scholarly journals Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment

2016 ◽  
Vol 13 (21) ◽  
pp. 6081-6093 ◽  
Author(s):  
Kristian Spilling ◽  
Kai G. Schulz ◽  
Allanah J. Paul ◽  
Tim Boxhammer ◽  
Eric P. Achterberg ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Ocean Acidification ◽  
Bacterial Production ◽  
Co2 Concentration ◽  
Carbon Fluxes ◽  
Co2 Levels ◽  
Standing Stocks ◽  
Co2 Treatment ◽  
Ambient Co2

Abstract. About a quarter of anthropogenic CO2 emissions are currently taken up by the oceans, decreasing seawater pH. We performed a mesocosm experiment in the Baltic Sea in order to investigate the consequences of increasing CO2 levels on pelagic carbon fluxes. A gradient of different CO2 scenarios, ranging from ambient ( ∼  370 µatm) to high ( ∼  1200 µatm), were set up in mesocosm bags ( ∼  55 m3). We determined standing stocks and temporal changes of total particulate carbon (TPC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) of specific plankton groups. We also measured carbon flux via CO2 exchange with the atmosphere and sedimentation (export), and biological rate measurements of primary production, bacterial production, and total respiration. The experiment lasted for 44 days and was divided into three different phases (I: t0–t16; II: t17–t30; III: t31–t43). Pools of TPC, DOC, and DIC were approximately 420, 7200, and 25 200 mmol C m−2 at the start of the experiment, and the initial CO2 additions increased the DIC pool by  ∼  7 % in the highest CO2 treatment. Overall, there was a decrease in TPC and increase of DOC over the course of the experiment. The decrease in TPC was lower, and increase in DOC higher, in treatments with added CO2. During phase I the estimated gross primary production (GPP) was  ∼  100 mmol C m−2 day−1, from which 75–95 % was respired,  ∼  1 % ended up in the TPC (including export), and 5–25 % was added to the DOC pool. During phase II, the respiration loss increased to  ∼  100 % of GPP at the ambient CO2 concentration, whereas respiration was lower (85–95 % of GPP) in the highest CO2 treatment. Bacterial production was  ∼  30 % lower, on average, at the highest CO2 concentration than in the controls during phases II and III. This resulted in a higher accumulation of DOC and lower reduction in the TPC pool in the elevated CO2 treatments at the end of phase II extending throughout phase III. The “extra” organic carbon at high CO2 remained fixed in an increasing biomass of small-sized plankton and in the DOC pool, and did not transfer into large, sinking aggregates. Our results revealed a clear effect of increasing CO2 on the carbon budget and mineralization, in particular under nutrient limited conditions. Lower carbon loss processes (respiration and bacterial remineralization) at elevated CO2 levels resulted in higher TPC and DOC pools than ambient CO2 concentration. These results highlight the importance of addressing not only net changes in carbon standing stocks but also carbon fluxes and budgets to better disentangle the effects of ocean acidification.

scholarly journals Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment

2016 ◽  
Author(s):  
Kristian Spilling ◽  
Kai G. Schulz ◽  
Allanah J. Paul ◽  
Tim Boxhammer ◽  
Eric P. Achterberg ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Ocean Acidification ◽  
Bacterial Production ◽  
Co2 Concentration ◽  
Carbon Fluxes ◽  
Co2 Levels ◽  
Standing Stocks ◽  
Co2 Treatment ◽  
Ambient Co2

