Occurrence of Nitrogen Fixing CyanobacteriumTrichodesmiumunder ElevatedpCO2Conditions in the Western Bay of Bengal

[摘要] Recent studies on the diazotrophic cyanobacteriumTrichodesmiumshowed that increasing CO2partial pressure (pCO2) enhances N2fixation and growth. We studied thein situand satellite-derived environmental parameters within and outside aTrichodesmiumbloom in the western coastal Bay of Bengal (BoB) during the spring intermonsoon 2009. Here we show that the single most important nitrogen fixer in today’s ocean,Trichodesmium erythraeum, is strongly abundant in high (≥300 μatm)pCO2concentrations. N : P ratios almost doubled (~10) at highpCO2region. This could enhance the productivity of N-limited BoB and increase the biological carbon sequestration. We also report presence of an oxygen minimum zone at Thamnapatnam. Earlier studies have been carried out using lab cultures, showing the increase in growth rate ofT. erythraeumunder elevatedpCO2conditions, but to our knowledge, this study is the first to report that in natural environment alsoT. erythraeumprefers blooming in highpCO2concentrations. The observed CO2sensitivity ofT. erythraeumcould thereby provide a strong negative feedback to rising atmospheric CO2but would also drive towards phosphorus limitation in a future high CO2world.

[学科分类] 地质学