How ocean ecosystems help fight climate change

Carbon recyclers:

how ocean ecosystems help fight climate change

Ocean ecosystems play a critical role in carbon storage and oxygen generation. Some of these ecosystems are under threat; others remain unexplored. Understanding how key players such as whales, plankton, seagrasses and other forms of sea life interact sheds light on Earth’s carbon cycle.

HOW CARBON

IS CAPTURED

Key to life

Carbon, a chemical element, is found in all organic matter on Earth, from the plants and animals alive today to fossil fuels buried underground.

 

It’s a key building block in the foods we eat, and in Earth’s most abundant greenhouse gases — carbon dioxide (CO2) and methane (CH4). Sunshine reflected off the planet’s surface back into the atmosphere causes those gas molecules to vibrate, warming the atmosphere. More CO2 leads to more warming, causing climate change.

Carbon

Sunlight

Land plants

Salt marsh

Mangrove

The carbon cycle

Animals release carbon in the form of CO2 when they breathe, while plants take in that gas along with sunshine to produce energy, a process called photosynthesis.

 

Carbon dioxide also dissolves in seawater, where it is absorbed by seagrasses and algae. Seagrasses, which are plants adapted to live in the sea, are different from kelp and other algae in that they have roots, veins, leaves — and even flowers and fruits.

Seagrass takes CO2

dissolved in the

water

Releases

oxygen

Fish species

Mollusks

Invertebrates

Crustaceans

Seagrass meadows

Seagrass meadows serve as excellent breeding grounds for sea mammals and habitats for baby fish. But scientists have estimated the world’s seagrass stocks are declining by about 7% per year.

 

For millennia, Earth’s natural systems kept carbon levels balanced in the environment. Industrial activities including the burning of fossil fuels, however, have increased atmospheric CO2 levels by nearly 50%, from 280 parts per million just over a century ago to about 417 ppm today.

Sea mammals

Sea turtles

That’s caused ocean CO2 levels to rise, making waters more acidic. But seagrasses can provide a buffer against that, too. By reducing the acidity of surrounding waters, seagrass ecosystems help protect animals with shells or external skeletons.

In the sunlit surface layer of oceans

Like land plants and seagrasses, microscopic marine algae known as phytoplankton also feed on CO2 and use photosynthesis to produce energy.

 

 

Phytoplankton

Releases

oxygen

Takes carbon

dioxide

Chloroplast

They live in both saltwater and freshwater environments, drifting freely with currents. And like plants, they also release oxygen, contributing at least 50% of the oxygen to Earth’s atmosphere.

CARBON IS TRANSFORMED

The food web

Seagrasses and phytoplankton near the ocean’s surface form the base of the aquatic food chain as they produce their own food, and then serve as food to others.

 

When carbon dioxide is consumed during photosynthesis, the carbon is incorporated in the phytoplankton and seagrasses, in the same way carbon is stored in the wood and leaves of a tree.

 

Carbon is then transferred to different layers of the ocean as primary producers are eaten by other organisms, which themselves reproduce, generate waste and die.

Phytoplankton

Zooplankton, krill

Medium

and large fish

Small fish

Large mammals

Body parts

Some plankton combine calcium and dissolved carbonates to form a calcium carbonate protective coating like the shells and other body parts of coral, clams or oysters.

 

Whales for example can absorb tons of carbon as their diet consists mainly of plankton and tiny shrimplike crustaceans called krill. A single whale can absorb around 33 tonnes, or 33,000 kilograms, of CO2 on average in its life while a tree can take in up to 22 kgs of CO2 a year.

Nutrient circulation

Phytoplankton, like land plants, require nutrients such as nitrate or calcium. They also need iron, which is scarce in large areas of the ocean. But when whales defecate, they release iron as well as other important nutrients like nitrogen in their feces. The liquid plume then stimulates phytoplankton growth, attracting fish and other organisms in a phenomenon known as the “whale pump”.

‘Whale pump’

CARBON SINK

Recycle

Crustaceans and fish transport carbon and nutrients by feeding in surface waters during the day and then migrating down the water column and excreting in deeper waters at night.

