prokaryotes Archives - Page 6 of 26

Posts Tagged 'prokaryotes'

Sponge organic matter recycling: reduced detritus production under extreme environmental conditions

Published 14 April 2023 Science Closed
Tags: abundance, biogeochemistry, biological response, BRcommunity, chemistry, field, multiple factors, otherprocess, oxygen, photosynthesis, physiology, phytoplankton, porifera, primary production, prokaryotes, respiration, South Pacific, temperature

Highlights

Sponge metabolism was measured at the natural laboratory of Bouraké where sponges are naturally exposed to extreme conditions associated with tidal phase.
The photosymbiotic HMA sponge Rhabdastrella globostellata was able to cope with extreme acidification and deoxygenation seawater.
Photosynthetic activity of sponge symbionts was negatively affected during extreme environmental conditions.
The sponge loop pathway was disrupted during low tide, which correlated with extreme acidification, deoxygenation and warming seawater.

Abstract

Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions. During two years (2018 and 2020), we measured the organic carbon, nutrient recycling, and photosynthetic activity of the massive HMA, photosymbiotic sponge Rhabdastrella globostellata at the natural laboratory of Bouraké in New Caledonia, where the physical and chemical composition of seawater regularly change according to the tide. We found that while sponges experienced acidification and low dissolved oxygen at low tide in both sampling years, a change in organic carbon recycling whereby sponges stopped producing detritus (i.e., the sponge loop) was only found when sponges also experienced higher temperature in 2020. Our findings provide new insights into how important trophic pathways may be affected by changing ocean conditions.

Continue reading ‘Sponge organic matter recycling: reduced detritus production under extreme environmental conditions’

Effect of ocean acidification on the growth, response and hydrocarbon degradation of coccolithophore-bacterial communities exposed to crude oil

Published 12 April 2023 Science Closed
Tags: abundance, biological response, BRcommunity, community composition, communityMF, laboratory, molecular biology, mortality, multiple factors, otherprocess, photosynthesis, phytoplankton, prokaryotes, toxicants

Hydrocarbon-degrading bacteria, which can be found living with eukaryotic phytoplankton, play a pivotal role in the fate of oil spillage to the marine environment. Considering the susceptibility of calcium carbonate-bearing phytoplankton under future ocean acidification conditions and their oil-degrading communities to oil exposure under such conditions, we investigated the response of non-axenic E. huxleyi to crude oil under ambient versus elevated CO₂ concentrations. Under elevated CO₂ conditions, exposure to crude oil resulted in the immediate decline of E. huxleyi, with concomitant shifts in the relative abundance of Alphaproteobacteria and Gammaproteobacteria. Survival of E. huxleyi under ambient conditions following oil enrichment was likely facilitated by enrichment of oil-degraders Methylobacterium and Sphingomonas, while the increase in relative abundance of Marinobacter and unclassified Gammaproteobacteria may have increased competitive pressure with E. huxleyi for micronutrient acquisition. Biodegradation of the oil was not affected by elevated CO₂ despite a shift in relative abundance of known and putative hydrocarbon degraders. While ocean acidification does not appear to affect microbial degradation of crude oil, elevated mortality responses of E. huxleyi and shifts in the bacterial community illustrates the complexity of microalgal-bacterial interactions and highlights the need to factor these into future ecosystem recovery projections.

Continue reading ‘Effect of ocean acidification on the growth, response and hydrocarbon degradation of coccolithophore-bacterial communities exposed to crude oil’

Acclimatization in a changing environment: linking larval and juvenile performance in the quahog Mercenaria mercenaria

Published 30 March 2023 Science Closed
Tags: biological response, community composition, field, growth, laboratory, molecular biology, mollusks, morphology, mortality, multiple factors, otherprocess, oxygen, physiology, prokaryotes, reproduction, temperature

Marine invertebrates in coastal communities are currently experiencing unprecedented, rapid environmental change. These symptoms of climate change and ocean acidification are projected to worsen faster than can be accommodated by evolutionary processes like adaptation via natural selection, necessitating investigations of alternative mechanisms that facilitate adaptive responses to environmental change. This dissertation posits that in the absence of adaptation, early development (larval) exposure to stressors can increase population tolerance by leveraging existing variation in the energy metabolism and host-microbial interactions. Focusing specifically on resiliency to acidification (low pH), hypoxia (low dissolved oxygen), and elevated temperature stress in the clam, Mercenaria mercenaria, this dissertation uses a combination of laboratory and field experiments in conjunction with next-generation sequencing and physiological assays to investigate the relationship between host health, microbial community structure, and environmental change.

