Microorganisms have been lying dormant for around 100 million years almost a hundred meters below the bottom of the pacific ocean. This is what japanese and u.S. Researchers write in the journal "nature communications.
They were able to propagate these tiny creatures under laboratory conditions. The team took several drill samples from the bottom of the south pacific ocean gyre from the research vessel joides resolution. The scientists drilled up to 74.5 meters into sediment layers that were formed between 13 million and 101.5 million years ago.
For decades, scientists have been collecting sediment samples from the bottom of the oceans to better understand past climate, plate tectonics and the deep marine ecosystem. A team led by microbiologist yuki morono from the japanese marine research agency JAMSTEC has now led an expedition to the south pacific ocean gyre. This covers about ten percent of the ocean’s surface, encompasses 37 million square kilometers and is one of the least explored regions on earth.
Because of the specific environmental conditions that prevail there, it is also often referred to as marine desert: the solar radiation in this area in the middle of the south pacific is very high, the uv index extreme and neither dust particles nor other influxes from the land still reach here. As a result, the water is not only extremely clear, but also very low in nutrients. "Our central question was whether life could exist in such a nutrient-poor environment, or whether this was an inanimate zone," yuki morono summarizes in a release. "And we wanted to know how long microbes can maintain their life with almost no food."
The seabed contains sediment layers consisting of so-called marine snow, i.E. Organic debris from the ocean surface, as well as dust and particles carried by the wind and ocean currents. Small life forms such as microbes are trapped in this sediment. These microbes or microorganisms include microscopic organisms that are invisible to the naked eye, such as bacteria, microalgae or protozoa. Most of them are single-celled organisms, but some fungi and algae with a coarseness of less than 0.03 millimeters are also part of it.
Using specific laboratory procedures that have been refined over the course of the study, the scientists treated the samples to stimulate the growth of the microbes contained in the sediment. In fact, those were not fossilized fossils, but were largely viable aerobic bacteria capable of dividing.
"At first i was skeptical, but we realized that up to 99.1 percent of the microbes deposited 101.5 million years ago were still alive in the sediments and ready to eat," said morono.
For his co-author steven D’hondt, this is the most exciting finding of the study: "it shows that life in the ancient sediments of the world’s oceans is unlimited, that there are still living organisms in the oldest sediments with the least amount of food, and that they can return, grow and reproduce."