Research Shows Red Tides In Ocean Occur Due To The Accumulation Of Microorganisms And Sediments

When one thinks of the blue immensity of the ocean, one does not imagine that the red color can be present. Red tides: this is the name given to the uncontrolled proliferation, above all, of microalgae on the surface of the waters. “In plants, photosynthesis enables the growth of leaves, stems and roots. But, in microalgae, this does not happen. They do not increase in size, but rather divide and increase the number of cells”, says Áurea Ciotti, a professor at USP’s Center for Marine Biology.

The accumulation, also called blooming, is carried out mainly by the type of algae called dinoflagellate, which, due to its pigments, turns the water red. However, depending on the species, there may even be green tides, brown tides, among others.

At first glance, red tides may seem harmless, just coloring the ocean, but they can have consequences that threaten marine life. “Some species produce toxins that bring risks to biodiversity, fishing and the cultivation of marine organisms, in addition to human health. This huge mass of cells, when decomposed, can also cause a lack of oxygen for other organisms, causing dead zones”, explains Áurea.

reasons
Eutrophication corresponds to an increase in the amount of organic matter in the aquatic environment. This phenomenon is closely related to the appearance of red tides, since the greater proliferation of waters comes from the availability of more nutrients. “This is observed in many coastal regions around the world, where the proliferation of microalgae is related to the increase of nutrients in the ocean, originating from urban sewage or fertilizers from agriculture”, comments the professor.

But nutrient abundance isn’t the only factor producing these algal tides. Rising ocean temperatures, which are strongly related to global warming, also enter the equation. According to Copernicus , a climate change agency linked to the European Union, the ocean temperature hit a record 20.96ºC in 2023.

The problem affects many levels of the marine chain, as Áurea points out: “Even without producing toxins, changes in the amount and composition of microalgae will affect the entire food web, as more food at the base of the chain will lead to a change in the number of individuals of other organisms and an ecological imbalance”. However, the problem has a solution: it is necessary to improve sanitation and agricultural practices, so that the entry of nutrients into the ocean is controlled, and also to combat climate change.