Posts Tagged 'prokaryotes'

Elevated pCO2 alters marine heterotrophic bacterial community composition and metabolic potential in response to a pulse of phytoplankton organic matter

Factors that affect the respiration of organic carbon by marine bacteria can alter the extent to which the oceans act as a sink of atmospheric carbon dioxide. We designed seawater dilution experiments to assess the effect of pCO2 enrichment on heterotrophic bacterial community composition and metabolic potential in response to a pulse of phytoplankton‐derived organic carbon. Experiments included treatments of elevated (1000 ppm) and low (250 ppm) pCO2, amended with 10 μmol L‐1 dissolved organic carbon from Emiliana huxleyi lysates, and were conducted using surface‐seawater collected from the South Pacific Subtropical Gyre. To assess differences in community composition and metabolic potential, shotgun metagenomic libraries were sequenced from low and elevated pCO2 treatments collected at the start of the experiment and following exponential growth. Our results indicate bacterial communities changed markedly in response to the organic matter pulse over time and was significantly affected by pCO2 enrichment. Elevated pCO2 also had disproportionate effects on the abundance of sequences related to proton pumps, carbohydrate metabolism, modifications of the phospholipid bilayer, resistance to toxic compounds and conjugative transfer. These results contribute to a growing understanding of the effects of elevated pCO2 on bacteria‐mediated carbon cycling during phytoplankton bloom conditions in the marine environment.

Continue reading ‘Elevated pCO2 alters marine heterotrophic bacterial community composition and metabolic potential in response to a pulse of phytoplankton organic matter’

Effects of elevated carbon dioxide on environmental microbes and its mechanisms: a review

Highlights

• Elevated CO2 shifts the community structure and lower the microbial diversity.
• CO2 leakage severely inhibits microbial growth.
• High CO2 levels destroy the cell structure of microbes.
• The microbial metabolism can be affected by CO2.
• Underlying mechanisms are summarized at the molecular and cellular levels.

Abstract

Before the industrial revolution, the atmospheric CO2 concentration was 180–330 ppm; however, fossil-fuel combustion and forest destruction have led to increased atmospheric CO2 concentration. CO2 capture and storage is regarded as a promising strategy to prevent global warming and ocean acidification and to alleviate elevated atmospheric CO2 concentration, but the leakage of CO2 from storage system can lead to rapid acidification of the surrounding circumstance, which might cause negative influence on environmental microbes. The effects of elevated CO2 on microbes have been reported extensively, but the review regarding CO2 affecting different environmental microorganisms has never been done previously. Also, the mechanisms of CO2 affecting environmental microorganisms are usually contributed to the change of pH values, while the direct influences of CO2 on microorganisms were often neglected. This paper aimed to provide a systematic review of elevated CO2 affecting environmental microbes and its mechanisms. Firstly, the influences of elevated CO2 and potential leakage of CO2 from storage sites on community structures and diversity of different surrounding environmental microbes were assessed and compared. Secondly, the adverse impacts of CO2 on microbial growth, cell morphology and membranes, bacterial spores, and microbial metabolism were introduced. Then, based on biochemical principles and knowledge of microbiology and molecular biology, the fundamental mechanisms of the influences of carbon dioxide on environmental microbes were discussed from the aspects of enzyme activity, electron generation and transfer, and key gene and protein expressions. Finally, key questions relevant to the environmental effect of CO2 that need to be answered in the future were addressed.

Continue reading ‘Effects of elevated carbon dioxide on environmental microbes and its mechanisms: a review’

Impacts of elevated pCO2 on estuarine phytoplankton biomass and community structure in two biogeochemically distinct systems in Louisiana, USA

Highlights

• Initial phytoplankton composition impacts community response to elevated pCO2.
• Elevated pCO2 decreased phytoplankton biomass.
• Phytoplankton nutritional value decreased at elevated pCO2.
• Several trace metal elements increased at elevated pCO2.

