//
you're reading...

Ocean Acidification

Stressed-out microbes in an acidifying ocean

 

Original Paper: FF Raulf, K Fabricius, S Uthicke, D de Beer, RMM Abed, A Ramette. 2015. Changes in microbial communities in coastal sediments along natural CO2 gradients at a volcanic vent in Papua New Guinea. Environmental Microbiology 17(10):3678-3691.

Nearly all life in the modern ocean has evolved under a constant level of water acidity. But human carbon emissions are threatening to dramatically alter the ocean’s acidity, with enormous ramifications for every organism that calls the ocean home.

As carbon dioxide is emitted into the atmosphere by fossil fuel burning, nearly one-third of that carbon dioxide is captured by the ocean and contributes to ocean acidification. Due to the staggering amount of carbon dioxide that humans have released in the span of only a few hundred years – atmospheric carbon dioxide concentrations have increased by 50% – the ocean is struggling to keep up and losing its natural balance of acidity in the process. Already, ocean acidity has increased by as much as 25%.

Meanwhile, many of the most charismatic ocean-dwelling organisms are struggling to adapt to this increase in acidity. Corals, for example, are dying off around the world at unprecedented rates; experts estimate that the world may lose more than half of its coral reefs in coming decades. Important fisheries have been hit hard as well – oyster aquaculture in the Pacific Northwest nearly collapsed after high-acidity waters led to mass die-offs.

Coral bleaching, which ultimately leads to coral death, is a result of ocean acidification. Scientists anticipate more than half of the world’s corals may be lost by the end of the century. Source: Slate.com

But among the numerous studies examining the impacts of ocean acidification on marine life, few have investigated the most abundant type of life in the ocean: microorganisms. Microbes living in the surface of the seafloor are the ocean’s carbon recyclers. By degrading dead fish and phytoplankton, they play a critical role in determining whether the carbon trapped in these dead organisms is buried in the seafloor or returned to the ocean. Buried carbon is harmless, since it cannot return to the ocean or atmosphere to contribute to ocean acidification or climate change. Carbon returned to the ocean by seafloor microbes, on the other hand, can further contribute to ocean acidification. However, it remains unclear whether microorganisms experience the same die-offs and community shifts as scientists observe for fish and coral communities under acidifying conditions.

Katharina Fabricius, one of the authors of the study, collecting samples in highly acidified waters above the carbon dioxide vent off Papua New Guinea. Source: Dallas News

To investigate this, a team of microbiologists traveled to a unique beach in Papua New Guinea where underground volcanic activity is venting carbon dioxide through shallow waters only about 10 feet deep. Because the vent is a point-source of carbon dioxide, a gradient of high- to low-acidity water forms with distance from the vent – creating a natural laboratory for exploring how increasing acidity affects microbial communities. Following this gradient, the researchers sampled sediments with overlying waters ranging from modern-day ocean acidity, around pH 8.3, to waters with the predicted ocean acidity in the year 2100, around pH 7.8, to extremely acidified waters with pH 6.9. Once all the sediments were collected, the researchers were able to extract the microorganisms from the mud and sand and sequence their DNA to determine what types of microbes were inhabiting each acidity regime.

What they found was a clear distinction between microorganisms living in a modern-day pH environment and those living in highly acidified environments. On average, only about 8% of the bacterial species were shared from one of the acidity gradient to the other.  More important, a pH of 7.8 – the pH expected for the world’s oceans under a business-as-usual carbon emissions scenario – appeared to be the tipping point for microbes. Microorganisms living in water at pH 7.9 were largely the same as those living at pH 8.3, whereas microbes living at pH 7.7 were more similar to the unusual communities living under the extreme acidity waters at pH 6.9.

Microorganisms living in water at pH 7.9 were largely the same as those living at pH 8.3, whereas microbes living at pH 7.7 were more similar to the unusual communities living under the extreme acidity waters at pH 6.9. In fact, the communities only shared 7.9% of microbial species. That’s a big deal since the tipping point of pH 7.8 is the same pH expected for the world’s oceans by the year 2100. Source: Raulf et al. 2015.

Interestingly, the DNA sequencing also revealed that microbial diversity was higher under high-acidity (low pH) conditions – that is, the community consisted of many different types of microorganisms, whereas under modern-day acidity the community consisted of a few dominant microbes. The researchers interpret this change in the structure of the community as a response to the stress imposed by high acidity. Essentially, none of the microbial species they identified perform well under acidified conditions, so none of them can thrive. While this added diversity may provide some critical metabolic functions to the stressed community, it remains to be tested whether this stressed community is as effective at recycling carbon as the microbial community present under modern-day ocean acidity.

This study raises more red flags about the potential effects of ocean acidification, especially since microorganisms are responsible for nearly all of the chemical and biological cycles that take place in the ocean. The finding that the water pH predicted for the year 2100 may be a tipping point for microbial communities is particularly critical, since this is an indication that the biology of the ocean may shift beyond recognition within our lifetimes. Most of all, the dramatic effects of ocean acidification on seafloor microbial communities revealed by this study make it clear that ocean acidification will be a challenge for all of the life in the ocean – not just the visible life.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 2 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 3 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 4 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 5 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 5 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 5 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 6 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 6 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 7 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 7 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 7 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 7 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 7 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 8 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 9 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 9 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 10 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 10 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 11 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 11 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