Specialized prokaryotes performing biological dinitrogen (N2) fixation (“diazotrophs”) provide an important source of fixed nitrogen in oligotrophic marine ecosystems such as tropical and subtropical oceans. In these waters, cyanobacterial photosynthetic diazotrophs are well known to be abundant and active, yet the role and contribution of non-cyanobacterial diazotrophs are currently unclear. T...

A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness ...

Thermally induced bleaching has caused a global decline in corals and the frequency of such bleaching events will increase. Thermal bleaching severely disrupts the trophic behaviour of the coral holobiont, reducing the photosynthetically derived energy available to the coral host. In the short term this reduction in energy transfer from endosymbiotic algae results in an energy deficit for the c...

It has been univocally shown that iron (Fe) is the primary limiting nutrient for phytoplankton metabolism in high-nutrient, low-chlorophyll (HNLC) waters, yet the question of how this trace metal affects heterotrophic microbial activity is far less understood. We investigated the role of Fe for bacterial heterotrophic production and growth at three contrasting sites in the naturally Fe-fertiliz...

Many of the current greenhouse based intensive marine shrimp production systems have used photoautotrophic algae systems to control inorganic nitrogen accumulation. A second strategy of nitrogen control used in some indoor intensive recirculating production systems is using large fixed-film bioreactors. This option utilizes chemosynthetic autotrophic bacteria, Ammonia Oxidizing Bacteria (AOB) a...

• Over 400 species of achlorophyllous vascular plants are thought to obtain all C from symbiotic fungi. Consequently, they are termed ‘myco-heterotrophic.’ However, direct evidence of myco-heterotrophy in these plants is limited. • During an investigation of the patterns of N and C stable isotopes of various ecosystem pools in two old-growth conifer forests, we sampled six species of mycohetero...

Heterotrophic activities on sinking particulate matter (SPM) play an important role in SPM fluxes in the ocean. To demonstrate regional differences in heterotrophic activities on SPM, we measured heterotrophic bacterial production (HBP) in seawater (HBP(SW)) and SPM (HBP(SPM)) as well as potential extracellular enzyme activity (EEA) in SPM on a transect along 155°E in the western North Pacific ...

Grazing by heterotrophic nanoflagellates and < 100 Fm microzooplankton on planktonic bacteria was followed during a mesocosm experiment in the Baltic Sea between 23 July and 12 August 1988 on the SW coast of Finland. During the succession of the planktonic community in one mesocosm, 4 grazing experiments were run with a size-fractionation technique. The size fractions used were: < 1 pm (bacteri...

The import of resources (food, nutrients) sustains biological production and food webs in resource-limited habitats. Resource export from donor habitats subsidizes production in recipient habitats, but the ecosystem-scale consequences of resource translocation are generally unknown. Here, I use a nutrient-phytoplankton-zooplankton model to show how dispersive connectivity between a shallow auto...

The effectiveness of various physical and chemical methods for the removal of contaminants from the microalgae, Tetraselmis suecica, culture was investigated. The information obtained was used as the basis for the development of improved protocol for the preparation of axenic culture to be adapted to heterotrophic cultivation. Repeated centrifugation and rinsing effectively removed the free bac...