 

When critters die, the carbon and nutrients in their bodies either becomes part of the food chain or sinks to the ocean floor.

 

Carbon is stored

At the bottom of the ocean, bacteria works to decompose the carbon fixed in the soft and hard tissues of organisms. When mollusks and other carbon-rich organisms die, their shells and body parts can accumulate in ocean sediments, forming carbonate-rich deposits.

Locked away

Seagrasses also trap carbon in underwater sediments around their roots, stems and leaves.

 

The grasses store twice as much carbon per square mile as tropical forests do on land. As seagrasses die, the carbon gets locked into the sediment, where it can persist for thousands of years.

While covering only 0.1% of the ocean bed, seagrass ecosystems account for 10%–18% of the carbon buried in the oceans, according to a January 2020 study in the journal Frontiers in Marine Science.

When whale carcasses sink to the seafloor, the carbon in their carcasses can create a feast for deep-sea critters and also be buried in marine sediments.

Ocean deposits are by far the biggest sinks of carbon on the planet. After long periods of time, these deposits can alter physically and chemically to become rocks and sediments themselves.

Major stores of carbon

on the Earth, in billions

of metric tons:

Marine sediments and

sedimentary rocks

66 million to 100 million

Oceans

38k to 40k

Other:

Atmosphere 766

Terrestrial plants 540 to 610

Soil organic matter 1.5k to 1.6k

Fossil fuel deposits 4k

 

Carbon recyclers:

how ocean ecosystems

help fight climate change

Ocean ecosystems play a critical role in carbon storage and oxygen generation. Some of these ecosystems are under threat; others remain unexplored. Understanding how key players such as whales, plankton, seagrasses and other forms of sea life interact sheds light on Earth’s carbon cycle.

HOW CARBON

IS CAPTURED

Key to life

Carbon, a chemical element, is found in all organic matter on Earth, from the plants and animals alive today to fossil fuels buried underground.

 

It’s a key building block in the foods we eat, and in Earth’s most abundant greenhouse gases — carbon dioxide (CO2) and methane (CH4). Sunshine reflected off the planet’s surface back into the atmosphere causes those gas molecules to vibrate, warming the atmosphere. More CO2 leads to more warming, causing climate change.

Carbon

Sunlight

CO2

Carbon

uptake by

photosynthesis

Carbon release

through respiration and

decomposition

Land plants

The carbon cycle

Mangrove

Salt marsh

Animals release carbon in the form of CO2 when they breathe, while plants take in that gas along with sunshine to produce energy, a process called photosynthesis.

 

Carbon dioxide also dissolves in seawater, where it is absorbed by seagrasses and algae. Seagrasses, which are plants adapted to live in the sea, are different from kelp and other algae in that they have roots, veins, leaves — and even flowers and fruits.

Seagrass

Seagrass

takes CO2

dissolved

in the water

Releases oxygen

Photosynthesis can occur in surface plants, mangroves, saltmarshes but also under narrow sunlit waters.

Seagrass meadows serve as excellent breeding grounds for sea mammals and habitats for baby fish. But scientists have estimated the world’s seagrass stocks are declining by about 7% per year.

 

For millennia, Earth’s natural systems kept carbon levels balanced in the environment. Industrial activities including the burning of fossil fuels, however, have increased atmospheric CO2 levels by nearly 50%, from 280 parts per million just over a century ago to about 417 ppm today.

 

 

Crustaceans

Mollusks

Fish species

Sea turtles

Sea mammals

That’s caused ocean CO2 levels to rise, making waters more acidic. But seagrasses can provide a buffer against that, too. By reducing the acidity of surrounding waters, seagrass ecosystems help protect animals with shells or external skeletons.

Invertebrates

Sunlight

In the sunlit surface layer of oceans

Like land plants and seagrasses, microscopic marine algae known as phytoplankton also feed on CO2 and use photosynthesis to produce energy.

 

They live in both saltwater and freshwater environments, drifting freely with currents. And like plants, they also release oxygen, contributing at least 50% of the oxygen to Earth’s atmosphere.

