Cambridge, As the world struggles to decarbonise, it is becoming clear that we will need to rapidly reduce emissions and actively remove carbon dioxide (CO₂) from the atmosphere. The latest Intergovernmental Panel on Climate Change report considers 230 ways to keep global warming below 1.5 degrees Celsius. All need to remove CO₂.
Some of the most promising CO₂ removal technologies receiving government funding in the United States, the United Kingdom, and Australia seek to harness the ocean's vast carbon storage capacity. These include fertilizing small plants and altering ocean chemistry.Ocean-based approaches are gaining popularity because they can potentially store carbon for one-tenth the cost of “direct air capture,” where CO₂ is sucked from the air with energy-intensive machinery. But marine The carbon cycle is very difficult to predict. Scientists must uncover the many complex natural processes that could alter the efficiency, efficacy, and safety of ocean-based CO₂ removal before moving forward.
In our new research, we shed light on a surprisingly important mechanism that was previously overlooked. If CO₂ removal technology alters the appetites of small animals at the base of the food chain, it could dramatically change how much carbon is actually stored.Tiny marine life forms called plankton play a huge role in ocean carbon cycling. These microscopic organisms drift in ocean currents, carrying the captured carbon throughout the ocean. Like plants on land, phytoplankton use sunlight and CO₂ to grow through photosynthesis.
Zooplankton, on the other hand, are small animals that eat mostly phytoplankton. They come in many shapes and sizes.If you put them in a row, you might think they came from different planets.
Despite all this diversity, zooplankton's appetites vary greatly. The hungrier they get, the faster they eat. Uneaten phytoplankton – and zooplankton poo – can sink to great depths, locking carbon out of the atmosphere for centuries. Some even sink to the ocean floor and eventually turn into fossil fuels.This transfer of carbon from the atmosphere to the ocean is known as the "biological pump". It keeps hundreds of billions of tons of carbon in the oceans and out of the atmosphere. This means approximately 400ppm CO₂ and 5°C cooling!
In our new research we wanted to better understand how zooplankton hunger affects the biological pump. First we had to find out how zooplankton hunger varies across the ocean.
We used a computer model to simulate the seasonal cycle of phytoplankton population growth.It is based on the balance of reproduction and death. The model simulates reproduction really well.
Zooplankton hunger largely determines mortality. But the model isn't so good at simulating mortality, because it doesn't have enough information about zooplankton hunger. So we tested dozens of different hungers and then checked our results against real-world data.To obtain a global overview of phytoplankton seasonal cycles without a fleet of ships, we used satellite data. This is possible even when phytoplankton are small, because their light-catching colors are visible from space.
We ran the model at more than 30,000 locations and found that there is huge variation in zooplankton appetite. This means that all those different types of zooplankton are not spread evenly in the ocean. They appear to gather around their favorite type of prey.In our latest research, we show how this diversity affects the biological pump.
We compared two models, one with only two types of zooplankton and the other with an unlimited number of zooplankton – each with different appetites, all individually tailored to their unique environments.
We found that incorporating realistic zooplankton diversity reduced the biological pump power by one billion tons of carbon each year. This is bad for humanity, because most of the carbon that does not go into the ocean gets released back into the atmosphere. Not all of the carbon in the bodies of phytoplankton will sink deep enough to keep it out of the atmosphere.But even if only a quarter did this, once converted to CO₂ it could be equivalent to the annual emissions of the entire aviation industry.
Many ocean-based CO₂ removal technologies will alter the composition and abundance of phytoplankton.
Biological ocean-based CO₂ removal technologies such as "ocean iron fertilization" attempt to enhance phytoplankton growth. It's a bit like spreading fertilizer over your garden, but on a much larger scale – sowing iron across the ocean with a fleet of ships. The goal is to remove CO₂ from the atmosphere and pump it into the deep ocean.However, because some phytoplankton crave more iron than others, feeding them iron can change the population structure.
Alternatively, non-biological ocean-based CO₂ removal technologies such as "ocean alkalinity enhancement" alter the chemical equilibrium, allowing more CO₂ to dissolve in the water before chemical equilibrium is reached. However, the most accessible sources of alkalinity are minerals including nutrients that encourage the growth of some phytoplankton more than others.
If these changes in phytoplankton favor different types of zooplankton with different sized appetites, they are likely to alter the strength of the biological pump. This could compromise – or complement – the efficiency of ocean-based CO₂ removal technologies.Emerging private sector CO₂ removal companies will need accreditation from credible carbon offset registries. This means they must demonstrate their technique:
Remove carbon for hundreds of years (sustainability)
Avoid major environmental impacts (safety) Be accountable for accurate monitoring (verification).
In the face of a sea of uncertainty, the time has now come for oceanographers to set the necessary standards.
