you're reading...


Sea Ice Modifies Biological Processes

Source: Hague, M., and M. Vichi (2018), A link between CMIP5 phytoplankton phenology and sea ice in the Atlantic Southern Ocean. Geophysical Research Letters, doi: 10.1029/2018GL078061

The Biggest Carbon Sink

The ocean plays a crucial role in regulating the earth’s climate by taking up excess heat and carbon dioxide from the atmosphere. The ocean surrounding Antarctica, called the Southern Ocean, absorbs a particularly large amount – nearly 30% of the carbon and 90% of the heat associated with anthropogenic climate change, which is the warming associated with fossil fuel burning by humans.

Tiny microalgae called phytoplankton are responsible for most of the transfer of carbon dioxide from the atmosphere to the ocean. Phytoplankton form the base of the marine food web and absorb carbon dioxide through photosynthesis, just like trees and other land plants. This carbon then gets stored in the deep ocean when the organisms die and sink to the seafloor. How important is this sinking of organic matter to the global carbon cycle? Scientists still don’t exactly know since it’s so difficult to measure phytoplankton activity in the ocean. Quantifying this pathway in regions that uptake a lot of carbon, like the Southern Ocean, is important to understanding and modeling atmospheric carbon dioxide concentrations and global climate.

Microscope image of a coccolithophore, a type phytoplankton with a shell made out of calcium carbonate (UNC Wilmington Microscopy Facility via Wikimedia Commons)

Ice Impacts Phytoplankton

While measuring phytoplankton activity is already difficult, taking measurements in the ocean surrounding Antarctica is even more challenging due to its remote location and harsh weather. Because there is so little available data, studying the role of Southern Ocean phytoplankton in the carbon cycle is difficult using observations alone. Therefore, a recent study by Mark Hague and Marcello Vichi at the University of Cape Town compared observations with several different complex models to try to understand how sea ice impacts biological productivity in the Antarctic. Models, like the ones used in this study, that integrate physical, chemical, and biological processes are becoming increasingly important as we try to untangle the complex feedbacks that drive changes in ecosystems and climate.


One of the key results from this study is that models consistently predicted phytoplankton growth earlier in the year than was observed. This is a problem since properly accounting for phytoplankton activity is necessary to model marine ecosystems and the global cycling of nutrients. The researchers attribute the early growth to issues with how the model represents sea ice processes. Ice cover limits the amount of light (which is necessary for photosynthesis) that reaches the upper ocean. Therefore, models must accurately characterize sea ice extent in order to predict when and where there will be enough light to support phytoplankton growth.

Satellite image of an ice-edge phytoplankton in the Southern Ocean (NASA Earth Observatory via Wikimedia Commons)

In addition to modulating light availability, sea ice also impacts phytoplankton by changing the vertical structure of density layers (stratification) in the upper ocean. Melting of sea ice adds freshwater to the ocean, while sea ice formation injects salt. This in turn impacts the stratification because the density of seawater depends on the amount of salt in it. Since sea ice melting and formation impacts vertical mixing, it also controls the supply of nutrients to the surface from the deep ocean.

Sea ice itself also contains nutrients like iron that are necessary for phytoplankton growth. Thus the ice melt can actually fertilize blooms. Sea ice impacts phytoplankton through a number of mechanisms, and it is difficult to untangle these complex feedbacks. The results from Hague and Vichi suggest that current climate models may have biases in sea ice processes that inhibit them from accurately predicting phytoplankton growth. Furthermore, addressing these biases is necessary given the role that phytoplankton play in the marine food web and the global carbon cycle.

How Strong of a Sink?

Carbon concentrations in the Southern Ocean are controlled by a complex combination of interaction with the atmosphere, sea ice dynamics, and biological processes. Because of this, scientists have different hypotheses about how the Southern Ocean’s ability to absorb carbon will change in the future. Some studies suggest that sea ice retreat will expose the ocean to more sunlight, which will increase productivity and allow the ocean to absorb more carbon. Others hypothesize that increasing ocean temperatures and sea ice melt will cause the ocean to become more stratified and eventually take up less carbon. By investigating the relationship between sea ice variability and phytoplankton growth in climate models, this study can help us understand and predict how the ocean’s ability to regulate climate might change in the future.


No comments yet.

Post a Comment


  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 6 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 9 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 9 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 10 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 10 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 11 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 11 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 12 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 1 year ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com