//
you're reading...

Ecology

Scientists set sail to survey the ocean’s plankton diversity

Journal source: Sunagawa, S., Acinas, S.G., Bork, P. et al. Tara Oceans: towards global ocean ecosystems biology. Nat Rev Microbiol 18, 428–445 (2020). https://doi.org/10.1038/s41579-020-0364-5

The diversity that surrounds us

The world’s oceans overflow with an immense array of life, from majestic whales, sharks, and dolphins, to amazingly fast and beautiful schools of glistening fish that scatter the sun’s rays throughout the water column. While views of these charismatic animals no doubt fill us with awe and inspire many to protect marine life, the ocean is also home to a diverse community of microscopic organisms. From viruses, single-celled archaea, and bacteria, to algae and tiny swimming zooplankton, many of which resemble shrimp and crabs, these tiny organisms form the cornerstone of oceanic food webs.

Planktonic organisms

Some examples of plankton collected at sea. Photo credit: Christian Sardet/CNRS/Tara expeditions via Wikimedia Commons.

This community of single-celled microorganisms, phytoplankton, and zooplankton, collectively called the plankton, is not easy to observe if you collect a bucket-full of ocean water and gaze into it without the aid of a microscope. Despite their tiny nature, these critters perform many functions, including primary production and nutrient cycling, which keep our oceans functioning by providing sustenance to organisms higher up in the food chain. Primary production is performed by algae, which fix light energy into nutritious sugars for organisms higher up the food chain. Nutrient cycling by bacteria and other microbes frees nitrogen and phosphorus, elements necessary for organism growth, from dead materials so that they can reenter the food web.

 

While marine scientists have long recognized the importance of the ocean’s plankton communities, a question that keeps many up at night is how many different species of microbes and zooplankton are living in the oceans. Although much of the life in the ocean has already been described, scientists reckon that we have barely scratched the surface in terms of identifying the full diversity of ocean life contained within the plankton. Knowing the diversity of the species that comprise the plankton, and how that diversity changes across different regions of the ocean is valuable as scientists work towards a more holistic understanding of how energy flows from microbes to higher up the food chain.

Additionally, global sampling of the ocean’s planktonic diversity across major ocean regions – the poles, temperate, and tropical zones – also has the potential to shed light on how environmental factors such as temperature impact plankton biodiversity. Furthermore, investigating how diversity changes across major geographic regions may shed light on the role of diversity in supporting primary production, as scientists in freshwater and terrestrial ecosystems often find that more diverse communities tend to be more productive.

The study

With the ambitious goal of characterizing the global ocean’s plankton diversity, a team of scientists initiated a long-term oceanic expedition called the TARA Ocean Project aboard a schooner named TARA. Imagine stepping aboard a sailboat, but one that is decked out in high-tech sampling gear, laboratory space, and more. The researchers set sail in 2009, collecting 35,000 water plankton samples from over 200 sites spanning from the Arctic Ocean to the Southern Ocean.

Sail boat

A view of TARA with scientists onboard. Photo credit: Fanny Schertzer via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Tara_-_Brest_2008-3.jpg

All organisms contain DNA, which is known as the blueprint of life, as it codes for each species’ unique characteristics and functions. RNA, like DNA, is another code of life, and it can tell scientists which species and what genes are active in different communities. Together, DNA and RNA can tell a story of what these planktonic communities look like, and what they are doing. To identify the different types of plankton present in the samples, the researchers measured the abundance and different types of DNA and RNA from the water. After sequencing thousands of segments of DNA and RNA, the scientists looked at how the composition and abundance of DNA and RNA changed across samples. This allowed them to examine plankton species diversity as well as the active genes present in different regions.

What did they find?

With over a trillion sequences of DNA, the scientists assembled a picture of the global oceanic plankton community. Planktonic diversity was highest in samples collected in tropical regions and decreased toward the North and South Poles. This decreasing trend in biodiversity from the equator to the poles is known as the latitudinal biodiversity gradient and is well-documented for land plants and animals.

In addition to describing plankton diversity patterns, Sunagawa and colleagues also discovered differences in how organisms in arctic, temperate, and tropical waters may adjust to climate change. Their analysis of active genes in these regions indicated that planktonic communities in the Arctic Ocean are more sensitive to changes in environmental conditions, while communities in temperate and tropical waters appeared to have more flexibility in adapting to changing environmental conditions.

The TARA Oceans expedition also revealed a diverse and abundant virus community. Oceanic viruses are often important predators of bacterial and eukaryotic microbes, and the TARA researchers found that the role of viruses in the ocean may be more complex than originally thought.

Virus structure

Virus structure. Photo credit: Chelsea Bonnain, Mya Breitbart and Kristen N. Buck via https://commons.wikimedia.org/wiki/File:Structure_of_a_Myoviridae_bacteriophage_2.jpg

First, they found that the diversity of viruses increased from the South Pole to the equator, and then diversity dipped a bit, and then reached the highest levels in Arctic waters. Furthermore, the scientists found evidence for viruses to play a role in carbon cycling, which is a process important for maintaining a stable climate and in energy transfer for organisms. This is an exciting finding, as carbon cycling was previously thought to be the job of protists, a group that contains algae and amoeba-like microbes. From these results, the researchers emphasize the need for intensive studies on the global virus community and its functions in marine food webs.

The bigger picture

Whale shark

Whale shark feasting on planktonic organisms. Photo credit: Jaontiveros via https://commons.wikimedia.org/wiki/File:Whale_shark_eating_plankton.JPG

You may have heard the adage, “it’s the small things in life that count.” The TARA Oceans expedition is dedicated to unraveling the unprecedented biodiversity within the largely invisible oceanic plankton communities. By generating a robust global inventory of plankton diversity, the TARA Oceans team has expanded knowledge of ocean biology and established a baseline of understanding just how complex and dynamic these tiny but mighty critters are. Even with such an extensive dataset, the authors emphasize that much of the plankton diversity has yet to be described.

 

 

 

 

 

 

 

 

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 2 hours 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 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 2 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 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 4 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 5 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 7 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 9 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 
WP2Social Auto Publish Powered By : XYZScripts.com