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Nitrate respiration and diel migration patterns of diatoms are linked in sediments underneath a microbial mat
Author(s) -
Merz Elisa,
Dick Gregory J.,
Beer Dirk,
Grim Sharon,
Hübener Thomas,
Littmann Sten,
Olsen Kirk,
Stuart Dack,
Lavik Gaute,
Marchant Hannah K.,
Klatt Judith M.
Publication year - 2021
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.15345
Subject(s) - diel vertical migration , nitrate , diatom , anoxic waters , phototroph , denitrification , population , environmental chemistry , dominance (genetics) , biology , ecology , algae , sediment , respiration , photosynthesis , botany , chemistry , nitrogen , paleontology , biochemistry , demography , organic chemistry , sociology , gene
Summary Diatoms are among the few eukaryotes known to store nitrate (NO 3 − ) and to use it as an electron acceptor for respiration in the absence of light and O 2 . Using microscopy and 15 N stable isotope incubations, we studied the relationship between dissimilatory nitrate/nitrite reduction to ammonium (DNRA) and diel vertical migration of diatoms in phototrophic microbial mats and the underlying sediment of a sinkhole in Lake Huron (USA). We found that the diatoms rapidly accumulated NO 3 − at the mat‐water interface in the afternoon and 40% of the population migrated deep into the sediment, where they were exposed to dark and anoxic conditions for ~75% of the day. The vertical distribution of DNRA rates and diatom abundance maxima coincided, suggesting that DNRA was the main energy generating metabolism of the diatom population. We conclude that the illuminated redox‐dynamic ecosystem selects for migratory diatoms that can store nitrate for respiration in the absence of light. A major implication of this study is that the dominance of DNRA over denitrification is not explained by kinetics or thermodynamics. Rather, the dynamic conditions select for migratory diatoms that perform DNRA and can outcompete sessile denitrifiers.