Greenhouse gas regulation

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Definition of Greenhouse gas regulation:
The balance and maintenance of the chemical composition of the atmosphere and oceans by maine living organisms[1].
This is the common definition for Greenhouse gas regulation, other definitions can be discussed in the article

Carbon sequestration

Marine ecosystems are an important regulator of the global CO2/O2 (carbon dioxide/oxygen) balance. The biogeochemical cycling of these gases is greatly controlled by the living biota existing on earth of which the marine realm is extremely important. For example, marine plants and animals aid in controlling carbon dioxide in the ocean, as phytoplankton remove it from the surface waters while releasing oxygen. When phytoplankton die, they sink and add to the supersaturation of carbon dioxide in the deep sea. This results in a vertical gradient of CO2 in the ocean, which has been termed the 'Biological Pump.' See Ocean carbon sink and Ocean acidification for further details.

Dimethyl sulfide (DMS)

Marine ecosystems mitigate greenhouse warming also by the production of dimethyl sulfide (DMS, (CH3)2S)[2]. In the atmosphere, DMS oxidizes to form sulfur dioxide (SO2) and methane sulfonic acid (H3CSO2OH), eventually leading to aerosol formation. These aerosols can grow to act as cloud condensation nuclei owing to their high hygroscopicity (absorption of moisture), thereby affecting the incoming solar radiation by increasing cloud albedo over the oceans. This process contributes to natural negative radiative forcing that influences the Earth’s climate.

Dimethylsulfide (DMS) and its precursor, dimethylsulphoniopropionate (DMSP, (CH3)2S+CH2CH2COO-), are mainly produced by algae and also by a few species of intertidal plants, bacteria, cnidarians and macro-invertebrates. DMSP, serves as antioxidant and osmolyte in algal cells and is also an important infochemical affecting trophic dynamics by attracting predators, such as seabirds, feeding on, for example, herbivorous crustaceans, thereby reducing the grazing pressure on phytoplankton. Moreover, it is also an important source of carbon and sulfur to marine bacterioplankton and may aid fish larva in locating their settlement habitat, thereby playing multiple fundamental roles in aquatic ecosystems[3].

DMS production from phytoplankton is affected by a variety of eco-physiological processes, such as ocean acidification, bacterial taxa and its decomposition pathway (lyase pathway or demethylation pathway of DMSP), nitrogen-to-phosphorous ratio and nitrogen limitation, zooplankton grazing on phytoplankton and also by the phytoplankton community composition. It has been estimated that ∼90% of the DMS production is degraded through microbial decomposition. Together with the degradation of photochemical oxidation, the DMS amount emitted from surface oceans to the atmosphere is less than 10% of the DMS production by phytoplankton in the ocean. Together, this indicates that the relationship between DMS concentration and phytoplankton is complex[3][4].

The global annual mean DMS concentration is estimated to be about 2.26 nM (1 nM = 10-9 mole/l). Large differences of up to 5 nM were observed on regional scales during certain months. The global sea-to-air flux of DMS is estimated at 27 (± 25%) Tg S/yr [5]. DMS-producing phytoplankton are particularly abundant in the Arctic and Antarctic oceans[6]. Factors such as decreases in sea ice extent, mixed-layer shallowing and increases in sea surface temperature may stimulate DMS production in these regions and possibly mitigate the effects of global warming. Field measurements by Deng et al. (2021[3]) suggest the highest DSM concentrations occur when the chlorophyll a concentration is around 5 mg Chl-A /m3, with loglinear decrease for lower and higher Chl-A values.

A strong relationship was found also between DMS concentrations and pH, with a breakpoint at pH = 8.09 ± 0.05. When pH declined from 8.3 to 7.49, the algal DMS production declined by ∼50%–60%, although no clear relationship emerged from field data between pH and the DMSP production from algae[3]. These results suggest that ocean acidification will likely cause a decline of average DMS concentrations, particularly at the poles. Analysis of global observational datasets also points to a negative correlation between the partial pressure of carbon dioxide (pCO2) and sea-surface DMS concentrations[7].

Trend analyses of DMS production lead to contrasting results[5][8]. The IPCC report Climate Change 2021 The Physical Science Basis, Chapter 6[9] suggests that DMS emissions will decrease as a result of multiple stressors, including climate warming, eutrophication, and ocean acidification. However, large uncertainties in process-based understanding of the mechanisms controlling DMS emissions, from physiological to ecological, limit our knowledge of past variations and our capacity to project future changes. Overall, there is low confidence in the magnitude and changes in marine aerosol emissions in response to shifts in climate and marine ecosystem processes.


Related articles

Ocean carbon sink
Ocean acidification
Green Ocean modelling
Blue carbon sequestration
Algal bloom dynamics


References

  1. ↑ Beaumont, N.J.; Austen, M.C.; Atkins, J.P.; Burdon, D.; Degraer, S.; Dentinho, T.P.; Derous, S.; Holm, P.; Horton, T.; van Ierland, E.; Marboe, A.H.; Starkey, D.J.; Townsend, M.; Zarzycki, T. (2007). Identification, definition and quantification of goods and services provided by marine biodiversity: implications for the ecosystem approach. Mar. Pollut. Bull. 54(3): 253-265
  2. ↑ O'Dowd, C. D. and De Leeuw, G. 2007. Marine aerosol production: A review of the current knowledge. Philosophical Transactions of the Royal Society A, 365: 1753–1774
  3. ↑ 3.0 3.1 3.2 3.3 Deng, X., Chen, J., Hansson, L-A., Zhao, X. and Xie, P. 2021. Eco-chemical mechanisms govern phytoplankton emissions of dimethylsulfide in global surface waters. National Science Review 8: nwaa140
  4. ↑ Jackson, R. and Gabric, A. 2022. Climate Change Impacts on the Marine Cycling of Biogenic Sulfur: A Review. Microorganisms 10, 1581
  5. ↑ 5.0 5.1 Hulswar, S., Simó, R., Galí, M., Bell, T.G., Lana, A., Inamdar, S., Halloran, P.R., Manville, G. and Mahajan, A.S. 2022. Third revision of the global surface seawater dimethyl sulfide climatology (DMS-Rev3). Earth Syst. Sci. Data 14, 2963–2987
  6. ↑ Park, K-T., Yoon, Y. J., Lee, K., Tunved, P., Krejci, R., Ström, J., Jang, E., Kang, H.J., Jang, S., Park, J., Lee, B.Y., Traversi, R., Becagli, S. and Hermansen, O. 2021. Dimethyl sulfide-induced increase in cloud condensation nuclei in the Arctic atmosphere. Global Biogeochemical Cycles, 35, e2021GB006969
  7. ↑ Zhao, J., Zhang, Y., Bie, S., Bilsback, K.R., Pierce, J.R.and Chen, Y. 2024. Changes in global DMS production driven by increased CO2 levels and its impact on radiative forcing. Climate and Atmospheric Science 7:18
  8. ↑ Joge, S.D., Mahajan, A.S., Hulswar, S., Marandino, C.A., Galí, M., Bell, T.G. and Simo, R. 2024. Dimethyl sulfide (DMS) climatologies, fluxes and trends - Part A: Differences between seawater DMS estimations. EGU https://doi.org/10.5194/egusphere-2024-173
  9. ↑ Szopa, S., V. Naik, B. Adhikary, P. Artaxo, T. Berntsen, W.D. Collins, S. Fuzzi, L. Gallardo, A. Kiendler-Scharr, Z. Klimont, H. Liao, N. Unger, and P. Zanis, 2021: Short-Lived Climate Forcers. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 817–922



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