Phytoplankton

Takes carbon

dioxide

Releases

oxygen

Chlorophyll

Chloroplast

CARBON IS TRANSFORMED

The food web

Seagrasses and phytoplankton near the ocean’s surface form the base of the aquatic food chain as they produce their own food, and then serve as food to others.

 

When carbon dioxide is consumed during photosynthesis, the carbon is incorporated in the phytoplankton and seagrasses, in the same way carbon is stored in the wood and leaves of a tree.

 

Carbon is then transferred to different layers of the ocean as primary producers are eaten by other organisms, which themselves reproduce, generate waste and die.

 

Phytoplankton

Zooplankton, krill

Medium fish

Small fish

Large mammals

Body parts

Some plankton combine calcium and dissolved carbonates to form a calcium carbonate protective coating like the shells and other body parts of coral, clams or oysters.

 

Whales for example can absorb tons of carbon as their diet consists mainly of plankton and tiny shrimplike crustaceans called krill. A single whale can absorb around 33 tonnes, or 33,000 kilograms, of CO2 on average in its life while a tree can take in up to 22 kgs of CO2 a year.

Nutrient circulation

Phytoplankton, like land plants, require nutrients such as nitrate or calcium. They also need iron, which is scarce in large areas of the ocean. But when whales defecate, they release iron as well as other important nutrients like nitrogen in their feces.

 

The liquid plume then stimulates phytoplankton growth, attracting fish and other organisms in a phenomenon known as the “whale pump”.

‘Whale pump’

Recycle

Crustaceans and fish transport carbon and nutrients by feeding in surface waters during the day and then migrating down the water column and excreting in deeper waters at night.

 

When critters die, the carbon and nutrients in their bodies either becomes part of the food chain or sinks to the ocean floor.

CARBON SINK

Carbon is stored

At the bottom of the ocean, bacteria works to decompose the carbon fixed in the soft and hard tissues of organisms. When mollusks and other carbon-rich organisms die, their shells and body parts can accumulate in ocean sediments, forming carbonate-rich deposits.

Locked away

Seagrasses also trap carbon in underwater sediments around their roots, stems and leaves.

The grasses store twice as much carbon per square mile as tropical forests do on land. As seagrasses die, the carbon gets locked into the sediment, where it can persist for thousands of years.

 

While covering only 0.1% of the ocean bed, seagrass ecosystems account for 10%–18% of the carbon buried in the oceans, according to a January 2020 study in the journal Frontiers in Marine Science.

When whale carcasses sink to the seafloor, the carbon in their carcasses can create a feast for deep-sea critters and also be buried in marine sediments.

 

Ocean deposits are by far the biggest sinks of carbon on the planet. After long periods of time, these deposits can alter physically and chemically to become rocks and sediments themselves.

Major stores of carbon on the Earth,

in billions of metric tons:

Marine sediments and

sedimentary rocks

66 million to 100 million

Oceans

38k to 40k

Other:

Atmosphere 766

Terrestrial plants 540 to 610

Soil organic matter 1.5k to 1.6k

Fossil fuel deposits 4k

 

Carbon recyclers: how ocean ecosystems help fight climate change

Ocean ecosystems play a critical role in carbon storage and oxygen generation. Some of these ecosystems are under threat; others remain unexplored. Understanding how key players such as whales, plankton, seagrasses and other forms of sea life interact sheds light on Earth’s carbon cycle.

HOW CARBON

IS CAPTURED

Key to life

Carbon, a chemical element, is found in all organic matter on Earth, from the plants and animals alive today to fossil fuels buried underground.

 

It’s a key building block in the foods we eat, and in Earth’s most abundant greenhouse gases — carbon dioxide (CO2) and methane (CH4). Sunshine reflected off the planet’s surface back into the atmosphere causes those gas molecules to vibrate, warming the atmosphere. More CO2 leads to more warming, causing climate change.

