The flower– understood as a red tide or harmful algal bloom (HAB) event– was uncommonly extensive and long-lived.
Phytoplankton blossoms are typical this time of year in Rio, however they usually include species that are advantageous to the ecosystem. The abundance of nutrients and sunshine at the ocean surface area activates blooms of diatoms and other phytoplankton, which are quickly taken in by zooplankton and fish larvae. The bloom shows up in the natural-color image (top) as a faint, dark swirl of water extending away from the coast. The flower is more distinct in the false-color image (second image).
December 26, 2021. False-color image from NASAs Aqua satellite.
Some types in a red tide can produce contaminants but, up until now, those types have not been observed in the Rio bloom. Instead, Lange called the blossom “stressing” since of its most likely effect on the marine food web.
From September to January of most years (spring and summer season in South America), cool, nutrient-rich water wells up from the depths of the ocean off Arraial do Cabo, replacing surface area waters that have been pressed offshore by winds and the Coriolis effect. The abundance of nutrients and sunshine at the ocean surface activates blooms of diatoms and other phytoplankton, which are soon consumed by zooplankton and fish larvae. Marine currents press the upwelled water masses west towards the city of Rio de Janeiro, and the warm, blue water off Rio normally turns dark and cold green.
Spring 2021 differed from most years. Lange and associates think six weeks of cloudiness and rain hampered the typical growth of diatoms and little flagellates, leaving the waters off Rio transparent and overflowing with nutrients. When the skies lastly cleared in early November, ample sunlight and low turbulence set the phase for the red tide. “Once there was light, the red folks– dinoflagellates, Mesodinium rubrum, and so on– flowered like insane!” Lange stated.
The change took place quickly. The very first visual observations of red tide were made on November 3, then verified by water samples drawn from a beach in Rio on November 16. The water off Rios beaches quickly ended up being extremely dark, and red seafoam developed.
In early December, the red tide reached Arraial do Cabo and “darkened the waters of Rios the majority of beautiful scuba dive paradise,” Lange stated. Satellite images from December 5 reveal the red-brown water spanning the length of the coastline in between the two cities.
By late December, the flower was fading but remained visible to the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASAs Aqua satellite, which acquired these images on December 26, 2021. The blossom reveals up in the natural-color image (top) as a faint, dark swirl of water extending away from the coast. An even fainter spot is visible to the left of the swirl. The bloom is more distinct in the false-color image (2nd image). In this view, tones of green illustrate concentrations of chlorophyll-a, the primary pigment utilized by phytoplankton to catch sunlight. The darkest shades of green program areas with the biggest chlorophyll concentrations.
Lange and associates will continue to observe how the bloom advances. Even after a massive flower fades, the impacts can be lasting.
NASA Earth Observatory images by Lauren Dauphin, utilizing MODIS information from NASA EOSDIS LANCE and GIBS/Worldview.
December 26, 2021. Natural-color image from NASAs Aqua satellite.
A dark, rainy spring paved the way to a huge, long-lived phytoplankton bloom off the coast of Brazil.
Beachgoers in the Brazilian state of Rio de Janeiro competed in late 2021 with unwanted ocean-dwelling visitors. Starting in November, countless microscopic phytoplankton collected along the coast, coloring the clear, blue waters a dark, reddish-brown. The blossom– known as a red tide or hazardous algal flower (HAB) occasion– was unusually widespread and long-lived.
Phytoplankton flowers are typical this time of year in Rio, however they typically contain types that are beneficial to the community. In contrast, hazardous algal blooms can appear whenever of year, normally stimulated by sewage effluents and heat waves; they tend to be last and small no longer than a couple of days. This red tide occasion covered more than 200 kilometers of the shoreline and lasted more than eight weeks. “It is extremely distressing,” stated Priscila Lange of the Department of Meteorology, Federal University of Rio de Janeiro.
