Effect of irradiance on the emission of short-lived halocarbons from three common tropical marine microalgae

Abstract

Marine algae have been reported as important sources of biogenic volatile halocarbons that are emitted into the atmosphere. These compounds are linked to destruction of the ozone layer, thus contributing to climate change. There may be mutual interactions between the halocarbon emission and the environment. In this study, the effect of irradiance on the emission of halocarbons from selected microalgae was investigated. Using controlled laboratory experiments, three tropical marine microalgae cultures, Synechococcus sp. UMACC 371 (cyanophyte), Parachlorella sp. UMACC 245 (chlorophyte) and Amphora sp. UMACC 370 (diatom) were exposed to irradiance of 0, 40 and 120 µmol photons m−2s−1. Stress in the microalgal cultures was indicated by the photosynthetic performance (Fv/Fm, maximum quantum yield). An increase in halocarbon emissions was observed at 120 µmol photons m−2s−1, together with a decrease in Fv/Fm. This was most evident in the release of CH3I by Amphora sp. Synechococcus sp. was observed to be the most affected by irradiance as shown by the increase in emissions of most halocarbons except for CHBr3 and CHBr2Cl. High positive correlation between Fv/Fm and halocarbon emission rates was observed in Synechococcus sp. for CH2Br2. No clear trends in correlation could be observed for the other halocarbons in the other two microalgal species. This suggests that other mechanisms like mitochondria respiration may contribute to halocarbon production, in addition to photosynthetic performance.

Rapid Release of Halocarbons from Saline Water by Iron-Based Photochemistry

“…Methyl halides are known to originate in large part from natural sources, including land plant emissions, marine algae, phytoplankton production, and biomass burning. − The ocean is an important source of methyl halides released into the atmosphere. For example, coastal areas and salt marshes have been identified as globally significant sources of CH 3 Cl and CH 3 Br. , According to the report, global coastal emissions were estimated at 0.5–3.6 Gg/year for CH 3 Br and 19–98 Gg/year for CH 3 Cl .…”