Continue reading ‘Acclimatization in a changing environment: linking larval and juvenile performance in the quahog Mercenaria mercenaria’

Effects of acidification on nitrification and associated nitrous oxide emission in estuarine and coastal waters

Published 22 March 2023 Science Closed
Tags: biogeochemistry, biological response, chemistry, field, laboratory, molecular biology, North Pacific, physiology, prokaryotes

In the context of an increasing atmospheric carbon dioxide (CO₂) level, acidification of estuarine and coastal waters is greatly exacerbated by land-derived nutrient inputs, coastal upwelling, and complex biogeochemical processes. A deeper understanding of how nitrifiers respond to intensifying acidification is thus crucial to predict the response of estuarine and coastal ecosystems and their contribution to global climate change. Here, we show that acidification can significantly decrease nitrification rate but stimulate generation of byproduct nitrous oxide (N₂O) in estuarine and coastal waters. By varying CO₂ concentration and pH independently, an expected beneficial effect of elevated CO₂ on activity of nitrifiers (“CO₂-fertilization” effect) is excluded under acidification. Metatranscriptome data further demonstrate that nitrifiers could significantly up-regulate gene expressions associated with intracellular pH homeostasis to cope with acidification stress. This study highlights the molecular underpinnings of acidification effects on nitrification and associated greenhouse gas N₂O emission, and helps predict the response and evolution of estuarine and coastal ecosystems under climate change and human activities.

Continue reading ‘Effects of acidification on nitrification and associated nitrous oxide emission in estuarine and coastal waters’

Deciphering pH-dependent microbial taxa and functional gene co-occurrence in the coral Galaxea fascicularis

Published 27 February 2023 Science Closed
Tags: biological response, community composition, corals, laboratory, molecular biology, North Pacific, otherprocess, prokaryotes

How the coral microbiome responds to oceanic pH changes due to anthropogenic climate change, including ocean acidification and deliberate artificial alkalization, remains an open question. Here, we applied a 16S profile and GeoChip approach to microbial taxonomic and gene functional landscapes in the coral Galaxea fascicularis under three pH levels (7.85, 8.15, and 8.45) and tested the influence of pH changes on the cell growth of several coral-associated strains and bacterial populations. Statistical analysis of GeoChip-based data suggested that both ocean acidification and alkalization destabilized functional cores related to aromatic degradation, carbon degradation, carbon fixation, stress response, and antibiotic biosynthesis in the microbiome, which are related to holobiont carbon cycling and health. The taxonomic analysis revealed that bacterial species richness was not significantly different among the three pH treatments, but the community compositions were significantly distinct. Acute seawater alkalization leads to an increase in pathogens as well as a stronger taxonomic shift than acidification, which is worth considering when using artificial ocean alkalization to protect coral ecosystems from ocean acidification. In addition, our co-occurrence network analysis reflected microbial community and functional shifts in response to pH change cues, which will further help to understand the functional ecological role of the microbiome in coral resilience.

Continue reading ‘Deciphering pH-dependent microbial taxa and functional gene co-occurrence in the coral Galaxea fascicularis’

Responses of free-living planktonic bacterial communities to experimental acidification and warming

Published 20 February 2023 Science Closed
Tags: biological response, community composition, mesocosms, molecular biology, multiple factors, otherprocess, prokaryotes, temperature

Climate change driven by human activities encompasses the increase in atmospheric CO₂ concentration and sea-surface temperature. Little is known regarding the synergistic effects of these phenomena on bacterial communities in oligotrophic marine ecosystems that are expected to be particularly vulnerable. Here, we studied bacterial community composition changes based on 16S rRNA sequencing at two fractions (0.1–0.2 and >0.2 μm) during a 10- day fully factorial mesocosm experiment in the eastern Mediterranean where the pH decreased by ~0.3 units and temperature increased by ~3 °C to project possible future changes in surface waters. The bacterial community experienced significant taxonomic differences driven by the combined effect of time and treatment; a community shift one day after the manipulations was noticed, followed by a similar state between all mesocosms at the third day, and mild shifts later on, which were remarkable mainly under sole acidification. The abundance of Synechococcus increased in response to warming, while the SAR11 clade immediately benefited from the combined acidification and warming. The effect of the acidification itself had a more persistent impact on community composition. This study highlights the importance of studying climate change consequences on ecosystem functioning both separately and simultaneously, considering the ambient environmental parameters.