Abstract. About a quarter of anthropogenic CO2 emissions are currently taken up by the oceans decreasing seawater pH. We performed a mesocosm experiment in the Baltic Sea in order to investigate the consequences of increasing CO2 levels on pelagic carbon fluxes. A gradient of different CO2 scenarios, ranging from ambient (~ 370 µatm) to high (~ 1200 µatm), were set up in mesocosm bags (~ 55 m3). We determined standing stocks and temporal changes of total particulate carbon (TPC), dissolved organic (DOC), dissolved inorganic (DIC) and particulate organic carbon (POC) of specific plankton groups. We also measured carbon flux via CO2 exchange with the atmosphere and sedimentation (export); and biological rate measurements of primary production, bacterial production and total respiration. The experiment lasted for 44 days and was divided into three different phases (I: t0–t16; II: t17–t30; III: t31–t43). Pools of TPC, DOC and DIC were approximately 420, 7200 and 25 200 mmol C m−2 at the start of the experiment, and the initial CO2 additions increased the DIC pool by ~ 7 % in the highest CO2 treatment. Overall, there was a decrease in TPC and increase of DOC over the course of the experiment. The decrease in TPC was lower, and increase in DOC higher, in treatments with added CO2. During Phase I the estimated gross primary production (GPP) was ~ 100 mmol C fixed m−2 d−1; from which 75–95 % were respired, ~ 1 % ended up in the TPC (including export) and 5–25 % added to the DOC pool. During Phase II, the respiration loss increased to ~ 100 % of GPP at the ambient CO2 concentration, whereas respiration was lower (85–95 % of GPP) in the highest CO2 treatment. Bacterial production was ~ 30 % lower, on average, at the highest CO2 concentration compared with the controls during Phases II and III. This resulted in a higher accumulation DOC standing stock and lower reduction in TPC in the elevated CO2 treatments at the end of Phase II extending throughout Phase III. The "extra" organic carbon at high CO2 remained fixed in an increasing biomass of small-sized plankton and in the DOC pool, and did not transferred into large, sinking aggregates. Our results revealed a clear effect of increasing CO2 on carbon production and mineralization, in particular under nutrient limited conditions. Lower carbon loss processes (respiration and bacterial remineralization) at elevated CO2 levels resulted in higher TPC and DOC pools compared with the ambient CO2 concentration. These results highlight the importance to address not only net changes in carbon standing stocks, but also carbon fluxes and budgets to better disentangle the effects of ocean acidification.

scholarly journals Dynamics of N<sub>2</sub> fixation and fate of diazotroph-derived nitrogen in a low nutrient low chlorophyll ecosystem: results from the VAHINE mesocosm experiment (New Caledonia)

2015 ◽  
Vol 12 (23) ◽  
pp. 19579-19626 ◽  
Author(s):  
S. Bonnet ◽  
H. Berthelot ◽  
K. Turk-Kubo ◽  
S. Fawcett ◽  
E. Rahav ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Particulate Organic Carbon ◽  
N2 Fixation ◽  
Bacterial Production ◽  
New Caledonia ◽  
Seawater Temperature ◽  
Global Ocean ◽  
Nitrogen And Phosphorus ◽  
Standing Stocks

Abstract. N2 fixation rates were measured daily in large (~ 50 m3) mesocosms deployed in the tropical South West Pacific coastal ocean (New Caledonia) to investigate the spatial and temporal dynamics of diazotrophy and the fate of diazotroph-derived nitrogen (DDN) in a low nutrient, low chlorophyll ecosystem. The mesocosms were intentionally fertilized with ~ 0.8 μM dissolved inorganic phosphorus (DIP) to stimulate diazotrophy. Bulk N2 fixation rates were replicable between the three mesocosms, averaged 18.5 ± 1.1 nmol N L−1 d−1 over the 23 days, and increased by a factor of two during the second half of the experiment (days 15 to 23) to reach 27.3 ± 1.0 nmol N L−1 d−1. These rates are higher than the upper range reported for the global ocean, indicating that the waters surrounding New Caledonia are particularly favourable for N2 fixation. During the 23 days of the experiment, N2 fixation rates were positively correlated with seawater temperature, primary production, bacterial production, standing stocks of particulate organic carbon, nitrogen and phosphorus, and alkaline phosphatase activity, and negatively correlated with DIP concentrations, DIP turnover time, nitrate, and dissolved organic nitrogen and phosphorus concentrations. The fate of DDN was investigated during the bloom of the unicellular diazotroph, UCYN-C, that occurred during the second half of the experiment. Quantification of diazotrophs in the sediment traps indicates that ~ 10 % of UCYN-C from the water column were exported daily to the traps, representing as much as 22.4 ± 5.5 % of the total POC exported at the height of the UCYN-C bloom. This export was mainly due to the aggregation of small (5.7 ± 0.8 μm) UCYN-C cells into large (100–500 μm) aggregates. During the same time period, a DDN transfer experiment based on high-resolution nanometer scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2 isotopic labelling revealed that 16 ± 6 % of the DDN was released to the dissolved pool and 21 ± 4 % was transferred to non-diazotrophic plankton, mainly picoplankton (18 ± 4 %) followed by diatoms (3 ± 2 %) within 24 h of incubation. This is consistent with the observed dramatic increase in picoplankton and diatom abundances, primary production, bacterial production and standing stocks of particulate organic carbon, nitrogen and phosphorus during the second half of the experiment in the mesocosms. These results offer insights into the fate of DDN during a bloom of UCYN-C in low nutrient, low chlorophyll ecosystems.

