Greatest Daily Migration on Earth

One of the amazing facts about life on our planet is the way living things fill every niche of the environment. As science extends our knowledge of Earth’s remote regions, we find massive amounts of life with incredible diversity. We find the largest animal population on the Earth in biomass, the volume of the Earth occupied, and numbers of individuals in water deeper than sunlight can reach. The ocean depths make up 90% of Earth’s living space, and we now understand that living there are more than a million species that science has not named or described. Furthermore, they are part of the greatest daily migration on Earth.

Every day, ten billion tons of animals known as zooplankton move upward from as far as 3,000 feet below the surface. The zooplankton include copepods, salps, krill, and fish larvae. At only 1,000 feet down, the water is 20 degrees Fahrenheit colder than at the surface, and the pressure is 30 times as great. For a tiny fish larva, making a 1000-foot journey in about an hour would be like a human swimmer going 50 miles in that amount of time. These animals begin their ascent at sunset and stay near the surface until sunrise when they descend back to the cold dark below.

The purpose of this greatest daily migration on Earth is to eat and avoid being eaten. These zooplankton animals feed on phytoplankton, the microscopic aquatic plants that live in the top few hundred feet of water. Fish and squid feed on the zooplankton, which find protection at the great ocean depths. The first hint of this massive migration occurred in World War II when ships and submarines used sonar to sweep the ocean for enemy subs. They discovered that the seafloor seemed to be moving up and down, creating a deep “scattering layer” that reflected sonar signals. Now we have research tools to explore this layer, which turns out to be alive.

Science is just now beginning to understand the importance of the greatest daily migration on Earth. This huge mass of animal life, their excrement, and their remains sequester carbon in the very deep waters, making them rich in nutrients. Winds along the shores of continents push the surface water from the continental edges out into the open ocean. Their exit causes water to come up from ocean depths to the surface along the continent’s edges, bringing nutrients with it.

Our understanding of this mass migration is helping us to understand the carbon cycle, climate change, and many ecological issues. This greatest daily migration on Earth is a part of God’s creation. It reminds us of Proverbs 8:28-29, which says that Wisdom was there, “…when He established the clouds above and fixed securely the fountains of the deep, when He gave the sea its boundary so the waters would not overstep His command, and when He marked out the foundations of the earth” (NIV).

— John N. Clayton © 2022

Reference: Scientific American, August 2022, pages 50 -67.