NASA’s Aqua satellite has helped researchers conduct the first global analysis of the health and productivity of ocean plants, “the first direct measurement of the health of the phytoplankton in the ocean,” as described by Michael Behrenfeld, a biologist who specializes in marine plants at Oregon State University.
“We have an important new tool for observing changes in phytoplankton every week, all over the planet,”goes on commenting the OSU researcher. Thakns to the new tool, ocean scientists can now remotely measure the amount of fluorescent red light emitted by phytoplankton and assess how efficiently these microscopic plants turn sunlight and nutrients into food through photosynthesis. Researchers also can study how changes in the global environment alter these processes at the center of the ocean food web.
The importance of single-celled phytoplankton is that they represent the most basic food source for marine animals, actually fueling all ocean ecosystems. Phytoplankton account for half of all photosynthetic activity on Earth and play a key role in the balance of carbon dioxide in the atmosphere. Their health and wellbeing affects the amount of carbon dioxide the ocean can absorb from the atmosphere and how the ocean responds to a changing climate.
The new measurement allowed scientists to discover large areas of the Indian Ocean where phytoplankton were under stress from iron deficiency. In the Fall and Winter and expecially the Summer, significant southwesterly winds over the Indian Ocean stir up ocean currents and bring more nutrients up from the depths for the phytoplankton to feed on. At the same time, the amount of iron-rich dust delivered by winds is reduced.
Climate change could mean stronger winds pick up more dust and blow it to the sea, or less intense winds leave waters dust-free. Some regions will become drier and others wetter, changing the regions where dusty soils accumulate and get swept up into the air. Phytoplankton will reflect and react to these global changes.