scholarly journals The ballast effect of lithogenic matter and its influences on the carbon fluxes in the Indian Ocean

2019 ◽  
Vol 16 (2) ◽  
pp. 485-503 ◽  
Author(s):  
Tim Rixen ◽  
Birgit Gaye ◽  
Kay-Christian Emeis ◽  
Venkitasubramani Ramaswamy
Keyword(s):  
Indian Ocean ◽  
Organic Carbon ◽  
Spatial Variability ◽  
Primary Production ◽  
Carbon Flux ◽  
Carbon Fluxes ◽  
Matter Content ◽  
Organic Carbon Flux ◽  
The Indian Ocean ◽  
Organic Carbon Fluxes

Abstract. Data obtained from long-term sediment trap experiments in the Indian Ocean in conjunction with satellite observations illustrate the influence of primary production and the ballast effect on organic carbon flux into the deep sea. They suggest that primary production is the main control on the spatial variability of organic carbon fluxes at most of our study sites in the Indian Ocean, except at sites influenced by river discharges. At these sites the spatial variability of organic carbon flux is influenced by lithogenic matter content. To quantify the impact of lithogenic matter on the organic carbon flux, the densities of the main ballast minerals, their flux rates and seawater properties were used to calculate sinking speeds of material intercepted by sediment traps. Sinking speeds in combination with satellite-derived export production rates allowed us to compute organic carbon fluxes. Flux calculations imply that lithogenic matter ballast increases organic carbon fluxes at all sampling sites in the Indian Ocean by enhancing sinking speeds and reducing the time of organic matter respiration in the water column. We calculated that lithogenic matter content in aggregates and pellets enhances organic carbon flux rates on average by 45 % and by up to 62 % at trap locations in the river-influenced regions of the Indian Ocean. Such a strong lithogenic matter ballast effect explains the fact that organic carbon fluxes are higher in the low-productive southern Java Sea compared to the high-productive western Arabian Sea. It also implies that land use changes and the associated enhanced transport of lithogenic matter from land into the ocean may significantly affect the CO2 uptake of the organic carbon pump in the receiving ocean areas.

scholarly journals Cymodocea nodosa response to simulated CO2-driven ocean acidification: a first insight from global transcriptome profiling

2015 ◽  
Author(s):  
Miriam Ruocco ◽  
Procaccini Gabriele ◽  
Francesco Musacchia ◽  
Remo Sanges ◽  
Irene Olivé ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Molecular Mechanisms ◽  
Transcriptome Assembly ◽  
Co2 Concentration ◽  
Marine Organisms ◽  
Photosynthetic Parameters ◽  
Cymodocea Nodosa ◽  
Field Station ◽  
High Co2 ◽  
Co2 Levels

