28．4％,实验结果还表明,Poly(3HB)的积累滞后于细胞生长,在培养前加入过量的碳源,不仅没有Poly(3HB)积累,还抑制细胞的生长,测定了与Poly(3HB)合成相关的PHA聚合酶,β-酮硫解酶和乙酰乙酰CoA还原酶的活性。结果表明,伴随Poly(3HB)合成,PHA聚合酶活性从无到有,β－酮硫解酶活性提高了10倍以上。进一步通过利用脂肪酸合成代谢抑制物－浅蓝菌素（cerulenin),研究了脂肪酸从头合成途径与Poly(3HB)合成途径的关系。发现浅蓝菌素能够明显降低细胞Poly(3HB)的累积。根据以上结果,推测在V.natrigens中可能存在两条代谢途径参与Poly(3HB)的合成。     

Ecology and Physics of Bacterial Chemotaxis in the Ocean

Summary: Intuitively, it may seem that from the perspective of an individual bacterium the ocean is a vast, dilute, and largely homogeneous environment. Microbial oceanographers have typically considered the ocean from this point of view. In reality, marine bacteria inhabit a chemical seascape that is highly heterogeneous down to the microscale, owing to ubiquitous nutrient patches, plumes, and gradients. Exudation and excretion of dissolved matter by larger organisms, lysis events, particles, animal surfaces, and fluxes from the sediment-water interface all contribute to create strong and pervasive heterogeneity, where chemotaxis may provide a significant fitness advantage to bacteria. The dynamic nature of the ocean imposes strong selective pressures on bacterial foraging strategies, and many marine bacteria indeed display adaptations that characterize their chemotactic motility as “high performance” compared to that of enteric model organisms. Fast swimming speeds, strongly directional responses, and effective turning and steering strategies ensure that marine bacteria can successfully use chemotaxis to very rapidly respond to chemical gradients in the ocean. These fast responses are advantageous in a broad range of ecological processes, including attaching to particles, exploiting particle plumes, retaining position close to phytoplankton cells, colonizing host animals, and hovering at a preferred height above the sediment-water interface. At larger scales, these responses can impact ocean biogeochemistry by increasing the rates of chemical transformation, influencing the flux of sinking material, and potentially altering the balance of biomass incorporation versus respiration. This review highlights the physical and ecological processes underpinning bacterial motility and chemotaxis in the ocean, describes the current state of knowledge of chemotaxis in marine bacteria, and summarizes our understanding of how these microscale dynamics scale up to affect ecosystem-scale processes in the sea.     

海水富营养化对海洋细菌影响的研究进展

综述了海水富营养化对海洋细菌影响的研究进展。随着海水富营养化程度的增加,海洋细菌数量或生物量增加;反硝化细菌、大肠菌群尤其是厌氧性的硫酸盐还原菌和产甲烷菌等典型细菌生理群数量增加;浮游细菌群落结构随富营养化递增趋于简单,物种多样性降低;富营养化也明显导致细菌群落正常功能活性的紊乱。海水富营养化对细菌群落的结构和功能有着深远的影响。     

Comparison of Bacterioneuston and Bacterioplankton Dynamics during a Phytoplankton Bloom in a Fjord Mesocosm

