//
you're reading...

Biochemistry

Iceberg Buffet: How giant icebergs bring food to plankton

Paper: Duprat, L.P.A.M., et al. 2016. Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs. Nature Geoscience, v. 9: 219–221.

Credit: Gérald Tapp.

Credit: Gérald Tapp.

While the whole world is suffering from the effects of climate change, the poles are being hit especially hard. The average temperature is rising more quickly than in other regions of Earth, the ice is melting faster, and icebergs are breaking off from glaciers at unprecedented rates. But for some lucky little critters, the increase in these massive icebergs is a good thing.

When icebergs break off from glaciers, they carry with them sediments that the glaciers have scraped off the land on their way to the ocean. These terrigenous sediments – sediments that are originally from land but have been transported into the ocean by rivers or other means –can carry nutrients and trace elements like iron that are fundamentally important for the growth of phytoplankton. This growth is also known as primary productivity, and is a major component of the ocean’s carbon cycle, taking excess carbon and CO2 from the ocean – atmosphere boundary and transporting it to the depths of the ocean.

Previous studies have shown that chlorophyll levels – which are used to measure the amount of primary productivity on the ocean surface – tend to be higher near icebergs. This occurs because the meltwater plumes from the icebergs contain significant concentrations of iron and other nutrients. Iron is rare and can limit phytoplankton growth in the Antarctic, so adding it to the surface – referred to as iron fertilization – can stimulate growth.

Giant iceberg in the South Atlantic. In June 2002, it was measured 50 km by 23.5 km. Credit: NASA Earth Observatory.

Giant iceberg in the South Atlantic. In June 2002, it was measured 50 km by 23.5 km. Credit: NASA Earth Observatory.

With icebergs less than 1 kilometer in length, chlorophyll levels up to three times higher than the average level have been detected, for up to six days after passage of the iceberg, up to a radius of a few kilometers. However, the influence of giant icebergs over 18 km in length on marine primary production in the Southern Ocean is less well studied, and fertilization from these icebergs may be much larger than previously suspected.

Smaller Numbers but Bigger Payload

Although rarer, giant icebergs exceeding 18 km in length make up about half of the total iceberg discharge volume from Antarctica, because of their immense size. This makes these slightly icebergs just as important to primary productivity as the “small” ones. Several dozen such icebergs exist in the Southern Ocean at any given time, and may linger for years. They also come from a range of geologic environments around Antarctica, and are thus likely to have different iron and nutrient characteristics.

Dr. Luis Duprat and colleagues at the University of Sheffield in the UK set out to study how these massive icebergs might feed plankton growth. Using remote sensing and the MODIS Aqua satellite, they analyzed 175 satellite images of open ocean color in the Antarctic Weddell Sea and Southern Ocean, before and after the passage of 17 giant icebergs between 2003 and 2013. The color was used to detect enhanced chlorophyll levels and primary productivity.

Figure 1: mean chlorophyll concentrations in the Southern Ocean in 2011 (a) and in 2014 (b). You can see the path of one sample giant iceberg by the black line in (b). Chlorophyll concentrations are higher in 2014, and also higher in the down-current path of the iceberg. Credit: Duprat et al.

Figure 1: mean chlorophyll concentrations in the Southern Ocean in 2011 (a) and in 2014 (b). You can see the path of one sample giant iceberg by the black line in (b). Chlorophyll concentrations are higher in 2014, and also higher in the down-current path of the iceberg. Credit: Duprat et al.

They found that these giant icebergs can create a radius of enhanced primary productivity levels up to 10 times the iceberg’s length. These patches can linger for more than a month after the iceberg has passed through the area, and are over an order of magnitude larger than the areas created by smaller icebergs. Additionally, there were no statistically significant differences between the geographical origins of giant icebergs in their fertilization effect a month after passage. However, there were differences that correlate well with the large-scale geology of Antarctica. Almost all of coastal East Antarctica is composed of rock that will be less easily weathered than the rocks of the Antarctica Peninsula, and thus icebergs from East Antarctica will tend to have more sediment and iron.

What does this all mean for climate change and the carbon cycle? The Southern Ocean is a significant sink in the ocean component of the global carbon cycle, contributing ∼10% of the ocean’s total carbon sequestration through a mixture of chemical and biologically driven processes. However, due to its low concentration of dissolved iron, its contribution is lower than that of the smaller South Pacific and Indian Oceans. Adding iron to the system from these massive icebergs boost the process. Duprat estimates that up to a fifth of the Southern Ocean’s downward carbon flux originates with giant iceberg fertilization, and suggests that if giant iceberg calving increases this century, as expected, this negative feedback on the carbon cycle may become more important.

Read more recent oceanbites posts on the relationship between plankton and sea ice:

Arctic could become more biologically productive as ice melts

Plankton fill up ice-free summer homes

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 weeks 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 1 month 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 3 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 3 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 3 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 3 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 4 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 4 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 4 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 5 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 5 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 5 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 6 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 6 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 7 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 7 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 8 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 8 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 9 months 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 
  • by oceanbites 9 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
WP2Social Auto Publish Powered By : XYZScripts.com