New Research Reveals the Crucial Role of Animals in Shaping Deep-Sea Ecosystems

Animals inhabiting the extreme environments beneath the ocean floor are not merely surviving, but are actively shaping their surroundings. According to recent research, these animals are transforming their environment by burrowing through sediment and creating pathways for other forms of life to thrive.

The Discovery in the Japan Trench

A team of researchers collected sediment cores from the Pacific Ocean’s Japan Trench, located off the coast of Honshu. The team investigated the hadal zone, the deepest part of the ocean, which is approximately 4.66 miles (7.5 kilometers) beneath the surface. Despite the harsh conditions, life has been found to exist even in this extreme environment. The research was published in the journal Nature Communications.

Bioturbation: An Engineering Process

Bioturbation is the process by which animals or plants oxygenate and irrigate sediment, often through burrowing. This process affects the cycling of nutrients through sediments in an ecosystem and, in turn, influences the functioning of the ecosystem as a whole. Many creatures engage in bioturbation, including those found beneath the seafloor.

A Surprising Variety of Life

"Deep-sea benthic communities have often been perceived as having low diversity and biomass due to harsh conditions such as limited food and energy," said study lead author Jussi Hovikoski, a sedimentologist at the Geological Survey of Finland, in an email to Gizmodo. "However, recent sampling in hadal trenches has revealed a surprising variety of life, including holothurians, polychaetes, bivalves, isopods, actinians, amphipods, gastropods, and bottom-dwelling fish."

Previous Discoveries and New Insights

Last year, a team of researchers discovered macroscopic life beneath the deep ocean’s seafloor, challenging our understanding of life in extreme environments and offering clues to the possibility of life beyond Earth. The recent study builds upon this discovery, demonstrating how deep-sea environments are transformed by the turnover of sediment, which refreshes the local environment with nutrients and oxygen.

Analyzing Sediment Cores

The researchers analyzed 20 sediment cores from the Japan Trench, using X-rays to understand the structure of the sediment and the sequence of inhabitants that dwelled within it. "The data show that as the turbidity current slows down at the bottom of the trench, its sediment particle cloud condenses, locally suffocating the benthic fauna," Hovikoski explained. "This is followed by intense colonization, where opportunistic benthic species return to exploit the new nutrient-rich and oxygenated bottom sediment."

Gravity Flows and Sediment Deposition

The sediment was deposited by gravity flows, which carried silt and other matter from higher up in the trench down to the sample site. As a result, the newly arrived sediment is relatively nutrient-rich and oxygenated, providing a welcome environment for deep-sea creatures.

Burrows and Trace Fossils

In the video below, a 3D scan of the trace fossil Pilichnus can be seen, showing burrows branching downward through the deep ocean sediment, likely created by bivalves.

Changes in the Microbial Community

"Over time, as organic matter decomposes, the bottom sediment becomes anoxic, and the metabolism of the microbial community changes," Hovikoski added. "This final phase of colonization is represented by invertebrate species that utilize the microbial communities. Based on burrow morphologies, these likely include certain bivalve species."

The Dynamic Deep-Sea Environment

The deep sea is a vibrant and dynamic environment, where creatures have adapted to the absence of sunlight by developing bioluminescence, and some rocks even produce oxygen. Recent upgrades to the Alvin submersible have expanded humanity’s ability to explore the ocean’s depths, and astronomers are eager to apply these findings to the search for life on nearby moons.

Implications for the Search for Life Beyond Earth

The discovery of life in the deep sea has significant implications for the search for life beyond Earth. The findings from the Japan Trench, combined with astronomical analyses of moons like Europa and Enceladus, suggest that life could exist in the subsurface oceans of these celestial bodies. However, the search for life beyond Earth will require further exploration and research. As scientists, we are eager to send a probe to these distant moons to uncover the secrets of the universe and potentially discover life beyond our planet.