Gulf of Alaska Seamounts 2019

Snowstorm Under the Sea

By Eric Collins, Professor in Oceanography - University of Alaska Fairbanks
August 1, 2019

When you imagine the ocean, you might picture a tropical paradise like Hawaii with deep, clear blue waters – but most of the ocean doesn’t look like that at all! Those clear waters are actually a result of nutrient depletion that limits the growth of phytoplankton, the “plants” of the sea. In other places, including the Gulf of Alaska, there are more nutrients, so phytoplankton can grow to such high abundance that they make the water cloudy or congeal into aggregates that sink through the water as marine snow.

While individual microbes are often too small to sink more than a couple of meters (or feet) per year, this “snow” can be big and heavy enough to make it to the bottom of the ocean (4,000 meters or 13,000 feet) within a week. These fluffy particles provide a critical food source for deep-sea animals and for benthos, the creatures that live in, on, and under the seafloor.

Video clip of marine snow in the deep Gulf of Alaska. Video courtesy of NOAA/UAF/Oceaneering. Download (mp4, 7.2 MB).

Marine snow and other particles like fecal pellets (aka, zooplankton poop) are also important because they transport carbon to the deep sea in a process called the biological pump. This process takes carbon out of the atmosphere and stores it in deep-sea sediments for thousands or millions of years, cooling down the planet. By limiting the influence of the greenhouse effect (through which carbon dioxide in the atmosphere traps heat from the sun), the biological pump is one of the most important ways that Earth’s thermostat is controlled.