scholarly journals Effect of CO<sub>2</sub> on the properties and sinking velocity of aggregates of the coccolithophore <i>Emiliania huxleyi</i>

2009 ◽  
Vol 6 (5) ◽  
pp. 9817-9848
Author(s):  
A. Biermann ◽  
A. Engel
Keyword(s):  
Organic Matter ◽  
Emiliania Huxleyi ◽  
Bacterial Degradation ◽  
High Co2 ◽  
Low Co2 ◽  
Order Of Magnitude ◽  
Excess Density ◽  
Vertical Export ◽  
Co2 Treatment ◽  
Sinking Velocity

Abstract. Coccolithophores play an important role in organic matter export due to their production of the mineral calcite that can act as ballast. Recent studies indicated that calcification in coccolithophores may be affected by changes in seawater carbonate chemistry. We investigated the influence of CO2 on the aggregation and sinking behaviour of the coccolithophore Emiliania huxleyi (PML B92/11) during a laboratory experiment. The coccolithophores were grown under low (~180 μatm), medium (~380 μatm), and high (~750 μatm) CO2 conditions. Aggregation of the cells was promoted using roller tables. Size and settling velocity of aggregates were determined during the incubation using video image analysis. The results show that CO2 induced changes in the inorganic carbon to organic carbon ratio (PIC/POC) influence the porosity and hence the sinking velocity of aggregates of Emiliania huxleyi. Average sinking velocity was highest for low CO2 aggregates (~1292 m d−1) that also had the highest PIC/POC ratio. Lowest PIC/POC ratios and lowest sinking velocity (~366 m d−1) at comparable sizes were observed for aggregates of the high CO2 treatment. Aggregates of the high CO2 treatment showed an excess density about one order of magnitude lower (~4.2×10−4 g cm−3) when compared to aggregates from the medium and low CO2 treatments (~1.7×10−3 g cm−3). Thus, the amount of calcite in aggregates is crucial for the degree of ballasting effect. In the high CO2 treatment, aggregates with lower calcite content had higher bacterial abundance, suggesting enhanced bacterial degradation. Thus, our findings indicate that a CO2 induced reduction of calcite content aggregates could affect the vertical export of organic matter in the ocean, particularly in areas dominated by coccolithophores blooms.

scholarly journals Effect of CO<sub>2</sub> on the properties and sinking velocity of aggregates of the coccolithophore <I>Emiliania huxleyi</I>

2010 ◽  
Vol 7 (3) ◽  
pp. 1017-1029 ◽  
Author(s):  
A. Biermann ◽  
A. Engel
Keyword(s):  
Organic Matter ◽  
Settling Velocity ◽  
Emiliania Huxleyi ◽  
High Co2 ◽  
Low Co2 ◽  
Aggregate Properties ◽  
Excess Density ◽  
Seawater Carbonate Chemistry ◽  
Co2 Treatment ◽  
Sinking Velocity

Abstract. Coccolithophores play an important role in organic matter export due to their production of the mineral calcite that can act as ballast. Recent studies indicated that calcification in coccolithophores may be affected by changes in seawater carbonate chemistry. We investigated the influence of CO2 on the aggregation and sinking behaviour of the coccolithophore Emiliania huxleyi (PML B92/11) during a laboratory experiment. The coccolithophores were grown under low (~180 μatm), medium (~380 μatm), and high (~750 μatm) CO2 conditions. Aggregation of the cells was promoted using roller tables. Size and settling velocity of aggregates were determined during the incubation using video image analysis. Our results indicate that aggregate properties are sensitive to changes in the degree of ballasting, as evoked by ocean acidification. Average sinking velocity was highest for low CO2 aggregates (~1292 m d−1) that also had the highest particulate inorganic to particulate organic carbon (PIC/POC) ratio. Lowest PIC/POC ratios and lowest sinking velocity (~366 m d−1) at comparable sizes were observed for aggregates of the high CO2 treatment. Aggregates of the high CO2 treatment showed a 4-fold lower excess density (~4.2×10−4 g cm−3) when compared to aggregates from the medium and low CO2 treatments (~1.7 g×10−3 cm−3). We also observed that more aggregates formed in the high CO2 treatment, and that those aggregates contained more bacteria than aggregates in the medium and low CO2 treatment. If applicable to the future ocean, our findings suggest that a CO2 induced reduction of the calcite content of aggregates could weaken the deep export of organic matter in the ocean, particularly in areas dominated by coccolithophores.

scholarly journals High-CO2 Treatment Prolongs the Postharvest Shelf Life of Strawberry Fruits by Reducing Decay and Cell Wall Degradation

