Sampriti Roy, University of Calcutta
If we notice the beautiful colour gradients across the image above, we would find bright green along with bluer areas. These areas altogether presented a very interesting finding detected initially by satellite images in late 2020. Colourful signatures of plankton blooms in Grande Bay, off of Argentina’s Santa Cruz province were captured by The Operational Land Imager (OLI) on Landsat 8 on 2nd January 2021 and off the coast of Argentina and around Falkland Islands (Islas Malvinas), the vivid imagery above was captured on 5th January 2021 by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite. This has been said to be a Goldilocks zone on Earth in the South Atlantic Ocean.
The Goldilocks zone refers to the habitable area around a star where the conditions are just right for the presence or existence of water and even life. The South Atlantic Ocean happens to have its kind of Goldilocks zone, which has sometimes been seen in the Argentine sea off the coast of Patagonia. In spring and summers, when conditions are just right for the growth of phytoplankton populations, these populations often explode into enormous blooms.
One of the major cause of phytoplankton blooms is the influx of nutrients and the area in focus has a few sources providing the same. Rivers such as the Santa Cruz carry nutrients from land and deliver them to the ocean, thus promoting phytoplankton growth. A cause of stimulation of the phytoplankton blooms is also said to be the complex circulation patterns of the ocean as well as the abundant fronts where water masses of varying and distinct salt content, nutrients and salinity meet. Along a front, the rising of a less-dense water mass can carry nutrients up to the surface, where phytoplankton are exposed to ample sunlight to fuel their growth. This can be well understood if we take the instance of the Brazil-Malvinas Confluence where warm water with comparatively more salt content meets the Southern Ocean’s cooler and fresher water flowing north.
For now, the scientists have stated that it is impossible to say for sure which type of phytoplankton are present in the images without collecting present-day samples. Previous observations on the phytoplankton blooms are as follows:
- Summer, 2003: Diatoms (Chaetocceros debilis) dominated a bloom in early summer
- Spring, 2005: Dinoflagellates (Prorocentrum minimum) were found during an intense bloom
- December 2008: Dense bloom of coccolithophores (Emiliania huxleyi), which tend to turn the ocean chalky green-blue were found.
It is known that coccolithophores are likely to dominate in the bluer areas and can continue to flourish in waters where iron has been depleted, while diatoms need both silicate and iron. It has been speculated that there could be a mix of dinoflagellates, diatoms and coccolithophores present in the area under discussion.
The scientists have said that the species found to be blooming (yet to be identified) indicates biological richness along Patagonia’s continental shelf, one of the world’s richest fisheries.
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Source: https://earthobservatory.nasa.gov/images/147753/phytoplankton-factory-in-the-argentine-sea
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