scholarly journals Bacterial extracellular enzyme activity in a future ocean

2021 ◽  
Author(s):  
◽  
Timothy James Burrell
Keyword(s):  
Organic Matter ◽  
Elevated Temperature ◽  
Secondary Production ◽  
Protease Activity ◽  
Low Ph ◽  
Open Ocean ◽  
Production Rates ◽  
Near Surface ◽  
Surface Ocean ◽  
Bacterial Secondary Production

<p>Heterotrophic bacteria are recognised as vital components in the cycling and regulation of inorganic and organic matter in the ocean. Research to date indicates that future changes in ocean conditions may influence bacterial extracellular enzyme hydrolysis rates, which could affect the strength of the microbial loop and consequently organic matter export. The aim of this thesis was to examine how changes in ocean acidification and warming predicted to occur by the end of the century will affect extracellular enzyme activities in the near-surface ocean and below the surface mixed layer in the South West Pacific.  A series of small-scale seawater incubations were conducted under three different perturbed conditions: elevated temperature (ambient +3°C), low pH (pCO₂ 750 ppmv; pHт 7.8) and greenhouse conditions (elevated temperature and low pH), with responses compared to ambient control samples. In particular, the response of protease activity (leucine- and arginine-aminopeptidase) and glucosidase activity (β- and α-glucosidase) were examined, as these enzymes are known to degrade the two major components of organic matter in the ocean, namely proteins and carbohydrates. Bacterial secondary production rates (³H-TdR & ³H-Leu incorporation) were also examined as a proxy for carbon turnover.  To investigate spatial variability, parameter responses from near-surface open ocean seawater consisting of different phytoplankton communities were compared with coastal seawater, as well as seawater collected from below the surface mixed layer. To determine temporal variability, both direct and indirect parameter responses were investigated. Finally, responses were determined from a shallow CO₂ vent that provided a natural low pH environment in coastal waters north of New Zealand. By comparing responses derived from vent water and artificially low pH water, vent plumes were also investigated for their utility as proxies for future low pH environments.  Incubation results showed that protease activity increased in response to low pH conditions in each seawater environment tested. However, near-surface open ocean incubations showed variability in the response of protease and glucosidase activity and bacterial cell numbers between different phytoplankton communities and treatments, suggesting that parameter responses were determined by direct and indirect effects. Elevated temperature had an overall positive effect on bacterial secondary production rates between different phytoplankton communities in the near-surface open ocean. Surprisingly, although elevated temperature and low pH treatments showed independent effects, no clear additive or synergistic effect was detected in any parameter under greenhouse conditions. In contrast to the near-surface ocean, greenhouse conditions had an additive effect on protease activity in seawater collected from below the surface mixed layer (100 m depth). Bacterial secondary production rates and bacterial numbers varied in response to elevated temperature in the subsurface ocean, while bacterial secondary production rates declined under greenhouse conditions. Glucosidase and protease activities were highest in the coastal seawater, with both enzymes responding positively to low pH conditions. Coastal seawater also contained the highest bacterial secondary production rates and bacterial cell numbers, however these parameters were not significantly affected by low pH conditions. Variation in the direct response of enzyme activity to low pH between ocean environments could indicate the synthesis of different extracellular enzymes by surface and subsurface bacteria. Importantly, results from a naturally low pH vent plume indicated that pH was not the only factor influencing the response of extracellular enzymes. Other influential factors could include high concentrations of dissolved nutrients and trace metal ions. Natural low pH vents off Whale Island in the Bay of Plenty were determined not suitable as proxies for future low pH environments based on vent variability and differences in seawater biogeochemistry when compared to the ambient ocean.  Overall, the incubation results show that under conditions predicted for the end of the century, protease activity will increase in open ocean and coastal waters which could accelerate and strengthen the heterotrophic microbial loop. Bacterial secondary production rates are expected to vary in the near-surface ocean, but decline in the subsurface. The resulting increase in surface ocean protease activity could increase heterotrophic metabolic respiration and reduce organic matter export, weaken the biological carbon pump and diminish long-term carbon sequestration. An increased turnover of proteins and amino acids in each environment tested could lead to nitrogen limitation and contribute to an expansion of oligotrophic waters. This future scenario may create a positive inorganic carbon feedback that would further exacerbate acidification of the surface ocean.</p>

