Gwenn Hennon and co-authors have published a new study in the journal Nature Climate Change describing how diatoms adjust metabolism and gene expression under rising CO2. Hennon et al. found that expression of carbon concentration and photorespiration genes are coordinated by signaling with the small molecule cyclic-AMP, which may be a deeply conserved mechanism of CO2-regulation in diatoms.
Prochlorococcus lives by day, dies by night
Francois Ribalet and co-authors have published a new study in Proceedings of the National Academy of Sciences where they used novel flow cytometry approaches to generate continuous estimates of growth and mortality rates of the abundant cyanobacterium Prochlorococcus across 2900 km of the subtropical Pacific gyre. They show that Prochlorococcus mortality is tightly synchronized to the day/night cycle, with essentially no cell loss during the day. This means that a pulse of Prochlorococcus-derived organic compounds is propagated each night through the food web, stabilizing multiple trophic interactions.
Francois Ribalet and co-authors have published a new study in the journal PLoS ONE on phytoplankton cell lysis associated with chemical compounds release by diatoms. The study present data from four oceanographic cruises that took place during diatom blooms in the northern Adriatic Sea where concentrations of particulate and dissolved aldehydes produced by diatoms were monitored along with phytoplankton cell lysis. Cell lysis was positively correlated with both concentrations of particulate and dissolved aldehydes, supporting the hypothesis that these compounds are released by cell lysis. These results also suggest that aldehydes may help shape plankton community composition and function in the oceans.
Gwenn Hennon and co-authors have published a new study in the Journal of Phycology on the physiological changes in the diatom Thalassiosira pseudonana under elevated CO2 in a nitrate-limited chemostat. The study finds that acclimation conditions modify the physiological response of the diatom to elevated CO2, with longer acclimations resulting in moderated physiological changes. These results suggest that gene expression or epigenetic changes over tens of generations may moderate some of the extreme physiological changes observed in diatoms under elevated CO2. Understanding these processes will be key in predicting changes to the marine carbon cycle as atmospheric carbon rises.
Shady Amin and coauthors published a new study on the copper requirements of ammonia-oxidizing archaea (AOA), a major group of prokaryotes that are believed to dominate ammonia oxidation in the oceans. The few publicly available AOA genomes suggested these organisms have a Cu requirement due to the presence of a high number of Cu metalloenzymes. Indeed, this study finds that the only marine AOA available in pure culture is Cu-limited at copper concentrations that are commonly found in the marine environment.
Silicification in Coastal Diatom Communities
Colleen A. Durkin and co-authors published a new study on diatom silicification. The authors used in situ incubation experiments, along with laboratory culturing experiments, to demonstrate that variation in silicic acid supply alters the silicification of coastal diatom blooms and diatom sinking rates. Click here to read more in Limnology and Oceanography: Silicic acid supplied to coastal diatom communities influences cellular silicification and the potential export of carbon