Nitrogen removal in marine environments: recent findings and future research challenges
Artikel i vetenskaplig tidskrift, 2005

Respiratory reduction of nitrate (denitrification) is recognized as the most important process converting biologically available (fixed) nitrogen to N-2. In current N cycle models, a major proportion of global marine denitrification (50-70%) is assumed to take place on the sea floor, particularly in organic rich continental margin sediments. Recent observations indicate that present conceptual views of denitrification and pathways of nitrate reduction and N, formation are incomplete. Alternative N cycle pathways, particularly in sediments. include anaerobic ammonium oxidation to nitrite, nitrate and N-2 by Mn-oxides, and anaerobic ammonium oxidation coupled to nitrite reduction and subsequent N, mobilization. The discovery of new links and feedback mechanisms between the redox cycles of, e.g., C, N, S, Mn and Fe casts doubt on the present general understanding of the global N cycle. Recent models of the oceanic N budget indicate that total inputs are significantly smaller than estimated fixed N removal. The occurrence of alternative N reaction pathways further exacerbates the apparent imbalance as they introduce additional routes of N removal. In this contribution, we give a brief historical background of the conceptual understanding of N cycling in marine ecosystems, emphasizing pathways of aerobic and anaerobic N mineralization in marine sediments, and the implications of recently recognized metabolic pathways for N removal in marine environments. (c) 2004 Elsevier B.V. All rights reserved.

FERROUS IRON

EARLY DIAGENETIC

NITRATE-REDUCING BACTERIA

OXIC-ANOXIC INTERFACE

MINERALIZATION

removal

ANAEROBIC AMMONIUM OXIDATION

BIOGEOCHEMICAL CYCLES

ORGANIC-MATTER

PROCESSES

marine

ESTUARINE SEDIMENT

nitrogen

EARTHS EARLY ATMOSPHERE

PROTEROZOIC OCEAN CHEMISTRY

Författare

Stefan Hulth

Göteborgs universitet

R. C Aller

D. E Canfield

T Dalsgaard

Pia Engström

Göteborgs universitet

F. Gilbert

Kristina Sundbäck

Göteborgs universitet

B Thamdrup

Marine Chemistry

Vol. 94 1-4 125-145

Ämneskategorier

Ekologi

Kemi

DOI

10.1016/j.marchem.2004.07.013