Abstract

Ocean acidification has the potential to impact the ocean’s biogeochemical cycles and food web dynamics, with phytoplankton in the distinctive position to profoundly influence both, as individual phytoplankton species play unique roles in energy flow and element cycling. Previous studies have focused on short-term exposure of monocultures to low pH, but do not reflect the competitive dynamics within natural phytoplankton communities. This study explores the use of experimental microcosms to expose phytoplankton assemblages to elevated pCO2 for an extended period of time. Phytoplankton communities were collected from two biogeochemically distinct Louisiana estuaries, Caillou Lake (CL) and Barataria Bay (BB), and cultured in lab for 16 weeks while bubbling CO2 enriched air corresponding to current (400 ppm) and future (1000 ppm) pCO2 levels. Results suggest that elevated pCO2 does not implicitly catalyze an increase in phytoplankton biomass (chlorophyll a). While pigment data showcased a parabolic trend and microscopic observations revealed a loss in species diversity within each major taxonomic class. By the end of the 16-week incubation, 10 out of the 12 cultures had a community structure analogous to that of the startup phytoplankton assemblage collected from the field. Natural phytoplankton assemblages exposed to elevated pCO2 experienced multiple transitional states over the course of a 16-week incubation, indicating that there is no deterministic successional pathway dictated by coastal acidification but community adaptation was observed.

Continue reading ‘Impacts of elevated pCO2 on estuarine phytoplankton biomass and community structure in two biogeochemically distinct systems in Louisiana, USA’

Effects of elevated CO2 and phytoplankton-derived organic matter on the metabolism of bacterial communities from coastal waters (update)

Microcosm experiments to assess the bacterioplankton’s response to phytoplankton-derived organic matter obtained under current and future ocean CO2 levels were performed. Surface seawater enriched with inorganic nutrients was bubbled for 8 days with air (current CO2 scenario) or with a 1000ppm CO2 air mixture (future CO2 scenario) under solar radiation. The organic matter produced under the current and future CO2 scenarios was subsequently used as an inoculum. Triplicate 12L flasks filled with 1.2µm of filtered natural seawater enriched with the organic matter inocula were incubated in the dark for 8 days under CO2 conditions simulating current and future CO2 scenarios, to study the bacterial response. The acidification of the media increased bacterial respiration at the beginning of the experiment, while the addition of the organic matter produced under future levels of CO2 was related to changes in bacterial production and abundance. This resulted in a 67% increase in the integrated bacterial respiration under future CO2 conditions compared to present CO2 conditions and 41% higher integrated bacterial abundance with the addition of the acidified organic matter compared to samples with the addition of non acidified organic matter. This study demonstrates that the increase in atmospheric CO2 levels can impact bacterioplankton metabolism directly, by changes in the respiration rate, and indirectly, by changes on the organic matter, which affected bacterial production and abundance.

Continue reading ‘Effects of elevated CO2 and phytoplankton-derived organic matter on the metabolism of bacterial communities from coastal waters (update)’

CO2 modulation of the rates of photosynthesis and light-dependent O2 consumption in Trichodesmium

We established the relationship between gross photosynthetic O2 evolution and light-dependent O2 consumption in Trichodesmium erythraeum IMS101 acclimated to three targeted pCO2 concentrations (180 µmol mol-1 = low-CO2, 380 µmol mol-1 = mid-CO2 and 720 µmol mol-1 = high-CO2). We found that biomass (carbon) specific, light-saturated maximum net O2 evolution rates (PnC,max) and acclimated growth rates increased from low- to mid-CO2, but did not differ significantly between mid- and high-CO2. Dark respiration rates were five-times higher than required to maintain cellular metabolism, suggesting that respiration provides a substantial proportion of the ATP and reductant for N2 fixation. Oxygen uptake increased linearly with gross O2 evolution across light intensities ranging from darkness to 1100 µmol photons m-2 s-1. The slope of this relationship decreased with increasing CO2, which we attribute to the increased energetic cost of operating the carbon concentrating mechanism (CCM) at lower CO2 concentrations. Our results indicate that net photosynthesis and growth of T. erythraeum IMS101 would have been severely CO2 limited at the last glacial maximum, but that the direct effect of future increases of CO2 may only cause marginal increases in growth.

