Microbial communities have been examined on and near deep-sea shipwrecks, indicating how important these long-lost ships can be to marine life.
The world was astonished in 2019 when the first crewed dive in nearly 14 years yielded startling new photographs of the Titanic’s wreckage. The famed ship’s two parts, which were discovered at a depth of 3,810 meters in Newfoundland, were unrecognizable. The corroding iron hull was not only covered in a dense layer of aquatic life, but it was also eroding. Researchers revealed that specialized metal-eating bacteria and other microbes were slowly but steadily eroding the vessel to its natural state, infusing new life into the surrounding environment. The Titanic, on the other hand, is just one illustration of how even the tiniest organisms can transform wrecked ships into biodiversity hotspots.
The earth is teeming with microscopic life, even if you can’t see it, and nowhere is this more true than in the deep water. All types of microorganisms, including bacteria and archea, are plentiful in the sediment coating the seafloor, which is over 10,000 times more abundant than in the ocean above.
This has been the case for millions of years, but things have changed dramatically in the last few hundred. Of course, we are to blame for the change. Numerous new man-made structures, such as oil rigs, mining equipment, and, of course, shipwrecks, now litter the seafloor. These deep-sea intruders, on the other hand, aren’t always unwelcome. Some of the deep’s most biologically rich communities could be built on the complex and chemically rich structures.
Microbes on the seafloor begin to cover these invasive structures with a sticky layer of bio-film over time. This layer of tiny life is made up of tough bacteria which can break down metals, wood, and other chemically rich substances and convert them to energy. This bio-film’s energy content attracts slightly larger animals like barnacles and algae, which in turn attract the deep’s worms, crabs, and starfish.
Within a short period of time, these structures are completely transformed into artificial reefs populated by octopuses, sharks, and other apex predators. All of which is thanks to the tiny microbes that transform these forgotten structures into biologically available energy.
Exploring The Deep
Shipwrecks, in particular, are perfect places for these artificial reefs because they are highly complex and contain a plethora of other objects and substances for bacteria to consume. Over 2,000 historical shipwrecks have been discovered in the Gulf of Mexico alone, spanning from over 500 years old from the 16th century up until WWII. This makes it an ideal location for observing this new occurrence up close. This is where Dr. Leila Hamden and her lab from the University of Southern Mississippi come in. They are experts in what is known as shipwreck microbial ecology. The specialty area of study includes archaeology, biology, ecology, and marine science, but it’s the bacteria that Dr. Hamden and her team are most interested in.
The crew visits shipwreck sites in the Gulf of Mexico using the research vessel Point Sur. They locate the wrecks using sonar and study them up close using an advanced ROV (remote operated vehicle) called Odysseus. For example, in 2018, they paid a visit to the Anona, a magnificent yacht built in the early twentieth century that sank 70 miles off the coast during a cruise to the British West Indies in 1944.
The ROV captures photographs of the marine animals that live there, as well as collecting samples from its hull to analyze the bacteria that surround it. This time on the Anona, though, the researchers also took core samples from the seafloor at various distances from the wreck. They repeated the operation in 2019 at two other locations with similar-sized yachts from the same time period. Although found at different respective depths, the wrecks were all found intact and upright.
Dr. Hamden presented some extremely fascinating findings on what they discovered at these sites at the recent 2020 Ocean Sciences Meeting in San Diego. They discovered two things after examining the quantity and diversity of microorganisms in each sample. To begin with, the microbial communities shifted as they got further away from the wreckage. The most distinct microorganisms were identified between 160 and 330 feet away from the actual ship, which Dr. Hamden says is to be expected as resources begin to disperse with time. On the other hand, only a few types of bacteria, those that digest cellulose contained in wood, were detected in larger numbers on the actual vessel. This indicates that microbial communities in shipwrecks are more dynamic and spatially complex than initially thought.
The second thing they noticed was that, despite the fact that the only thing that separated the sites was depth, these intricate communities differed greatly between them. This was a far more unexpected discovery for the scientists, and it shows that the placement of these artificial habitats is critical in how they mature.
When you consider that other shipwrecks vary widely in size, form, materials, and duration on the seafloor, it’s safe to assume that no two microbial populations will be alike.This is a significant breakthrough since it means that each shipwreck in our oceans, which number in the tens of thousands if not millions, might support its own ecosystem. That is, we have created hundreds of life-filled, solitary underwater islands dispersed throughout the ocean.
What Makes Them So Unique?
The team’s new discovery highlighted the question of how the microbial communities around shipwrecks could alter so much when the only thing that varied was their depth. Do different bacteria get transported to different depths? Or are all microbes present on the seafloor but prefer different depths? These questions remain unanswered. Dr. Hamden believes it is the latter, and that all deep-sea bacteria can be found at any place, but that the environment at each site will dictate which species thrive and which are pushed to the background. While depth is the most significant difference across locations, other factors such as temperature, pressure, and salinity may also play a role.
Isolated But Not Invulnerable
These underwater islands are not just an important area of research. They’re also becoming important ecosystems that supply an abundance of energy and nutrients to deep-sea life in waters that are devoid of any light. Their uniqueness as a result of isolation could be critical in preserving ecologically diverse and rich oceans, which are already under decline owing to human-caused challenges. However, these man-made ecosystems, which are helping fix man-made issues, are also vulnerable to man-made dangers as well.
In 2014, Dr. Hamden and her colleagues collaborated on a research project with the Bureau of Ocean Energy Management in New Orleans that revealed that these new habitats are especially vulnerable to oil spills. Oil was discovered to inhibit the capacity of microbial communities to grow on adjacent shipwrecks during the Deepwater Horizon catastrophe, which saw approximately 4 million barrels of oil spill into the ocean. Although this may not be the most significant consequence of a big oil spill like this one, it does go to show that the more we pollute and invade the ocean, the more unforeseen consequences we will face.