Cetiner, Jaclyn E. P. and Berelson, William M. and Rollins, Nick E. and Barnhart, Holly A. and Liu, Xuewu and Dong, Sijia and Byrne, Robert H. and Adkins, Jess F. (2022) Novel device to collect deep-sea porewater in situ: A focus on benthic carbonate chemistry. Limnology and Oceanography: Methods . ISSN 1541-5856. doi:10.1002/lom3.10530. (In Press) https://resolver.caltech.edu/CaltechAUTHORS:20230104-586485300.11
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Abstract
We have designed, built, tested, and deployed a novel device to extract porewater from deep-sea sediments in situ, constructed to work with a standard multicorer. Despite the importance of porewater measurements for numerous applications, many sampling artifacts can bias data and interpretation during traditional porewater processing from shipboard-processed cores. A well-documented artifact occurs in deep-sea porewater when carbonate precipitates during core recovery as a function of temperature and pressure changes, while porewater is in contact with sediment grains before filtration, thereby lowering porewater alkalinity and dissolved inorganic carbon (DIC). Here, we present a novel device built to obviate these sampling artifacts by filtering porewater in situ on the seafloor, with a focus near the sediment–water interface on cm-scale resolution, to obtain accurate porewater profiles. We document 1–10% alkalinity loss in shipboard-processed sediment cores compared to porewater filtered in situ, at depths of 1600–3200 m. We also show that alkalinity loss is a function of both weight % sedimentary CaCO₃ and water column depth. The average ratio of alkalinity loss to DIC loss in shipboard-processed sediment cores relative to in situ porewater is 2.2, consistent with the signal expected from carbonate precipitation. In addition to collecting porewater for defining natural profiles, we also conducted the first in situ dissolution experiments within the sediment column using isotopically labeled calcite. We present evidence of successful deployments of this device on and adjacent to the Cocos Ridge in the Eastern Equatorial Pacific across a range of depths and calcite saturation states.
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Additional Information: | This work was supported by NSF Ocean Acidification (OCE-1834475). J.E.P.C. thanks the USC Wrigley Institute for Environmental Studies for PhD funding. H.A.B. thanks the Resnick Sustainability Institute for PhD funding. The authors would like to thank the editors, as well as David Burdige and an anonymous reviewer for their helpful questions and comments that improved the manuscript. The authors would like to sincerely thank Kalla Fleger for alkalinity and pH measurements on board; Matthew Quinan for dissolved silicate measurements; Rucha Wani and Emma Johnson for their contributions to the SIPR team at sea; and the science party, captain, and crew of the R/V Sally Ride SR2113 cruise. We also appreciate the discussions and laboratory support from Abby Lunstrum and assistance with silicate measurements from Doug Hammond. The authors also thank the Southern California Marine Institute and the captain and crew of the R/V Yellowfin for allowing us many SIPR test deployments. | ||||||||||||||||
Group: | Division of Geological and Planetary Sciences, Resnick Sustainability Institute | ||||||||||||||||
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DOI: | 10.1002/lom3.10530 | ||||||||||||||||
Record Number: | CaltechAUTHORS:20230104-586485300.11 | ||||||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20230104-586485300.11 | ||||||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||||||
ID Code: | 118672 | ||||||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||||||
Deposited By: | Research Services Depository | ||||||||||||||||
Deposited On: | 08 Feb 2023 01:36 | ||||||||||||||||
Last Modified: | 08 Feb 2023 16:35 |
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