Enhancement of diatom growth and phytoplankton productivity with reduced O2 availability is moderated by rising CO2.

Many marine organisms are exposed to decreasing O2 levels due to warming-induced expansion of hypoxic zones and ocean deoxygenation (DeO2). Nevertheless, effects of DeO2 on phytoplankton have been neglected due to technical bottlenecks on examining O2 effects on O2-producing organisms. Here we show that lowered O2 levels increased primary productivity of a coastal phytoplankton assemblage, and enhanced photosynthesis and growth in the coastal diatom Thalassiosira weissflogii. Mechanistically, reduced O2 suppressed mitochondrial respiration and photorespiration of T. weissflogii, but increased the efficiency of their CO2 concentrating mechanisms (CCMs), effective quantum yield and improved light use efficiency, which was apparent under both ambient and elevated CO2 concentrations leading to ocean acidification (OA). While the elevated CO2 treatment partially counteracted the effect of low O2 in terms of CCMs activity, reduced levels of O2 still strongly enhanced phytoplankton primary productivity. This implies that decreased availability of O2 with progressive DeO2 could boost re-oxygenation by diatom-dominated phytoplankton communities, especially in hypoxic areas, with potentially profound consequences for marine ecosystem services in coastal and pelagic oceans.

[Association between aldosterone synthase gene polymorphism and hypertrophic cardiomyopathy].

OBJECTIVE: To investigate the relationship between aldosterone synthase (CYP11B2) gene polymorphism and hypertrophic cardiomyopathy (HCM). METHODS: Fifteen HCM patients and 18 healthy subjects were enrolled in this study. Peripheral blood samples were collected from these subjects to exact genome DNA. PCR and Hae III restriction endonuclease digestion were employed to study -344C/T polymorphism of CYP11B2 gene. RESULTS: CYP11B2 gene showed a significant difference in CT genotype distribution in HCM groups as compared with that in the control groups (P<0.05). CONCLUSION: CT genotype of CYP11B2 gene may be one of factors responsible for the pathogenesis of HCM in a proportion of patients.