Sunlight

Carbon

Land plants

Salt marsh

Mangrove

The carbon cycle

Animals release carbon in the form of CO2 when they breathe, while plants take in that gas along with sunshine to produce energy, a process called photosynthesis.

 

Carbon dioxide also dissolves in seawater, where it is absorbed by seagrasses and algae. Seagrasses, which are plants adapted to live in the sea, are different from kelp and other algae in that they have roots, veins, leaves — and even flowers and fruits.

Seagrass takes CO2

dissolved in the

water

Releases

oxygen

Fish species

Crustaceans

Mollusks

Invertebrates

Seagrass meadows

Seagrass meadows serve as excellent breeding grounds for sea mammals and habitats for baby fish. But scientists have estimated the world’s seagrass stocks are declining by about 7% per year.

 

For millennia, Earth’s natural systems kept carbon levels balanced in the environment. Industrial activities including the burning of fossil fuels, however, have increased atmospheric CO2 levels by nearly 50%, from 280 parts per million just over a century ago to about 417 ppm today.

Sea mammals

Sea turtles

That’s caused ocean CO2 levels to rise, making waters more acidic. But seagrasses can provide a buffer against that, too. By reducing the acidity of surrounding waters, seagrass ecosystems help protect animals with shells or external skeletons.

In the sunlit surface layer

of oceans

Like land plants and seagrasses, microscopic marine algae known as phytoplankton also feed on CO2 and use photosynthesis to produce energy.

 

 

Phytoplankton

Releases

oxygen

Takes carbon

dioxide

Chloroplast

They live in both saltwater and freshwater environments, drifting freely with currents. And like plants, they also release oxygen, contributing at least 50% of the oxygen to Earth’s atmosphere.

CARBON IS TRANSFORMED

The food web

Seagrasses and phytoplankton near the ocean’s surface form the base of the aquatic food chain as they produce their own food, and then serve as food to others.

 

When carbon dioxide is consumed during photosynthesis, the carbon is incorporated in the phytoplankton and seagrasses, in the same way carbon is stored in the wood and leaves of a tree.

 

Carbon is then transferred to different layers of the ocean as primary producers are eaten by other organisms, which themselves reproduce, generate waste and die.

Phytoplankton

Zooplankton, krill

Medium

and large fish

Small fish

Large mammals

Body parts

Some plankton combine calcium and dissolved carbonates to form a calcium carbonate protective coating like the shells and other body parts of coral, clams or oysters.

 

Whales for example can absorb tons of carbon as their diet consists mainly of plankton and tiny shrimplike crustaceans called krill. A single whale can absorb around 33 tonnes, or 33,000 kilograms, of CO2 on average in its life while a tree can take in up to 22 kgs of CO2 a year.

Nutrient circulation

Phytoplankton, like land plants, require nutrients such as nitrate or calcium. They also need iron, which is scarce in large areas of the ocean. But when whales defecate, they release iron as well as other important nutrients like nitrogen in their feces. The liquid plume then stimulates phytoplankton growth, attracting fish and other organisms in a phenomenon known as the “whale pump”.

‘Whale pump’

CARBON SINK

Recycle

Crustaceans and fish transport carbon and nutrients by feeding in surface waters during the day and then migrating down the water column and excreting in deeper waters at night.

 

When critters die, the carbon and nutrients in their bodies either becomes part of the food chain or sinks to the ocean floor.

 

Carbon is stored

At the bottom of the ocean, bacteria works to decompose the carbon fixed in the soft and hard tissues of organisms. When mollusks and other carbon-rich organisms die, their shells and body parts can accumulate in ocean sediments, forming carbonate-rich deposits.

Locked away

Seagrasses also trap carbon in underwater sediments around their roots, stems and leaves.

The grasses store twice as much carbon per square mile as tropical forests do on land. As seagrasses die, the carbon gets locked into the sediment, where it can persist for thousands of years.

While covering only 0.1% of the ocean bed, seagrass ecosystems account for 10%–18% of the carbon buried in the oceans, according to a January 2020 study in the journal Frontiers in Marine Science.

