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Marine Snow: Keeps Life Going

The snow we commonly know is defined as atmospheric water vapor frozen into ice crystals. In this blog, we will be discussing how “snow” can also be present deep beneath the surface of our ocean. Marine snow provides a plethora of benefits for animals living in the ocean and also contributes to the carbon cycle, which circulates the carbon that is present in all living organisms.

Let’s first address what Marine Snow really is. Marine Snow, as defined by theNational Oceanic and Atmospheric Administration (NOAA), is “a shower of organic material falling from upper water to the deep ocean.” The organic material mentioned here can be anything from tissues of dead animals and algae to fecal matter produced by marine organisms in the sea. As we know, all living things eventually reach the end of their life. On land, the organism’s tissue slowly starts to decay and decompose with the help of natural decomposers that are present within our environment. Some examples of these helpful decomposers include bacteria, fungi, and insects such as cockroaches and flies. Similarly, when marine organisms such as algae, fish, or plankton die and decay, the decomposers of the ocean such as crabs, marine microbes, sea stars, and marine worms feed on the remains of these organisms. When minute remnants of the organism are left, those small particles slowly begin their descension to the bottom of the ocean.

The Mesopelagic (Twilight Zone) includes species of squid (middle), sea jellies (to the left and right of squid), and fish such as viperfish (bottom left) and hatchet fish (bottom right) | Photo Courtesy by Woods Hole Oceanographic Institution

As the particles of marine organisms fall deeper and deeper into the depths of the ocean, they may have a white and fuzzy appearance that is similar to that of snow, hence the name. Aside from its appearance, it is important to mention that marine snow plays a crucial role in providing food for organisms living in all zones of the ocean. The ocean’s zones include the epipelagic zone (sunlight zone), mesopelagic zone (twilight zone), bathypelagic zone (midnight zone), and the abyssopelagic zone (abyss).

In the mesopelagic zone, a diverse range of organisms such as microscopic bacteria, zooplankton, crustaceans, fish, squid, and many other kinds of gelatinous animals such as sea jellies reside in this section of the ocean. At 100 -1000 meters beneath the ocean’s surface, there is little to no light from the sun. This means that photosynthesis, which is the process used by plants, algae, and phytoplankton that converts sunlight into energy in the form of sugar, is not an option for organisms beyond the mesopelagic zone. Since there is not enough sunlight to sustain marine algae and phytoplankton at deeper depths of the ocean, these organisms rely on marine snow falling from the sunlight zone for food.

Deep in the mesopelagic zone, a vampire squid is captured swimming in water surrounded by marine snow | Photo Courtesy by Ocean Exploration Trust

Many deep-sea creatures such as spider crabs, remora fish, and osedax worms, also benefit from marine snow by filtering it from the water or scavenging it from the seabed floor. Any remaining bits of marine snow that manage to reach the bottom of the ocean ultimately become apart of deep ocean floor, and are then decomposed through biological activities over time.

A depiction of one of the Biogeochemical Cycles—The Carbon Cycle | Photo Courtesy by Encyclopedia Britannica, Inc.

So what role does marine snow play in the grand scheme of everything? To start from a more general standpoint, there are 4 crucial biogeochemical cycles that explain how biotic and abiotic things are circulated through the biosphere, atmosphere, hydrosphere, and lithosphere. The cycles include the water cycle, carbon cycle, nitrogen cycle, and the phosphorus cycle. These cycles are not the only cycles that exist, however, they are the major contributors. According to the Sloan Digital Sky Survey (SDSS), more than 97% of our bodies are made up of the most common elements on Earth which are carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus.

A diagram of the ocean’s carbon cycle with yellow arrows depicting carbon and nutrient flow | Photo Courtesy of Oak Ridge National Lab

Out of the Biogeochemical Cycles, marine snow is found in the carbon cycle. Specifically, it is introduced via the Ocean’s Biological Pump. The Biological Pump, or marine carbon pump, refers to the process in which the biological activity of marine organisms helps to contain and transfer carbon from our atmosphere into the ocean. Recall that animals in the twilight zone benefit greatly from marine snow as it provides them with a sustainable source of food. In return, the twilight zone provides food for large predators such as whales, sharks, tuna, and swordfish. These predators are crucial to the stability of not only marine food webs, but also the balance of the entire marine ecosystem as they directly keep primary, secondary, and tertiary consumer populations in check, in addition to indirectly keeping producer populations under control.

The ocean can absorb a large amount of carbon dioxide to the point where it is sometimes called a carbon sink. This helps to remove and store carbon dioxide from the atmosphere which can and is greatly reducing the impact of greenhouse gases on our planet. However, this carbon sink has a threshold and large amounts of carbon dioxide can contribute to ocean acidification over time, which directly impacts marine life with calcium carbonate shells. Marine snow is a huge component in regulating the ocean’s carbon cycle and in keeping populations in deeper parts of the ocean alive. In a nutshell, it is paramount to acknowledge the benefits that marine snow has on the marine biome and global biosphere.

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