Continue reading ‘CO2 modulation of the rates of photosynthesis and light-dependent O2 consumption in Trichodesmium’

Spatio-temporal influence of physicochemical parameters on phytoplankton assemblage in coastal brackish lagoon: Gomishan Lagoon, Caspian Sea, Iran

The objective of this study was to determine the spatiotemporal distribution pattern of phytoplankton assemblage due to physico-chemical heterogeneity in coastal brackish lagoon of Gomishan. An inter-annual cycle of sampling period (April 2014-March 2015) and spatially stratified random sampling were established to examine 24 spatiotemporal scenarios. Water samples were preserved in 1 and 0.5 liter dark Polythene bottles from each station for assessing plankton community and chlorophyll a, respectively. The applied multivariate approach including hierarchical cluster analysis for (dis)similarity test of environmental factors, principle component analysis (PCA) and canonical correspondence analysis (CCA) was used to illustrate the pattern of phytoplankton variability in relation to environmental characteristics. The results showed that mean salinity, temperature, pH, total nitrogen, phosphorus, silica, turbidity, and electrical conductivity (EC) were 22.8±5.9 (ppt), 23.4° C, 8.18, 2.49 (mg.l-1), 0.258 (mg.l-1), 3.39 (mg.l-1), 42.12 (NTU), and 3.78 (dS/m3), respectively. Scenarios S5AT, S5W, S6W, S6AT were distinguished from other scenarios with more than 90% similarity, subsequently S1SU and S5SU with about 80% similarity. Inter-annual mean density of total phytoplankton (cell.l-1) was 2.45×106, whereas in northern sector it was constant with only a peak in June, but in southern sector it was more tolerant, so in April it tended to increase with a peak (7.2×106) in July which was the maximum density over the year. The phytoplankton assemblage of the lagoon comprised 47 species from 5 different classes including Bacillariophyta, Pyrrophyta, Chlorophyta, Cyanophyta, and Euglenophyta.

Continue reading ‘Spatio-temporal influence of physicochemical parameters on phytoplankton assemblage in coastal brackish lagoon: Gomishan Lagoon, Caspian Sea, Iran’

Elevated CO2 has little influence on the bacterial communities associated with the pH-tolerant coral, massive Porites spp.

Ocean acidification (OA) as a result of increased anthropogenic CO2 input into the atmosphere carries consequences for all ocean life. Low pH can cause a shift in coral-associated microbial communities of pCO2-sensitive corals, however, it remains unknown whether the microbial community is also influenced in corals known to be more tolerant to high pCO2/low pH. This study profiles the bacterial communities associated with the tissues of the pCO2-tolerant coral, massive Porites spp., from two natural CO2 seep sites in Papua New Guinea. Amplicon sequencing of the hypervariable V3-V4 regions of the 16S rRNA gene revealed that microbial communities remained stable across CO2 seep sites (pH = 7.44–7.85) and adjacent control sites (ambient pH = 8.0–8.1). Microbial communities were more significantly influenced by reef location than pH, with the relative abundance of dominant microbial taxa differing between reefs. These results directly contrast with previous findings that increased CO2 has a strong effect on structuring microbial communities. The stable structure of microbial communities associated with the tissues of massive Porites spp. under high pCO2/low pH conditions confirms a high degree of tolerance by the whole Porites holobiont to OA, and suggest that pH tolerant corals such as Porites may dominate reef assemblages in an increasingly acidic ocean.

Continue reading ‘Elevated CO2 has little influence on the bacterial communities associated with the pH-tolerant coral, massive Porites spp.’


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