scholarly journals Bacterial extracellular enzyme activity in a future ocean

2021 ◽  
Author(s):  
◽  
Timothy James Burrell
Keyword(s):  
Organic Matter ◽  
Elevated Temperature ◽  
Secondary Production ◽  
Protease Activity ◽  
Low Ph ◽  
Open Ocean ◽  
Production Rates ◽  
Near Surface ◽  
Surface Ocean ◽  
Bacterial Secondary Production

<p>Heterotrophic bacteria are recognised as vital components in the cycling and regulation of inorganic and organic matter in the ocean. Research to date indicates that future changes in ocean conditions may influence bacterial extracellular enzyme hydrolysis rates, which could affect the strength of the microbial loop and consequently organic matter export. The aim of this thesis was to examine how changes in ocean acidification and warming predicted to occur by the end of the century will affect extracellular enzyme activities in the near-surface ocean and below the surface mixed layer in the South West Pacific.  A series of small-scale seawater incubations were conducted under three different perturbed conditions: elevated temperature (ambient +3°C), low pH (pCO₂ 750 ppmv; pHт 7.8) and greenhouse conditions (elevated temperature and low pH), with responses compared to ambient control samples. In particular, the response of protease activity (leucine- and arginine-aminopeptidase) and glucosidase activity (β- and α-glucosidase) were examined, as these enzymes are known to degrade the two major components of organic matter in the ocean, namely proteins and carbohydrates. Bacterial secondary production rates (³H-TdR & ³H-Leu incorporation) were also examined as a proxy for carbon turnover.  To investigate spatial variability, parameter responses from near-surface open ocean seawater consisting of different phytoplankton communities were compared with coastal seawater, as well as seawater collected from below the surface mixed layer. To determine temporal variability, both direct and indirect parameter responses were investigated. Finally, responses were determined from a shallow CO₂ vent that provided a natural low pH environment in coastal waters north of New Zealand. By comparing responses derived from vent water and artificially low pH water, vent plumes were also investigated for their utility as proxies for future low pH environments.  Incubation results showed that protease activity increased in response to low pH conditions in each seawater environment tested. However, near-surface open ocean incubations showed variability in the response of protease and glucosidase activity and bacterial cell numbers between different phytoplankton communities and treatments, suggesting that parameter responses were determined by direct and indirect effects. Elevated temperature had an overall positive effect on bacterial secondary production rates between different phytoplankton communities in the near-surface open ocean. Surprisingly, although elevated temperature and low pH treatments showed independent effects, no clear additive or synergistic effect was detected in any parameter under greenhouse conditions. In contrast to the near-surface ocean, greenhouse conditions had an additive effect on protease activity in seawater collected from below the surface mixed layer (100 m depth). Bacterial secondary production rates and bacterial numbers varied in response to elevated temperature in the subsurface ocean, while bacterial secondary production rates declined under greenhouse conditions. Glucosidase and protease activities were highest in the coastal seawater, with both enzymes responding positively to low pH conditions. Coastal seawater also contained the highest bacterial secondary production rates and bacterial cell numbers, however these parameters were not significantly affected by low pH conditions. Variation in the direct response of enzyme activity to low pH between ocean environments could indicate the synthesis of different extracellular enzymes by surface and subsurface bacteria. Importantly, results from a naturally low pH vent plume indicated that pH was not the only factor influencing the response of extracellular enzymes. Other influential factors could include high concentrations of dissolved nutrients and trace metal ions. Natural low pH vents off Whale Island in the Bay of Plenty were determined not suitable as proxies for future low pH environments based on vent variability and differences in seawater biogeochemistry when compared to the ambient ocean.  Overall, the incubation results show that under conditions predicted for the end of the century, protease activity will increase in open ocean and coastal waters which could accelerate and strengthen the heterotrophic microbial loop. Bacterial secondary production rates are expected to vary in the near-surface ocean, but decline in the subsurface. The resulting increase in surface ocean protease activity could increase heterotrophic metabolic respiration and reduce organic matter export, weaken the biological carbon pump and diminish long-term carbon sequestration. An increased turnover of proteins and amino acids in each environment tested could lead to nitrogen limitation and contribute to an expansion of oligotrophic waters. This future scenario may create a positive inorganic carbon feedback that would further exacerbate acidification of the surface ocean.</p>