Global climate changes are imposing multiple pressures to marine organisms. The rising atmospheric CO2 concentration is causing substantial changes in ocean physics, chemistry and biology. At least three synergic environmental stressors have been recognized as primary driven by CO2 emissions: ocean warming, oxygen loss and ocean acidification. The effects of CO2-driven ocean acidification on seagrass metabolism remain largely understudied. A few studies have been conducted near submarine volcanic vents, which mimic the future ocean acidification scenarios, allowing researchers to investigate the performance of marine organisms under long-term exposure to high-CO2 levels. Apart from these, some mesocosm-based experiments have investigated growth and physiological responses to high CO2. For this work, we built an outdoor mesocosm facility at the Centre of Marine Sciences’ field station in Algarve, Portugal, to experimentally manipulate CO2 levels and investigate the effects of high-CO2/low pH on seagrass metabolism and underlying molecular mechanisms. Cymodocea nodosa plants were collected in Cadiz Bay at the end of January 2014 and transported to the mesocosm facility. After a one week acclimation period, C. nodosa were either kept under normal (400 ppm) or elevated (1200 ppm) CO2 concentration for 12 days. Water physico-chemical parameters, irradiance, and chlorophyll-fluorescence-derived photosynthetic parameters were monitored on a daily basis. Here we present, for the first time in this species, results obtained using Illumina RNAseq technology and de-novo transcriptome assembly. Using C. nodosa RNAs extracted at the beginning and the end of the experiment, we assembled more than 70 thousands unique transcripts and were able to annotate more than 90% of them using the Annocript pipeline. Differential expression analysis revealed about 500 transcripts significantly differentially regulated between plants kept under control and high-CO2 conditions. Pathways showing largest changes in gene expression included isoprenoid and amino-acid biosynthesis, porphyrin-containing compound metabolism, amine and polyamine biosynthesis, lipid and carbohydrate metabolism. Transcriptome sequencing also significantly increases the molecular resources available for C. nodosa, almost completely absent before this study.

scholarly journals Ocean acidification and hypoxia alter organic carbon fluxes in marine soft sediments

2019 ◽  
Vol 25 (12) ◽  
pp. 4165-4178 ◽  
Author(s):  
Chiara Ravaglioli ◽  
Fabio Bulleri ◽  
Saskia Rühl ◽  
Sophie J. McCoy ◽  
Helen S. Findlay ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Ocean Acidification ◽  
Carbon Fluxes ◽  
Soft Sediments ◽  
Organic Carbon Fluxes

scholarly journals Cymodocea nodosa response to simulated CO2-driven ocean acidification: a first insight from global transcriptome profiling

2015 ◽  
Author(s):  
Miriam Ruocco ◽  
Procaccini Gabriele ◽  
Francesco Musacchia ◽  
Remo Sanges ◽  
Irene Olivé ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Molecular Mechanisms ◽  
Transcriptome Assembly ◽  
Co2 Concentration ◽  
Marine Organisms ◽  
Photosynthetic Parameters ◽  
Cymodocea Nodosa ◽  
Field Station ◽  
High Co2 ◽  
Co2 Levels

Global climate changes are imposing multiple pressures to marine organisms. The rising atmospheric CO2 concentration is causing substantial changes in ocean physics, chemistry and biology. At least three synergic environmental stressors have been recognized as primary driven by CO2 emissions: ocean warming, oxygen loss and ocean acidification. The effects of CO2-driven ocean acidification on seagrass metabolism remain largely understudied. A few studies have been conducted near submarine volcanic vents, which mimic the future ocean acidification scenarios, allowing researchers to investigate the performance of marine organisms under long-term exposure to high-CO2 levels. Apart from these, some mesocosm-based experiments have investigated growth and physiological responses to high CO2. For this work, we built an outdoor mesocosm facility at the Centre of Marine Sciences’ field station in Algarve, Portugal, to experimentally manipulate CO2 levels and investigate the effects of high-CO2/low pH on seagrass metabolism and underlying molecular mechanisms. Cymodocea nodosa plants were collected in Cadiz Bay at the end of January 2014 and transported to the mesocosm facility. After a one week acclimation period, C. nodosa were either kept under normal (400 ppm) or elevated (1200 ppm) CO2 concentration for 12 days. Water physico-chemical parameters, irradiance, and chlorophyll-fluorescence-derived photosynthetic parameters were monitored on a daily basis. Here we present, for the first time in this species, results obtained using Illumina RNAseq technology and de-novo transcriptome assembly. Using C. nodosa RNAs extracted at the beginning and the end of the experiment, we assembled more than 70 thousands unique transcripts and were able to annotate more than 90% of them using the Annocript pipeline. Differential expression analysis revealed about 500 transcripts significantly differentially regulated between plants kept under control and high-CO2 conditions. Pathways showing largest changes in gene expression included isoprenoid and amino-acid biosynthesis, porphyrin-containing compound metabolism, amine and polyamine biosynthesis, lipid and carbohydrate metabolism. Transcriptome sequencing also significantly increases the molecular resources available for C. nodosa, almost completely absent before this study.

