Undergraduate led study on food webs in ocean’s deepest trenches

Andrew Tokuda, a senior in SOEST’s Global Environmental Sciences (GES) program, is the lead author of a recently published scientific study on the food webs in the Mariana and Kermadec ocean trenches. This rare achievement by an undergraduate student is the result of Tokuda’s passion and keen interest in natural science, exceptional mentors and impactful research opportunities available to students in the School of Ocean and Earth Science and Technology (SOEST).

The study, published in Deep Sea Research and conceived by Tokuda’s mentor and research advisor, UH Mānoa oceanographer Jeffrey Drazen, was the first to analyze interactions between echinoderms, such as sea stars, urchins and sea cucumbers; crustaceans, such as amphipods and shrimps; and fishes in these trenches in the western Pacific Ocean.

Given the remote location and challenging conditions in the ocean’s hadal zone—depths between 20,000 to 36,000 feet—little is known about the sources of nutrition and how energy cycles through food webs in these ecosystems.

“Our research showed that food webs in the Mariana and Kermadec trenches are very complex and dynamic!” said Tokuda. “We gained numerous insights from this work such as the possibility of multiple sources of nutrition in each trench, food web interactions being depth-dependent, and even trench topography influencing food input to trench communities.”

In each trench, Tokuda, Drazen and their co-authors collected organisms using baited traps, remotely-operated vehicles and sediment cores. With partial support from the UH Mānoa Undergraduate Research Opportunities Program, they assessed the various isotopes of carbon and nitrogen in the ecosystem to determine how nutrients flow through food webs and analyze predator-to-prey relationships.

Their findings suggest that hadal inhabitants are strongly connected to a variety of larger scale physical and chemical processes and that these animals may ultimately have a substantial impact on the carbon cycle, which is essential for all life on Earth. 

“It has been thrilling to be able to work with samples from one of the most inaccessible habitats on the planet,” said Tokuda. “It is one of the things that has made this research experience incredible.”

Sharing science and aloha

Ever since he was a child, Tokuda has been passionate about natural sciences, exploration, and geopolitics. He came to SOEST after graduating from Roosevelt High School on Oʻahu to pursue his interests and goals.

“I have definitely been fortunate to have exceptional mentors, like Jeff Drazen, who has been very patient with my learning and inspired me to spread knowledge to others about the endless wonders of the deep-sea! I have had the great opportunity to share our research through various conferences and even with my own friends.”

As a cadet in the UH Mānoa Warrior Battalion, Tokuda is set to commission as an officer in the United States Army upon graduating college.

“My ultimate goal is to contribute as much as I can to the country I truly love and to facilitate the dialogue between military personnel and environmental scientists for the betterment of our future generations,” said Tokuda.

Related UH News Story: Soldiering in the pursuit of excellence, November 5, 2018

Nicknamed “Fisherman Andy” by friends and colleagues in the GES program, Tokuda is known for his enthusiastic and generous spirit.

“Andrew is a role model to those who have the privilege to know him and sharing his achievements will no doubt inspire more GES students to shoot for the stars,” said Noah Howins, graduate researcher in the Oceanography Department. “He is an exemplary student, human being, and young scientist.”

“Andrew has been a fantastic student and citizen in the GES Program,” added program director Michael Guidry. “Not only has he excelled academically in both his coursework and the published research mentored by Dr. Drazen, but also as a positive mentor for many other GES students.”

“He’s going to be a leader,” said Drazen.

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