The impacts of pulsed nutrient injections or extreme runoff events on marine ecosystems are far less studied than those associated with long‐term eutrophication, particularly in regard to mechanisms regulating the response of plankton community structure. Over 800 million liters of nutrient‐rich water from a fertilizer mine were discharged over a 2‐week period into Tampa Bay, Florida, in 2021, providing a unique opportunity to document the plankton response. A 3D‐coupled hydrodynamic biogeochemical model was developed to investigate this response and to understand the observed succession of a large, short diatom bloom followed by a secondary
Diatoms are among the few eukaryotes known to store nitrate (NO3−) and to use it as an electron acceptor for respiration in the absence of light and O2. Using microscopy and15N 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 NO3−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.
more » « less- Award ID(s):
- 1637066
- NSF-PAR ID:
- 10452352
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Environmental Microbiology
- Volume:
- 23
- Issue:
- 3
- ISSN:
- 1462-2912
- Page Range / eLocation ID:
- p. 1422-1435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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