scholarly journals Ocean acidification decreases plankton respiration: evidence from a mesocosm experiment

2016 ◽  
Author(s):  
K. Spilling ◽  
A. J. Paul ◽  
N. Virkkala ◽  
T. Hastings ◽  
S. Lischka ◽  
...  
Keyword(s):  
Primary Production ◽  
Ocean Acidification ◽  
Community Composition ◽  
Carbon Fixation ◽  
Plankton Community ◽  
Community Respiration ◽  
Carbon Export ◽  
High Co2 ◽  
Respiration Rates ◽  
Co2 Levels

Abstract. Anthropogenic carbon dioxide (CO2) emissions are reducing the pH in the world's oceans. The plankton community is a key component driving biogeochemical fluxes, and the effect of increased CO2 on plankton is critical for understanding the ramifications of ocean acidification on global carbon fluxes. We determined the plankton community composition and measured primary production, respiration rates and carbon export (defined here as carbon sinking out of a shallow, coastal area) during an ocean acidification experiment. Mesocosms (~ 55 m3) were set up in the Baltic Sea with a gradient of CO2 levels initially ranging from ambient (~ 240 μatm), used as control, to high CO2 (up to ~ 1330 μatm). The phytoplankton community was dominated by dinoflagellates, diatoms, cyanobacteria and chlorophytes, and the zooplankton community by protozoans, heterotrophic dinoflagellates and cladocerans. The plankton community composition was relatively homogenous between treatments. Community respiration rates were lower at high CO2 levels. The carbon-normalized respiration was approximately 40 % lower in the high CO2 environment compared with the controls during the latter phase of the experiment. We did not, however, detect any effect of increased CO2 on primary production. This could be due to measurement uncertainty, as the measured total particular carbon (TPC) and combined results presented in this special issue suggest that the reduced respiration rate translated into higher net carbon fixation. The percent carbon derived from microscopy counts (both phyto- and zooplankton), of the measured total particular carbon (TPC) decreased from ~ 26 % at t0 to ~ 8 % at t31, probably driven by a shift towards smaller plankton (< 4 μm) not enumerated by microscopy. Our results suggest that reduced respiration lead to increased net carbon fixation at high CO2. However, the increased primary production did not translate into increased carbon export, and did consequently not work as a negative feedback mechanism for increasing atmospheric CO2 concentration.

Growth Responses on Young Wheat Plants to a Range of Ambient CO2 Levels

1978 ◽  
Vol 5 (1) ◽  
pp. 45 ◽  
Author(s):  
TF Neales ◽  
AO Nicholls
Keyword(s):  
Plant Biomass ◽  
Growth Parameters ◽  
Co2 Enrichment ◽  
Co2 Concentration ◽  
Plant Age ◽  
Growth Responses ◽  
Wheat Seedlings ◽  
Co2 Levels ◽  
Sequential Experiments ◽  
Ambient Co2

The growth of wheat seedlings in a closed environment was measured from day 10 to day 24 after germination, in 12 separate and sequential experiments, in which the imposed variable was the ambient CO2 concentration. CO2 levels between 200 and 800 volumes per million (vpm) and a daily irradiance of 6.5 MJ m-2 were used. The effects of CO2 concentration on various growth parameters strongly interacted with plant age. For instance, in the 10-day-old plants, relative growth rate and net assimilation rate were increased (by 35 and 55% respectively) by an increase in CO2 levels from 200 to 800 vpm, whereas these two growth parameters were reduced (by 44 and 16%) in 24-day-old plants over the same interval of CO2 concentration. Also, increasing CO2 levels reduced the leafiness (leaf area ratio) of the plant, and increased the dry matter in the leaves (specific leaf weight). It is suggested that the observed large interactions on plant growth of plant age and CO2 concentration account for the relatively small enhancement by CO2 enrichment of total plant biomass and economic yield that are reported in the literature.

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