Dimethylsulfide (DMS), marine biogenic aerosols and the ecophysiology of coral reefs

Abstract

Abstract. Global climate change and the impacts of ocean warming, ocean acidification and declining water quality are adversely affecting coral-reef ecosystems. This is of great concern, as coral reefs provide numerous ecosystem, economic and social services. Corals are also recognised as being amongst the strongest individual sources of natural atmospheric sulfur, through stress-induced emissions of dimethylsulfide (DMS). In the clean marine boundary layer, biogenic sulfates contribute to new aerosol formation and the growth of existing particles, with important implications for the radiative balance over the ocean. Evidence suggests that DMS is not only directly involved in the coral stress response, alleviating oxidative stress, but also may create an “ocean thermostat” which suppresses sea surface temperature through changes to aerosol and cloud properties. This review provides a summary of the current major threats facing coral reefs and describes the role of dimethylated sulfur compounds in coral ecophysiology and the potential influence on climate. The role of coral reefs as a source of climatically important compounds is an emerging topic of research; however the window of opportunity to understand the complex biogeophysical processes involved is closing with ongoing degradation of the world's coral reefs. The greatest uncertainty in our estimates of radiative forcing and climate change is derived from natural aerosol sources, such as marine DMS, which constitute the largest flux of oceanic reduced sulfur to the atmosphere. Given the increasing frequency of coral bleaching events, it is crucial that we gain a better understanding of the role of DMS in local climate of coral reefs.

Parameterizing the Impact of Seawater Temperature and Irradiance on Dimethylsulfide (DMS) in the Great Barrier Reef and the Contribution of Coral Reefs to the Global Sulfur Cycle

“…Other studies have demonstrated that temperature has a stronger influence on DMS production in algae, where increased production in response to temperature outweighed the decline in biosynthesis due to acidification (Arnold et al, 2013). Ongoing coral reef degradation, due to coral bleaching, crown of thorns outbreaks and changing water quality may also affect DMS w concentration in reef seawaters (discussed in Jackson et al (2020)). A decline in coral-derived DMS w could occur with reduced coral cover; however, DMS-producing marine algae can dominate degraded coral reef ecosystems (De'ath & Fabricius, 2010;McCook & Diaz-Pulido, 2002) and counteract a decline in coral-derived DMS production.…”

“…Global modeling studies have found that marine DMS is an important source of sulfate aerosol, influencing climate (Gabric et al., 2013; Mahajan et al., 2015; Thomas et al., 2010; Woodhouse et al., 2010) and providing a cooling effect of up to 0.45 °C (Fiddes et al., 2018). Given that coral reefs are strong regional sources of DMS, it is hypothesized that DMS emissions may influence the local radiative balance (Jackson et al., 2020; Jones et al., 2018; Swan et al., 2016) via a negative feedback on aerosol and cloud formation (e.g., Cropp et al., 2007). However, this coral reef source of atmospheric sulfur is not currently accounted for in global climatologies.…”

“…Ongoing coral reef degradation, due to coral bleaching, crown of thorns outbreaks and changing water quality may also affect DMS w concentration in reef seawaters (discussed in Jackson et al. (2020)). A decline in coral‐derived DMS w could occur with reduced coral cover; however, DMS‐producing marine algae can dominate degraded coral reef ecosystems (De'ath & Fabricius, 2010; McCook & Diaz‐Pulido, 2002) and counteract a decline in coral‐derived DMS production.…”

“…The Great Barrier Reef (GBR), Australia, has been recognized as a significant source of DMS, with the potential to influence local climate in NE Australia (Jackson et al., 2020; Jones et al., 2018). Acropora spp.…”

Foreword to the research front on ‘Fluxes and Chemistry of Marine Biogenic Volatile Organic Compounds’

“…Coral reefs as a source of marine biogenic aerosols is an emerging topic, and DMS can play a significant role in coral ecophysiology (e.g. alleviation of oxidative stress and contribution to 'thermostat'; Jackson et al 2020). In addition, the impact of ocean acidification on production of marine trace gases may cause potentially large modifications of DMS and nitrous oxide (N 2 O) fluxes (Hopkins et al 2020).…”