scholarly journals Antarctic Bacteria, Sea Ice Ecosystem Dynamics, and Global Climate Change

2021 ◽  
Author(s):  
◽  
Andrew Robert Martin
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Microbial Community ◽  
Dissolved Organic Matter ◽  
Southern Ocean ◽  
Sea Ice ◽  
Metabolic Activity ◽  
Bacterial Response ◽  
Pack Ice ◽  
Fast Ice

<p>Productivity in the Southern Ocean reflects both the spatial and temporal dynamics of the sea ice ecosystem, as well as the complex cycling of energy through the microbial community. Marine bacteria are thought to be integral to trophodynamics and the functioning of a microbial loop within the ice matrix, but there is no clear understanding of the distribution and diversity of bacteria or the importance of bacterial production. Understanding the bacterial response to environmental change in the sea ice ecosystem may provide an insight into the potential changes to the physical oceanography and ecology of the Southern Ocean. In this study, a multivariate statistical approach was used to compare the distribution and abundance of bacteria occurring in pack ice at the tongue of the Mertz Glacier (George V Coast, Antarctica) with bacteria from fast ice at Cape Hallett (Victoria Land coastline, Antarctica). Estimates of bacterial abundance were derived using both epifluorescence microscopy and flow cytometry and correlated with algal and chlorophyll a data. Significant differences in the vertical distribution of cells within the ice were observed between the Mertz Glacier and Cape Hallett, but no overall difference in cell abundance was found between the two locations with 7.6 ± 1.2 x 109 cells per m2 and 8.7 ± 1.6 x 109 cells per m2 respectively. Bacteria and algae were positively correlated in pack ice of the Mertz Glacier indicating a functional microbial loop, but no discernable relationship was exhibited in multiyear ice at Cape Hallett. These findings support the general consensus that the generation of bacterial biomass from algal-derived dissolved organic matter is highly variable across seasons and habitats. The tetrazolium salt 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) was used to investigate the bacterial response to experimentally induced changes in light and salinity in fast ice at Cape Hallett. Two distinct assemblages were examined; the brine channel assemblage near the surface of the ice and the interstitial or bottom assemblage. This study presents preliminary evidence that the metabolic activity of brine bacteria is influenced by light stimulus, most likely as a response to increased levels of algal-derived dissolved organic matter. No cells were deemed to be metabolically active when incubated in the dark, while on average thirty-eight percent of the cells incubated at 150 =mol photons m-2 s-1 were metabolically active. Additional results indicate that salt concentration is more significant than light irradiance in influencing the metabolic response of cells present in the interstitial region of the sea ice profile. When acclimated over a period of eight hours, cells exhibited a tolerance to changing saline concentrations, but after a further eight hours there is some evidence to suggest activity is reduced at either end of the saline regime. Bacterial metabolic activity in each assemblage is thus thought to reflect the fundamentally different light and saline environments within the sea ice. Metabolic probes such as CTC will prove useful in providing a mechanistic understanding of productivity and trophodynamics in the Antarctic coastal ecosystem, and may contribute to prognostic models for qualifying the resilience of the microbial community to climate change.</p>

scholarly journals Antarctic Bacteria, Sea Ice Ecosystem Dynamics, and Global Climate Change

2021 ◽  
Author(s):  
◽  
Andrew Robert Martin
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Microbial Community ◽  
Dissolved Organic Matter ◽  
Southern Ocean ◽  
Sea Ice ◽  
Metabolic Activity ◽  
Bacterial Response ◽  
Pack Ice ◽  
Fast Ice

