//
you're reading...

deep sea

Are we ready to mine the seafloor?

Vonnahme, Tobias R., et al. “Effects of a deep-sea mining experiment on seafloor microbial communities and functions after 26 years.” Science Advances 6.18 (2020): eaaz5922. https://advances.sciencemag.org/content/6/18/eaaz5922/tab-pdf

Polymetallic nodules, as the name suggests, are globular structures that contain a variety of metals. These nodules are found on the seabed and are usually rich in valuable metals such as cobalt, manganese, nickel, and copper. Terrestrial mining has severe impacts on land ecosystems, and some think deep-sea mining might be a lucrative alternative. However, mining for manganese nodules involves massive disturbance to the uppermost surface sediments. Despite this, several nations around the globe are actively scanning the seafloor to look for the mining sites. But are we ready to mine these habitats without ascertaining impacts on the organisms living on and around these nodules? How long will it take for the seafloor to recover from the impacts of mining? A team of scientists led by T.R Vonnahame is working to answer some of these questions.

Fig 1: Implications of Deep Sea Mining.

 

DISCOL

DISCOL is a unique DISturbance and ReloCOLization experiment that is being carried out at the Peru Basin (4150 m deep, roughly the distance from California to Florida) in the South Pacific. In 1989 the site was first ploughed in an area of 11 km2 to replicate the effects of deep-sea mining on the seabed. Ploughing mimics, the mining activity whereby heavy gears are pulled along the seafloor, non-selectively. Scientists have gone back to the site in 1992, 1996, and, most recently, in 2015 to study the impacts of ploughing by comparing it to three undisturbed sites nearby. In the current study, the scientists have particularly focused on the microbial community. They focused on microbes to ascertain if the number of microbes and their activities are sensitive to seafloor disturbance and could further be utilized as indicators of disturbance.

Diving In

On returning to the DISCOL site, the scientist could easily identify the original plough track even after 26 years. As surprising as this may seem, this is common in disturbed deep sea beds because it takes really long for the sediment to sink to such depths. DISCOL was divided into four zones of disturbance: i) minor disturbance outside the tracks; ii) furrows (depression) created by ploughing; iii) ridges from ploughing; and iv) areas of deep ploughing, these were the areas where surface sediments that usually contain a lot of tiny organisms were lost entirely. Many things organisms need to survive, like food (carbon) and oxygen, were quite different at the four locations. The first significant takeaway of the experiment is that disturbances impact food and oxygen for these microbes, and conditions can take a really long time to return to normal.

 

Fig 2: Plough track showing different zones. (ROV Kiel  6000 Team, GEOMAR)

Fig 3: The undisturbed site nearby.

To compare the long term and the short-term impacts of mining, the scientists ploughed the experiment site five weeks prior to the sampling. Food particles from the water column settle on the surface sediments, and this results in an increase in the number of microbes in the surface sediments, but mining activity disturbs the surface sediments. This study found the fresh (5 weeks), and the 26-year-old disturbance showed a decline in the number of microbes. The reduction in bacterial numbers at the fresh disturbance was 50%, and even after 26 years, the number of bacteria was lower than undisturbed sediment by 30%. This is due to the slow buildup, from 20 to 30 thousand years, of food particles at the seafloor. Mining activity removes not only the bacteria but also their food, preventing new communities from taking over.

Fig 4: Ipnops, one of the many organisms found near the sea floor.

Interestingly, the scientists noted that, despite the reduction in the numbers of microbes, no new microbes took over at both the disturbance sites, i.e., the species of the microbes remained the same. The decline of the microbial community is also particularly alarming because microbes form the base of the food chain on the seafloor. Smaller organisms depend on microbes to break down the bigger food particles and make them easier to eat. Because microbes break down larger particles, usually with the help of oxygen, scientists also measured oxygen uptake at the disturbed sites and found a decline compared to undisturbed sites. This tells us that the microbes are not breaking down food particles effectively at the disturbed sites. Therefore, a decline in bacterial population and their activity could mean the scarcity of food for other organisms higher in the food chain.

What does this mean for deep-sea mining?

Current technologies disturb the surface layer over hundreds and thousands of square kilometers per year. This would mean loss of ecological functions at a large scale and would take several decades to recover from. The authors suggest that the disturbance mainly depends on the technology being employed to mine the seafloor, and therefore future ecologically sustainable technologies should avoid removal of the bio-active surface layer, which harbors and supports a variety of organisms.

 

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 6 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 9 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