By Annabelle Adams-Beyea
Today, the surface of Mars is mapped better than the surface below the ocean. From what scientists have discovered, the ocean floor consists of many diverse environments supporting a plethora of life. One critical component of the ocean floor that many may not think of as a habitable environment is the subsurface layer of the ocean called the ocean crust. This environment is of great importance to scientists because the majority of global bacterial biomass is predicted to exist in deep subsurface environments such as the ocean crust. Ocean crust microbes could contribute to a wealth of undiscovered information including providing insight into life on other planets, an understanding of ocean nutrient cycling and global chemical cycling, the discovery of new enzymes for industry, and adding to the tree of life as more novel microorganisms are found.
The ocean crust is the layer of rock that lies below the ocean water. Parts of the ocean crust are directly below the water column while other parts lie beneath a sediment layer. Small holes throughout the rock allow for ocean water to enter the crust and circulate through it. At any given point, about 2% of the ocean volume is contained in the oceanic crust with the total volume of the ocean circulating through this rock every 100,000 – 1,000,000 years. As the water circulates through, seawater-rock chemical reactions provide nutrients for microorganisms allowing them to survive in this nutrient-poor, high pressure, and high-temperature environment.
The Orcutt Lab studies what microbes are living within the ocean crust and how they are surviving in this extreme environment. In 2011 and 2019, research cruises traveled 100 miles off the coast of Washington State in the Pacific Ocean to the Juan de Fuca oceanic plate. There, crustal fluid was accessed by using a well drilled into the ocean crust. During these research cruises, a robot travels from the research ship down to the well, collects crustal fluid, and brings pristine crustal fluid back onboard the ship.
Within the crustal fluid samples from 2011 and 2019, a bacteria called Aminicentates was identified at the phylum level. Among taxonomic rankings, the phylum level is very broad – humans along with tigers, sea squirts, and sharks are all within the same phylum even though these organisms are very different. Due to the broad level of classification for Aminicentates, it is not surprising that this bacteria has been found in many diverse environments such as marine environments, freshwater environments, soil, bioreactors, and within the ocean crust.
This summer, Bigelow Laboratory for Ocean Science Scientists Dr. Booker, Dr. Brown, Dr. Orcutt and I are investigating how the crustal fluid Aminicentates relates to other environmental Aminicentates adding to the limited information about the classification of this bacteria. Additionally, we are researching life strategies Aminicentates may use to live the ocean crust, and what implications these strategies may have on the local ocean crust environment, nutrient cycling in the ocean, and global chemical cycling.
Annabelle Adams-Beyea is a The New School student in Bigelow Laboratory for Ocean Science’s Research Experience for Undergraduates program. This intensive experience provides an immersion in ocean research with an emphasis on state-of-the-art methods and technologies.
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