Wooden shipwrecks from the 19th century can fuel massive deep-sea microbiomes
It is estimated that there are three million shipwrecks around the world, and only less than 1 percent of the total wreckage has been discovered yet. While it’s exciting to uncover the story behind these shipwrecks and unearth their locations, it is also fascinating to know that they can turn out to be thriving habitats for sea life, according to a new study.
Microbes are essential to all of Earth’s ecosystems; they’re the fundamental contributors to ecological processes such as fixation, production, and decomposition and are the base of the food chains of their ecosystems. A group of researchers from the University of Southern Mississippi and Stockholm University chose two wooden shipwrecks that sank in the Gulf of Mexico in the late 19th century to study the microbiome living in the sites.
The researchers set down pine and oak pieces at different distances from the shipwreck, ranging from 0 to 650 feet (0 to 200 meters), to collect samples of the microbiome. In a period of four months, the samples were ready to reveal surprising results.
The most diverse composition was recorded on the samples placed at about 125 meters away from the shipwrecks, not on the samples that were closest to the site as one would probably expect. So one of the factors that affected the diversity was the proximity to the sites. Additionally, the type of wood had the most impact on the bacterial diversity, and it didn’t do much when it came to other organisms, 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. 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," said corresponding author Dr. Leila Hamdan of the University of Southern Mississippi.
It was concluded that shipwrecks played an essential role in increasing microbial richness in the sites while changing the microbiome formation and dispersal. The overall distribution of the microbiome changed based on the water depth and proximity to nutrient sources.
Wood arrives on the seabed from natural and anthropogenic sources (e.g., wood falls and wooden shipwrecks, respectively) and creates seafloor habitats for macro-, meio- and microbiota. The way these habitats shape microbial communities and their biogeographic patterns in the deep sea requires study. The objective of this work was to investigate how historic wooden-hulled shipwrecks impact the dispersal of wood-colonizing microbial biofilms. The study addressed how proximity to wooden shipwrecks shapes diversity, richness, and community composition in the surrounding environment. Study sites included two historic shipwrecks in the northern Gulf of Mexico identified as wooden-hulled sailing vessels dating to the late 19th century. Two experimental microbial recruitment arrays containing pine and oak samples were deployed by remotely operated vehicle proximate (0–200 m) to each shipwreck and used to establish new wooden habitat features to be colonized by biofilms. The experiments remained in place for approximately 4 months, were subsequently recovered, and biofilms were analyzed using 16S rRNA gene amplification and sequencing for bacteria and archaea and ITS2 region amplification and sequencing for fungi to determine alpha diversity metrics and community composition. The work examined the influence of wood type, proximity to shipwrecks, and environmental context on the biofilms formed on the surfaces. Wood type was the most significant feature shaping bacterial composition, but not archaeal or fungal composition. Proximity to shipwrecks was also a significant influence on bacterial and archaeal composition and alpha diversity, but not on fungal communities. In all 3 domains, a peak in alpha diversity and richness was observed on pine and oak samples placed ~125 m from the shipwrecks. This peak may be evidence of an ecotone, or convergence zone, between the shipwreck influenced seabed and the surrounding seafloor. This study provides evidence that historic wooden shipwrecks influence microbial biofilm dispersal in the deep sea.
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