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

2015 ◽  
Vol 12 (2) ◽  
pp. 607-621 ◽  
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 the 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 hydrolyzable 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 revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Alteration state was also assessed by trends in C / N ratio, %D-AA and degradation index. 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 Decomposition of dissolved organic matter released by an isolate of Microcystis aeruginosa and morphological profile of the associated bacterial community

2011 ◽  
Vol 71 (1) ◽  
pp. 57-63 ◽  
Author(s):  
IC. Moreira ◽  
I. Bianchini Jr. ◽  
AAH. Vieira
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Bacterial Community ◽  
Dissolved Organic Matter ◽  
Microcystis Aeruginosa ◽  
Rate Constants ◽  
Bacterial Density ◽  
Bacterial Degradation ◽  
Order Kinetic ◽  
Order Kinetic Model

This study concerns the kinetics of bacterial degradation of two fractions (molecular mass) of dissolved organic matter (DOM) released by Microcystis aeruginosa. Barra Bonita Reservoir (SP, Brazil) conditions were simulated in the laboratory using the associated local bacterial community. The extent of degradation was quantified as the amount of organic carbon transferred from each DOM fraction (< 3 kDa and 3-30 kDa) to bacteria. The variation of bacteria morphotypes associated with the decomposition of each fraction was observed. To find the degradation rate constants (kT), the time profiles of the total, dissolved and particulate organic carbon concentrations were fitted to a first-order kinetic model. These rate constants were higher for the 3-30 kDa fraction than for the lighter fraction. Only in the latter fraction the formation of refractory dissolved organic carbon (DOC R) compounds could be detected and its rate of mass loss was low. The higher bacterial density was reached at 24 and 48 hours for small and higher fractions, respectively. In the first 48 hours of decomposition of both fractions, there was an early predominance of bacillus, succeeded by coccobacillus, vibrios and coccus, and from day 5 to 27, the bacterial density declined and there was greater evenness among the morphotypes. Both fractions of DOM were consumed rapidly, corroborating the hypothesis that DOM is readily available in the environment. This also suggests that the bacterial community in the inocula readily uses the labile part of the DOM, until this community is able to metabolise efficiently the remaining of DOM not degraded in the first moment. Given that M. aeruginosa blooms recur throughout the year in some eutrophic reservoirs, there is a constant supply of the same DOM which could maintain a consortium of bacterial morphotypes adapted to consuming this substrate.

Sources of Energy in Subterranean Environments

2019 ◽  
pp. 24-42
Author(s):  
David C. Culver ◽  
Tanja Pipan
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Surface Waters ◽  
Carbon Fluxes ◽  
The Other ◽  
Other Hand

Although subterranean habitats in general and caves in particular are often held to be extremely energy-poor (oligotrophic) environments, not all are. Compared to surface habitats, subterranean habitats are nutrient-poor, especially because there is no photo-autotrophic production and chemoautotrophy appears to be uncommon. On the other hand, these differences are not always pronounced. For example, the quantities of carbon fluxes in cave streams are in the range of those reported from surface streams. In some subterranean systems, chemoautotrophy is the main source of energy, but more typically subterranean communities depend on allochthonous sources of organic carbon. The major source of carbon in interstitial habitats is Dissolved Organic Matter (DOM) from surface waters. The major sources of carbon for cave communities are (1) water percolating from the surface, (2) sinking streams that enter caves, and (3) activities of animals moving in and out of caves.

scholarly journals The composition and distribution of semi-labile dissolved organic matter across the southwest Pacific

2019 ◽  
Vol 16 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Christos Panagiotopoulos ◽  
Mireille Pujo-Pay ◽  
Mar Benavides ◽  
France Van Wambeke ◽  
Richard Sempéré
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Residence Time ◽  
Surface Waters ◽  
Euphotic Zone ◽  
South Pacific ◽  
Bacterial Degradation ◽  
The South ◽  
Energy Limitation ◽  
South Pacific Gyre

