The role of symbiotic relationships of plants with the rhizosphere bacteria and fungi on Earth’s climate has not been given due attention. A recent study by Mohr et al. (2021) suggests that seagrasses met their nitrogen deficiency through symbiosis with the bacterial population in their root (endophytic bacteria), the first observation in seagrass. Thus, they can grow well and oxygenate the water column in nitrogen-limited coastal areas like the Meditterennian Sea.
In an earlier work by Pohl et al. (2021) about the vertical decoupling of the ocean in Late Ordovician anoxia (around 440-460 million years ago), there was an expansion of bottom water deoxygenation, though upper oceanic water remained well-oxygenated. Please note seagrasses evolved only around 100 million years ago, and we are not aware of anything that contributed to a well-oxygenated water column during Late Ordovician anoxia.
Seagrasses are one of the significant contributors to the global carbon cycle akin to the mangroves. As nitrogen limitation is more prevalent than phosphorus limitation in the world’s oceans, symbiotic relations promoting nitrogen fixation and its availability to plants have wide-ranging implications in understanding and predicting future climate. Especially under rising sea levels, if the submerged coastal areas tend to favour the growth of seagrass, they can have the potential to subdue or reverse global warming.
Now the question remains when did the symbiosis start in Earth’s history? What are its implications in nutrient cycling and global climate - both on the continents and oceans?
Further reading:
Mohr, W., Lehnen, N., Ahmerkamp, S., Marchant, H.K., Graf, J.S., Tschitschko, B., Yilmaz, P., Littmann, S., Gruber-Vodicka, H., Leisch, N., Weber, M., Lott, C., Schubert, C.J., Milucka, J., Kuypers, M.M.M., 2021. Terrestrial-type nitrogen-fixing symbiosis between seagrass and a marine bacterium. Nature. https://doi.org/10.1038/s41586-021-04063-4
Pohl, A., Lu, Z., Lu, W., Stockey, R.G., Elrick, M., Li, M., Desrochers, A., Shen, Y., He, R., Finnegan, S., Ridgwell, A., 2021. Vertical decoupling in Late Ordovician anoxia due to reorganization of ocean circulation. Nat. Geosci. 14, 868–873. https://doi.org/10.1038/s41561-021-00843-9
No comments:
Post a Comment