Modeled diversity effects on microbial ecosystem functions of primary production, nutrient uptake, and remineralization.

Ecosystem-wide primary productivity generally increases with primary producer diversity, emphasizing the importance of diversity for ecosystem function. However, most studies that demonstrate this positive relationship have focused on terrestrial and aquatic benthic systems, with little attention to the diverse marine pelagic primary producers that play an important role in regulating global climate. Here we show how phytoplankton biodiversity enhances overall marine ecosystem primary productivity and other ecosystem functions using a self-organizing ecosystem model.

Abundance and distribution of major groups of diazotrophic cyanobacteria and their potential contribution to N₂ fixation in the tropical Atlantic Ocean.

The abundances of six N₂-fixing cyanobacterial phylotypes were profiled at 22 stations across the tropical Atlantic Ocean during June 2006, and used to model the contribution of the diazotrophs to N₂ fixation. Diazotroph abundances were measured by targeting the nifH gene of Trichodesmium, unicellular groups A, B, C (UCYN-A, UCYN-B and UCYN-C), and diatom-cyanobiont symbioses Hemiaulus-Richelia, Rhizosolenia-Richelia and Chaetoceros-Calothrix. West to east gradients in temperature, salinity and nutrients [NO₃⁻ + NO₂⁻, PO₄³⁻, Si(OH)₄] showed the influence of the Amazon River plume and its effect on the distributions of the diazotrophs.

GROWTH AND CARBON CONTENT OF THREE DIFFERENT-SIZED DIAZOTROPHIC CYANOBACTERIA OBSERVED IN THE SUBTROPICAL NORTH PACIFIC(1).

To develop tools for modeling diazotrophic growth in the open ocean, we determined the maximum growth rate and carbon content for three diazotrophic cyanobacteria commonly observed at Station ALOHA (A Long-term Oligotrophic Habitat Assessment) in the subtropical North Pacific: filamentous nonheterocyst-forming Trichodesmium and unicellular Groups A and B. Growth-irradiance responses of Trichodesmium erythraeum Ehrenb. strain IMS101 and Crocosphaera watsonii J.