When whale carcasses sink to the seafloor, the carbon in their carcasses can create a feast for deep-sea critters and also be buried in marine sediments.

Ocean deposits are by far the biggest sinks of carbon on the planet. After long periods of time, these deposits can alter physically and chemically to become rocks and sediments themselves.

Major stores of carbon

on the Earth, in billions

of metric tons:

Marine sediments and

sedimentary rocks

66 million to 100 million

Oceans

38,000 to 40,000

Other:

Atmosphere 766

Terrestrial plants 540 to 610

Soil organic matter 1.5k to 1.6k

Fossil fuel deposits 4k

 

Carbon recyclers:

how ocean ecosystems help fight climate change

Ocean ecosystems play a critical role in carbon storage and oxygen generation. Some of these ecosystems are under threat; others remain unexplored. Understanding how key players such as whales, plankton, seagrasses and other forms of sea life interact sheds light on Earth’s carbon cycle.

HOW CARBON

IS CAPTURED

Key to life

Carbon, a chemical element, is found in all organic matter on Earth, from the plants and animals alive today to fossil fuels buried underground.

 

It’s a key building block in the foods we eat, and in Earth’s most abundant greenhouse gases — carbon dioxide (CO2) and methane (CH4). Sunshine reflected off the planet’s surface back into the atmosphere causes those gas molecules to vibrate, warming the atmosphere. More CO2 leads to more warming, causing climate change.

Sunlight

Carbon

Land plants

Mangrove

Salt marsh

The carbon cycle

Seagrass

Animals release carbon in the form of CO2 when they breathe, while plants take in that gas along with sunshine to produce energy, a process called photosynthesis.

 

Carbon dioxide also dissolves in seawater, where it is absorbed by seagrasses and algae. Seagrasses, which are plants adapted to live in the sea, are different from kelp and other algae in that they have roots, veins, leaves — and even flowers and fruits.

Seagrass takes CO2

dissolved in the

water

Releases

oxygen

Fish species

Crustaceans

Mollusks

Invertebrates

Seagrass meadows

Seagrass meadows serve as excellent breeding grounds for sea mammals and habitats for baby fish. But scientists have estimated the world’s seagrass stocks are declining by about 7% per year.

 

For millennia, Earth’s natural systems kept carbon levels balanced in the environment. Industrial activities including the burning of fossil fuels, however, have increased atmospheric CO2 levels by nearly 50%, from 280 parts per million just over a century ago to about 417 ppm today.

Sea mammals

Sea turtles

That’s caused ocean CO2 levels to rise, making waters more acidic. But seagrasses can provide a buffer against that, too. By reducing the acidity of surrounding waters, seagrass ecosystems help protect animals with shells or external skeletons.

Phytoplankton

In the sunlit surface layer

of oceans

Like land plants and seagrasses, microscopic marine algae known as phytoplankton also feed on CO2 and use photosynthesis to produce energy.

 

 

Phytoplankton

Releases

oxygen

Takes carbon

dioxide

Chloroplast

They live in both saltwater and freshwater environments, drifting freely with currents. And like plants, they also release oxygen, contributing at least 50% of the oxygen to Earth’s atmosphere.

CARBON IS TRANSFORMED

The food web

Seagrasses and phytoplankton near the ocean’s surface form the base of the aquatic food chain as they produce their own food, and then serve as food to others.

 

When carbon dioxide is consumed during photosynthesis, the carbon is incorporated in the phytoplankton and seagrasses, in the same way carbon is stored in the wood and leaves of a tree.

 

Carbon is then transferred to different layers of the ocean as primary producers are eaten by other organisms, which themselves reproduce, generate waste and die.

Phytoplankton

Zooplankton, krill

Medium

and large fish

Small fish

Large mammals

Body parts

Some plankton combine calcium and dissolved carbonates to form a calcium carbonate protective coating like the shells and other body parts of coral, clams or oysters.

 

Whales for example can absorb tons of carbon as their diet consists mainly of plankton and tiny shrimplike crustaceans called krill. A single whale can absorb around 33 tonnes, or 33,000 kilograms, of CO2 on average in its life while a tree can take in up to 22 kgs of CO2 a year.

