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Coral reefs release dimethyl sulfide (DMS), a sulfur-containing gas that can enter the atmosphere and contribute to aerosol formation. That creates a plausible pathway from reef biology to clouds and local climate—but it does not show that reefs cool the planet or meaningfully change cloud cover. A Great Barrier Reef modeling study found no significant aerosol response to reef-derived DMS in its modeled case.
How do coral reefs affect climate?
The pathway begins with dimethylsulfoniopropionate (DMSP), a sulfur-bearing compound made or held by marine organisms. DMSP is a precursor, not the gas released to the air. Corals, their symbiotic algae, and associated microbes together form the coral holobiont, which produces and transforms DMSP through several competing biological routes. DMSP also has roles in algae that include stress response and osmotic functions.
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From DMSP to DMS
Some enzymes cleave DMSP into DMS and acrylate. Other microbes demethylate DMSP to methanethiol, while biological and photochemical processes also consume DMS. As a result, a measurement of DMSP alone cannot tell how much DMS a reef will release: the balance among these pathways matters. NOAA’s overview of marine sulfur, aerosols, and climate processes describes the broader atmospheric context.
From seawater to aerosols
A fraction of dissolved DMS escapes seawater into the marine boundary layer. Atmospheric oxidation produces sulfur-containing compounds that can contribute to sulfate aerosol formation and particle growth. Aerosols can participate in cloud condensation, but the strength of this connection depends on factors including atmospheric chemistry, existing particles, weather, and location. Each step is a possible link; aerosol production does not by itself establish a measurable cloud or climate effect.
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Can heat, sunlight, or low tide change reef DMS emissions?
They can affect the biology and release of sulfur compounds, but results depend on species and conditions. In a 2016 laboratory study of three Indo-Pacific coral species, gas-phase DMS rose by an order of magnitude during air exposure and rose again after the corals were re-submerged. The experiment suggests a possible protective role for DMS during oxidative stress; it does not establish that all corals respond alike or that the same increase occurs across natural reefs. Raina et al.’s study reports the experimental result.
Review literature also describes changes in DMSP and microbial pathway genes under heat or high-light stress. Shallow reefs may experience these conditions alongside exposure during low tides, but stress-related changes in sulfur chemistry are not a universal emission multiplier. The 2023 review of sulfur compounds and coral-reef climate discusses these interacting biological pathways.
How much DMS do coral reefs emit?
Jackson et al. (2021) used Great Barrier Reef (GBR) field data to parameterize the relationship between seawater DMS, sea-surface temperature, and photosynthetically active radiation (PAR). Their regression explained 71% of the observed variance in DMS concentration. The resulting flux figures are estimates, not direct measurements of total emissions from every reef.
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| Estimate | What it represents | Qualification |
|---|---|---|
| 0.03–0.05 Tg DMS per year | GBR reef and lagoon waters | Jackson et al. (2021) modeled estimate based on their parameterization and flux assumptions. |
| 0.06–0.08 Tg DMS per year | Tropical coral reefs globally | Jackson et al. (2021) extrapolation that assumes production and flux remain constant across reefs; it is not a direct global observation. |
The GBR analysis could not precisely separate DMS contributions from corals and marine algae, and the authors called for more reef-water observations. Its regional relationship should not automatically be applied to reefs with different temperatures, light, microbial communities, or environmental conditions. See Jackson et al. (2021), in Journal of Geophysical Research: Oceans, for the parameterization and its limits.
Does reef-derived DMS measurably change clouds or climate?
That part of the pathway is less certain than the biology and emissions. Fiddes et al. (2022) modeled the contribution of coral-reef-derived DMS to the aerosol burden over the GBR using WRF-Chem and data from an October 2016 campaign. Including reef DMS produced no significant change in modeled sulfate aerosol mass or total aerosol number in that case. The authors offered anthropogenic aerosol sources along the Queensland coast as one reason a reef signal might be difficult to distinguish. This is a result for a particular regional simulation, not proof that reef DMS has no atmospheric effect elsewhere.
A 2023 review reports a projected 10–14% increase in GBR DMS emissions under future temperature and irradiance projections, while judging that increase unlikely to significantly influence the regional atmosphere. That is a modeled projection discussed in a review, not a measured future trend or evidence of cooling. Neither the projected emissions nor the possible aerosol pathway establishes a coral-specific climate feedback. The 2022 GBR aerosol modeling study details the regional result.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Can reef heat-stress monitoring show sulfur emissions?
No. NOAA Coral Reef Watch’s Thermal History product tracks satellite sea-surface-temperature histories and heat-stress events; it does not measure DMS, DMSP, or sulfur flux. Version 3.7, released January 9, 2026, includes Degree Heating Week (DHW) thresholds for heat-stress events above 0, significant bleaching-level heat stress at 4 or more, and severe bleaching-level heat stress at 8 or more. These indicators help describe thermal conditions, not prove a sulfur-mediated feedback.
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What the evidence supports
- Established pathway: Reef organisms cycle DMSP; some becomes volatile DMS, which can escape seawater and contribute to atmospheric sulfur chemistry.
- Measured and estimated emissions: Laboratory experiments show coral DMS release under specified exposure conditions, and GBR observations underpin a regional flux estimate. The global figure is an extrapolation.
- Unsettled climate consequence: Aerosol formation provides a possible route to influence local radiative balance, but a significant cloud or climate effect from coral DMS has not been established.
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