Biogeochemical plumbing of pioneer mangrove intertidal flats in French Guiana

Migrating mudbanks are characteristic features of the vast Amazon-Guianas coastline along Northeastern South America. As illustrated by sites in French Guiana, consolidating mudflats that periodically transition to mangrove forest are permeated by extensive crustacean burrow systems, sometimes in isolation but more often in close association with morpho-sedimentary structures such as tidal pools and channels. Burrow structures are critical to mangrove growth. In this study, we evaluated the ways in which burrows act as complex conduits that plumb deposits for solute exchange with overlying water. We sampled burrows during low tide when irrigation is inhibited and burrow water rapidly becomes anoxic. The products of diagenetic reactions, for example: NH4+, N2, and Si(OH)4, build up with time, revealing sedimentary reaction rates and fluxes. When oxygenated, burrow walls are zones of intense coupled redox reactions such as nitrification-denitrification. Build-up often is lower in burrows connected directly to tidal pools where photosynthetic activity consumes remineralized nutrients, and burrows can remain periodically irrigated at low tide. During flood, burrows, particularly those that connect tidal pools laterally to channels, can be rapidly flushed and oxygenated as channel water rises and then spreads across flats. Burrow flushing produces enhanced concentrations of nutrients within the leading edge of the flood as seawater moves progressively towards and into adjacent mangroves. Estimates of burrow volumes obtained from drone surveys together with burrow solute production rates allow upscaling of burrow-sourced metabolite fluxes; however, these are extremely variable due to variable burrow geometries, connections between burrows, pools, and channels, and burrow water residence times (oxygenation). The flushing of burrows during flood results in a rectification of sediment-water fluxes shoreward and enhances the delivery of nutrients from the flats into adjacent mangroves and pools, presumably stimulating colonization and forest growth.

Keyword(s)

Guiana coast mudbank processes, Crustacean burrow biogeochemistry, Burrow solute fluxes, Crustacean burrow-mangrove interactions

Full Text

FilePagesSizeAccess
Publisher's official version
133 Mo
Supplementary file1
3985 Ko
Supplementary file2
-174 Ko
Supplementary file3
1211 Ko
Supplementary file4
1636 Ko
Supplementary file5
1134 Ko
Supplementary file6
1220 Ko
How to cite
Aller Robert, Klingensmith Issac, Stieglitz Thomas, Heilbrun Christina, Waugh Stuart, Aschenbroich Adelaide, Thouzeau Gerard, Michaud Emma (2024). Biogeochemical plumbing of pioneer mangrove intertidal flats in French Guiana. Regional Environmental Change. 24 (3). 117 (13p.). https://doi.org/10.1007/s10113-024-02272-x, https://archimer.ifremer.fr/doc/00902/101379/

Copy this text