you're reading...

Biological oceanography

Phytoplankton Expanding Northward as Arctic Sea Ice Retreats

Source: Renaut, S., E. Devred, and M. Babin (2018), Northward Expansion and Intensification of Phytoplankton Growth During the Early Ice-Free Season in Arctic. Geophysical Research Letters, doi: 10.1029/2018GL078995

Just as flowers and other land plants go through a period of intense growth in the spring, so too do marine microalgae called phytoplankton. This is referred to as a bloom, and accounts for more than half of the annual primary production in some regions of the Arctic Ocean.

The past few decades have seen dramatic declines in Arctic sea ice extent, as shown in the plot below from the National Snow and Ice Data Center. Sea ice retreat has the capacity to change many aspects of marine ecosystems, however, the exact impacts are not well understood. This is because of the complex combination of both physical and biological processes at play. For example, sea ice is white and therefore reflects a lot of sunlight. Newly ice-free regions have more incoming sunlight necessary for photosynthesis, which could increase phytoplankton growth. On the other hand, melting of sea ice adds freshwater to the surface ocean, which enhances the stratification (since the density of seawater depends on the amount of salt in it). This could in turn, prevent the delivery of nutrients to the upper ocean, impeding phytoplankton growth.

Average monthly Arctic sea ice extent from 1979-2012, showing a significant decrease over the past several decades. Source: NSIDC via Wikimedia Commons

In order to tease out these different mechanisms, a recent study led by Sophie Renaut uses satellite data to investigate how Arctic sea ice retreat impacts the distribution of phytoplankton blooms. The researchers use satellite chlorophyll data, which is indicative of phytoplankton biomass, to show that blooms in the Arctic expanded northward by 1° of latitude from 2003 to 2013. They also find that net primary productivity, which is the rate that photosynthetic (and chemosynthetic) organisms make organic compounds, increased by 31 percent during this period. These changes are likely due to an increase in the extent of ice-free regions, which results in more light reaching the surface ocean.


Changes in the amount, extent, and timing of blooms have major implications for marine ecosystems since phytoplankton are the base of the marine food web. Blooms were observed in regions where they did not exist before, and therefore other organisms, like zooplankton, that graze the phytoplankton might also expand their range. There are other things to consider though such as the lifecycle of grazers, which is tied to the timing of blooms. Since the ice retreat is beginning earlier each year, blooms are also occurring earlier in the season as well. If the blooms occur too early, this could actually limit the growth of zooplankton due to a mismatch between their lifecycle and the bloom timing. In other words, the changes to Arctic blooms resulting from sea ice retreat will influence the distribution of other marine organisms, but exactly how is not clear.

Satellite image of ocean color showing the signature of a spring phytoplankton bloom (Source: NASA Earth Observatory)

Phytoplankton take up carbon dioxide from the atmosphere through photosynthesis, just like trees and other land plants. Therefore, these results also have implications for the ability of the Arctic to act as a carbon sink. On the one hand, increased primary production implies that the ocean will take up more carbon. However, this carbon only gets stored in the ocean interior if the phytoplankton are not grazed. Further research is necessary to see how changes in phytoplankton distribution will impact Arctic ecosystems and the strength of the Arctic carbon sink. It is also crucial to continue monitoring these changes in the future to see if the expansion continues at the rate observed during the decade of data used for this study.


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 7 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 8 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 9 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 10 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 11 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 12 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