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Updated: Jun 19, 2026
05:04
Visualization of Productivity Zones Based on Nitrogen Mass Balance Model in Narragansett Bay, Rhode Island
Published on: July 14, 2023
Coastal eutrophication thresholds: a matter of sediment microbial processes.
Jouni Lehtoranta1, Petri Ekholm, Heikki Pitkänen
1Finnish Environment Institute, Helsinki, Finland. jouni.lehtoranta@ymparisto.fi
Ambio
|October 29, 2009
Summary
Marine sediment microbial processes, iron (Fe(III)) oxide reduction and sulfate reduction, impact aquatic ecosystems differently. Iron reduction limits phosphorus, while sulfate reduction releases phosphorus, favoring nitrogen-fixing algae.
Area of Science:
- Marine microbial ecology
- Biogeochemical cycles
- Aquatic ecosystem dynamics
Background:
- Marine sediments host anaerobic mineralization via Fe(III) oxide and sulfate reduction.
- These pathways critically influence nutrient cycling and primary productivity in aquatic systems.
Purpose of the Study:
- To elucidate the distinct impacts of iron (Fe(III)) oxide reduction versus sulfate reduction on aquatic ecosystems.
- To explain the mechanisms driving shifts between phosphorus-limited and nitrogen-limited states in marine environments.
Main Methods:
- Conceptual modeling of microbial mineralization pathways in marine sediments.
- Analysis of nutrient (phosphorus, nitrogen) dynamics and their control on primary production.
- Investigation of factors influencing regime shifts, including organic carbon flux and hydrodynamics.
Main Results:
- Iron reduction sequesters phosphorus, leading to phosphorus-limited primary production (State 1).
- Sulfate reduction releases phosphorus and favors nitrogen-fixing algae due to altered N:P ratios (State 2).
- Increased organic carbon flux and reduced oxygen transport can trigger shifts from State 1 to State 2.
Conclusions:
- Microbial mineralization pathways in sediments have profound, contrasting effects on aquatic ecosystem states.
- Eutrophication and altered hydrodynamics can drive irreversible shifts in ecosystem nutrient limitation.
- Understanding these processes is crucial for managing coastal ecosystem health and productivity.
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