The waters around New Zealand’s Chatham Islands teem with life. The highly productive waters support massive phytoplankton blooms that sustain valuable stocks of fish. This image, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on December 5, 2010, shows the large annual spring-time bloom.
The bloom is an array of colors from deep green to electric blue, and is probably made up of many different types of marine life, primarily phytoplankton. The phytoplankton, plant-like organisms, contribute to making the ocean in this region a carbon sink, a place where the ocean takes in more carbon dioxide than it releases into the atmosphere.
The ocean is productive in this region because the topography of the ocean floor brings two currents together around the Chatham Islands. The islands sit on the Chatham Rise, an underwater plateau that stretches from New Zealand’s South Island east to just beyond the Chatham Islands. The water north and south of the plateau is very deep. Cold, nutrient-rich, but iron-poor water from the Antarctic flows south of the Chatham Rise. To the north is mostly warm, nutrient-poor, but iron-rich water from the subtropics.
The two pools of water come together in a current that rides over the plateau, mixing cold water with warm. The mixed water in the current provides both the nutrients and iron fertilizers needed to support large blooms around the Chatham Islands. The current, and therefore, the bloom, is strongest in the spring and fall.
NASA image courtesy Norman Kuring, Ocean Color Team at NASA Goddard Space Flight Center. Caption by Holli Riebeek.