<p>Productivity in the Southern Ocean reflects both the spatial and temporal dynamics of the sea ice ecosystem, as well as the complex cycling of energy through the microbial community. Marine bacteria are thought to be integral to trophodynamics and the functioning of a microbial loop within the ice matrix, but there is no clear understanding of the distribution and diversity of bacteria or the importance of bacterial production. Understanding the bacterial response to environmental change in the sea ice ecosystem may provide an insight into the potential changes to the physical oceanography and ecology of the Southern Ocean. In this study, a multivariate statistical approach was used to compare the distribution and abundance of bacteria occurring in pack ice at the tongue of the Mertz Glacier (George V Coast, Antarctica) with bacteria from fast ice at Cape Hallett (Victoria Land coastline, Antarctica). Estimates of bacterial abundance were derived using both epifluorescence microscopy and flow cytometry and correlated with algal and chlorophyll a data. Significant differences in the vertical distribution of cells within the ice were observed between the Mertz Glacier and Cape Hallett, but no overall difference in cell abundance was found between the two locations with 7.6 ± 1.2 x 109 cells per m2 and 8.7 ± 1.6 x 109 cells per m2 respectively. Bacteria and algae were positively correlated in pack ice of the Mertz Glacier indicating a functional microbial loop, but no discernable relationship was exhibited in multiyear ice at Cape Hallett. These findings support the general consensus that the generation of bacterial biomass from algal-derived dissolved organic matter is highly variable across seasons and habitats. The tetrazolium salt 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) was used to investigate the bacterial response to experimentally induced changes in light and salinity in fast ice at Cape Hallett. Two distinct assemblages were examined; the brine channel assemblage near the surface of the ice and the interstitial or bottom assemblage. This study presents preliminary evidence that the metabolic activity of brine bacteria is influenced by light stimulus, most likely as a response to increased levels of algal-derived dissolved organic matter. No cells were deemed to be metabolically active when incubated in the dark, while on average thirty-eight percent of the cells incubated at 150 =mol photons m-2 s-1 were metabolically active. Additional results indicate that salt concentration is more significant than light irradiance in influencing the metabolic response of cells present in the interstitial region of the sea ice profile. When acclimated over a period of eight hours, cells exhibited a tolerance to changing saline concentrations, but after a further eight hours there is some evidence to suggest activity is reduced at either end of the saline regime. Bacterial metabolic activity in each assemblage is thus thought to reflect the fundamentally different light and saline environments within the sea ice. Metabolic probes such as CTC will prove useful in providing a mechanistic understanding of productivity and trophodynamics in the Antarctic coastal ecosystem, and may contribute to prognostic models for qualifying the resilience of the microbial community to climate change.</p>

scholarly journals Illuminating microbial metabolic activities in the dark deep ocean with metaproteomics

2018 ◽  
Author(s):  
Zhang-Xian Xie ◽  
Shu-Feng Zhang ◽  
Hao Zhang ◽  
Ling-Fen Kong ◽  
Lin Lin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Dissolved Organic Matter ◽  
Metabolic Activity ◽  
Deep Ocean ◽  
Viral Proteins ◽  
Life Forms ◽  
Cytoplasmic Proteins ◽  
Proteomic Study ◽  
Metabolic Activities

AbstractThe deep ocean is the largest habitat on earth and holds diverse microbial life forms. Significant advances have been made in microbial diversity and their genomic potential in the deep ocean, however, little is known about microbial metabolic activity that is crucial to regulate the bathypelagic carbon sequestration. Here, we characterized proteomes covering large particulate (>0.7 μm), small particulate (0.2-0.7 μm) and dissolved (10 kDa-0.2 μm) fractions collected at a depth of 3000 m in the South China Sea. The Rhodospirillales, SAR324, SAR11, Nitrosinae/Tectomicrobia were the major contributors in the particulate fraction whereas Alteromonadales and viruses dominated the dissolved counterpart. Frequent detection of transcription or translation proteins in the particulate fractions indicated active metabolism of SAR324, Archaea, SAR11, and possible viable surface microbes, e.g. Prochlorococcus. Transporters for diverse substrates were the most abundant functional groups, and numerous spectra of formate dehydrogenases and glycine betaine transporters unveiled the importance of methylated compounds for the survival of deep-sea microbes. Notably, abundant non-viral proteins, especially transporters and cytoplasmic proteins, were detected in the dissolved fraction, indicating their potential roles in nutrient scavenging and the stress response. Our size-based proteomic study implied the holistic microbial activity mostly acting on the labile dissolved organic matter as well as the potential activities of surface microbes and dissolved non-viral proteins in the deep ocean.ImportanceThe deep ocean produces one third of the biological CO2 in the ocean. However, little is known about metabolic activity of the bathypelagic microbial community which is crucial for understanding the biogeochemical cycling of organic matter, especially the formation of bulk refractory dissolved organic matter (DOM), one of the largest reservoirs of reduced carbon on Earth. This study provided the protein evidence firstly including both particulate and dissolved fractions to comprehensively decipher the active microbes and metabolic processes involved in the DOM recycling in the deep ocean. Our data supported the hypothesis of the carbon and energy supply from the labile DOM after the solution of sinking particles to the bathypelagic microbial community.

