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Kelp deposition changes mineralization pathways and microbial communities in a sandy beach
Author(s) -
Erk Marit R.,
Meier Dimitri V.,
Ferdelman Timothy,
Harder Jens,
Bussmann Ingeborg,
Beer Dirk
Publication year - 2020
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11574
Subject(s) - kelp , environmental chemistry , microbial population biology , mineralization (soil science) , anoxic waters , deposition (geology) , chemistry , ecology , sediment , biology , bacteria , paleontology , genetics , soil water
We investigated the impact of kelp deposition on the geochemistry and microbial community composition of beach sands on the island of Helgoland (North Sea). The composition of the microbial community at a beach with regular kelp deposition appeared shaped by this regular input of organic material, as indicated by significantly higher proportions of aerobic degraders, fermenters, and sulfur cycling microorganisms. Rapid degradation of deposited kelp by this community leads to high levels of dissolved organic and inorganic carbon and nutrients, a lower pH and anoxia. Aerobic respiration, fermentation, Fe‐ and SO 4 2− reduction, and methanogenesis were strongly enhanced, with SO 4 2− reduction being the main process in kelp degradation. SO 4 2− reduction rates increased 20‐ to 25‐fold upon addition of kelp. The main route of electrons from kelp to SO 4 2− was not via CO and H 2 , as expected, but via organic fermentation products. O 2 supply by the tides was not sufficient and reduced intermediates escaped from the sediment with tidal water retraction. The resulting extremely high levels of free sulfide (>10 mmol L −1 ) lead to abundant filamentous growth of sulfur‐oxidizing bacteria largely composed of a rare O 2 ‐adapted Sulfurovum lacking the expected denitrification genes. Our results show that regular kelp deposition strongly enhances the thermodynamic disequilibrium in the beach sand habitat, leading to a dramatic enhancement of the sulfur cycle.