Quantitative Link Between Sedimentary Chlorin and Sea‐Surface Chlorophyll‐a

Primary productivity in the ocean plays a major role in the global carbon cycle. To estimate its changes through geological time, different sedimentary proxies are used. However, the relative weights of the various processes driving the sedimentary accumulation of organic matter are not fully constr...

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Bibliographic Details
Published in:Journal of geophysical research. Biogeosciences 2022-05, Vol.127 (5), p.e2021JG006514-n/a
Main Authors: Raja, M., Rosell‐Melé, A.
Format: Article
Language:English
Subjects:
Algae
Atmospheric Processes
Biogeochemistry
Biogeosciences
Calibration
Carbon cycle
Chlorophyll
Chlorophyll a
Diagenesis
Geological time
global export and burial
marine sediments
Organic matter
Paleoceanography
Paleoclimatology
Paleoclimatology and Paleoceanography
Primary production
primary productivity
Productivity
Proxies
proxy
Remote sensing
Sediment
Sediments
Spatial distribution
Surface water
Tropical climate
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Summary:Primary productivity in the ocean plays a major role in the global carbon cycle. To estimate its changes through geological time, different sedimentary proxies are used. However, the relative weights of the various processes driving the sedimentary accumulation of organic matter are not fully constrained or represent the flux of specific algal classes. Here, we compare sea‐surface chlorophyll‐a (SSchla) abundance estimated from remote sensing data over the last 20 years with the sedimentary concentration of its derivatives (i.e., chlorin) on a suite of 140 core‐top sediments from different biogeochemical regions. We estimate with field data that only 0.33% of SSchla in tropical and subtropical regions is transferred to surface sediments in the form of chlorin. Despite the small fraction of chlorin that arrive to the sea‐floor, the sedimentary spatial distribution of chlorin is driven primarily by SSchla concentration in high and moderate productivity locations (SSchla > 0.20 mg·m−3). Our calibration paves the way for the use of chlorin as quantitative proxies of primary productivity in paleoreconstructions and cautions on their use in low primary productivity settings. Plain Language Summary Chlorophyll‐a derivatives named chlorin are commonly used to reconstruct past primary productivity. However, their value has been questioned as they are posited to be controlled by diagenetic processes and often limited to draw qualitative inferences on the carbon cycle. In fact, most proxies have not been globally appraised with ocean biogeochemical data. Here, we use a combination of remote sensing and geochemical data to provide the first calibration of chlorin proxy. We estimate that 0.33% of the chlorophyll‐a produced in surface waters is transferred to surface sediments. Despite the small fraction of chlorin that arrive to the sea‐floor, we show chlorin concentration is spatially correlated with sea‐surface chlorophyll‐a in high and moderate productivity locations (SSchla > 0.20 mg·m−3). Our calibration paves the way for the use of chlorin as quantitative proxies of primary productivity in past periods and cautions on their use in low primary productivity settings. Key Points Chlorin concentration higher than 1 μg·g−1 reflects chlorophyll‐a abundance in tropical and subtropical surface waters The transfer of chlorophyll‐a from the ocean surface to sediments at low latitudes (40°N–40°S) is estimated to be 0.33% Chlorin are a potential proxy to estimate quantitativ
ISSN:2169-8953
2169-8961
DOI:10.1029/2021JG006514