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.
Highlights
Long-lived anthropogenic substances such as chlorofluorocarbons are widely known as the main cause of the depletion of stratospheric ozone, but more recently, especially since preindustrial times, very short-lived substances, typically of lifetimes no longer than sixHow to cite this article Lim Y-K, Keng FS-L, Phang S-M, Sturges WT, Malin G, Abd Rahman N. 2019
Higher irradiance level of more than 1,000 μmol photons m−2 s−1 is usually encountered in the open waters of the tropical region, this study provides useful insight to the capability of the selected microalgae to emit halocarbons after a short-term shift to higher irradiance (120 μmol photons m−2 s−1) as compared to the control at 40 μmol photons m−2 s−1
While Moore et al (1996) reported that there was no clear trend of ‘‘higher level of illumination produces higher halocarbon concentration’’, this present study showed significant (Table S3) differences in emission rates due to exposure to higher irradiance
Summary
Long-lived anthropogenic substances such as chlorofluorocarbons are widely known as the main cause of the depletion of stratospheric ozone, but more recently, especially since preindustrial times, very short-lived substances, typically of lifetimes no longer than sixHow to cite this article Lim Y-K, Keng FS-L, Phang S-M, Sturges WT, Malin G, Abd Rahman N. 2019. A balanced upper tropospheric and lower stratospheric chemistry consisting of inorganic bromine-containing compounds (Bry) were once thought to be derived entirely from long-lived anthropogenic compounds such as bromomethane (CH3Br) and halons (Montzka & Reimann, 2011; Quack et al, 2004). These compounds in the stratosphere were lately found to be contributed substantially by short-lived biogenic bromocarbons such as tribromomethane (CHBr3) and dibromomethane (CH2Br2) (Tegtmeier et al, 2012; Fiehn et al, 2017; Ball et al, 2018). Future increases in their emissions would drive a negative forcing and thereby counterbalance a small fraction of the projected global warming influence due to greenhouse gases (Hossaini et al, 2015)
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