scholarly journals Blue carbon: past, present and future, with emphasis on macroalgae

2018 ◽  
Vol 14 (10) ◽  
pp. 20180336 ◽  
Author(s):  
John Raven
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Net Primary Productivity ◽  
Great Majority ◽  
Temperature Limit ◽  
Blue Carbon ◽  
Marine Macroalgae ◽  
Tidal Marshes ◽  
Surface Ocean ◽  
Subsequent Storage

Blue carbon did not originally include macroalgal ecosystems; however evidence is mounting that macroalgal ecosystems function in marine carbon sequestration. The great majority of present day marine macroalgal net primary productivity (NPP) involves haptophytic algae on eroding shores. For these organisms the long-term storage of particulate organic carbon involves export from the site of production of biomass that has evaded parasites and grazers, and that some of the exported biomass is sedimented and stored rather than being mineralized en route by detritivores (microbes and fauna). Export from eroding shores, and subsequent storage, of haptophytic marine macroalgal particulate organic carbon could have started by 1.6 Ga. Storage on depositing shores close to the site of NPP by rhizophytic macroalgae and then by rhizophytic coastal seagrasses, tidal marshes and mangroves began not less than 209 Ma ago. Future increases in surface ocean temperatures may bring tropical marine macroalgae to their upper temperature limit, while temperate marine macroalgae will migrate poleward, in both cases assuming that temperature increases faster than genetic adaptation to higher temperature. Increased CO 2 in the surface ocean will generally favour uncalcified over calcified marine macroalgae. This results in decreased CO 2 release from decreased calcification, as well as decreased ballasting by CaCO 3 of exported particulate organic carbon resulting in decreasing sedimentation. While much more work is needed, the available information suggests that macroalgae play a significant role in marine organic carbon storage.

scholarly journals Not all calcite ballast is created equal: differing effects of foraminiferan and coccolith calcite on the formation and sinking of aggregates

2013 ◽  
Vol 10 (9) ◽  
pp. 14861-14885 ◽  
Author(s):  
K. Schmidt ◽  
C. L. De La Rocha ◽  
M. Gallinari ◽  
G. Cortese
Keyword(s):  
Calcium Carbonate ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Deep Ocean ◽  
Simple Experiment ◽  
Surface Ocean

Abstract. Correlation between particulate organic carbon (POC) and calcium carbonate sinking through the deep ocean has led to the idea that ballast provided by calcium carbonate is important for the export of POC from the surface ocean. While this idea is certainly to some extent true, it is worth considering in more nuance, for example, examining the different effects on the aggregation and sinking of POC of small, non-sinking calcite particles like coccoliths and large, rapidly sinking calcite like planktonic foraminiferan tests. We have done that here in a simple experiment carried out in roller tanks that allow particles to sink continuously without being impeded by container walls. Coccoliths were efficiently incorporated into aggregates that formed during the experiment, increasing their sinking speed compared to similarly sized aggregates lacking added calcite ballast. The foraminiferan tests, which sank as fast as 700 m d−1, became associated with only very minor amounts of POC. In addition, when they collided with other, larger, foraminferan-less aggregates, they fragmented them into two smaller, more slowly sinking aggregates. While these effects were certainly exaggerated within the confines of the roller tanks, they clearly demonstrate that calcium carbonate ballast is not just calcium carbonate ballast- different forms of calcium carbonate ballast have notably different effects on POC aggregation, sinking, and export.

scholarly journals Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

2006 ◽  
Vol 3 (3) ◽  
pp. 803-836 ◽  
Author(s):  
M. Gehlen ◽  
L. Bopp ◽  
N. Emprin ◽  
O. Aumont ◽  
C. Heinze ◽  
...  
Keyword(s):  
Particle Size ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Carbon Fluxes ◽  
Ocean Model ◽  
Size Spectrum ◽  
Water Interface ◽  
Standard Version ◽  
Surface Ocean ◽  
Organic Carbon Fluxes

Abstract. This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1) the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2) an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3) a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. The integrated representation of material fluxes from the productive surface ocean down to the sediment-water interface allows taking advantage of surface ocean observations, sediment trap data and exchange fluxes at the sediment-water interface. The capability of the model to reproduce yearly averaged particulate organic carbon fluxes and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Model results obtained with the standard version and with the one including a particle size spectrum and prognostic sinking speed are not significantly different. Both model versions overestimate particulate organic carbon between 1000 and 2000 m, while deep fluxes are of the correct order of magnitude. Predicted benthic oxygen fluxes correspond with respect to their large scale distribution and magnitude to data based estimates. Modeled particulate organic C fluxes across the mesopelagos are most sensitive to the intensity of zooplankton flux feeding. An increase of the intensity of flux feeding in the standard version results in lower mid- and deep-water particulate organic carbon fluxes, shifting model results to an underestimation of particulate organic carbon fluxes in the deep. The corresponding benthic oxygen fluxes are too low. The model version including the mineral ballast parameterization yields an improved fit between modeled and observed particulate organic carbon fluxes below 2000 m and down to the sediment-water interface. Our results suggest that aggregate formation alone might not be sufficient to drive an intense biological pump. The later is most likely driven by the combined effect of aggregate formation and mineral ballasting.