Continue reading ‘Responses of free-living planktonic bacterial communities to experimental acidification and warming’

Impact of ultraviolet radiation nearly overrides the effects of elevated pCO2 on a prominent nitrogen-fixing cyanobacterium

Published 17 January 2023 Science Closed
Tags: biological response, laboratory, light, morphology, multiple factors, photosynthesis, physiology, prokaryotes

Although the marine N₂-fixers Trichodesmium spp. are affected by increasing pCO₂ and by ultraviolet radiation (UVR) in their habitats, little is known on their potential responses to future ocean acidification in the presence of UVR. We grew Trichodesmium at two pCO₂ levels (410 and 1000 μatm) under natural sunlight, documented the filament length, growth, and chlorophyll content after its acclimation to the pCO₂ treatments, and measured its carbon and N₂ fixation rates under different solar radiation treatments with or without UVR. We showed that the elevated pCO₂ did not significantly alter the diazotroph’s growth, filament length, or pigment content, and its photosynthetic rate was only affected by solar radiation treatments rather than the pCO₂ levels. The presence of UV-A and UV-B inhibited photosynthesis by 10–22% and 17–21%, respectively. Inhibition of N₂ fixation by UV-B was proportional to its intensity, whereas UV-A stimulated N₂ fixation at low, but inhibited it at high, intensities. Elevated pCO₂ only stimulated N₂ fixation under moderate levels of solar radiation. The simulated depth profile of N₂ fixation in the water column showed that UV-induced inhibition dominated the combined effects of elevated pCO₂ and UVR at 0–30 m depth and the combination of these factors enhanced N₂ fixation at 30–60 m depth, but this effect diminished in deeper water. Our results suggest that Trichodesmium could be influenced more by UVR than by pCO₂ and their combined action result in negative effects on N₂ fixation under high solar radiation, but positive effects under low to moderate solar radiation.

Continue reading ‘Impact of ultraviolet radiation nearly overrides the effects of elevated pCO2 on a prominent nitrogen-fixing cyanobacterium’

Wild oyster population resistance to ocean acidification adversely affected by bacterial infection

Published 22 December 2022 Science Closed
Tags: biological response, laboratory, molecular biology, mollusks, multiple factors, North Pacific, pathogens, physiology, prokaryotes

The carbon dioxide induced ocean acidification (OA) process is well known to have profound effects on physiology, survival and immune responses in marine organisms, and particularly calcifiers including edible oysters. At the same time, some wild populations could develop a complex and sophisticated immune system to cope with multiple biotic and abiotic stresses, such as bacterial infections and OA, over the long period of coevolution with the environment. However, it is unclear how immunological responses and the underlying mechanisms are altered under the combined effect of OA and bacterial infection, especially in the ecologically and economically important edible oysters. Here, we collected the wild population of oyster species Crassostrea hongkongensis (the Hong Kong oyster) from their native estuarine area and carried out a bacterial challenge with the worldwide pervasive pathogen of human foodborne disease, Vibrio parahaemolyticus, to investigate the host immune responses and molecular mechanisms under the high-CO₂ and low pH-driven OA conditions. The wild population had a high immune resistance to OA, but the resistance is compromised under the combined effect of OA and bacterial infection both in vivo or in vitro. We classified all transcriptomic genes based on expression profiles and functional pathways and identified the specifically switched on and off genes and pathways under combined effect. These genes and pathways were mainly involved in multiple immunological processes including pathogen recognition, immune signal transduction and effectors. This work would help understand how the immunological function and mechanism response to bacterial infection in wild populations and predict the dynamic distribution of human health-related pathogens to reduce the risk of foodborne disease under the future climate change scenario.

Continue reading ‘Wild oyster population resistance to ocean acidification adversely affected by bacterial infection’

Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community (update)

Published 21 December 2022 Science Closed
Tags: abundance, biogeochemistry, biological response, chemistry, community composition, communitymodeling, field, laboratory, mesocosms, modeling, otherprocess, phytoplankton, prokaryotes, South Pacific

