Effects of instantaneous changes in temperature, light, and salinity on the dynamics of dissolved organic carbon release by Sargassum thunbergii

Although macroalgae are regarded as the emerging fourth category of blue carbon, few studies are available on the dynamics of dissolved organic carbon (DOC) release. Sargassum thunbergii is a typical intertidal macroalgae; and tidal action usually triggers instantaneous changes in temperature, light and salinity. Therefore, we inves-tigated the mechanism of short-term changes in temperature, light and salinity on DOC release by S. thunbergii. As well as these factors coupled with desiccation, the combined effect of DOC release was revealed. The results showed the DOC release rate of S. thunbergii was from 0.028 to 0.037 mg C g-1(FW) h-1 under different photosynthetically active radiation (PAR, 0-1500 mu mol photons m- 2 s- 1). The DOC release rate of S. thunbergii was from 0.008 to 0.208 mg C g-1(FW) h-1 under different salinity (5-40). The DOC release rate of S. thunbergii was from 0.031 to 0.034 mg C g-1(FW) h-1 under different temperature (10-30 degrees C). Either the increase in intracellular organic matter concentration due to increased photosynthesis (change in PAR and temperature, active), cell dehydration due to dry-out process (passive) or the decrease in extracellular salt concentration (passive) would lead to an increase in the difference in osmotic pressure and promote DOC release.

Automated summary

Few studies have investigated the dynamics of dissolved organic carbon (DOC) release in macroalgae. This study examined the short-term changes in temperature, light, and salinity on DOC release in Sargassum thunbergii. The results showed that different levels of photosynthetically active radiation, salinity, and temperature all influenced the rate of DOC release in S. thunbergii.