scholarly journals Bacteria and phytoplankton production rates in eight river stretches of the middle Rio Doce hidrographic basin (southeast Brazil)

2005 ◽  
Vol 48 (3) ◽  
pp. 487-496 ◽  
Author(s):  
Mauricio Mello Petrucio ◽  
Francisco Antônio R. Barbosa ◽  
Sidinei Magela Thomaz
Keyword(s):  
Secondary Production ◽  
Carbon Fixation ◽  
Human Impacts ◽  
Phytoplankton Production ◽  
Production Rates ◽  
Lotic Ecosystems ◽  
Streams And Rivers ◽  
Southeast Brazil ◽  
Bacterial Secondary Production ◽  
Dry And Rainy Seasons

Measurements of bacterial secondary production (BSP), together with primary phytoplanktonic production (PPP) were conducted during dry and rainy seasons, in eight rivers of different orders submitted to different degrees of human impacts (different trophic degree). We aimed to determine and compare the importance of BSP and PPP in carbon fixation in these different lotic ecosystems. Our results showed that the Ipanema River was the most modified system by anthropogenic effluents inputs. These inputs altered the trophic degree and BSP rates of these streams and rivers.

scholarly journals Over-calcified forms of the coccolithophore <i>Emiliania huxleyi</i> in high-CO<sub>2</sub> waters are not preadapted to ocean acidification

2018 ◽  
Vol 15 (5) ◽  
pp. 1515-1534 ◽  
Author(s):  
Peter von Dassow ◽  
Francisco Díaz-Rosas ◽  
El Mahdi Bendif ◽  
Juan-Diego Gaitán-Espitia ◽  
Daniella Mella-Flores ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Large Population ◽  
Emiliania Huxleyi ◽  
Low Ph ◽  
Production Rates ◽  
High Co2 ◽  
Surface Ocean ◽  
Population Sizes ◽  
Multicellular Organisms ◽  
Correlated Factors

Abstract. Marine multicellular organisms inhabiting waters with natural high fluctuations in pH appear more tolerant to acidification than conspecifics occurring in nearby stable waters, suggesting that environments of fluctuating pH hold genetic reservoirs for adaptation of key groups to ocean acidification (OA). The abundant and cosmopolitan calcifying phytoplankton Emiliania huxleyi exhibits a range of morphotypes with varying degrees of coccolith mineralization. We show that E. huxleyi populations in the naturally acidified upwelling waters of the eastern South Pacific, where pH drops below 7.8 as is predicted for the global surface ocean by the year 2100, are dominated by exceptionally over-calcified morphotypes whose distal coccolith shield can be almost solid calcite. Shifts in morphotype composition of E. huxleyi populations correlate with changes in carbonate system parameters. We tested if these correlations indicate that the hyper-calcified morphotype is adapted to OA. In experimental exposures to present-day vs. future pCO2 (400 vs. 1200 µatm), the over-calcified morphotypes showed the same growth inhibition (−29.1±6.3 %) as moderately calcified morphotypes isolated from non-acidified water (−30.7±8.8 %). Under the high-CO2–low-pH condition, production rates of particulate organic carbon (POC) increased, while production rates of particulate inorganic carbon (PIC) were maintained or decreased slightly (but not significantly), leading to lowered PIC ∕ POC ratios in all strains. There were no consistent correlations of response intensity with strain origin. The high-CO2–low-pH condition affected coccolith morphology equally or more strongly in over-calcified strains compared to moderately calcified strains. High-CO2–low-pH conditions appear not to directly select for exceptionally over-calcified morphotypes over other morphotypes, but perhaps indirectly by ecologically correlated factors. More generally, these results suggest that oceanic planktonic microorganisms, despite their rapid turnover and large population sizes, do not necessarily exhibit adaptations to naturally high-CO2 upwellings, and this ubiquitous coccolithophore may be near the limit of its capacity to adapt to ongoing ocean acidification.