Ocean alkalinity enhancement (OAE) is a proposed method to counteract climate change by increasing the alkalinity of the surface ocean and thus the chemical storage capacity of seawater for atmospheric CO₂. The impact of OAE on marine ecosystems, including phytoplankton communities which make up the base of the marine food web, is largely unknown. To investigate the influence of OAE on phytoplankton communities, we enclosed a natural plankton community from coastal Tasmania for 22 d in nine microcosms during a spring bloom. Microcosms were split into three groups, (1) the unperturbed control, (2) the unequilibrated treatment where alkalinity was increased (+495 ± 5.2 µmol kg⁻¹) but seawater CO₂ was not in equilibrium with atmospheric CO₂, and (3) the equilibrated treatment where alkalinity was increased (+500 ± 3.2 µmol kg⁻¹) and seawater CO₂ was in equilibrium with atmospheric CO₂. Both treatments have the capacity to increase the inorganic carbon sink of seawater by 21 %. We found that simulated OAE had significant but generally moderate effects on various groups in the phytoplankton community and on heterotrophic bacteria. More pronounced effects were observed for the diatom community where silicic acid drawdown and biogenic silica build-up were reduced at increased alkalinity. Observed changes in phytoplankton communities affected the temporal trends of key biogeochemical parameters such as the organic matter carbon-to-nitrogen ratio. Interestingly, the unequilibrated treatment did not have a noticeably larger impact on the phytoplankton (and heterotrophic bacteria) community than the equilibrated treatment, even though the changes in carbonate chemistry conditions were much more severe. This was particularly evident from the occurrence and peak of the phytoplankton spring bloom during the experiment, which was not noticeably different from the control. Altogether, the inadvertent effects of increased alkalinity on the coastal phytoplankton communities appear to be rather limited relative to the enormous climatic benefit of increasing the inorganic carbon sink of seawater by 21 %. We note, however, that more detailed and widespread investigations of plankton community responses to OAE are required to confirm or dismiss this first impression.

Continue reading ‘Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community (update)’

Community context and pCO₂ impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Published 22 November 2022 Science Closed
Tags: biological response, BRcommunity, growth, laboratory, molecular biology, physiology, prokaryotes

Many microbial photoautotrophs depend on heterotrophic bacteria for accomplishing essential functions. Environmental changes, however, could alter or eliminate such interactions. We investigated the effects of changing pCO₂ on gene transcription in co-cultures of 3 strains of picocyanobacteria (Synechococcus strains CC9311 and WH8102 and Prochlorococcus strain MIT9312) paired with the ‘helper’ bacterium Alteromonas macleodii EZ55. Co-culture with cyanobacteria resulted in a much higher number of up- and down-regulated genes in EZ55 than pCO₂ by itself. Pathway analysis revealed significantly different transcription of genes involved in carbohydrate metabolism, stress response, and chemotaxis, with different patterns of up- or down-regulation in co-culture with different cyanobacterial strains. Gene transcription patterns of organic and inorganic nutrient transporter and catabolism genes in EZ55 suggested resources available in the culture media were altered under elevated (800 ppm) pCO₂ conditions. Altogether, changing transcription patterns were consistent with the possibility that the composition of cyanobacterial excretions changed under the two pCO₂ regimes, causing extensive ecophysiological changes in both members of the co-cultures. Additionally, significant downregulation of oxidative stress genes in MIT9312/EZ55 cocultures at 800 ppm pCO₂ were consistent with a link between the predicted reduced availability of photorespiratory byproducts (i.e., glycolate/2PG) under this condition and observed reductions in internal oxidative stress loads for EZ55, providing a possible explanation for the previously observed lack of “help” provided by EZ55 to MIT9312 under elevated pCO₂. If similar broad alterations in microbial ecophysiology occur in the ocean as atmospheric pCO₂ increases, they could lead to substantially altered ecosystem functioning and community composition.

Continue reading ‘Community context and pCO₂ impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria’

Phosphate limitation intensifies negative effects of ocean acidification on globally important nitrogen fixing cyanobacterium

Published 10 November 2022 Science Closed
Tags: abundance, biological response, field, individualmodeling, laboratory, modeling, molecular biology, multiple factors, North Pacific, nutrients, otherprocess, photosynthesis, physiology, prokaryotes

Growth of the prominent nitrogen-fixing cyanobacterium Trichodesmium is often limited by phosphorus availability in the ocean. How nitrogen fixation by phosphorus-limited Trichodesmium may respond to ocean acidification remains poorly understood. Here, we use phosphate-limited chemostat experiments to show that acidification enhanced phosphorus demands and decreased phosphorus-specific nitrogen fixation rates in Trichodesmium. The increased phosphorus requirements were attributed primarily to elevated cellular polyphosphate contents, likely for maintaining cytosolic pH homeostasis in response to acidification. Alongside the accumulation of polyphosphate, decreased NADP(H):NAD(H) ratios and impaired chlorophyll synthesis and energy production were observed under acidified conditions. Consequently, the negative effects of acidification were amplified compared to those demonstrated previously under phosphorus sufficiency. Estimating the potential implications of this finding, using outputs from the Community Earth System Model, predicts that acidification and dissolved inorganic and organic phosphorus stress could synergistically cause an appreciable decrease in global Trichodesmium nitrogen fixation by 2100.

