Millions of shipwrecks lie deep beneath the world’s oceans. These provide new habitats for sea life, but also impact microbial communities. The United Nations Educational, Scientific and Cultural Organization (UNESCO) estimates that there are as many as three million shipwrecks around the world, most of which are made of wood.
A new study published by Frontiers has found that wooden shipwrecks provide microbial habitats similar to naturally occurring geological seabed structures. This research is the first to show the impact of human activity on ocean microbial environments.
“Microbial communities are important to be aware of and understand because they provide early and clear evidence of how human activities change life in the ocean,” said corresponding author Dr. Leila Hamdan of the University of Southern Mississippi.
For the study, the research team chose two wooden sailing ships that sank in the Gulf of Mexico in the late 19th century. The team collected samples by placing pieces of pine and oak between zero and 200 meters from the shipwreck. After four months, they measured all of the bacteria, archaea and fungi using gene sequencing.
The results showed that different types of wood had varying impacts on bacterial diversity (oak was more favorable than pine). Microbial diversity also varied depending on the proximity to the shipwreck site.
The researchers were surprised to find that samples taken closest to the shipwrecks did not show the most diversity, which instead peaked at about 125 meters from the wreck sites.
“Ocean scientists have known that natural hard habitats, some of which have been present for hundreds to thousands of years shape the biodiversity of life on the seafloor,” said Dr. Hamdan. “This work is the first to show that built habitats (places or things made or modified by humans) impact the films of microbes (biofilms) coating these surfaces as well. These biofilms are ultimately what enable hard habitats to transform into islands of biodiversity.”
The presence of shipwrecks overall increased microbial richness in the surrounding area. The distribution of biofilms also depended on environmental factors such as the depth of the water and proximity to a nutrient source like the Mississippi River delta.
While this study is focused on wooden structures, there are thousands of oil platforms and pipelines in oceans around the world. The impact of these structures requires further research to better understand.
“While we are aware human impacts on the seabed are increasing through the multiple economic uses, scientific discovery is not keeping pace with how this shapes the biology and chemistry of natural under sea landscapes,” said Dr. Hamdan.
The researchers hope that their findings will encourage further research on how built habitats are changing the world’s oceans.
The study is published in the journal Frontiers in Marine Science.