Porewater Carbonate Chemistry Dynamics in a Temperate and a Subtropical Seagrass System
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Porewater Carbonate Chemistry Dynamics in a Temperate and a Subtropical Seagrass System Theodor Kindeberg1,2,3 · Nicholas R. Bates4,5 · Travis A. Courtney1 · Tyler Cyronak1,7 · Alyssa Griffin1 · Fred T. Mackenzie6 · May‑Linn Paulsen1 · Andreas J. Andersson1 Received: 13 December 2018 / Accepted: 1 May 2020 © The Author(s) 2020
Abstract Seagrass systems are integral components of both local and global carbon cycles and can substantially modify seawater biogeochemistry, which has ecological ramifications. However, the influence of seagrass on porewater biogeochemistry has not been fully described, and the exact role of this marine macrophyte and associated microbial communities in the modification of porewater chemistry remains equivocal. In the present study, carbonate chemistry in the water column and porewater was investigated over diel timescales in contrasting, tidally influenced seagrass systems in Southern California and Bermuda, including vegetated (Zostera marina) and unvegetated biomes (0–16 cm) in Mission Bay, San Diego, USA and a vegetated system (Thallasia testudinium) in Mangrove Bay, Ferry Reach, Bermuda. In Mission Bay, dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited strong increasing gradients with sediment depth. Vertical porewater profiles differed between the sites, with almost twice as high concentrations of DIC and TA observed in the vegetated compared to the unvegetated sediments. In Mangrove Bay, both the range and vertical profiles of porewater carbonate parameters such as DIC and TA were much lower and, in contrast to Mission Bay where no distinct temporal signal was observed, biogeochemical parameters followed the semi-diurnal tidal signal in the water column. The observed differences between the study sites most likely reflect a differential influence of biological (biomass, detritus and infauna) and physical processes (e.g., sediment permeability, residence time and mixing) on porewater carbonate chemistry in the different settings. Keywords Carbonate chemistry · Carbon cycling · Estuarine processes · Blue carbon · Ocean acidification · Sediment · Early diagenesis · Interstitial water
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1049 8-020-09378-8) contains supplementary material, which is available to authorized users. * Theodor Kindeberg [email protected] Extended author information available on the last page of the article
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Aquatic Geochemistry
1 Introduction Coastal ecosystems play an important role in the global carbon cycle, largely due to the lateral transport of carbon and nutrients from rivers, terrestrial runoff and groundwater, intense benthic and pelagic metabolism and carbon transformation pathways in biomes such as seagrass beds, coral reefs, kelp forests, wetlands and saltmarshes (Duarte et al. 2005; Bauer et al. 2013). Seagrass beds are among the most productive marine ecosystems on Earth, trapping and storing a significant amount of carbon in their biomass an
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