Continue reading ‘Phosphate limitation intensifies negative effects of ocean acidification on globally important nitrogen fixing cyanobacterium’

Variable pH and subsequent change in pCO₂ modulates the biofilm formation, synthesis of extracellular polymeric substances, and survivability of a marine bacterium Bacillus stercoris GST-03

Published 14 September 2022 Science Closed
Tags: biological response, Indian, laboratory, physiology, prokaryotes

Biofilm-forming bacteria adhere to the substrates and engage in the nutrient cycling process. However, environmental conditions may interrupt the biofilm formation ability, which ultimately may affect various biogeochemical cycles. The present study reports the effect of varying pH and subsequent change in pCO₂ on the survivability, biofilm formation, and synthesis of extracellular polymeric substances (EPS) of a biofilm-forming marine bacterium Bacillus stercoris GST-03 isolated from the Bhitarkanika mangrove ecosystem, Odisha, India. Understanding the pH-dependent alteration in EPS constituents, and associated functional groups of a marine bacterium will provide better insight into the adaptability of the bacteria in future ocean acidification scenarios. The strain was found to tolerate and form biofilm up to pH 4, with the maximum biofilm formation at pH 6. EPS yield and the synthesis of the key components of the EPS, including carbohydrate, protein, and lipid, were found maximum at pH 6. Changes in biofilm formation patterns and various topological parameters at varying pH/pCO₂ conditions were observed. A cellular chaining pattern was observed at pH 4, and maximum biofilm formation was obtained at pH 6 with biomass of 5.28582 ± 0.5372 μm³/μm² and thickness of 9.982 ± 1.5288 μm. Structural characterization of EPS showed changes in various functional groups of constituent macromolecules with varying pH. The amorphous nature of the EPS and the changes in linkages and associated functional groups (-R₂CHOR, –CH₃, and –CH₂) with pH variation was confirmed. EPS showed a two-step degradation with a maximum weight loss of 59.147% and thermal stability up to 480 °C at pH 6. The present work efficiently demonstrates the role of EPS in providing structural and functional stability to the biofilm in varying pH conditions. The findings will provide a better understanding of the adaptability of marine bacteria in the future effect of ocean acidification.

Continue reading ‘Variable pH and subsequent change in pCO₂ modulates the biofilm formation, synthesis of extracellular polymeric substances, and survivability of a marine bacterium Bacillus stercoris GST-03′

Interactive effects of CO₂, temperature, irradiance, and nutrient limitation on the growth and physiology of the marine cyanobacterium Synechococcus (Cyanophyceae)

Published 14 September 2022 Science Closed
Tags: biological response, growth, individualmodeling, laboratory, light, modeling, molecular biology, multiple factors, North Atlantic, nutrients, photosynthesis, physiology, prokaryotes, temperature

The marine cyanobacterium Synechococcus elongatus was grown in a continuous culture system to study the interactive effects of temperature, irradiance, nutrient limitation, and the partial pressure of CO₂ (pCO2) on its growth and physiological characteristics. Cells were grown on a 14:10 h light:dark cycle at all combinations of low and high irradiance (50 and 300 μmol photons ⋅ m⁻² ⋅ s⁻¹, respectively), low and high pCO₂ (400 and 1000 ppmv, respectively), nutrient limitation (nitrate-limited and nutrient-replete conditions), and temperatures of 20–45°C in 5°C increments. The maximum growth rate was ~4.5 · d⁻¹ at 30–35°C. Under nutrient-replete conditions, growth rates at most temperatures and irradiances were about 8% slower at a pCO₂ of 1000 ppmv versus 400 ppmv. The single exception was 45°C and high irradiance. Under those conditions, growth rates were ~45% higher at 1000 ppmv. Cellular carbon:nitrogen ratios were independent of temperature at a fixed relative growth rate but higher at high irradiance than at low irradiance. Initial slopes of photosynthesis–irradiance curves were higher at all temperatures under nutrient-replete versus nitrate-limited conditions; they were similar at all temperatures under high and low irradiance, except at 20°C, when they were suppressed at high irradiance. A model of phytoplankton growth in which cellular carbon was allocated to structure, storage, or the light or dark reactions of photosynthesis accounted for the general patterns of cell composition and growth rate. Allocation of carbon to the light reactions of photosynthesis was consistently higher at low versus high light and under nutrient-replete versus nitrate-limited conditions.

