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.

Influence of allochthonous organic matter on bacterioplankton biomass and activity in a eutrophic, sub-tropical estuary

Heterotrophic bacterial and phytoplankton biomass, production, specific growth rates, and growth efficiencies were studied in the Northern region of the Cananeia-Iguape estuarine system, which has recently experienced an intense eutrophication due to anthropogenic causes. Two surveys were carried out during spring and neap tide periods of the dry season of 2005 and the rainy season of 2006. This region receives large freshwater inputs with organic seston and phosphate concentrations that reach as high as 1.0 mg l(-1) and 20.0 mu M, respectively. Strong decreasing gradients of seston and dissolved inorganic nutrients were observed from the river/estuary boundary to the estuary/coastal interface. Gradients were also observed in phytoplankton and bacterial production rates. The production rates of phytoplankton were 5.6-fold higher (mean 8.5 mu g Cl(-1) h(-1)) during the dry season. Primary production rates (PP) positively correlated with salinity and euphoric depth, indicating that phytoplankton productivity was light-limited. On the other hand, bacterial biomass (BB) and production rates (BP) were 1.9- and 3.7-fold higher, respectively, during the rainy season, with mean values of up to 40.4 mu g Cl(-1) and 7.9 mu g Cl(-1) h-1, respectively. Despite such a high BP, bacterial abundance remained <2 x 106 cells ml(-1), indicating that bacterial production and removal were coupled. Mean specific growth rates ranged between 0.9 and 5.5 d(-1). BP was inversely correlated with salinity and positively correlated with temperature, organic matter, exopolymer particles, and particulate-attached bacteria; this last accounted for as much as 89.6% of the total abundance. During the rainy season, BP was generally much higher than PP, and values of BP/PP > 20 were registered during high freshwater input, suggesting that under these conditions, bacterial activity was predominantly supported by allochthonous inputs of organic carbon. In addition, BB probably represented the main pathway for the synthesis of high-quality (low C:N) biomass that may have been available to the heterotrophic components of the plankton food web, particularly nanoheterotrophs. (C) 2008 Elsevier Ltd. All rights reserved.

Abundance and biomass of bacterioplankton in waters of the Kara Sea and the Ob and Yenisey Rivers

Bacterial cell number in the water column of the Kara Sea and estuary areas of the Ob and Yenisey Rivers was determined in water samples collected at 32 stations at depths from the surface to 200 m. The samples were analyzed by direct microscopy. In most parts of the sea microorganism concentrations ranged generally from 103 to 104 cells per ml and their biomasses from milligrams to tens of mg/m**3. Bacterioplankton concentration of river waters was much higher than in the open sea, especially in Ob waters. The highest bacteria concentrations, hundreds of thousands cells per ml with biomass exceeding 200 mg/m**3, were found in the southern part of the Ob section. Minimal concentrations were observed in the northeastern part and near the southeastern part of the Ob section and the southeastern coast of Novaya Zemlya. Dark CO2 fixation rates determined at some stations indicated low bacteria biomass production.

Bacterioplankton and bacteriobenthos in surface layer waters and sediments between the Sakhalin Island and the Eastern Asia in June 2006

This work presents results of a study of plankton and benthic microbiocenoses of the Amur River estuary. It is shown that distribution of total abundance and indicator groups of bacteriobenthos are characterized by stronger heterogeneity compared with bacterioplankton and that it depends on the Amur River runoff and bottom type. The river runoff helps by increasing overall bacterioplankton abundance in the near-mouth part of the estuary. Microorganisms utilizing low concentrations of organic matter (OM) play major role in processes of OM utilization in water and bottom sediments. Saprophytic bacteria play a significant role in OM utilization only in water at certain sampling sites in the Tatarsky Strait and Sakhalin Bay and in bottom sediments sampled in the mouth part of the estuary. Some parts of the estuary subjected to organic contamination are found according to microbiological characteristics. It is shown that fluctuation of salinity leads to change of the role of bacteria with different food demands in the microbial community.

Composition of bacterioplankton in the North Atlantic subtropical gyre

Subtropical oceanic gyres are the most extensive biomes on Earth where SAR11 and Prochlorococcus bacterioplankton numerically dominate the surface waters depleted in inorganic macronutrients as well as in dissolved organic matter. In such nutrient poor conditions bacterioplankton could become photoheterotrophic. We assessed the photoheterotrophy of the key microbial taxa in the North Atlantic oligotrophic gyre and adjacent regions. The experimental work was performed on board the Royal Research Ship James Cook (cruise no. JC53, October-November 2010) as part of the Atlantic Meridional Transect programme, and on board the Royal Research Ship Discovery (cruise no. D369, August-September 2011). At each station, samples were collected from 20m depth with a sampling rosette of 20-l Niskin bottles mounted on aconductivity-temperature-depth profiler. Samples were collected in 1 l thermos flasks (washed with10% v/v HCl) in the dark and processed immediately. Depth of 20m was chosen because it represents the mixed layer and it was the shallowest depth unaffected by the ship's movement, including thrusting, that could artificially affect microbial metabolism in nutrient-depleted stratified surfacewaters. Molecular identification of flow-sorted cells CARD-FISH was performed on flow-sorted cells to identify the groups for which uptake rates were measured. High nucleic acid-containing bacteria, based on SYBR Green DNA staining, that had virtually undetectable chlorophyll autofluorescence, were phylogenetically affiliated with Prochlorococcus,in agreement with our previously reported results (Zubkov et al., 2007; doi:10.1111/j.1462-2920.2007.01324.x).