Decolorisation of natural organic matter by Phanerochaete chrysosporium: the effect of environmental conditions

2004 ◽  
Vol 4 (4) ◽  
pp. 175-182 ◽  
Author(s):  
K. Rojek ◽  
F.A. Roddick ◽  
A. Parkinson
Keyword(s):  
Organic Matter ◽  
Ionic Strength ◽  
Natural Organic Matter ◽  
Phanerochaete Chrysosporium ◽  
Fungal Growth ◽  
Low Ph ◽  
Colour Removal ◽  
Humic Material ◽  
Carbon And Nitrogen ◽  
Carbon And Nitrogen Content

Phanerochaete chrysosporium was shown to rapidly decolorise a solution of natural organic matter (NOM). The effect of various parameters such as carbon and nitrogen content, pH, ionic strength, NOM concentration and addition of Mn2+ on the colour removal process was investigated. The rapid decolorisation was related to fungal growth and biosorption rather than biodegradation as neither carbon nor nitrogen limitation, nor Mn2+ addition, triggered the decolorisation process. Low pH (pH 3) and increased ionic strength (up to 50 g L‒1 added NaCl) led to greater specific removal (NOM/unit biomass), probably due to increased electrostatic bonding between the humic material and the biomass. Adsorption of NOM with viable and inactivated (autoclaved or by sodium azide) fungal pellets occurred within 24 hours and the colour removal depended on the viability, method of inactivation and pH. Colour removal by viable pellets was higher under the same conditions, and this, combined with desorption data, confirmed that fungal metabolic activity was important in the decolorisation process. Overall, removals of up to 40–50% NOM from solution were obtained. Of this, removal by adsorption was estimated as 60–70%, half of which was physicochemical, the other half metabolically-dependent biosorption and bioaccumulation. The remainder was considered to be removed by biodegradation, although some of this may be ascribed to bioaccumulation and metabolically-dependent biosorption.

scholarly journals Effect of Plant Growth Regulators on Protease Activity in Forest Floor of Norway Spruce Stand

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 665
Author(s):  
Ladislav Holik ◽  
Jiří Volánek ◽  
Valerie Vranová
Keyword(s):  
Organic Matter ◽  
Proteolytic Activity ◽  
Protease Activity ◽  
Forest Floor ◽  
Soil Microbial Activity ◽  
Inhibitory Effects ◽  
Chlorocholine Chloride ◽  
Soil Microbial ◽  
Native Soil ◽  
Transformation Processes

Soil proteases are involved in organic matter transformation processes and, thus, influence ecosystem nutrient turnovers. Phytohormones, similarly to proteases, are synthesized and secreted into soil by fungi and microorganisms, and regulate plant rhizosphere activity. The aim of this study was to determine the effect of auxins, cytokinins, ethephon, and chlorocholine chloride on spruce forest floor protease activity. It was concluded that the presence of auxins stimulated native proteolytic activity, specifically synthetic auxin 2-naphthoxyacetic acid (16% increase at added quantity of 5 μg) and naturally occurring indole-3-acetic acid (18%, 5 μg). On the contrary, cytokinins, ethephon and chlorocholine chloride inhibited native soil protease activity, where ethephon (36% decrease at 50 μg) and chlorocholine chloride (34%, 100 μg) showed the highest inhibitory effects. It was concluded that negative phytohormonal effects on native proteolytic activity may slow down organic matter decomposition rates and hence complicate plant nutrition. The study enhances the understanding of rhizosphere exudate effects on soil microbial activity and soil nitrogen cycle.

