Biological Brilliance: Filaments of Phytoplankton in Australia

Cool, upwelling water supports an array of marine life and draws the occasional filmmaker to the Bonney Coast region.

When satellites passed over South Australia’s Bonney Coast in January 2024, they captured images showing splotches of blue and green swirling through surface waters. These colorful filaments of phytoplankton were blooming right on time. The microscopic plant-like organisms thrive here in the summer, when cold, nutrient-rich water wells up from deep in the ocean.

This image, captured by the VIIRS (Visible Infrared Imaging Radiometer Suite) sensor aboard the Suomi NPP satellite, shows an elongated bloom on January 10, 2024. Images collected by NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>NASA’s Terra and Aqua satellite shows the bloom first becoming visible from space in late December 2023.

Scientific Analysis of the Phytoplankton Blooms

“The green filament is definitely a phytoplankton bloom extending along the shelf break, which is around 150 meters deep,” said Jochen Kaempf, a Flinders UniversityFounded in 1966, Flinders University is a public university in Adelaide, South Australia. It was named in honor of British navigator Matthew Flinders, who explored and surveyed the South Australian coastline in the early 19th century.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Flinders University oceanographer who has published several studies about phytoplankton in this area. “The bluer signal could be sediment located in very shallow water or perhaps a different phytoplankton speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>species.”

Waters samples collected from the surface would be needed to confirm the phytoplankton species. However, one of Kaempf’s recent studies indicates that diatoms often dominate the larger blooms in this area.

Temperature Anomalies and Upwelling Events

Signs of cool water upwelling were also apparent in satellite observations. Sea surface temperature data from NASA’s MUR SST (Multi-scale Ultra-high Resolution) project indicated that water temperatures on January 10 in much of Long Bay were about 3 degrees CelsiusThe Celsius scale, also known as the centigrade scale, is a temperature scale named after the Swedish astronomer Anders Celsius. In the Celsius scale, 0 °C is the freezing point of water and 100 °C is the boiling point of water at 1 atm pressure.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Celsius (5.4 degrees FahrenheitThe Fahrenheit scale is a temperature scale, named after the German physicist Daniel Gabriel Fahrenheit and based on one he proposed in 1724. In the Fahrenheit temperature scale, the freezing point of water freezes is 32 °F and water boils at 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Fahrenheit) cooler than the long-term average temperature (2003–2014) for that date.

The cool water is the result of the Great South Australian Coastal Upwelling System, a seasonal phenomenon that spans from Ceduna, South Australia, to Portland, Victoria—a distance of about 800 kilometers (500 miles). Upwelling events in this area occur in the summer (December to May), when seasonal winds from the southeast blow parallel to the shoreline. These winds push coastal surface waters offshore, via a process called Ekman transport, and draw up cold water from a depth of about 300 meters.

The Importance of Upwelling for Marine Life

Water from deep in the ocean is typically rich with nutrients because the remains of dead sea life constantly sink to the ocean floor and decompose. The nutrients released, especially nitrogen and phosphorous, are critical for the growth of phytoplankton. When nutrient-rich water reaches the upper layer of the ocean that receives abundant light (the photic zone), it can fuel the growth of phytoplankton populations, leading to blooms like this one and causing surface concentrations of chlorophyll-a, one type of green pigment involved in photosynthesis, to increase by tenfold.

Phytoplankton blooms nourish an array of marine life. Marine biologists estimate that the Bonney Coast upwelling attracts roughly 80 blue whales each year to graze on diatoms. Many species of filter feeders and crabs, as well as robust populations of sardines, anchovies, tuna, and other types of fish thrive here due to the abundance of phytoplankton.

According to one estimate from NOAAThe National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States government that is focused on understanding and predicting changes in Earth's oceans, atmosphere, and climate. It is headquartered in Silver Spring, Maryland and is a part of the Department of Commerce. NOAA conducts research and provides information, products, and services that are used to protect life and property, and to support economic growth and development. It also works to conserve and manage natural resources, including fisheries, wildlife, and habitats. Some of the specific activities that NOAA is involved in include weather forecasting, climate monitoring, marine biology and fisheries research, and satellite and remote sensing.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>NOAA, upwelling zones cover just 1 percent of the ocean’s area but are the source of about 50 percent of all fish caught. The abundance of marine life in this area even draws large numbers of great white sharks—so much so that parts of the original “Jaws” movie was filmed in nearby Dangerous Reef.

NASA Earth Observatory image by Wanmei Liang, using VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, and the Suomi National Polar-orbiting Partnership.