Nutrient circulation

Phytoplankton, like land plants, require nutrients such as nitrate or calcium. They also need iron, which is scarce in large areas of the ocean. But when whales defecate, they release iron as well as other important nutrients like nitrogen in their feces. The liquid plume then stimulates phytoplankton growth, attracting fish and other organisms in a phenomenon known as the “whale pump”.

‘Whale pump’

CARBON SINK

Recycle

Crustaceans and fish transport carbon and nutrients by feeding in surface waters during the day and then migrating down the water column and excreting in deeper waters at night.

 

When critters die, the carbon and nutrients in their bodies either becomes part of the food chain or sinks to the ocean floor.

 

Carbon is stored

At the bottom of the ocean, bacteria works to decompose the carbon fixed in the soft and hard tissues of organisms. When mollusks and other carbon-rich organisms die, their shells and body parts can accumulate in ocean sediments, forming carbonate-rich deposits.

Locked away

Seagrasses also trap carbon in underwater sediments around their roots, stems and leaves.

The grasses store twice as much carbon per square mile as tropical forests do on land. As seagrasses die, the carbon gets locked into the sediment, where it can persist for thousands of years.

While covering only 0.1% of the ocean bed, seagrass ecosystems account for 10%–18% of the carbon buried in the oceans, according to a January 2020 study in the journal Frontiers in Marine Science.

When whale carcasses sink to the seafloor, the carbon in their carcasses can create a feast for deep-sea critters and also be buried in marine sediments.

Ocean deposits are by far the biggest sinks of carbon on the planet. After long periods of time, these deposits can alter physically and chemically to become rocks and sediments themselves.

Major stores of carbon

on the Earth, in billions

of metric tons:

Marine sediments and

sedimentary rocks

66 million to 100 million

Oceans

38k to 40k

Other:

Atmosphere 766

Terrestrial plants 540 to 610

Soil organic matter 1.5k to 1.6k

Fossil fuel deposits 4k

 

Other:

Carbon recyclers:

how ocean ecosystems

help fight climate change

Ocean ecosystems play a critical role in carbon storage and oxygen generation. Some of these ecosystems are under threat; others remain unexplored. Understanding how key players such as whales, plankton, seagrasses and other forms of sea life interact sheds light on Earth’s carbon cycle.

HOW CARBON

IS CAPTURED

Key to life

Carbon, a chemical element, is found in all organic matter on Earth, from the plants and animals alive today to fossil fuels buried underground.

 

It’s a key building block in the foods we eat, and in Earth’s most abundant greenhouse gases — carbon dioxide (CO2) and methane (CH4). Sunshine reflected off the planet’s surface back into the atmosphere causes those gas molecules to vibrate, warming the atmosphere. More CO2 leads to more warming, causing climate change.

Carbon

Sunlight

CO2

Carbon

uptake by

photosynthesis

Carbon release

through respiration and

decomposition

Land plants

CO2

The carbon cycle

Mangrove

Animals release carbon in the form of CO2 when they breathe, while plants take in that gas along with sunshine to produce energy, a process called photosynthesis.

 

Carbon dioxide also dissolves in seawater, where it is absorbed by seagrasses and algae. Seagrasses, which are plants adapted to live in the sea, are different from kelp and other algae in that they have roots, veins, leaves — and even flowers and fruits.

Salt marsh

Seagrass

Seagrass

takes CO2

dissolved

in the water

Releases oxygen

Photosynthesis can occur in surface plants, mangroves, saltmarshes but also under narrow sunlit waters.

Seagrass meadows serve as excellent breeding grounds for sea mammals and habitats for baby fish. But scientists have estimated the world’s seagrass stocks are declining by about 7% per year.

 

For millennia, Earth’s natural systems kept carbon levels balanced in the environment. Industrial activities including the burning of fossil fuels, however, have increased atmospheric CO2 levels by nearly 50%, from 280 parts per million just over a century ago to about 417 ppm today.

