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Journal article
Production of dissolved carbon and alkalinity during macroalgal wrack degradation on beaches: a mesocosm experiment with implications for blue carbon
Biogeochemistry, Vol.160(2), pp.159-175
09/07/2022
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Abstract
Marine macroalgae are a key primary producer in coastal ecosystems, but are often overlooked in blue carbon inventories. Large quantities of macroalgal detritus deposit on beaches, but the fate of wrack carbon (C) is little understood. If most of the wrack carbon is respired back to CO2, there would be no net carbon sequestration. However, if most of the wrack carbon is converted to bicarbonate (alkalinity) or refractory DOC, wrack deposition would represent net carbon sequestration if at least part of the metabolic products (e.g., reduced Fe and S) are permanently removed (i.e., long-term burial) and the DOC is not remineralised. To investigate the release of macroalgal C via porewater and its potential to contribute to C sequestration (blue carbon), we monitored the degradation of
Ecklonia radiata in flow-through mesocosms simulating tidal flushing on sandy beaches. Over 60 days, 81% of added
E. radiataorganic matter (OM) decomposed. Per 1 mol of detritus C, the degradation produced 0.48 ± 0.34 mol C of dissolved organic carbon (DOC) (59%) and 0.25 ± 0.07 mol C of dissolved inorganic carbon (DIC) (31%) in porewater, and a small amount of CO
2(0.3 ± 0.0 mol C; ca. 3%) which was emitted to the atmosphere. A significant amount of carbonate alkalinity was found in porewater, equating to 33% (0.27 ± 0.05 mol C) of the total degraded C. The degradation occurred in two phases. In the first phase (days 0–3), 27% of the OM degraded, releasing highly reactive DOC. In the second phase (days 4–60), the labile DOC was converted to DIC. The mechanisms underlyingE. radiatadegradation were sulphate reduction and ammonification. It is likely that the carbonate alkalinity was primarily produced through sulphate reduction. The formation of carbonate alkalinity and semi-labile or refractory DOC from beach wrack has the potential to play an overlooked role in coastal carbon cycling and contribute to marine carbon sequestration.
Details
- Title
- Production of dissolved carbon and alkalinity during macroalgal wrack degradation on beaches: a mesocosm experiment with implications for blue carbon
- Creators
- Anita K. Perkins - Southern Cross UniversityIsaac R. Santos - Southern Cross UniversityAndrew L. Rose - Southern Cross UniversityKai G. Schulz - Southern Cross UniversityHans-Peter Grossart - University of PotsdamBradley D. Eyre - Southern Cross UniversityBrendan P. Kelaher - Southern Cross UniversityJoanne M. Oakes - Southern Cross University
- Publication Details
- Biogeochemistry, Vol.160(2), pp.159-175
- Comment
- We thank Dr Bennan Chen and James Tucker for their assistance with building the mesocosms and Ceylena Holloway, Matheus Carvalho de Carvalho, Iain Alexander and Natasha Carlson-Perret for their laboratory support.
- Publisher
- Springer International Publishing
- Grant note
- Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB) im Forschungsverbund Berlin e.V. (3473). Open Access funding enabled and organized by Projekt DEAL.
- Identifiers
- 991013048813802368
- Copyright
- © The Author(s) 2022 Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
- Academic Unit
- Faculty of Science and Engineering; Engineering; Science; Office of the Vice Chancellor; Centre for Coastal Biogeochemistry; National Marine Science Centre
- Language
- English
- Resource Type
- Journal article