Algae bloom in the Mid-Atlantic Bight

Algae bloom in the Mid-Atlantic Bight

From the end of March onwards, a weak phytoplankton bloom was observed in the Mid-Atlantic Bight, an area stretching from Cape Hatteras in North Carolina to Martha’s Vineyard in Massachusetts, extending offshore to around the 100 m isobath. Over the following weeks, the bloom intensified, turning the Atlantic coastal waters of New York, New Jersey, Delaware, Maryland, and Virginia milky-blue and green.
This was likely driven by a combination of longer days, rising sea surface temperatures, and coastal upwelling. Upwelling occurs when winds push surface waters away from the coast, allowing deeper, nutrient-rich water to rise to the surface and stimulate increased phytoplankton growth.
Significant quantities of suspended matter from numerous river systems enter the coastal waters of this region providing additional nutrients that promote algal growth.
Analysis of the presented Sentinel-2 image (Figure 1) suggests the possible presence of both diatoms and coccolithophores. Diatom-dominated waters typically appear greenish in natural-colour satellite images, while coccolithophore blooms are characterised by a brighter colour ranging from milky-white to turquoise, due to the strong light-scattering properties of suspended calcite plates.
As the phytoplankton bloom progresses in spring, nutrient concentrations in the surface waters gradually decline due to intensive biological uptake. Without additional nutrients, the bloom weakens and eventually ends.
The attached animation (Figure 2) illustrates the spatial distribution and development of phytoplankton blooms in the Mid-Atlantic Bight in May 2026.

Further reading

Blooms off Both North American Coasts (NASA Science)
Color Off the Mid-Atlantic Coast (NASA Science)
Atlantic Ocean turns tropical, turquoise blue ahead of peak tourism season on the East Coast (Fox Weather)
NASA Satellites Capture Giant Ghostly Blue-Green Bloom Forming Off The Eastern Coast Of The USA (IFL Science)
Mid-Atlantic Bight (NOAA IEA)

Fig. 1

Fig. 2

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