scholarly journals The impact of the freeze–melt cycle of land-fast ice on the distribution of dissolved organic matter in the Laptev and East Siberian seas (Siberian Arctic)

2021 ◽  
Vol 18 (12) ◽  
pp. 3637-3655
Author(s):  
Jens A. Hölemann ◽  
Bennet Juhls ◽  
Dorothea Bauch ◽  
Markus Janout ◽  
Boris P. Koch ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Sea Ice ◽  
River Water ◽  
Set Covering ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Spring Freshet ◽  
Fast Ice ◽  
The Impact

Abstract. Permafrost degradation in the catchment of major Siberian rivers, combined with higher precipitation in a warming climate, could increase the flux of terrestrially derived dissolved organic matter (tDOM) into the Arctic Ocean (AO). Each year, ∼ 7.9 Tg of dissolved organic carbon (DOC) is discharged into the AO via the three largest rivers that flow into the Laptev Sea (LS) and East Siberian Sea (ESS). A significant proportion of this tDOM-rich river water undergoes at least one freeze–melt cycle in the land-fast ice that forms along the coast of the Laptev and East Siberian seas in winter. To better understand how growth and melting of land-fast ice affect dissolved organic matter (DOM) dynamics in the LS and ESS, we determined DOC concentrations and the optical properties of coloured dissolved organic matter (CDOM) in sea ice, river water and seawater. The data set, covering different seasons over a 9-year period (2010–2019), was complemented by oceanographic measurements (T, S) and determination of the oxygen isotope composition of the seawater. Although removal of tDOM cannot be ruled out, our study suggests that conservative mixing of high-tDOM river water and sea-ice meltwater with low-tDOM seawater is the major factor controlling the surface distribution of tDOM in the LS and ESS. A case study based on data from winter 2012 and spring 2014 reveals that the mixing of about 273 km3 of low-tDOM land-fast-ice meltwater (containing ∼ 0.3 Tg DOC) with more than 200 km3 of high-tDOM Lena River water discharged during the spring freshet (∼ 2.8 Tg DOC yr−1) plays a dominant role in this respect. The mixing of the two low-salinity surface water masses is possible because the meltwater and the river water of the spring freshet flow into the southeastern LS at the same time every year (May–July). In addition, budget calculations indicate that in the course of the growth of land-fast ice in the southeastern LS, ∼ 1.2 Tg DOC yr−1 (± 0.54 Tg) can be expelled from the growing ice in winter, together with brines. These DOC-rich brines can then be transported across the shelves into the Arctic halocline and the Transpolar Drift Current flowing from the Siberian Shelf towards Greenland. The study of dissolved organic matter dynamics in the AO is important not only to decipher the Arctic carbon cycle but also because CDOM regulates physical processes such as radiative forcing in the upper ocean, which has important effects on sea surface temperature, water column stratification, biological productivity and UV penetration.

scholarly journals Microbial Community Structure Affects Marine Dissolved Organic Matter Composition

2016 ◽  
Vol 3 ◽  
Author(s):  
Elizabeth B. Kujawinski ◽  
Krista Longnecker ◽  
Katie L. Barott ◽  
Ralf J. M. Weber ◽  
Melissa C. Kido Soule
Keyword(s):  
Organic Matter ◽  
Community Structure ◽  
Microbial Community ◽  
Dissolved Organic Matter ◽  
Microbial Community Structure ◽  
Organic Matter Composition

scholarly journals Selective incorporation of dissolved organic matter (DOM) during sea ice formation

