The ocean floor is a graveyard to over three million shipwrecks, most of them made of wood. While they do alter the microbial habitat of the seafloor, new research has found that the impact is not all bad, and that they may even boost productivity.
“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,” says author Dr Leila Hamdan of the University of Southern Mississippi, US.
A study on the microbial life around two 19th-century shipwreck sites in the Gulf of Mexico investigates the diversity among these human-made habitats. Samples of biofilms were collected using pieces of pine and oak placed at the shipwreck, and up to 200 metres away from the shipwreck. After fourth months, microbes were measured using gene sequencing, including all bacteria, archaea and fungi
“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,” says 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 results showed that bacteria preferred oak over pine, but that the type of wood had less impact on archaea or fungi diversity. Diversity also varied depending on the proximity to the wreck site, where surprisingly, the greatest diversity was not at the wreck site, but peaked at 125 metres away. The depth of the water, and proximity to a nutrient source like the Mississippi River delta, also played a part in the distribution of biofilms.
Though this study informs on wooden shipwrecks and the impact on microbial diversity, there are also thousands of oil and gas platforms and oil pipelines in the Gulf of Mexico alone that warrant further research to understand their microbial impacts too.
“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 undersea landscapes,” says Hamdan. “We hope this work will begin a dialogue that leads to research on how built habitats are already changing the deep sea.”
Read more about this research published in Frontiers in Marine Science.
Qamariya Nasrullah holds a PhD in evolutionary development from Monash University and an Honours degree in palaeontology from Flinders University.
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