Related Experiment Video
Updated: Jul 11, 2026
10:11
The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
Published on: August 3, 2016
Evidence for complete denitrification in a benthic foraminifer.
Nils Risgaard-Petersen1, Alexandra M Langezaal, Signe Ingvardsen
1Department of Marine Ecology, National Environmental Research Institute, Vejlsøvej 25, DK-8600 Silkeborg, Denmark. nri@dmu.dk
Nature
|September 8, 2006
Summary
Benthic foraminifera store and respire intracellular nitrate, enabling survival in anoxic marine environments. This finding reveals a previously undescribed anaerobic metabolism crucial for nitrogen cycling.
Area of Science:
- Marine Biology
- Geochemistry
- Microbiology
Background:
- Benthic foraminifera are abundant unicellular eukaryotes in marine sediments.
- Many species inhabit anoxic environments, but sustainable anaerobic metabolism was not well-understood.
Purpose of the Study:
- To investigate the anaerobic metabolism of benthic foraminifera.
- To determine if foraminifera can utilize stored nitrate for respiration in oxygen-free habitats.
Main Methods:
- Quantification of intracellular nitrate stores in foraminifera.
- Respiration experiments to confirm nitrate utilization.
- Field sampling in Swedish fjord and Chilean continental shelf sediments.
Main Results:
- Demonstrated that Globobulimina pseudospinescens accumulates and respires intracellular nitrate to dinitrogen gas.
- Estimated nitrate stores sufficient for over a month of respiration.
- Detected high intracellular nitrate concentrations in multiple dominant benthic foraminifera species.
Conclusions:
- Foraminifera possess a sustainable anaerobic metabolic pathway using intracellular nitrate.
- Foraminifera likely play a significant role in marine nitrogen cycling.
- Current understanding of the marine nitrogen cycle requires further refinement to include foraminiferal contributions.
More Related Videos
Related Concept Videos
01:15Metabolism of Chemolithotrophs
Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation. However, because inorganic electron donors...
01:22Inorganic Nitrogen Assimilation
Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...
01:27Diversity of Protists III
Rhizaria are a diverse group of unicellular protists characterized by their threadlike cytoplasmic extensions known as pseudopodia. These structures aid in both locomotion and feeding, giving Rhizaria an amoeboid appearance. Their amoeboid morphology once led to taxonomic confusion, but molecular phylogenetics has clarified their evolutionary placement and emphasized their shared use of pseudopodia despite divergent lineages.This clade comprises diverse lineages such as Chlorarachniophyta,...
01:25Microbial Mats
Microbial communities forming biofilms and mats represent complex, spatially structured ecosystems where metabolic processes are stratified according to light, oxygen, and nutrient gradients. Biofilms are initial colonization stages, only a few millimeters thick, while mature microbial mats can reach centimeter-scale thickness and display intricate vertical organization. Their structural and functional heterogeneity allows microorganisms to occupy distinct ecological niches within a few...
01:26Microbes and the Nitrogen Cycle
The nitrogen cycle is a complex biogeochemical process critical to maintaining the balance of nitrogenous compounds in ecosystems. This cycle involves multiple microbial-mediated transformations through which nitrogen changes oxidation states, supporting essential ecological functions and contributing to plant and microbial growth.Nitrogen Fixation and AmmonificationNitrogen fixation initiates the cycle by converting inert atmospheric nitrogen (N₂) into bioavailable ammonia (NH₃), a process...
01:18Deep Sea Microbial Ecology
The deep ocean and its underlying sediments represent vast, largely unexplored microbial habitats that extend far beyond the sunlit photic zone. The photic (euphotic) zone typically spans the upper ~100–200 meters of pelagic waters in the open ocean, but its depth varies geographically and seasonally, where sufficient light supports photosynthetic life. Below this lies the deep sea, spanning roughly 1000–6000 meters (bathypelagic to abyssal zones), with deeper hadal trenches extending beyond...