Young Voices

From Field to Lab: How Carbon Seeps Provide a Chance to See Future Impacts of Ocean Acidification

Tiny organisms found on ARMS
A diversity of organisms are found in ARMS. (Sarah Leinbach, Smithsonian)

Every year, humans spew billions of tons of carbon dioxide (CO2) into the atmosphere by burning fossil fuels, like coal, oil and natural gas. The world’s oceans absorb some of it, but unfortunately this leads to a phenomenon known as ocean acidification. (Read more about the science behind ocean acidification here.)

Nature provides us with the perfect location to study this. In the crystal blue waters of Papua New Guinea, there are areas where CO2 seeps out of the seafloor naturally and causes the surrounding seawater to become more acidic. Scientists study these sites in order to catch a glimpse of what our oceans might look like in the future.

But what is the process from the seafloor to the lab bench? Let's walk through it together. 

Here you can see a healthy reef in Papa New Guinea, alive with vibrant colors and an abundance of coral and fish. 

A Healthy Coral Reef

A healthy and vibrant coral reef in Papua New Guinea.
These reefs surround the CO2 seeps (you can see the bubbles) which makes the water more acidic. Close to the volcanic CO2 seeps, the vast diversity of corals that exists in less-acidic waters is replaced by a "monoculture" of boulder corals.

Carbon Dioxide Volcanic Seep

Intense volcanic CO2 vents in Ili Ili Bua Bua, Normanby Island, Papua New Guinea.

Lonely Seagrass in Acidic Waters

Where the pH is the lowest, corals can no longer grow - sand, rubble and seagrasses replace the reef.
In order to study the reefs in Papua New Guinea, scientists use devices known as Autonomous Reef Monitoring Structures (ARMS). The ARMS have eight layers of plastic plates that mimic the structure of coral reefs, attracting species of sponges and algae, as well as crabs, mollusks and other small invertebrates. Researchers install the ARMS onto the reefs at different distances away from the CO2 seeps and leave them there for one to two years. 

Picture of ARMS in Papua New Guinea

Two ARMS sit on the ocean floor.
While the ARMS are deployed on the reef, organisms of all sorts colonize the surfaces—from the tiniest snails to the biggest fish. The ARMS device is taken off the reef at a certain pre-determined time and brought back to the lab for analysis.  

ARMS Covered in Growth

An ARMS covered in growth after being underwater for a specified period of time.
All the organisms on the ARMS are taken back to the lab to be studied. Everything is detached or removed from the plates, yielding a hodge-podge of organisms mixed together with pieces of sand and other assorted debris. All the extra material needs to be removed in order to study the organisms more closely.  

ARMS Sample Before Cleaning

A view through a microscope of animals collected on an ARMS.
Once the organisms are separated out, scientists use DNA to assess the biodiversity at each reef site. Every organism has a unique code in their DNA that can be used to identify the species, the same way a cashier uses a barcode to scan items at the store.

It's All In the DNA

NMNH intern in the lab.
Traditional barcoding methods do not work for all organisms. Some animals are far too small and numerous to be analyzed separately. Instead, scientists use a cutting-edge technique known as metabarcoding. Metabarcoding involves analyzing the DNA of whole communities of organisms, instead of barcoding them one by one. This allows scientists to uncover the “hidden diversity” of reefs. They can determine the species of tiny creatures that might go unnoticed by traditional barcoding methods.

Hidden Diversity

Tiny organisms found on ARMS
By comparing the distribution of species on healthy coral reefs and acidified coral reefs, patterns begin to emerge. It is evident that coral reefs in less acidic water tend to be much more diverse than coral reefs in highly acidic water. You can see the abundance of creatures found in this image from less acidic water, further from the carbon dioxide seeps.

Motile High pH

Organisms found in high pH ARMS
Here is an example of the animals found in acidified water. It’s plain to see there is less diversity. Not only are healthy coral reefs much more mesmerizing to look at, but they also provide more abundant resources for both the ecosystem as a whole and humans. 

Motile Low pH

Organisms found in low pH ARMS
November 2017