Foods ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1649
Author(s):  
Hyang-Lan Eum ◽  
Seung-Hyun Han ◽  
Eun-Jin Lee
Keyword(s):  
Cell Wall ◽  
Shelf Life ◽  
Physiological Mechanism ◽  
Pectate Lyase ◽  
Pectin Methylesterase ◽  
Cell Wall Degradation ◽  
Cell Wall Degrading Enzymes ◽  
High Co2 ◽  
Genes Encoding ◽  
Co2 Treatment

Improved methods are needed to extend the shelf life of strawberry fruits. The objective of this study was to determine the postharvest physiological mechanism of high-CO2 treatment in strawberries. Harvested strawberries were stored at 10 °C after 3 h of exposure to a treatment with 30% CO2 or air. Pectin and gene expression levels related to cell wall degradation were measured to assess the high-CO2 effects on the cell wall and lipid metabolism. Strawberries subjected to high-CO2 treatment presented higher pectin content and firmness and lower decay than those of control fruits. Genes encoding cell wall-degrading enzymes (pectin methylesterase, polygalacturonase, and pectate lyase) were downregulated after high-CO2 treatment. High-CO2 induced the expression of oligogalacturonides, thereby conferring defense against Botrytis cinerea in strawberry fruits, and lowering the decay incidence at seven days after its inoculation. Our findings suggest that high-CO2 treatment can maintain strawberry quality by reducing decay and cell wall degradation.

scholarly journals Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO<sub>2</sub> tolerance in phytoplankton productivity

2018 ◽  
Vol 15 (1) ◽  
pp. 209-231 ◽  
Author(s):  
Stacy Deppeler ◽  
Katherina Petrou ◽  
Kai G. Schulz ◽  
Karen Westwood ◽  
Imojen Pearce ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ocean Acidification ◽  
Primary Productivity ◽  
Phytoplankton Community ◽  
Bacterial Abundance ◽  
Critical Threshold ◽  
Bacterial Productivity ◽  
High Co2 ◽  
Chl A ◽  
Antarctic Marine

Abstract. High-latitude oceans are anticipated to be some of the first regions affected by ocean acidification. Despite this, the effect of ocean acidification on natural communities of Antarctic marine microbes is still not well understood. In this study we exposed an early spring, coastal marine microbial community in Prydz Bay to CO2 levels ranging from ambient (343 µatm) to 1641 µatm in six 650 L minicosms. Productivity assays were performed to identify whether a CO2 threshold existed that led to a change in primary productivity, bacterial productivity, and the accumulation of chlorophyll a (Chl a) and particulate organic matter (POM) in the minicosms. In addition, photophysiological measurements were performed to identify possible mechanisms driving changes in the phytoplankton community. A critical threshold for tolerance to ocean acidification was identified in the phytoplankton community between 953 and 1140 µatm. CO2 levels  ≥ 1140 µatm negatively affected photosynthetic performance and Chl a-normalised primary productivity (csGPP14C), causing significant reductions in gross primary production (GPP14C), Chl a accumulation, nutrient uptake, and POM production. However, there was no effect of CO2 on C : N ratios. Over time, the phytoplankton community acclimated to high CO2 conditions, showing a down-regulation of carbon concentrating mechanisms (CCMs) and likely adjusting other intracellular processes. Bacterial abundance initially increased in CO2 treatments  ≥ 953 µatm (days 3–5), yet gross bacterial production (GBP14C) remained unchanged and cell-specific bacterial productivity (csBP14C) was reduced. Towards the end of the experiment, GBP14C and csBP14C markedly increased across all treatments regardless of CO2 availability. This coincided with increased organic matter availability (POC and PON) combined with improved efficiency of carbon uptake. Changes in phytoplankton community production could have negative effects on the Antarctic food web and the biological pump, resulting in negative feedbacks on anthropogenic CO2 uptake. Increases in bacterial abundance under high CO2 conditions may also increase the efficiency of the microbial loop, resulting in increased organic matter remineralisation and further declines in carbon sequestration.

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

Formation of mesopyrophaeophorbide a during anaerobic bacterial degradation of the marine prymnesiophyte Emiliania huxleyi

1995 ◽  
Vol 22 (1) ◽  
pp. 225-229 ◽  
Author(s):  
N. Spooner ◽  
J.M. Getliff ◽  
M.A. Teece ◽  
R.J. Parkes ◽  
J.W. Leftley ◽  
...  
Keyword(s):  
Emiliania Huxleyi ◽  
Bacterial Degradation

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 Mimicking floodplain reconnection and disconnection using <sup>15</sup>N mesocosm incubations

2012 ◽  
Vol 9 (11) ◽  
pp. 4263-4278 ◽  
Author(s):  
N. Welti ◽  
E. Bondar-Kunze ◽  
M. Mair ◽  
P. Bonin ◽  
W. Wanek ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Nitrogen Retention ◽  
Danube River ◽  
Nitrous Oxide Emissions ◽  
Organic Matter Quality ◽  
Main River Channel ◽  
Order Of Magnitude ◽  
Floodplain Reconnection ◽  
Floodplain Sediments

