Because they may play an extensive role in the carbon cycle and eventual deep-sea carbon storage, understanding their activity is an essential step toward addressing climate change. Scientists have found that some zooplankton from the sunlit zone migrate down into the midnight zone during the day to avoid predators. The midnight zone is also where many larvae spend time developing before they migrate to other regions of the ocean as adults. Most zooplankton spend their entire lives drifting, but the larvae of many fish and bottom-living animals, before they develop adult forms, are also part of this group. Another major category is the gelatinous zooplankton or jellies, unrelated groups that all have soft, transparent bodies and spend much of their life drifting in the water column.

WATCH: New England-based researchers share rare video from ocean’s ‘Twilight Zone’

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• Aruda studies some of the smallest animals in the ocean—barely visible crustaceans called copepods and the bacteria that hitchhike on them.

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• Jellyfish are among the simplest animals on Earth and are considered plankton, but some individuals have been measured at 130 feet long, longer than a blue whale.

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• Every evening in the ocean, animals that spend their days in the deep, dark waters of the ocean’s twilight zone swim to the surface to feed.

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• Both salps and krill also live in the Southern Ocean near Antarctica, and both feed directly on the great abundance of phytoplankton there.
• The solubility carbon pump, which stores much larger amounts of carbon, operates on timescales in the thousands of years and is a much slower mixing process.

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• This process removes carbon dioxide dissolved in the water as phytoplankton incorporate the carbon as they grow.

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Zooplankton fill a crucial link between phytoplankton (“the grass of the sea”) and larger, open-ocean animals. Advisor, and with MIT biologist Martin Polz, who studies Vibrio on tiny marine animals, or zooplankton, such as copepods. Aruda studies some of the smallest animals in the ocean—barely visible crustaceans called copepods and the bacteria that hitchhike on them. Through photosynthesis these organisms transform inorganic carbon in the atmosphere and in seawater into organic compounds, making them an essential part of Earth’s carbon cycle. As the level of carbon dioxide in Earth’s atmosphere rises, the ocean’s pH—a measure of alkalinity and acidity—has fallen, meaning that it has become less alkaline and more acidic. Both salps and krill also live in the Southern Ocean near Antarctica, and both feed directly on the great abundance of phytoplankton there.

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• Researchers in Polz’s lab found that some Vibrios on living zooplankton produce antimicrobial compounds, maybe deterring other microbes.

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• Scientists generally consider carbon to be sequestered once it reaches a depth of 500 meters (1,640 feet).

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• Scientists have found that some zooplankton from the sunlit zone migrate down into the midnight zone during the day to avoid predators.

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• The ocean’s so-called biological carbon pump removes carbon from the atmosphere and stores it deep in the ocean on timescales that are important to the lifespan of humans.
• Many creatures called zooplankton are also tiny protists, but the category simultaneously includes animals on the other end of the size scale.
• Aruda uses rapid genetic sequencing to identify which gene sequences in the copepods “turned on” in response to the harmful and harmless treatments.

Paul Caiger hunts for things that glow in the Ocean Twilight Zone

Many creatures called zooplankton are also tiny protists, but the category simultaneously includes animals on the other end of the size scale. Jellyfish are among the simplest animals on Earth and are considered plankton, but some individuals have been measured at 130 feet long, longer than a blue whale. Understanding how the biological carbon pump works to export carbon to the deep sea can help researchers improve models of the ocean’s role in climate.

• Small marine animals called zooplankton feed on phytoplankton and are, in turn, eaten by larger marine organisms.
• Scientists now know these bacteria are responsible for half of the ocean’s primary productivity and are the most abundant organisms in the sea.

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• The midnight zone is also where many larvae spend time developing before they migrate to other regions of the ocean as adults.

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• An account of the tools that have been employed to collect zooplankton has been recently prepared by Wiebe and Benfield (2000), and provides a description of standard sampling methods.

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• Without it, the amount of carbon dioxide added to the atmosphere would be twice as large as what humans have already added.

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• As the level of carbon dioxide in Earth’s atmosphere rises, the ocean’s pH—a measure of alkalinity and acidity—has fallen, meaning that it has become less alkaline and more acidic.

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Scientists think that the extent of sea ice and the temperature of the ocean each year may influence the balance between salp and krill populations. Unfortunately, the gelatinous salps have much lower nutritional content and therefore are not good food for those higher-level animals. Aruda uses rapid genetic sequencing to identify which gene sequences in the copepods “turned on” in response to the harmful and harmless treatments. Researchers in Polz’s lab found that some Vibrios on living zooplankton produce antimicrobial compounds, maybe deterring other microbes.

Are warming Alaskan Arctic waters a new toxic algal hotspot?

Every evening in the ocean, animals that spend their days in the deep, dark waters of the ocean’s twilight zone swim to the surface to feed. By feeding at the surface before returning to deeper waters, these animals actively carry carbon deeper into the water column. When sunlight hits the ocean’s surface waters, it stimulates Kilobet tiny marine plants called phytoplankton to photosynthesize. This process removes carbon dioxide dissolved in the water as phytoplankton incorporate the carbon as they grow. As carbon dioxide levels in surface waters decrease, water is then able to absorb more carbon dioxide from the atmosphere. Small marine animals called zooplankton feed on phytoplankton and are, in turn, eaten by larger marine organisms.