Cyanobacteria are now recognized as the primary nitrogen-fixing (diazotrophic) microorganisms in the oceans as contributing significantly to the biogeochemistry of the global nitrogen cycle. The evolution of a remarkable range of morphologies and metabolic capacities has led to a behavioural versatility that helps them to proliferate and combat nutrient limitations in oceanic ecosystems. Advanc...

The concept of biogeochemical provinces in the ocean was implicit in Longhurst’s (1) classic monograph, Ecological Geography of the Sea. Longhurst identified distinct oceanic zones based on the relationships of oceanic biology (using chlorophyll, a proxy for phytoplankton biomass, and primary production) to physical forcing (e.g., surface currents, mixing depth, and upwelling). As we have advan...

MOTIVATION Fixed nitrogen is an essential requirement for the biosynthesis of cellular nitrogenous compounds. Some cyanobacteria can fix nitrogen, contributing significantly to the nitrogen cycle, agriculture and biogeochemical history of Earth. The rate and position on the species phylogeny of gains and losses of this ability, as well as of the underlying nif genes, are controversial. RESULT...

The main purpose of this study is to perform a nitrogen budget survey for the entire Brazilian Amazon region. The main inputs of nitrogen to the region are biological nitrogen fixation occurring in tropical forests (7.7 Tg.yr(-1)), and biological nitrogen fixation in agricultural lands mainly due to the cultivation of a large area with soybean, which is an important nitrogen-fixing crop (1.68 T...

Ammonia is an important component of the nitrogen cycle and because it is oxidized in the environment by microorganisms (i.e., nitrification), it is a large source of available nitrogen in the environment (Raven & Johnson 1989). The complexity of the nitrogen cycle, various rate determining environmental conditions for nitrification (e.g., pH, temperature), and the physical behaviour of ammonia...