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A new scientific model is providing researchers with a comprehensive global view of the activities of clams, worms, and other invertebrate animals that burrow at the ocean's bottom. This research may offer new insights into how these mud-churning species affect ocean chemistry, carbon sequestration, and marine life globally.

Scientists have long debated the role of “bioturbation” — the excavation and stirring up of seafloor sediments caused by these species. Understanding how interactions between these animals and their surroundings influence bioturbation patterns and marine ecosystems worldwide has been challenging.

New research published in the journal Current Biology offers extensive data that may help address these questions. "Through our analysis, we discovered that not just one, but multiple environmental factors jointly influence seafloor bioturbation and the ecosystem services these animals provide," said co-author Lidya Tarhan, assistant professor of Earth and planetary sciences at Yale’s Faculty of Arts and Sciences. "This includes factors that directly impact food supply, underlying the complex relationships that sustain marine life, both today and in Earth’s past."

The study utilized global seafloor and seawater data along with machine learning techniques to map out ocean environments where marine invertebrates live and determine what factors shape environmental conditions globally.

In previous studies, researchers sought a single controlling factor to explain variations in bioturbation observations. In contrast, Tarhan and her colleagues found that bioturbation is influenced by a combination of factors acting together. The most important global factors identified are seawater depth, nutrient levels in water, and sediment composition.

"Knowing how bioturbation links to other aspects of the environment means that we are now better equipped to predict how these systems might change in response to climate change," said lead author Shuang Zhang, formerly a Ph.D. student at Yale who is now an assistant professor in the Department of Oceanography at Texas A&M University.

The study also provided insights into various ways animals excavate the seafloor — showing how similar animal behaviors can be shaped by entirely different sets of environmental factors on a global scale. For example, environmental factors driving deep-sea bioturbation differ significantly from those influencing coastal and shallow ocean waters' seafloor communities. In deep ocean waters, seawater nutrient levels remain impactful while water depth and sediment type appear less important; instead, surface ocean current velocity and organic matter enrichment play key roles.

These findings have significant implications for ocean conservation strategies aimed at mitigating habitat deterioration and protecting marine biodiversity. "Our analysis suggests that the present global network of marine protected areas does not sufficiently protect important seafloor processes like bioturbation," Tarhan noted. "Protection measures need to be better catered to promote ecosystem health."

Co-author Martin Solan from the University of Southampton added: "We have known for some time that ocean sediments are extremely diverse and play a fundamental role in mediating ocean health; only now do we have insights about where—and by how much—these communities contribute."

The research was funded by support from the Natural Environment Research Council and Yale University.