Abstract. The distribution and dynamics of dissolved organic carbon (DOC) and dissolved combined neutral sugars (DCNS) were studied across an increasing oligotrophic gradient (18 to 22∘ S latitude) in the tropical South Pacific Ocean, spanning from the Melanesian Archipelago (MA) area to the western part of the South Pacific gyre (WGY), in austral summer as a part of the OUTPACE project. Our results show that DOC and DCNS concentrations exhibited no statistical differences between the MA and WGY areas (0–200 m: 47–81 µM C for DOC and 0.2-4.2 µM C for DCNS). However, due to a deepening of the euphotic zone, a deeper penetration of DOC was noticeable at 150 m of depth at the WGY area. Excess DOC (DOCEX) was determined as the difference between surface and deep-sea DOC values, and euphotic zone integrated stocks of both DOC and DOCEX were higher in the WGY than the MA area. Considering DOCEX as representative of semi-labile DOC (DOCSL), its residence time was calculated as the ratio of DOCSL to bacterial carbon demand (BCD). This residence time was 176±43 days (n=3) in the WGY area, about 3 times longer than in the MA area (Tr=51±13 days, n=8), suggesting an accumulation of semi-labile dissolved organic matter (DOM) in the surface waters of WGY. Average epipelagic (0–200 m) DCNS yields (DCNS × DOC−1) based on volumetric data were roughly similar in both areas, accounting for ∼2.8 % of DOC. DCNS exhibited a longer residence time in WGY (Tr=91±41 days, n=3) than in MA (Tr=31±10 days, n=8), further suggesting that this DCNS pool persists longer in the surface waters of the WGY. The accumulation of DOCEX in the surface waters of WGY is probably due to very slow bacterial degradation due to nutrient and/or energy limitation of heterotrophic prokaryotes, indicating that biologically produced DOC can be stored in the euphotic layer of the South Pacific gyre for a long period.

scholarly journals The microbial carbon pump and the oceanic recalcitrant dissolved organic matter pool

2011 ◽  
Vol 9 (7) ◽  
pp. 555-555 ◽  
Author(s):  
Nianzhi Jiao ◽  
Gerhard J. Herndl ◽  
Dennis A. Hansell ◽  
Ronald Benner ◽  
Gerhard Kattner ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Carbon Pump ◽  
Organic Matter Pool ◽  
Microbial Carbon ◽  
Microbial Carbon Pump

scholarly journals Impact of aquaculture on distribution of dissolved organic matter in coastal Jeju Island, Korea, based on absorption and fluorescence spectroscopy

2021 ◽  
Author(s):  
Jeonghyun Kim ◽  
Yeseul Kim ◽  
Sung Eun Park ◽  
Tae-Hoon Kim ◽  
Bong-Guk Kim ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Fluorescence Spectroscopy ◽  
Dissolved Organic Matter ◽  
Coastal Water ◽  
Coastal Region ◽  
Principal Component ◽  
Distribution Patterns ◽  
Organic Pollution ◽  
Jeju Island

AbstractIn Jeju Island, multiple land-based aquafarms were fully operational along most coastal region. However, the effect of effluent on distribution and behaviours of dissolved organic matter (DOM) in the coastal water are still unknown. To decipher characteristics of organic pollution, we compared physicochemical parameters with spectral optical properties near the coastal aquafarms in Jeju Island. Absorption spectra were measured to calculate the absorption coefficient, spectral slope coefficient, and specific UV absorbance. Fluorescent DOM was analysed using fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured using high-temperature catalytic oxidation. The DOC concentration near the discharge outlet was twice higher than that in natural groundwater, and the TDN concentration exponentially increased close to the outlet. These distribution patterns indicate that aquafarms are a significant source of DOM. Herein, principal component analysis was applied to categorise the DOM origins. There were two distinct groups, namely, aquaculture activity for TDN with humic-like and high molecular weights DOM (PC1: 48.1%) and natural biological activity in the coastal water for DOC enrichment and protein-like DOM (PC2: 18.8%). We conclude that the aquafarms significantly discharge organic nitrogen pollutants and provoke in situ production of organic carbon. Furthermore, these findings indicate the potential of optical techniques for the efficient monitoring of anthropogenic organic pollutants from aquafarms worldwide.

scholarly journals Distribution of inorganic and organic nutrients in the South Pacific Ocean − evidence for long-term accumulation of organic matter in nitrogen-depleted waters