scholarly journals Inorganic and black carbon hotspots constrain blue carbon mitigation services across tropical seagrass and temperate tidal marshes

2021 ◽  
Author(s):  
John Barry Gallagher ◽  
Vishnu Prahalad ◽  
John Aalders
Keyword(s):  
Salt Marsh ◽  
Organic Carbon ◽  
Salt Marshes ◽  
Inorganic Carbon ◽  
Blue Carbon ◽  
Tidal Marshes ◽  
Carbon Mitigation ◽  
Seagrass Meadows ◽  
First Time ◽  
Particulate Inorganic Carbon

Abstract Total organic carbon (TOC) sediment stocks as a CO2 mitigation service require exclusion of allochthonous black (BC) and particulate inorganic carbon corrected for water–atmospheric equilibrium (PICeq). For the first time, we address this bias for a temperate salt marsh and a coastal tropical seagrass in BC hotspots that represent two different blue carbon ecosystems of Malaysia and Australia. Seagrass TOC stocks were similar to the salt marshes with soil depths < 1 m (59.3 ± 11.3 and 74.9 ± 18.9 MgC ha− 1, CI 95% respectively). Both ecosystems showed larger BC constraints than their pristine counterparts did. However, the seagrass meadows’ mitigation services were largely constrained by both higher BC/TOC and PICeq/TOC fractions (38.0% ± 6.6% and 43.4% ± 5.9%, CI 95%) and salt marshes around a third (22% ± 10.2% and 6.0% ± 3.1% CI 95%). The results provide useful data from underrepresented regions, and, reiterates the need to consider both BC and PIC for more reliable blue carbon mitigation assessments.

scholarly journals Not all calcite ballast is created equal: differing effects of foraminiferan and coccolith calcite on the formation and sinking of aggregates

2014 ◽  
Vol 11 (1) ◽  
pp. 135-145 ◽  
Author(s):  
K. Schmidt ◽  
C. L. De La Rocha ◽  
M. Gallinari ◽  
G. Cortese
Keyword(s):  
Calcium Carbonate ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Deep Ocean ◽  
Simple Experiment ◽  
Surface Ocean

Abstract. Correlation between particulate organic carbon (POC) and calcium carbonate sinking through the deep ocean has led to the idea that ballast provided by calcium carbonate is important for the export of POC from the surface ocean. While this idea is certainly to some extent true, it is worth considering in more nuance, for example, examining the different effects on the aggregation and sinking of POC of small, non-sinking calcite particles like coccoliths and large, rapidly sinking calcite like planktonic foraminiferan tests. We have done that here in a simple experiment carried out in roller tanks that allow particles to sink continuously without being impeded by container walls. Coccoliths were efficiently incorporated into aggregates that formed during the experiment, increasing their sinking speed compared to similarly sized aggregates lacking added calcite ballast. The foraminiferan tests, which sank as fast as 700 m d−1, became associated with only very minor amounts of POC. In addition, when they collided with other, larger, foram-less aggregates, they fragmented them into two smaller, more slowly sinking aggregates. While these effects were certainly exaggerated within the confines of the rolling tanks, they clearly demonstrate that calcium carbonate ballast is not just calcium carbonate ballast – different forms of calcium carbonate ballast have notably different effects on POC aggregation, sinking, and export.

scholarly journals Inorganic and black carbon hotspots constrain blue carbon mitigation services across tropical seagrass and temperate tidal marshes

2020 ◽  
Author(s):  
John Barry Gallagher ◽  
Vishnu Prahalad ◽  
John Aalders
Keyword(s):  
Salt Marsh ◽  
Organic Carbon ◽  
Salt Marshes ◽  
Inorganic Carbon ◽  
Blue Carbon ◽  
Tidal Marshes ◽  
Carbon Mitigation ◽  
Seagrass Meadows ◽  
First Time ◽  
Particulate Inorganic Carbon

AbstractTotal organic carbon (TOC) sediment stocks as a CO2 mitigation service requires exclusion of allochthonous black (BC) and particulate inorganic carbon corrected for water– atmospheric equilibrium (PICeq). For the first time, we address this bias for a temperate salt marsh and a coastal tropical seagrass in BC hotspots. Seagrass TOC stocks were similar to the salt marshes with soil depths < 1 m (59.3 ± 11.3 and 74.9 ± 18.9 MgC ha-1, CI 95% respectively) and sequestration rates of 1.134 MgC ha-1 yr-1. Both ecosystems showed larger BC constraints than their pristine counterparts. However, the seagrass meadows’ mitigation services were largely constrained by both higher BC/TOC and PICeq/TOC fractions (38.0% ± 6.6% and 43.4% ± 5.9%, CI 95%) and salt marshes around a third (22% ± 10.2% and 6.0% ± 3.1% CI 95%). The results demonstrate a need to account for both BC and PIC within blue carbon mitigation assessments.

scholarly journals Biominerals and the vertical flux of particulate organic carbon from the surface ocean

2010 ◽  
Vol 37 (22) ◽  
pp. n/a-n/a ◽  
Author(s):  
W. M. Balch ◽  
B. C. Bowler ◽  
D. T. Drapeau ◽  
A. J. Poulton ◽  
P. M. Holligan
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Vertical Flux ◽  
Surface Ocean
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