scholarly journals Global high-resolution monthly <i>p</i>CO<sub>2</sub> climatology for the coastal ocean derived from neural network interpolation

2017 ◽  
Vol 14 (19) ◽  
pp. 4545-4561 ◽  
Author(s):  
Goulven G. Laruelle ◽  
Peter Landschützer ◽  
Nicolas Gruber ◽  
Jean-Louis Tison ◽  
Bruno Delille ◽  
...  
Keyword(s):  
Neural Network ◽  
Spatial Resolution ◽  
Seasonal Variations ◽  
Open Ocean ◽  
Global Perspective ◽  
Strong Increase ◽  
Spatial And Temporal Variability ◽  
Surface Ocean ◽  
Shelf Seas ◽  
Artificial Neural Network Method

Abstract. In spite of the recent strong increase in the number of measurements of the partial pressure of CO2 in the surface ocean (pCO2), the air–sea CO2 balance of the continental shelf seas remains poorly quantified. This is a consequence of these regions remaining strongly under-sampled in both time and space and of surface pCO2 exhibiting much higher temporal and spatial variability in these regions compared to the open ocean. Here, we use a modified version of a two-step artificial neural network method (SOM-FFN; Landschützer et al., 2013) to interpolate the pCO2 data along the continental margins with a spatial resolution of 0.25° and with monthly resolution from 1998 to 2015. The most important modifications compared to the original SOM-FFN method are (i) the much higher spatial resolution and (ii) the inclusion of sea ice and wind speed as predictors of pCO2. The SOM-FFN is first trained with pCO2 measurements extracted from the SOCATv4 database. Then, the validity of our interpolation, in both space and time, is assessed by comparing the generated pCO2 field with independent data extracted from the LDVEO2015 database. The new coastal pCO2 product confirms a previously suggested general meridional trend of the annual mean pCO2 in all the continental shelves with high values in the tropics and dropping to values beneath those of the atmosphere at higher latitudes. The monthly resolution of our data product permits us to reveal significant differences in the seasonality of pCO2 across the ocean basins. The shelves of the western and northern Pacific, as well as the shelves in the temperate northern Atlantic, display particularly pronounced seasonal variations in pCO2,  while the shelves in the southeastern Atlantic and in the southern Pacific reveal a much smaller seasonality. The calculation of temperature normalized pCO2 for several latitudes in different oceanic basins confirms that the seasonality in shelf pCO2 cannot solely be explained by temperature-induced changes in solubility but are also the result of seasonal changes in circulation, mixing and biological productivity. Our results also reveal that the amplitudes of both thermal and nonthermal seasonal variations in pCO2 are significantly larger at high latitudes. Finally, because this product's spatial extent includes parts of the open ocean as well, it can be readily merged with existing global open-ocean products to produce a true global perspective of the spatial and temporal variability of surface ocean pCO2.

The stability of the stratospheric ozone layer during the end-Permian eruption of the Siberian Traps

2007 ◽  
Vol 365 (1856) ◽  
pp. 1843-1866 ◽  
Author(s):  
David J Beerling ◽  
Michael Harfoot ◽  
Barry Lomax ◽  
John A Pyle
Keyword(s):  
Organic Matter ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Ultraviolet B ◽  
Large Reservoir ◽  
Near Surface ◽  
Siberian Traps ◽  
Northern Latitudes ◽  
The Stability ◽  
Mutagenic Effects