 

 

Invertebrates

Crustaceans

Mollusks

Fish species

Sea turtles

Sea mammals

Phytoplankton

That’s caused ocean CO2 levels to rise, making waters more acidic. But seagrasses can provide a buffer against that, too. By reducing the acidity of surrounding waters, seagrass ecosystems help protect animals with shells or external skeletons.

Sunlight

In the sunlit surface layer of oceans

Like land plants and seagrasses, microscopic marine algae known as phytoplankton also feed on CO2 and use photosynthesis to produce energy.

 

They live in both saltwater and freshwater environments, drifting freely with currents. And like plants, they also release oxygen, contributing at least 50% of the oxygen to Earth’s atmosphere.

Phytoplankton

Takes carbon

dioxide

Releases

oxygen

Chlorophyll

CARBON IS TRANSFORMED

Chloroplast

The food web

Seagrasses and phytoplankton near the ocean’s surface form the base of the aquatic food chain as they produce their own food, and then serve as food to others.

 

When carbon dioxide is consumed during photosynthesis, the carbon is incorporated in the phytoplankton and seagrasses, in the same way carbon is stored in the wood and leaves of a tree.

 

Carbon is then transferred to different layers of the ocean as primary producers are eaten by other organisms, which themselves reproduce, generate waste and die.

 

Phytoplankton

Zooplankton, krill

Medium fish

Small fish

Large mammals

Body parts

Some plankton combine calcium and dissolved carbonates to form a calcium carbonate protective coating like the shells and other body parts of coral, clams or oysters.

 

Whales for example can absorb tons of carbon as their diet consists mainly of plankton and tiny shrimplike crustaceans called krill. A single whale can absorb around 33 tonnes, or 33,000 kilograms, of CO2 on average in its life while a tree can take in up to 22 kgs of CO2 a year.

Nutrient circulation

Phytoplankton, like land plants, require nutrients such as nitrate or calcium. They also need iron, which is scarce in large areas of the ocean. But when whales defecate, they release iron as well as other important nutrients like nitrogen in their feces.

 

The liquid plume then stimulates phytoplankton growth, attracting fish and other organisms in a phenomenon known as the “whale pump”.

‘Whale pump’

Recycle

Crustaceans and fish transport carbon and nutrients by feeding in surface waters during the day and then migrating down the water column and excreting in deeper waters at night.

 

When critters die, the carbon and nutrients in their bodies either becomes part of the food chain or sinks to the ocean floor.

CARBON SINK

Carbon is stored

At the bottom of the ocean, bacteria works to decompose the carbon fixed in the soft and hard tissues of organisms. When mollusks and other carbon-rich organisms die, their shells and body parts can accumulate in ocean sediments, forming carbonate-rich deposits.

Locked away

Seagrasses also trap carbon in underwater sediments around their roots, stems and leaves.

The grasses store twice as much carbon per square mile as tropical forests do on land. As seagrasses die, the carbon gets locked into the sediment, where it can persist for thousands of years.

 

While covering only 0.1% of the ocean bed, seagrass ecosystems account for 10%–18% of the carbon buried in the oceans, according to a January 2020 study in the journal Frontiers in Marine Science.

When whale carcasses sink to the seafloor, the carbon in their carcasses can create a feast for deep-sea critters and also be buried in marine sediments.

 

Ocean deposits are by far the biggest sinks of carbon on the planet. After long periods of time, these deposits can alter physically and chemically to become rocks and sediments themselves.

Major stores of carbon on the Earth,

in billions of metric tons:

Marine sediments and

sedimentary rocks

66 million to 100 million

Oceans

38k to 40k

Other:

Atmosphere 766

Terrestrial plants 540 to 610

Soil organic matter 1.5k to 1.6k

Fossil fuel deposits 4k

 

Graphic by Samuel Granados
Edited by Katy Daigle, Lisa Shumaker, Jon McClure and Simon Scarr

Sources: United Nations Environment Program, U.S. National Oceanic and Atmospheric Administration, Frontiers, NASA, Earth.org, International Monetary Fund; REUTERS