The bacterioneuston is the community of Bacteria present in surface microlayers, the thin surface film that forms the interface between aquatic environments and the atmosphere. In this study we compared bacterial cell abundances and bacterial community structures of the bacterioneuston and the bacterioplankton (from the subsurface water column) during a phytoplankton bloom mesocosm experiment. Bacterial cell abundance, determined by flow cytometry, followed a typical bacterioplankton response to a phytoplankton bloom, with Synechococcus and high-nucleic acid content (HNA) bacterial cell numbers initially falling, probably due to selective protist grazing. Subsequently HNA and low-nucleic acid content bacterial cells increased in abundance, but Synechococcus cells did not. There was no significant difference between bacterioneuston and bacterioplankton cell abundances during the experiment. Conversely, distinct and consistent differences between the bacterioneuston and the bacterioplankton community structures were observed. This was monitored simultaneously by Bacteria 16S rRNA gene terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis. The conserved patterns of community structure observed in all of the mesocosms indicate that the bacterioneuston is distinctive and nonrandom.Determining and understanding both spatial and temporal patterns in bacterioplankton community structure are a core aim of marine microbial ecology (15). Distributions of bacterioplankton over space and time can be correlated to environmental parameters, and subsequent links can therefore be made to ecosystem function. A broad range of spatial studies made on macro- (34), meso- (20), and microscales (27) have shown clear patterns in distribution of the bacterioplankton.The sea surface microlayer is part of the air-sea interface and is generally considered to be the top 1 mm or less of the ocean (26). Surface microlayers have a fundamental role in regulating transport processes between the ocean and the atmosphere (26) and are often referred to as the neuston (28, 31). For more than 25 years it has been hypothesized that the sea surface microlayer is a hydrated gelatinous layer (40) that contains surface-active organic compounds such as carbohydrates, proteins, lipids, and humic substances in relatively high concentrations (17, 45, 48). Recently, gel-like transparent expolymer particles (TEP) have been shown to be enriched in the surface microlayer, supporting the concept of a gelatinous interfacial layer (46).Bacteria present in surface microlayers or the neuston are regarded as the bacterioneuston. There are relatively few studies which have directly compared the community structure of the bacterioneuston with that of the cognate subsurface (bacterioplankton) in the marine environment. Analysis of Bacteria 16S rRNA gene clone libraries constructed using DNA isolated from surface microlayer and subsurface water (<1 m) samples from the North Sea revealed that the bacterioneuston was dominated by two operational taxonomic units which accounted for 81% of clones analyzed (13). Community structure profiling using denaturing gradient gel electrophoresis (DGGE) of the bacterioneuston at three sites around Oahu Island in the Pacific Ocean showed that the bacterioneuston forms consistent and distinct community structures. Conversely, the archaeal community structure of the same samples using Archaea 16S rRNA gene DGGE analysis did not show the same surface microlayer-specific response, indicating that bacteria and archaea respond to their environment in fundamentally different ways in the neuston (7).Other studies have, however, reported no consistent differences between the bacterioneuston and the bacterioplankton. Samples collected from two separate sites in the Mediterranean Sea were analyzed using single-strand conformation polymorphism of Bacteria 16S rRNA genes (1). The authors did not report any significant differences between the surface microlayer and subsurface samples using this community profiling method.Nonmarine studies of the bacterioneuston and Archaea communities in estuarine (10) and freshwater (5, 19) environments have also shown distinct microbial community structures present in the surface microlayer compared to those in subsurface water ≤1 m below.Recurring phytoplankton blooms are a key feature of coastal waters and strongly influence bacterioplankton community structure and succession (4, 14, 38). Phytoplankton blooms stimulate the bacterioplankton by the release of dissolved organic matter (22) or affect bacterioplankton negatively by direct competition for resources (6). Bacterioplankton community structure may also be influenced by grazing flagellates or viral lysis (47).Mesocosm experiments have been used to study plankton ecology for many decades (33). Mesocosms facilitate study of the effects of key environmental parameters, such as temperature, on plankton communities and allow the succession of natural plankton communities that resemble those found in the marine environment (11). The enclosed water mass means that experiments can be designed which manipulate physicochemical parameters to observe biological effects. Furthermore, with replicated mesocosms, the data collected can be analyzed with statistics rigorously. In this study we monitored the dynamics of the bacterioneuston and the bacterioplankton in mesocosms of fjord surface water during an artificially induced phytoplankton bloom and compared bacterial abundances and bacterial community structures in the surface microlayer and subsurface water.     

Geochemical cycling of heavy metals in a marine coastal area: benthic flux determination from pore water profiles and in situ measurements using benthic chambers

Concentrations of the heavy metals Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured in sea water, suspended matter, sediments and pore water samples collected in a coastal area of the middle Tyrrhenian Sea. Concentration factors between pore water (extracted from the first centimeter of the sediments) and the overlying sea water (taken 30 cm above the sea bed) were less than 1 for Cr, Cu and Pb, 1–10 for Cd and Ni, 10–100 for Fe and Co, 100–1000 for Mn, and 1–100 for Zn.The benthic fluxes of heavy metals at the sediment-water interface were measured directly using in situ benthic chambers and calculated using Fick's first law during two experimental periods, one in 1986 and the other in 1988. The fluxes of Cu, Ni, Pb and Zn varied significantly over time; this appeared to be related to their relatively low ( 10) concentration factors. From the benthic chamber experiments, metals with positive fluxes were in the order: Mn > Fe > Co > Cd, while those with negative fluxes were: Zn > Pb > Ni Cu. Fluxes calculated using Fick's Law were: positive – Mn > Fe > Zn (or Zn > Fe) > Ni > Co > Cd, negative fluxes Pb > Cu > Cr.Measured (benthic chamber) and calculated (Fick's first law) fluxes for Co, Cd, Mn, Pb and Fe were comparable within an order of magnitude, although less agreement was found for Cu, Ni and Zn. Removal of Ni and Zn at the sediment-water interface has been proposed to explain the fact that the measured and calculated fluxes have opposite directions for these metals.     

