Effects of Temperature and Light on Methane Production of Widespread Marine Phytoplankton

Abstract

Methane (CH 4) production in the ocean surface mixed layer is a widespread but still largely unexplained phenomenon. In this context marine algae have recently been described as a possible source of CH 4 in surface waters. In the present study we investigated the effects of temperature and light intensity (including daylength) on CH 4 formation from three widespread marine algal species Emiliania huxleyi, Phaeocystis globosa, and Chrysochromulina sp. Rates of E. huxleyi increased by 210% when temperature increased in a range from 10°C to 21.5°C, while a further increase in temperature (up to 23.8°C) showed reduction of CH 4 production rates. Our results clearly showed that CH 4 formation of E. huxleyi is controlled by light: When light intensity increased from 30 to 2,670 μmol m −2 s −1 , CH 4 emission rates increased continuously by almost 1 order of magnitude and was more than 1 order of magnitude higher when the daylength (light period) was extended from 6/18 hr light-dark cycle to continuous light. Furthermore, light intensity is also an important factor controlling CH 4 emissions of Chrysochromulina sp. and P. globosa and could therefore be a species-independent regulator of phytoplankton CH 4 production. Based on our results, we might conclude that extensive blooms of E. huxleyi could act as a main regional source of CH 4 in surface water, since blooming of E. huxleyi is related to the seasonal increase in both light and temperature, which also stimulate CH 4 production. Under typical global change scenarios, E. huxleyi will increase its CH 4 production in the future. Plain Language Summary Methane is a gas that affects the Earth's climate and is typically produced by microbes in the absence of oxygen or through geological processes. Surprisingly, methane is also produced in oceanic surface waters that are well oxygenated, known as the ocean-methane paradox. Marine phytoplankton has recently been discovered as a methane source, which might help to explain the paradox. Environmental factors such as light and temperature might be important for controlling methane production from marine algae. In order to understand how environmental factors affect methane formation from phytoplankton, we performed several experiments under laboratory conditions. We find that temperature, light intensity, and day length strongly control methane production of phytoplankton. The field blooms of marine algae, which are often strongly related to the seasonal increase of light and temperature, could act as an important regional source of methane in oceanic surface waters. Under typical global change scenarios, marine algae might increase their methane production in the 21th century.

Detailed Patterns of Methane Distribution in the German Bight

“…The waters around the East Frisian islands (south from our study area) are known for a predominant anaerobic degradation of organic matter (Schwichtenberg et al, 2020), which could lead to a small water mass associated with low oxygen and high methane content. (2) The aerobic CH 4 production by marine phytoplankton (Lenhart et al, 2016;Klintzsch et al, 2020); however, it is unknown if this occurs in our study area. (3) The aerobic CH 4 production from microbial decomposition of certain organic phosphorus compounds (Karl et al, 2008;Repeta et al, 2016).…”

Ultraviolet Radiation Drives Emission of Climate‐Relevant Gases From Marine Phytoplankton

“…Their production rates of 0.7 and 3.1 μg CH 4 g −1 POC d −1 , respectively, from cultures in an exponential growth phase, are much lower than our rate of 2.56 μg CH 4 g −1 POC h −1 due to our higher measured POC values. Subsequently, Klintzsch et al (2020) showed that the level of PAR could control CH 4 production by over an order of magnitude and was increased by continuous illumination compared to a 6/18h light cycle. Microbial degradation of DOM phosphonates was shown to produce CH 4 and C 2 H 4 by Repeta et al (2016), Perez-Coronel and Beman (2020), and Sosa et al (2020), while Bižić et al (2020) reported CH 4 production from metabolism of 17 marine, freshwater, and terrestrial cyanobacteria (independent of methylated precursors e.g., methylphosphonate).…”

“…Their production rates of 0.7 and 3.1 μg CH4 g -1 POC d -1 respectively, from cultures in an exponential growth phase, are much lower than our rate of 2.56 μg CH4 g -1 POC h -1 due to our higher measured POC values. Subsequently, Klintzsch et al (2020) showed that the level of PAR could control CH4 production by over an order of magnitude and was increased by continuous illumination compared to a 6/18h light cycle.…”

“…CH 4 production in the widespread marine coccolithophore Emiliania huxleyi was observed under visible light by Lenhart et al (2016) and also in the haptophytes Phaeocystis globosa and a Chrysochromulina sp. by Klintzsch et al (2019Klintzsch et al ( , 2020. These studies all relate CH 4 production with phytoplankton metabolism rather than photochemical transformation of cell components.…”

Effects of Arctic Warming on Microbes and Methane in Different Land Types in Svalbard

“…Examples include ice algae and phytoplankton, such as some Phaeocystis, which produce dimethylsulfoniopropionate (DMSP) and thereby have a negative effect on global warming [1][2][3]. By contrast, some species of archaea, bacteria, microalgae and protozoa can produce methane (CH 4 ) [4][5][6][7][8] and greenhouse gases, such as CO 2 (through biological respiration), which contributes to global warming. So even though these organisms are small, their functions are not insignificant.…”