生物圏におけるストリーム・デニトリフィケーションと,人類による窒素負荷に対するその反応
Patrick J Mulholland1, Ashley M Helton, Geoffrey C Poole
1Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. mulhollandpj@ornl.gov
Nature
|March 14, 2008
まとめ
流は窒素汚染を吸収しますが,汚染レベルが上昇すると効率は低下します. これは,汚染が大きいときに,より多くの窒素がより大きな水域に逃れ,自然フィルターとしてより小さな小川を圧倒することを意味します.
科学分野:
- 環境科学 環境科学
- エコロジー エコロジー エコロジー
- バイオジオケミストリー バイオジオケミストリー
背景:
- 人為的な窒素 (N) の投入の増加は,陸上の生態系を飽和させています.
- 窒素の飽和は地下水と地表水に高濃度の窒素をもたらします.
- 河川は海洋に大量に窒素を排出するので,景観の沈殿地は極めて重要です.
研究 の 目的:
- 生物利用可能な窒素のシンクとしてストリームを調査する.
- 窒素濃度の窒素吸収と脱窒化への影響を定量化する.
- ストリームサイズがNの輸出効率にどのように影響するか評価する.
主な方法:
- 8つのバイオームの72のストリームで窒素安定同位体トレーサー実験を実施しました.
- ストリームナイトレート濃度との関係で分析されたバイオティック吸収と脱窒化率.
- N輸出をシミュレートするためにストリームネットワークモデルを使用しました.
主要な成果:
- バイオティクスの吸収と窒素酸塩の脱窒化は,ストリーム窒素酸塩濃度とともに増加します.
- 流による窒素除去の効率は,窒素濃度が上昇するにつれて低下します.
- 過剰な窒素酸塩は,N輸出を不均衡に増加させ,Nが沈むにつれて小流の役割を減少させます.
結論:
- ストリームNの除去効率は濃度に依存し,より高い負荷で減少します.
- 生態系の光合成と呼吸は,それぞれNの吸収と脱窒化に影響を与えます.
- ストリームネットワークの構造と窒素濃度は,受水域へのNの輸出に重大な影響を及ぼします.
さらに関連する動画
関連する概念動画
The Nitrogen Cycle
46.5K
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...
46.5K
Overview of Nitrogen Metabolism
8.6K
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...
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this...
8.6K
Metabolism of Chemolithotrophs
1.3K
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.
1.3K
Inorganic Nitrogen Assimilation
936
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...
936
Freshwater Microbial Ecology
66
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...
66
Microbes and Climate Change
100
Microorganisms are pivotal agents in Earth's biogeochemical cycles, significantly influencing climate dynamics through their metabolic activities. These microbes modulate the levels of key greenhouse gases by both contributing to and helping mitigate climate change.Microbial Contributions to Greenhouse Gas EmissionsRising global temperatures accelerate microbial metabolism, which, in turn, speeds up the decomposition of organic matter. This process releases carbon dioxide (CO₂) through...
100