Continue reading ‘Interactive effects of CO₂, temperature, irradiance, and nutrient limitation on the growth and physiology of the marine cyanobacterium Synechococcus (Cyanophyceae)’

Effect of rising temperature and carbon dioxide on the growth, photophysiology, and elemental ratios of marine Synechococcus: a multistressor approach

Published 9 September 2022 Science Closed
Tags: biological response, growth, laboratory, multiple factors, photosynthesis, physiology, prokaryotes, temperature

Marine picocyanobacteria belonging to the genus Synechococcus are one of the most abundant photosynthetic organisms on Earth. They are often exposed to large fluctuations in temperature and CO₂ concentrations in the ocean, which are expected to further change in the coming decades due to ocean acidification and warming resulting from rising atmospheric CO₂ levels. To decipher the effect of changing temperature and CO₂ levels on Synechococcus, six Synechococcus strains previously isolated from various coastal and open ocean sites were exposed to a matrix of three different temperatures (22 °C, 24 °C and 26 °C) and CO₂ levels (400 ppm, 600 ppm and 800 ppm). Thereafter, the specific growth rates, photophysiological parameters (σ_PSII and F_v/F_m), C/N (mol/mol) ratios and the nitrogen stable isotopic composition (δ¹⁵N (‰)) of the strains were measured. Temperature was found to be a stronger driver of the changes in specific growth rates and photophysiology in the Synechococcus strains. Carbon-concentrating mechanisms (CCM) operational in these strains that shield the photosynthetic machinery from directly sensing ambient changes in CO₂ possibly played a major role in causing minimal changes in the specific growth rates under the varying CO₂ levels.

Continue reading ‘Effect of rising temperature and carbon dioxide on the growth, photophysiology, and elemental ratios of marine Synechococcus: a multistressor approach’

Physical and biological controls on anthropogenic CO₂ sink of the Ross Sea

Published 8 September 2022 Science Closed
Tags: Antarctic, biogeochemistry, biological response, chemistry, field, prokaryotes

The Antarctic continental shelf is known as a critical anthropogenic CO₂ (C_ant) sink due to its cold waters, high primary productivity, and unique circulation, which allow it to sequester large amounts of organic and inorganic carbon into the deep ocean. However, climate change is currently causing significant alteration to the Antarctic marine carbon cycle, with unknown consequences on the C_ant uptake capacity, making model-based estimates of future ocean acidification of polar regions highly uncertain. Here, we investigated the marine carbonate system in the Ross Sea in order to assess the current anthropogenic carbon content and how physical–biological processes can control the C_ant sequestration along the shelf-slope continuum. The Winter Water mass generated from convective events was characterized by high C_ant level (28 µmol kg⁻¹) as a consequence of the mixed layer break-up during the cold season, whereas old and less-ventilated Circumpolar Deep Water entering the Ross Sea revealed a very scarce contribution of anthropogenic carbon (7 µmol kg⁻¹). The C_ant concentration was also different between polynya areas and the shelf break, as a result of their specific hydrographic characteristics and biological processes: surface waters of the Ross Sea and Terra Nova Bay polynyas served as strong CO₂ sink (up to −185 mmol m⁻²), due to the remarkable net community production, estimated from the summertime surface-dissolved inorganic carbon deficit. However, a large amount of the generated particulate organic carbon was promptly consumed by intense microbial activity, giving back carbon dioxide into the intermediate and deep layers of the continental shelf zone. Further C_ant also derived from High-Salinity Shelf Water produced during winter sea ice formation (25 µmol kg⁻¹), fueling dense shelf waters with additional input of C_ant, which was finally stored into the abyssal sink through continental slope outflow (19 µmol kg⁻¹). Our results suggest that summer biological activity over the Ross Sea shelf is pivotal for the shunt of anthropogenic CO₂ between the organic and inorganic carbon pools, enhancing the ocean acidification of the upper mesopelagic zone and the long-term C_ant sequestration into the deep ocean.

