The Chatham Islands and Phytoplankton Bloom : Geographical and Ecological Significance

Recently, during the Southern Hemisphere summer (January 2026), an unusual phytoplankton bloom was observed in the ocean around the Chatham Islands. The bloom was so extensive that it was clearly visible from space through the VIIRS sensor of the NOAA-20 satellite. Swirling green and blue patterns appeared on the sea surface, indicating intense biological activity.

Phytoplankton are microscopic, photosynthetic organisms and form the foundation of the marine food chain. A sudden increase in their population affects marine ecosystems, fishery resources, and even the global carbon cycle.

Chatham Islands: Geographical Overview

The Chatham Islands are an archipelago located in the South Pacific Ocean. They represent the easternmost territory of New Zealand and lie about 800 km east of the South Island. The group consists of around 10 islands, but only two have permanent settlements:

• Chatham Island (the largest)
• Pitt Island

Physical Characteristics

• The islands are primarily of volcanic origin.
• The presence of limestone in some areas suggests that these islands were once connected to the New Zealand landmass.
• The southern part of Chatham Island has high plateaus and steep cliffs, while the northern part features extensive wetlands, waterways, and long sandy beaches.

Key Facts

• It is considered the world’s first human-created time zone, where the sunrise is seen earliest each day.
• Main settlement: Waitangi
• Other settlements: Te One, Port Hutt, Kaingaroa, and Owenga

Historical and Cultural Background

• The earliest inhabitants were the Moriori people, who called the islands “Rekohu,” meaning misty sky or cloudy sun.
• Later, European sealers and whalers arrived.
• Subsequently, Māori migrants from New Zealand settled here and named the islands “Wharekauri.”
• Descendants of the Moriori community still live on the islands today.

Scientific Causes of the Phytoplankton Bloom

The Chatham Islands are located on a submerged oceanic plateau known as the Chatham Rise.

Role of the Chatham Rise

• It is a relatively shallow underwater plateau extending eastward from New Zealand’s South Island.
• Deep ocean basins lie to its north and south.
• Two major ocean currents converge here:
  • Cold, nutrient-rich currents from the Antarctic region, and
  • Warm, nutrient-poor currents from subtropical regions.

The mixing of these currents increases the availability of nutrients in seawater. During summer, longer daylight hours and stronger sunlight enhance the rate of photosynthesis, leading to rapid phytoplankton growth.

Ecological and Economic Importance

1. Base of the Marine Food Chain

Phytoplankton are primary producers, supporting the entire marine ecosystem.

2. Rich Fishery Resources

The region is a highly productive fishing ground with major species such as:

• Pāua (abalone)
• Rock lobster
• Blue cod

These contribute significantly to the local economy.

3. High Biodiversity

• About 5 species of seals
• More than 25 species of whales and dolphins

The area is an important habitat for marine mammals.

4. Risk of Whale Stranding

• The region is also sensitive to mass strandings of whales and dolphins.
• Possible causes include seafloor topography, complex ocean currents, and the influence of sound waves (acoustic disturbances).