The discovery of mutated palynomorphs in end-Permian rocks led to the hypothesis that the eruption of the Siberian Traps through older organic-rich sediments synthesized and released massive quantities of organohalogens, which caused widespread O 3 depletion and allowed increased terrestrial incidence of harmful ultraviolet-B radiation (UV-B, 280–315 nm; Visscher et al . 2004 Proc. Natl Acad. Sci. USA 101 , 12 952–12 956). Here, we use an extended version of the Cambridge two-dimensional chemistry–transport model to evaluate quantitatively this possibility along with two other potential causes of O 3 loss at this time: (i) direct effects of HCl release by the Siberian Traps and (ii) the indirect release of organohalogens from dispersed organic matter. According to our simulations, CH 3 Cl released from the heating of coals alone caused comparatively minor O 3 depletion (5–20% maximum) because this mechanism fails to deliver sufficiently large amounts of Cl into the stratosphere. The unusual explosive nature of the Siberian Traps, combined with the direct release of large quantities of HCl, depleted the model O 3 layer in the high northern latitudes by 33–55%, given a main eruptive phase of less than or equal to 200 kyr. Nevertheless, O 3 depletion was most extensive when HCl release from the Siberian Traps was combined with massive CH 3 Cl release synthesized from a large reservoir of dispersed organic matter in Siberian rocks. This suite of model experiments produced column O 3 depletion of 70–85% and 55–80% in the high northern and southern latitudes, respectively, given eruption durations of 100–200 kyr. On longer eruption time scales of 400–600 kyr, corresponding O 3 depletion was 30–40% and 20–30%, respectively. Calculated year-round increases in total near-surface biologically effective (BE) UV-B radiation following these reductions in O 3 layer range from 30–60 (kJ m −2  d −1 ) BE up to 50–100 (kJ m −2  d −1 ) BE . These ranges of daily UV-B doses appear sufficient to exert mutagenic effects on plants, especially if sustained over tens of thousands of years, unlike either rising temperatures or SO 2 concentrations.

scholarly journals Biogeochemical Regimes in Shallow Aquifers Reflect the Metabolic Coupling of the Elements Nitrogen, Sulfur, and Carbon

2018 ◽  
Vol 85 (5) ◽  
Author(s):  
Carl-Eric Wegner ◽  
Michael Gaspar ◽  
Patricia Geesink ◽  
Martina Herrmann ◽  
Manja Marz ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Groundwater Flow ◽  
Inorganic Nitrogen ◽  
Sulfur Metabolism ◽  
Ammonium Oxidation ◽  
Metabolic Potential ◽  
Differentiation Potential ◽  
Near Surface ◽  
Monitoring Wells

ABSTRACTNear-surface groundwaters are prone to receive (in)organic matter input from their recharge areas and are known to harbor autotrophic microbial communities linked to nitrogen and sulfur metabolism. Here, we use multi-omic profiling to gain holistic insights into the turnover of inorganic nitrogen compounds, carbon fixation processes, and organic matter processing in groundwater. We sampled microbial biomass from two superimposed aquifers via monitoring wells that follow groundwater flow from its recharge area through differences in hydrogeochemical settings and land use. Functional profiling revealed that groundwater microbiomes are mainly driven by nitrogen (nitrification, denitrification, and ammonium oxidation [anammox]) and to a lesser extent sulfur cycling (sulfur oxidation and sulfate reduction), depending on local hydrochemical differences. Surprisingly, the differentiation potential of the groundwater microbiome surpasses that of hydrochemistry for individual monitoring wells. Being dominated by a few phyla (Bacteroidetes,Proteobacteria,Planctomycetes, andThaumarchaeota), the taxonomic profiling of groundwater metagenomes and metatranscriptomes revealed pronounced differences between merely present microbiome members and those actively participating in community gene expression and biogeochemical cycling. Unexpectedly, we observed a constitutive expression of carbohydrate-active enzymes encoded by different microbiome members, along with the groundwater flow path. The turnover of organic carbon apparently complements for lithoautotrophic carbon assimilation pathways mainly used by the groundwater microbiome depending on the availability of oxygen and inorganic electron donors, like ammonium.IMPORTANCEGroundwater is a key resource for drinking water production and irrigation. The interplay between geological setting, hydrochemistry, carbon storage, and groundwater microbiome ecosystem functioning is crucial for our understanding of these important ecosystem services. We targeted the encoded and expressed metabolic potential of groundwater microbiomes along an aquifer transect that diversifies in terms of hydrochemistry and land use. Our results showed that the groundwater microbiome has a higher spatial differentiation potential than does hydrochemistry.

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