Continue reading ‘Physical and biological controls on anthropogenic CO₂ sink of the Ross Sea’

Perceived intensification in harmful algal blooms is a wave of cumulative threat to the aquatic ecosystems

Published 16 June 2022 Science Closed
Tags: biological response, multiple factors, oxygen, physiology, phytoplankton, prokaryotes, review, temperature

Aquatic pollution is considered a major threat to sustainable development across the world, and deterioration of aquatic ecosystems is caused usually by harmful algal blooms (HABs). In recent times, HABs have gained attention from scientists to better understand these phenomena given that these blooms are increasing in intensity and distribution with considerable impacts on aquatic ecosystems. Many exogenous factors such as variations in climatic patterns, eutrophication, wind blowing, dust storms, and upwelling of water currents form these blooms. Globally, the HAB formation is increasing the toxicity in the natural water sources, ultimately leading the deleterious and hazardous effects on the aquatic fauna and flora. This review summarizes the types of HABs with their potential effects, toxicity, grazing defense, human health impacts, management, and control of these harmful entities. This review offers a systematic approach towards the understanding of HABs, eliciting to rethink the increasing threat caused by HABs in aquatic ecosystems across the world. Therefore, to mitigate this increasing threat to aquatic environments, advanced scientific research in ecology and environmental sciences should be prioritized.

Continue reading ‘Perceived intensification in harmful algal blooms is a wave of cumulative threat to the aquatic ecosystems’

The influence of climate change on marine bacterioplankton communities and greenhouse gases in New Zealand waters

Published 13 June 2022 Science Closed
Tags: biogeochemistry, biological response, BRcommunity, chordata, communitymodeling, field, mesocosms, modeling, molecular biology, multiple factors, phytoplankton, prokaryotes, South Pacific, temperature, zooplankton

Bacterioplankton communities play a fundamental role in the cycling of carbon and nitrogen in the oceans. Cycling of these nutrients by bacterioplankton also contributes to the production of nitrous oxide and methane, resulting in the oceans being a net source of both these greenhouse gases. Climate change is impacting the oceans through warming and acidification resulting in alteration of planktonic ecosystems, via changes in productivity, biomass, and species composition. The response of marine bacterioplankton communities to the direct effects of ocean warming and lowered pH, and to the indirect effects of changes in phytoplankton and zooplankton, has implications for biogeochemical cycling and therefore the production of nitrous oxide and methane. This thesis investigates the impact of both direct and indirect climate pressures by determining the influence of ocean warming and lowered pH on bacterioplankton and the production of methane and nitrous oxide in New Zealand coastal waters. It also assesses how open ocean bacterioplankton communities and dissolved methane and nitrous oxide are influenced by water mass properties and, in particular, how they may be affected by climate-induced changes in the distribution and abundance of salps, a dominant group of zooplankton.

To determine the impact of lower pH and warming on bacterioplankton community, production and abundance, coastal water was manipulated in three mesocosm experiments to projected future ocean temperature and pH. The experiments ran for 18-21 days using 4000-Litre mesocosms filled with coastal water and associated plankton communities, with pH and temperature continuously regulated. High-throughput sequencing of the 16S rRNA gene was used to determine bacterioplankton community composition and leucine incorporation was used to measure bacterial production during the experiments. Minor but significant increases in alpha diversity were seen under low pH and warming. However, overall results from the mesocosm experiments indicate resilience to ocean warming and low pH in coastal bacterioplankton communities, with no significant impacts on production, abundance or beta-diversity found. Bacterioplankton communities in coastal sites are likely to experience high natural variability, which may result in lack of sensitivity to projected climate change.

…

Continue reading ‘The influence of climate change on marine bacterioplankton communities and greenhouse gases in New Zealand waters’

Phototrophic sponge productivity may not be enhanced in a high CO2 world

Published 9 June 2022 Science Closed
Tags: biological response, field, photosynthesis, physiology, porifera, prokaryotes, respiration, South Pacific, vents

Sponges are major components of benthic communities across the world and have been identified as potential “winners” on coral reefs in the face of global climate change as result of their tolerance to ocean warming and acidification (OA). Previous studies have also hypothesised that photosymbiont-containing sponges might have higher productivity under future OA conditions as a result of photosymbionts having increased access to CO₂ and subsequently greater carbon production. Here we test this hypothesis for a widespread and abundant photosymbiont-containing sponge species Lamellodysidea herbacea at a CO₂ seep in Papua New Guinea simulating OA conditions. We found seep sponges had relatively higher cyanobacterial abundance, chlorophyll concentrations and symbiont photosynthetic efficiency than non-seep sponges, and a three-fold higher sponge abundance at the seep site. However, while gross oxygen production was the same for seep and non-seep sponges, seep sponge dark respiration rates were higher and instantaneous photosynthesis: respiration (P:R) ratios were lower. We show that while photosymbiont containing sponges may not have increased productivity under OA, they are able to show flexibility in their relationships with microbes and offset increased metabolic costs associated with climate change associated stress.