2008 ◽  
Vol 5 (2) ◽  
pp. 281-298 ◽  
Author(s):  
P. Raimbault ◽  
N. Garcia ◽  
F. Cerutti
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Dissolved Organic Carbon ◽  
Chlorophyll A ◽  
Organic Phosphorus ◽  
South Pacific ◽  
Nutrient Concentrations ◽  
The South ◽  
Photic Layer

Abstract. During the BIOSOPE cruise the RV Atalante was dedicated to study the biogeochemical properties in the South Pacific between the Marquesas Islands (141° W–8° S) and the Chilean upwelling (73° W–34° S). Over the 8000 km covered by the cruise, several different trophic situations were encountered, in particular strong oligotrophic conditions in the South Pacific Gyre (SPG, between 123° W and 101° W). In this isolated region, nitrate was undetectable between the surface and 160–180 m and only trace quantities (<20 nmoles l−1) of regenerated nitrogen (nitrite and ammonium) were detected, even in the subsurface maximum. Integrated nitrate over the photic layer, which reached 165 m, was close to zero. Despite this severe nitrogen-depletion, phosphate was always present in significant concentrations (≈0.1 μmoles l−1), while silicic acid was maintained at low but classical oceanic levels (≈1 μmoles l−1). In contrast, the Marquesas region (MAR) to the west and Chilean upwelling (UPW) to the east were characterized by high nutrient concentrations, one hundred to one thousand fold higher than in the SPG. The distribution of surface chlorophyll reflected the nitrate gradient, the lowest concentrations (0.023 nmoles l−1) being measured at the centre of the SPG, where integrated value throughout the photic layer was very low (≈ 10 mg m−2). However, due to the relatively high concentrations of chlorophyll-a encountered in the DCM (0.2 μg l−1), chlorophyll-a concentrations throughout the photic layer were less variable than nitrate concentrations (by a factor 2 to 5). In contrast to chlorophyll-a, integrated particulate organic matter (POM) remained more or less constant along the study area (500 mmoles m−2, 60 mmoles m−2 and 3.5 mmoles m−2 for particulate organic carbon, particulate organic nitrogen and particulate organic phosphorus, respectively), with the exception of the upwelling, where values were two fold higher. The residence time of particulate carbon in the surface water was only 4–5 days in the upwelling, but up to 30 days in the SPG, where light isotopic δ15N signal noted in the suspended POM suggests that N2-fixation provides a dominant supply of nitrogen to phytoplankton. The most striking feature was the large accumulation of dissolved organic matter (DOM) in the SPG compared to the surrounding waters, in particular dissolved organic carbon (DOC) where concentrations were at levels rarely measured in oceanic waters (>100 μmoles l−1). Due to this large pool of DOM in the SPG photic layer, integrated values followed a converse geographical pattern to that of inorganic nutrients with a large accumulation in the centre of the SPG. Whereas suspended particulate matter in the mixed layer had a C/N ratio largely conforming to the Redfield stochiometry (C/N≈6.6), marked deviations were observed in this excess DOM (C/N≈16 to 23). The marked geographical trend suggests that a net in situ source exists, mainly due to biological processes. Thus, in spite of strong nitrate-depletion leading to low chlorophyll biomass, the closed ecosystem of the SPG can accumulate large amounts of C-rich dissolved organic matter. The implications of this finding are examined, the conclusion being that, due to weak lateral advection, the biologically produced dissolved organic carbon can be accumulated and stored in the photic layer for very long periods. In spite of the lack of seasonal vertical mixing, a significant part of new production (up to 34%), which was mainly supported by dinitrogen fixation, can be exported to deep waters by turbulent diffusion in terms of DOC. The diffusive rate estimated in the SPG (134 μmolesC m−2 d−1), was quite equivalent to the particles flux measured by sediments traps.

scholarly journals Bioavailability and bacterial degradation rates of dissolved organic matter in a temperate coastal area during an annual cycle

2009 ◽  
Vol 113 (3-4) ◽  
pp. 219-226 ◽  
Author(s):  
Christian Lønborg ◽  
Keith Davidson ◽  
Xosé A. Álvarez–Salgado ◽  
Axel E.J. Miller
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Annual Cycle ◽  
Coastal Area ◽  
Bacterial Degradation ◽  
Degradation Rates
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