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Related Concept Videos

Freshwater Microbial Ecology01:24

Freshwater Microbial Ecology

Freshwater systems such as streams, rivers, and lakes exhibit distinct physical and biological characteristics that influence their microbial communities. These environments are broadly categorized into lotic systems—those with flowing waters like streams and most rivers—and lentic systems, which include still or slow-moving waters such as lakes, ponds, and marshes.In lentic systems, phytoplankton drive primary production, generating autochthonous organic carbon. In contrast, lotic systems...
Inorganic Nitrogen Assimilation01:22

Inorganic 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...
Microbes and the Nitrogen Cycle01:26

Microbes 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...
The Nitrogen Cycle01:49

The Nitrogen Cycle

Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of nitrogen on Earth is nitrogen gas, which cannot be used by most animals and plants. Thus, nitrogen gas must first be converted into a usable form by nitrogen-fixing bacteria before it can be cycled through other living organisms. The use of nitrogen-containing fertilizers and animal waste products in human agriculture has greatly influenced the...
Carbon-dioxide Fixation01:28

Carbon-dioxide Fixation

Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ecosystems, and contributing to the global carbon cycle. It also has industrial applications in carbon capture and bioproduct synthesis. Autotrophic organisms rely on this process to utilize CO₂ as a carbon source in diverse environments.The Calvin CycleThe Calvin cycle is the most widespread carbon fixation mechanism, primarily used by...
Overview of Nitrogen Metabolism01:20

Overview of Nitrogen Metabolism

Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of  ammonia, ammonium ions, nitrate, nitrite, or  nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...

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Related Experiment Video

Updated: Jul 12, 2026

Establishment of Microbial Eukaryotic Enrichment Cultures from a Chemically Stratified Antarctic Lake and Assessment of Carbon Fixation Potential
14:38

Establishment of Microbial Eukaryotic Enrichment Cultures from a Chemically Stratified Antarctic Lake and Assessment of Carbon Fixation Potential

Published on: April 20, 2012

Nitrogen Fixation in Lakes.

R Dugdale, V Dugdale, J Neess

    Science (New York, N.Y.)
    |October 2, 1959
    PubMed
    Summary

    This study measured nitrogen fixation in natural lakes using N(15) isotope tracing. Results show significant nitrogen fixation rates in diverse lake ecosystems.

    Area of Science:

    • Environmental Science
    • Limnology
    • Biogeochemistry

    Background:

    • Nitrogen is a crucial nutrient for aquatic ecosystems.
    • Estimating nitrogen fixation rates is vital for understanding lake productivity.
    • Natural lake waters are complex environments with varying nitrogen dynamics.

    Purpose of the Study:

    • To quantify primary nitrogen fixation rates in natural lake waters.
    • To assess the variability of nitrogen fixation across different geographic locations.
    • To establish N(15) incorporation as a method for estimating nitrogen fixation.

    Main Methods:

    • Utilized the stable isotope N(15) to trace nitrogen incorporation.
    • Conducted experiments in Pymatuning Reservoir (Pennsylvania), Lake Mendota (Wisconsin), and two Alaskan lakes.

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    The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
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    Published on: August 3, 2016

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    Establishment of Microbial Eukaryotic Enrichment Cultures from a Chemically Stratified Antarctic Lake and Assessment of Carbon Fixation Potential
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    Published on: April 20, 2012

    Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
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    The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
    10:11

    The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

    Published on: August 3, 2016

  • Measured the incorporation of N(15) into the particulate organic nitrogen fraction.

    • Main Results:

    • Demonstrated measurable rates of nitrogen fixation in all studied lakes.
    • Observed sometimes high rates of nitrogen fixation, indicating significant biological activity.
    • N(15) incorporation proved effective for quantifying nitrogen fixation.

    Conclusions:

    • Primary nitrogen fixation occurs at significant rates in natural lake waters.
    • Geographic location and lake characteristics influence nitrogen fixation rates.
    • The N(15) method provides a reliable approach for assessing nitrogen cycling in aquatic systems.