2013 ◽  
Vol 155 ◽  
pp. 148-157 ◽  
Author(s):  
Susann Müller ◽  
Anssi V. Vähätalo ◽  
Colin A. Stedmon ◽  
Mats A. Granskog ◽  
Louiza Norman ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Sea Ice ◽  
Ice Formation ◽  
Selective Incorporation

scholarly journals Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean

2014 ◽  
Vol 11 (10) ◽  
pp. 14097-14132 ◽  
Author(s):  
L. Tremblay ◽  
J. Caparros ◽  
K. Leblanc ◽  
I. Obernosterer
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Southern Ocean ◽  
Surface Waters ◽  
Bacterial Degradation ◽  
Natural Iron ◽  
Average Proportion ◽  
Carbon Pump ◽  
Microbial Carbon

Abstract. Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolysable AA accounted for 21–25% of surface particulate organic carbon (%POCAA) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POCAA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9–4.4% of dissolved organic carbon (%DOCAA) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOCAA decreased from ∼2% in the surface waters to 0.9% near 300 m. These AA yields and other markers revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ∼15% of POM and ∼30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron, likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms.

scholarly journals Low Salinity and High-Level UV-B Radiation Reduce Single-Cell Activity in Antarctic Sea Ice Bacteria

2009 ◽  
Vol 75 (23) ◽  
pp. 7570-7573 ◽  
Author(s):  
Andrew Martin ◽  
Julie Hall ◽  
Ken Ryan
Keyword(s):  
Sea Ice ◽  
Metabolic Activity ◽  
Cell Activity ◽  
Ice Formation ◽  
Freeze Thaw ◽  
Low Salinity ◽  
Antarctic Sea Ice ◽  
Single Cell Activity ◽  
Fast Ice ◽  
High Level

ABSTRACT Experiments simulating the sea ice cycle were conducted by exposing microbes from Antarctic fast ice to saline and irradiance regimens associated with the freeze-thaw process. In contrast to hypersaline conditions (ice formation), the simulated release of bacteria into hyposaline seawater combined with rapid exposure to increased UV-B radiation significantly reduced metabolic activity.

scholarly journals Evidence for significant protein-like dissolved organic matter accumulation in Sea of Okhotsk sea ice

2015 ◽  
Vol 56 (69) ◽  
pp. 1-8 ◽  
Author(s):  
Mats A. Granskog ◽  
Daiki Nomura ◽  
Susann Müller ◽  
Andreas Krell ◽  
Takenobu Toyota ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Sea Ice ◽  
Surface Waters ◽  
Sea Of Okhotsk ◽  
Sea Water ◽  
First Year ◽  
Ice Melt ◽  
Ultraviolet Range ◽  
Considerable Excess

AbstractAbsorption and fluorescence of chromophoric dissolved organic matter (CDOM) in sea ice and surface waters in the southern Sea of Okhotsk was examined. Sea-water CDOM had featureless absorption increasing exponentially with shorter wavelengths. Sea ice showed distinct absorption peaks in the ultraviolet, especially in younger ice. Older first-year sea ice had relatively flat absorption spectra in the ultraviolet range. Parallel factor analysis (PARAFAC) identified five fluorescent CDOM components, two humic-like and three protein-like. Sea water was largely governed by humic-like fluorescence. In sea ice, protein-like fluorescence was found in considerable excess relative to sea water. The accumulation of protein-like CDOM fluorescence in sea ice is likely a result of biological activity within the ice. Nevertheless, sea ice does not contribute excess CDOM during melt, but the material released will be of different composition than that present in the underlying waters. Thus, at least transiently, the CDOM introduced during sea-ice melt might provide a more labile source of fresher protein-like DOM to surface waters in the southern Sea of Okhotsk.

Sign in / Sign up

Export Citation Format

Share Document