Today’s Image of the Day from NASA Earth Observatory features a striking phytoplankton bloom off the coast of southeast Greenland.

While satellite imagery suggested that the bloom emerged in May, persistent cloud cover had obstructed optical sensors from capturing a clear view.

A break in the clouds

The situation changed in mid-June when a brief gap in the clouds over the North Atlantic Ocean revealed the bloom’s vibrant swirls.

The captivating phenomenon was captured on June 16, 2024, by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Aqua satellite. 

The image depicts an 800-kilometer-wide expanse of the North Atlantic Ocean, positioned east of Greenland and south of Iceland, with the bloom extending far beyond the image’s boundaries.

Ecological role of phytoplankton 

Phytoplankton blooms are large concentrations of microscopic, plant-like organisms that usually float near the surface of the ocean.

These tiny organisms play a fundamental role in marine ecosystems by serving as the primary food source for a wide range of marine life, from other small plankton to larger fish and mammals. 

Phytoplankton are also essential for the global carbon cycle and oxygen production, as they absorb carbon dioxide during photosynthesis and release oxygen.

Unknown source of the phytoplankton bloom

The exact type of phytoplankton in this bloom cannot be determined from this natural-color image alone. It might include coccolithophores, which are characterized by their white calcium carbonate plates that can lend the ocean a milky appearance. 

Alternatively, the bloom could consist of diatoms, a form of microscopic algae with silica shells and abundant chlorophyll, giving them a green hue.

Regardless of the species, the timing of this bloom is notable. Phytoplankton blooms typically emerge at lower latitudes first, subsequently appearing in the high latitudes of the North Atlantic by spring and mid-summer.

More about phytoplankton blooms

Phytoplankton blooms occur when conditions such as sunlight, temperature, and nutrient availability are optimal for rapid phytoplankton growth.

These conditions are often found in nutrient-rich waters, particularly where upwelling currents bring nutrients from the ocean depths to the surface. 

When the ideal conditions align, phytoplankton reproduce rapidly, leading to visible blooms that can cover large areas of the ocean.

How do phytoplankton blooms affect marine life?

Phytoplankton blooms have a profound impact on marine life. As primary producers, phytoplankton form the base of the oceanic food web, supporting a wide array of marine organisms. 

Food availability 

When a bloom occurs, the abundance of phytoplankton provides a substantial food source for zooplankton, which in turn feed fish, crustaceans, and other larger marine animals. 

This increase in food availability can lead to a temporary surge in populations of these species, promoting the overall health and diversity of the marine ecosystem.

Harmful blooms

However, not all effects of phytoplankton blooms are beneficial. When blooms become excessively large, they can lead to harmful algal blooms (HABs). 

These blooms can produce toxins that are harmful to marine life, causing mass die-offs of fish, shellfish, and other marine animals. 

Moreover, as the bloom decays, the decomposition process consumes large amounts of oxygen from the water, leading to hypoxic conditions or “dead zones” where oxygen levels are too low to support most marine life. This can result in significant disruptions to marine ecosystems and loss of biodiversity.

Image Credit: NASA Earth Observatory 

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