Nitrogen

Definition

Nitrogen is a chemical element with the symbol N and atomic number 7, making up about 78% of Earth's atmosphere. It is essential for life as it is a key component of amino acids, proteins, and nucleic acids, which are crucial for cellular functions and the formation of DNA and RNA. In marine ecosystems, nitrogen plays a pivotal role in primary production and food webs by influencing the growth of phytoplankton, which forms the base of the marine food chain.

5 Must Know Facts For Your Next Test

1. Nitrogen is primarily available to marine organisms in the form of nitrate (NO3-) and ammonium (NH4+), both of which are crucial for phytoplankton growth.
2. The process of nitrogen fixation converts atmospheric nitrogen into forms usable by living organisms, mainly performed by certain bacteria and archaea.
3. In marine food webs, nitrogen availability directly influences primary production rates, which can affect entire ecosystems by impacting species diversity and biomass.
4. Excessive nitrogen runoff from agricultural activities can lead to eutrophication, causing harmful algal blooms that deplete oxygen in water and create dead zones.
5. Marine organisms such as fish rely on nitrogen-rich diets to obtain essential amino acids necessary for their growth and reproduction.

Review Questions

• How does nitrogen influence the growth of phytoplankton in marine ecosystems?
  • Nitrogen is a critical nutrient for phytoplankton as it is a building block for proteins and nucleic acids. Its availability in forms like nitrate and ammonium directly affects phytoplankton growth rates. When nitrogen levels are sufficient, phytoplankton can thrive, leading to increased primary production, which supports higher trophic levels in the marine food web.
• Discuss the impact of anthropogenic nitrogen input on marine food webs and the potential consequences for aquatic ecosystems.
  • Anthropogenic nitrogen input, mainly from agricultural runoff and sewage discharge, can lead to nutrient overload in marine systems. This excess nitrogen can cause eutrophication, promoting algal blooms that disrupt normal food web dynamics. Such blooms can result in oxygen depletion, negatively impacting fish populations and other marine life due to hypoxia or anoxia.
• Evaluate how changes in nitrogen availability might alter the structure of marine food webs over time.
  • Changes in nitrogen availability can significantly reshape marine food webs by affecting primary production levels. An increase in nitrogen could initially boost phytoplankton populations, enhancing energy flow to higher trophic levels. However, if nutrient levels exceed optimal thresholds, it may lead to harmful algal blooms and decreased biodiversity. Over time, this can result in a shift towards less diverse communities dominated by opportunistic species, altering predator-prey relationships and ecosystem stability.

Related terms

Nitrogen Cycle: The series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms, including nitrogen fixation, nitrification, and denitrification.

Phytoplankton:

Microscopic marine organisms that perform photosynthesis and are a primary source of oxygen and organic matter in aquatic ecosystems.

Eutrophication:

A process where water bodies receive excess nutrients (especially nitrogen and phosphorus), leading to overgrowth of algae and depletion of oxygen, harming aquatic life.