Abstract. Floodplain restoration changes the nitrate delivery pattern and dissolved organic matter pool in backwaters, though the effects these changes have are not yet well known. We performed two mesocosm experiments on floodplain sediments to quantify the nitrate metabolism in two types of floodplains. Rates of denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and anammox were measured using 15N-NO3 tracer additions in mesocosms of undisturbed floodplain sediments originating from (1) restored and (2) disconnected sites in the Alluvial Zone National Park on the Danube River downstream of Vienna, Austria. DNRA rates were an order of magnitude lower than denitrification and neither rate was affected by changes in nitrate delivery pattern or organic matter quality. Anammox was not detected at any of the sites. Denitrification was out-competed by assimilation, which was estimated to use up to 70% of the available nitrate. Overall, denitrification was higher in the restored sites, with mean rates of 5.7 ± 2.8 mmol N m−2 h−1 compared to the disconnected site (0.6 ± 0.5 mmol N m−2 h−1). In addition, ratios of N2O : N2 were lower in the restored site indicating a more complete denitrification. Nitrate addition had neither an effect on denitrification, nor on the N2O : N2 ratio. However, DOM (dissolved organic matter) quality significantly changed the N2O : N2 ratio in both sites. Addition of riverine-derived organic matter lowered the N2O : N2 ratio in the disconnected site, whereas addition of floodplain-derived organic matter increased the N2O : N2 ratio in the restored site. These results demonstrate that increasing floodplains hydrological connection to the main river channel increases nitrogen retention and decreases nitrous oxide emissions.

scholarly journals Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

2020 ◽  
Vol 44 (1) ◽  
pp. 103-122
Author(s):  
Julia M. Moriarty ◽  
Marjorie A. M. Friedrichs ◽  
Courtney K. Harris
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Water Column ◽  
Primary Productivity ◽  
Environmental Changes ◽  
Light Attenuation ◽  
Sediment Resuspension ◽  
Nitrogen Dynamics ◽  
Biogeochemical Model ◽  
Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

scholarly journals Formation of Chromophoric Dissolved Organic Matter by Bacterial Degradation of Phytoplankton-Derived Aggregates

2018 ◽  
Vol 4 ◽  
Author(s):  
Joanna D. Kinsey ◽  
Gabrielle Corradino ◽  
Kai Ziervogel ◽  
Astrid Schnetzer ◽  
Christopher L. Osburn
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Bacterial Degradation ◽  
Chromophoric Dissolved Organic Matter

Photosynthetic utilisation of inorganic carbon and its regulation in the marine diatom Skeletonema costatum

2004 ◽  
Vol 31 (10) ◽  
pp. 1027 ◽  
Author(s):  
Xiongwen Chen ◽  
Kunshan Gao
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Skeletonema Costatum ◽  
Co2 Concentration ◽  
Marine Diatom ◽  
Disulfonic Acid ◽  
High Co2 ◽  
Low Co2 ◽  
Diatom Skeletonema Costatum ◽  
Very High

Photosynthetic uptake of inorganic carbon and regulation of photosynthetic CO2 affinity were investigated in Skeletonema costatum (Grev.) Cleve. The pH independence of K1/2(CO2) values indicated that algae grown at either ambient (12 μmol L–1) or low (3 μmol L–1) CO2 predominantly took up CO2 from the medium. The lower pH compensation point (9.12) and insensitivity of photosynthetic rate to di-isothiocyanatostilbene disulfonic acid (DIDS) indicated that the alga had poor capacity for direct HCO3– utilisation. Photosynthetic CO2 affinity is regulated by the concentration of CO2 rather than HCO3–, CO32– or total dissolved inorganic carbon (DIC) in the medium. The response of photosynthetic CO2 affinity to changes in CO2 concentration was most sensitive within the range 3–48 μmol L–1 CO2. Light was required for the induction of photosynthetic CO2 affinity, but not for its repression, when cells were shifted between high (126 μmol L–1) and ambient (12 μmol L–1) CO2. The time needed for cells grown at high CO2 (126 μmol L–1) to fully develop photosynthetic CO2 affinity at ambient CO2 was approximately 2 h, but acclimation to low or very low CO2 levels (3 and 1.3 μmol L–1, respectively) took more than 10 h. Cells grown at low CO2 (3 μmol L–1) required approximately 10 h for repression of all photosynthetic CO2 affinity when transferred to ambient or high CO2 (12 or 126 μmol L–1, respectively), and more than 10 h at very high CO2 (392 μmol L–1).

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