Our research shows that CO₂ removal technologies that alter phytoplankton communities may also alter carbon storage by modulating zooplankton appetite. Before we can accurately predict how well these technologies will work and how we should monitor them, we need to understand them better.This will require tremendous effort to overcome the challenges of observation, modeling and prediction of zooplankton dynamics. But the payoff is huge. A more reliable regulatory framework could pave the way for a trillion-dollar, ethically mandated, emerging CO₂ removal industry.(Conversation)
RUP
Some of the most promising CO₂ removal technologies receiving government funding in the United States, the United Kingdom, and Australia seek to harness the ocean's vast carbon storage capacity. These include fertilizing small plants and altering ocean chemistry.Ocean-based approaches are gaining popularity because they can potentially store carbon for one-tenth the cost of “direct air capture,” where CO₂ is sucked from the air with energy-intensive machinery. But marine The carbon cycle is very difficult to predict. Scientists must uncover the many complex natural processes that could alter the efficiency, efficacy, and safety of ocean-based CO₂ removal before moving forward.
In our new research, we shed light on a surprisingly important mechanism that was previously overlooked. If CO₂ removal technology alters the appetites of small animals at the base of the food chain, it could dramatically change how much carbon is actually stored.Tiny marine life forms called plankton play a huge role in ocean carbon cycling. These microscopic organisms drift in ocean currents, carrying the captured carbon throughout the ocean. Like plants on land, phytoplankton use sunlight and CO₂ to grow through photosynthesis.
Zooplankton, on the other hand, are small animals that eat mostly phytoplankton. They come in many shapes and sizes.If you put them in a row, you might think they came from different planets.
Despite all this diversity, zooplankton's appetites vary greatly. The hungrier they get, the faster they eat. Uneaten phytoplankton – and zooplankton poo – can sink to great depths, locking carbon out of the atmosphere for centuries. Some even sink to the ocean floor and eventually turn into fossil fuels.This transfer of carbon from the atmosphere to the ocean is known as the "biological pump". It keeps hundreds of billions of tons of carbon in the oceans and out of the atmosphere. This means approximately 400ppm CO₂ and 5°C cooling!
In our new research we wanted to better understand how zooplankton hunger affects the biological pump. First we had to find out how zooplankton hunger varies across the ocean.
We used a computer model to simulate the seasonal cycle of phytoplankton population growth.It is based on the balance of reproduction and death. The model simulates reproduction really well.
Zooplankton hunger largely determines mortality. But the model isn't so good at simulating mortality, because it doesn't have enough information about zooplankton hunger. So we tested dozens of different hungers and then checked our results against real-world data.To obtain a global overview of phytoplankton seasonal cycles without a fleet of ships, we used satellite data. This is possible even when phytoplankton are small, because their light-catching colors are visible from space.
We ran the model at more than 30,000 locations and found that there is huge variation in zooplankton appetite. This means that all those different types of zooplankton are not spread evenly in the ocean. They appear to gather around their favorite type of prey.In our latest research, we show how this diversity affects the biological pump.
We compared two models, one with only two types of zooplankton and the other with an unlimited number of zooplankton – each with different appetites, all individually tailored to their unique environments.
We found that incorporating realistic zooplankton diversity reduced the biological pump power by one billion tons of carbon each year. This is bad for humanity, because most of the carbon that does not go into the ocean gets released back into the atmosphere. Not all of the carbon in the bodies of phytoplankton will sink deep enough to keep it out of the atmosphere.But even if only a quarter did this, once converted to CO₂ it could be equivalent to the annual emissions of the entire aviation industry.
Many ocean-based CO₂ removal technologies will alter the composition and abundance of phytoplankton.
Biological ocean-based CO₂ removal technologies such as "ocean iron fertilization" attempt to enhance phytoplankton growth. It's a bit like spreading fertilizer over your garden, but on a much larger scale – sowing iron across the ocean with a fleet of ships. The goal is to remove CO₂ from the atmosphere and pump it into the deep ocean.However, because some phytoplankton crave more iron than others, feeding them iron can change the population structure.
Alternatively, non-biological ocean-based CO₂ removal technologies such as "ocean alkalinity enhancement" alter the chemical equilibrium, allowing more CO₂ to dissolve in the water before chemical equilibrium is reached. However, the most accessible sources of alkalinity are minerals including nutrients that encourage the growth of some phytoplankton more than others.
If these changes in phytoplankton favor different types of zooplankton with different sized appetites, they are likely to alter the strength of the biological pump. This could compromise – or complement – the efficiency of ocean-based CO₂ removal technologies.Emerging private sector CO₂ removal companies will need accreditation from credible carbon offset registries. This means they must demonstrate their technique:
Remove carbon for hundreds of years (sustainability)
Avoid major environmental impacts (safety) Be accountable for accurate monitoring (verification).
In the face of a sea of uncertainty, the time has now come for oceanographers to set the necessary standards.
Our research shows that CO₂ removal technologies that alter phytoplankton communities may also alter carbon storage by modulating zooplankton appetite. Before we can accurately predict how well these technologies will work and how we should monitor them, we need to understand them better.This will require tremendous effort to overcome the challenges of observation, modeling and prediction of zooplankton dynamics. But the payoff is huge. A more reliable regulatory framework could pave the way for a trillion-dollar, ethically mandated, emerging CO₂ removal industry.(Conversation)
RUP