Abundance and community composition of bacterioplankton in the Northern South China Sea during winter: geographic position and water layer influences

The abundance and composition of bacterioplankton of the Northern South China Sea (NSCS) were investigated using flow cytometry and high-throughput sequencing. The results showed that the absolute abundance of bacterioplankton retained high values in surface waters at both continental shelf and oceanic sites and Proteobacteria, Cyanobacteria, and Bacteroidetes represented the three typical dominant phyla in NSCS. The average bacterioplankton abundances at 5 m, 75 m, and 200 m were 9.55, 5.04, and 1.32?×?10⁵ cells mL^?1, respectively, and there was a significantly positive correlation between bacterioplankton abundance and Chl a content (r?=?0.84, p?<?0.01). Drastic changes of the bacterioplankton community occurred in different water layers. Three operational taxonomic units (OTUs), whose distribution were significantly different between 5-m and 75-m water layers, all belonged to Flavobacteriales of the Bacteroidetes (p?<?0.05). In addition, bacterioplankton community richness and diversity at the continental shelf (CS) was generally higher than at oceanic stations (SB and KI). Five OTUs, which favored the habitat of continental shelf, belonged to Alphaproteobacteria including the orders of the SAR11 cluster, Rhodospirillales, Rhodobacterales and other unclassified orders (p?<?0.05). Two OTUs, which favored the habitat of oceanic stations, were assigned to the orders of Flavobacteriales and Alteromonadales. Furthermore, the abundances of two OTUs belonging to the Cyanobacteria phylum and Verrucomicrobiales order were significantly different between the sea basin (SB) and Kuroshio influenced area (KI) stations (p?<?0.05).     

Between estuaries and the sea

Dissolved and particulate materials and living organisms are exchanged between estuaries and the sea. Net material fluxes, import or export, appear to depend on physical and biological processes within both estuarine and coastal ecosystems. In temperate zone lagoonal systems, the marsh-estuarine continuum hypothesis can provide a reasonable synthetic explanation of transport based on the level of ecosystem maturity within the system. The relative importance of riverine and lagoonal material exchanges with the coastal ocean are at present entirely speculative and make the estimation of the regional influences of material transports between estuaries and the coastal ocean uncertain. Organismic exchanges depend on both passive and active behavior mechanisms and are species specific. Few quantitative estimates of organismic fluxes exist and the role of non-commercial invertebrates and fish in these fluxes are unknown.     

Chemical Constituents of a Heat-dried Chinese Mushroom,Hohenbuehelia serotina

Several compounds were isolated from a Chinese mushroom, Huangmo, the heat-dried fruiting body of Hohenbuehelia serotina. They were identified as linoleic acid (I), hexadecanoic acid (II), β-sitosterol (IV), benzoic acid (V), D-mannitol (VI), sucrose (VII), and L-rhamnose (VIII). In addition, six acidic substances were identified. (Table I). Also, ethyl linoleate, hexadecanoic acid, and 9,12-octadecadienoic acid (Z-Z) ethyl esters, IV, V, and VI were identified for the first time from this mushroom.     

Flow cytometry assessment of bacterioplankton in tropical marine environments

Flow cytometry was used to characterize bacterioplankton from two tropical environments in Brazil: the eutrophic Guanabara Bay and the oligotrophic southwest Atlantic Ocean. Bacterial abundance was evaluated by flow cytometry, and cells were stained with SYTO 13, allowing demonstration of differences in nucleic acid content. Bacterial production was also evaluated by means of 3H-leucine incorporation. Bacterial numbers were different for both sites. In Atlantic Ocean samples, we found a maximum of 5.50 x 10(5) cells ml(-1), and low nucleic acid content organisms predominated. In Guanabara Bay, bacterial numbers were one order of magnitude higher than in the ocean, and they varied from outer bay (1.01 x 10(6) cells ml(-1)) to inner bay (6.90 x 10(6) cells ml(-1)). Bacterial activity in ocean samples varied from 4.6 to 126 ng C l(-1) h(-1), while in the bay, mean values ranged from 1.95 microg C l(-1) h(-1) (outer bay) to 7.35 microg C l(-1) h(-1) (inner bay). Values found for both parameters are characteristic of different trophic situations. These results illustrate the utility of cytometric analyses of bacterioplankton populations in characterizing their large spatial and temporal scales of distribution in aquatic ecosystems.