How Deep-Sea Hydrothermal Vents Create Thriving Microbial Food Webs

Deep-sea hydrothermal vents in the Gorda Ridge have been found to spread vent fluids across the center of the northeast Pacific Ocean, creating a unique hub of deep-sea biological activity. In the darkest depths of the ocean, a one-of-a-kind food web has flourished, thriving not on photosynthesis but on chemical energy given off by venting fluids.

One of the creatures found to enjoy feasting at vents at the Gorda Ridge is a vast assortment of microbial eukaryotes, better known as protists, grazing on chemosynthetic archaea and bacteria.

Deep-Sea Hydrothermal Vents Explained

In 1977, according to National Geographic, scientists exploring the mid-ocean ridge known as the Galapagos Rift stumbled upon a new discovery when temperature data spiked. Scientists discovered deep-sea hydrothermal vents.

Subsequently, the team realized that a unique ecosystem was thriving near deep-sea vents, including hundreds of undiscovered species. Despite the drastic temperatures, toxic minerals, pressure, and lack of sunlight, species found were thriving in extreme circumstances.

Hydrothermal vents are similar to hot springs or geysers on ocean food. Along the mid-ocean ridge, where tectonic plates spread apart, magma rises up and cools to form a new oceanic crust and volcanic mountain chains.

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Microbial Food Webs that Thrive in Deep-Sea Hydrothermal Vents

In a study published in the journal Proceedings of the National Academy of Sciences of the United States of America, entitled "Protistan grazing impacts microbial communities and carbon cycling at deep-sea hydrothermal vents," researchers found that protistan grazing was a key mechanism for the transport of carbon and the recycling in microbial food webs. Likewise, the team found that the mechanisms exerted a higher predation pressure at the sites of the hydrothermal vents surrounding the deep-sea environment.

Researchers note that the latest findings provide the first-ever estimations of protistan grazing pressure in hydrothermal vent food webs, which highlights the key role of diverse deep-sea protistan communities plays in carbon cycling.

Scientists found that protists consumed roughly 28-62% daily of stock of bacteria and archaea biomass in the perimeter of discharging hydrothermal vent fluids in the Gorda Ridge, located roughly 200 kilometers off the southern Oregon coast.

Additionally, researchers estimate that the grazing of protistan could account for consuming about 22% of carbon by the chemosynthetic population in the hydrothermal vent fluids. Although the fate of carbon consumed is unclear, the paper states that the protistan grazing will release some of the organic carbon into a microbial loop as a result of egestion, excretion, and sloppy feeding.

After collecting vent fluids samples, researchers conducted various grazing experiments, which presents some technical challenges. Such as prepping a quality meal for protists has proven to be difficult for the team, according to Sarah Hu, the lead author of the study and a postdoctoral investigator from the Marine Chemistry and Geoc chemistry Department at the Woods Hole Oceanographic Institution.

Authors of the paper highlight that quantitative measurements of the mechanism are vital in understanding how food webs operate at undisturbed vent sites that may occur in different places across the globe Phys.Org reports.