Continue reading ‘Phototrophic sponge productivity may not be enhanced in a high CO2 world’

Synergistic promoting effect of increasing aquatic ammonium and CO2 on Microcystis aeruginosa

Published 8 June 2022 Science Closed
Tags: biological response, laboratory, light, morphology, multiple factors, nutrients, photosynthesis, physiology, prokaryotes

Highlights

NO₃－-grown M. aeruginosa more prone to accumulate C-rich products.
As CO₂ increased, shift from NO₃－ to NH₄⁺ led to greater increases in Chl a.
Elevated CO₂ reduced ROS of NH₄⁺ -grown M. aeruginosa under suitable light.
Under strong light, elevated CO₂ greatly increased ROS in NO₃－-grown M. aeruginosa.
Under strong light, only NH₄⁺-grown M. aeruginosa showed improved growth as CO₂ rose.

Abstract

Owing to climate change and intensive agricultural development, freshwater bodies have been affected by increases in both CO₂ levels and chemically-reduced forms of N. However, little is known about how these changes affect cyanobacterial growth and blooms. This study explored a range of light conditions (30, 80, 130, or 200 μmol photons/m²/s) wherein Microcystis aeruginosa, a widespread bloom-forming species, was exposed to different concentrations of CO₂ (400 parts per million (ppm) and 1000 ppm) in a medium containing NH₄⁺ or NO₃－. The interactive effects of N sources and CO₂ levels on the C/N metabolic balance and energy balance were examined to assess changes in the growth of M. aeruginosa. When the light intensity was 80 μmol photons/m²/s, elevated CO₂ could reduce intracellular reactive oxygen species (ROS) in NH₄⁺-grown M. aeruginosa. Meanwhile, cell density and chlorophyll a (Chl a) increased with increasing CO₂ levels, and the increase in Chl a was significantly greater in NH₄⁺-grown M. aeruginosa than in NO₃－-grown M. aeruginosa. Under light conditions of 200 μmol photons/m²/s, elevated CO₂ concentration caused NO₃－-grown M. aeruginosa to be affected by a large amount of ROS, and the growth of NO₃－-grown M. aeruginosa was finally suppressed. However, NH₄⁺-grown M. aeruginosa had a smaller amount of ROS and showed improved growth as CO₂ was elevated. This difference can be attributed to the faster metabolic pathways in the NH₄⁺ environment, which manifested in a lower accumulation of 2-oxoglutarate and fatty acids as CO₂ was elevated. These findings suggest that the simultaneous increase in ammonium and CO₂ in aquatic ecosystems confers cyanobacteria with greater advantages than the combination of nitrate and CO₂, which may aggravate cyanobacterial blooms.

Continue reading ‘Synergistic promoting effect of increasing aquatic ammonium and CO2 on Microcystis aeruginosa’

Differential responses of dominant and rare epiphytic bacteria from a submerged macrophyte to elevated CO2

Published 28 April 2022 Science Closed
Tags: algae, biological response, BRcommunity, community composition, laboratory, otherprocess, prokaryotes

Epiphytic bacteria develop complex interactions with their host macrophytes and play an important role in the ecological processes in freshwater habitats. However, how dominant and rare taxa respond to elevated atmospheric CO₂ remains unclear. A manipulated experiment was carried out to explore the effects of elevated CO₂ on the diversity or functional characteristics of leaf epiphytic dominant and rare bacteria from a submerged macrophyte. Three levels (high, medium, normal) of dissolved inorganic carbon (DIC) were applied to the overlying water. The physicochemical properties of the overlying water were measured. Elevated atmospheric CO₂ significantly decreased the pH and dissolved oxygen (DO) of overlying water. Proteobacteria, Cyanobacteria, Bacteroidetes, Planctomycetes, and Actinobacteria are the dominant phyla of leaf epiphytic bacteria from Myriophyllum spicatum, occupying over 90% of the accumulated relative abundances. The aquatic DIC level and further pH significantly drove the epiphytic community composition differences among the three DIC levels. For dominant epiphytic bacteria, the functional potential of nutrient processes and mutualistic relationships were strongly affected by a high DIC level, while responses of rare epiphytic bacteria were more related to trace element processes, pathogens, and defense strategies under a high DIC level. Our results showed the responses of epiphytic bacteria to elevated CO₂ varied across dominant and rare taxa.

Continue reading ‘Differential responses of dominant and rare epiphytic bacteria from a submerged macrophyte to elevated CO2’

« Previous Page — Next Page »

Posts Tagged 'prokaryotes'

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Share this post!

Like this:

Subscribe

Search

OA-ICC Highlights

Resources

Top Posts