Grove City College Professor of Mechanical Engineering Erik J. Anderson’s research and expertise in fluid dynamics is part of a major study that could lead to breakthroughs in the study of blue whales and the overall health of the world’s oceans.
Anderson is a co-author, along with scientists from New Jersey Institute of Technology, Georgia Tech, Stanford and UC Santa Cruz, of “Remoras pick where they stick on blue whales,” a peer-reviewed article published by the Journal of Experimental Biology. The study is gaining attention internationally, with coverage by The New York Times, New Scientist, SciTechDaily and Science Daily.
The article looks at where and how remora – popularly known as suckerfish – attach themselves to larger marine animals such as sharks, marlin, turtles, dolphins and whales. It’s a symbiotic relationship. Remoras hitching a ride on larger animals are able to travel farther, avoid predators, eat the “crumbs” of prey and find mates. In return they feed on parasites that might otherwise impact the larger animal’s health.
Marine biologists are interested in remora for many reasons, but in the case of this study, their ability to adhere to blue whales in specific conditions and the locations they choose were the issue. The answers the research yields may have a major impact on the design and placement of instrumented tags that are used to track whales as part of efforts to understand their biology and protect them, Anderson said.
“We were interested in three questions,” Anderson said. “One, what is the drag on a remora when it is riding on a whale, two, what does that tell about where they decide to attach and how they behave near the whale, and three, can remora help whale biologists decide what the best locations are to put tags on whales?”
Anderson specializes in fluid dynamics in research conducted on campus with students and at Woods Hole Oceanographic Institution in Massachusetts.
“This work was especially interesting to me because it involved boundary layers--the thin layer of fluid around any object with flow moving over it where a lot of important things happen. The flow in the boundary layer determines the ‘friction drag’ on an object, like a swimming whale or fish,” Anderson explained. “Understanding the drag on organisms living in moving fluids can be a window to understanding their behavior and energy use--information that's important if you are trying to monitor the ecological health of a species.”
Many organisms are adapted to minimize drag and energy use, Anderson said, but the twist in this work is that it involves an organism – remora – that live in or partly in another’s boundary layer. “It reminds me of those Russian stacking Matryoshka dolls,” he said.
To determine the drag on a fish living in the boundary layer of another swimming organism involved using existing aerodynamic data about the drag of nearby or attached objects – which is often greater than the sum of the drag of the two objects when measured separately – and calculating the flow of over a blue whale using computational fluid dynamics using a supercomputer in Barcelona, Spain.
“We needed an international and multidisciplinary team of scientists to pull this off, including biologists, programmers, and engineers,” Anderson said.
The study utilized the first-ever continuous recording of remora behavior on a host organism, using advanced biosensing tags with video recording capabilities. The footage shows remora freely moving around whales 30 times their size, using previously unknown surfing and skimming behaviors along special low-draft traveling lanes in the boundary layer just off the surface of the whale’s body. The researchers found that drag in that area is reduced by up to 72 percent compared to the much more forceful “free stream” just above it.
“In the end we found that remora do generally seek out locations on whales where they experience lower drag, but we also learned that their suction device on the top of their head is so strong that they can hang on just about anywhere if they want to--even the whale's tail fluke! Nevertheless, in general, they go for the easy ride,” Anderson said.
“This probably saves the remora energy and makes life less costly as they hitchhike on and skim over the whale surface like a NASA probe over an asteroid like it is some mini-world,” he said. “Hopefully the work will inform whale tagging both in terms of where to place tags and how to design the suction cups used to hold them on. Those remora clearly know a thing or two about hanging on!”
Anderson has been conducting research of whale tags and remora for several years with students in his lab at both Grove City College and at Woods Hole Oceanographic Institution (WHOI) in Massachusetts, where he is a guest investigator. Anderson’s student Spencer Garborg ’15 was an author on a 2017 paper regarding whale tags in the journal PLOS One, as was Ellen (Turner) Zerbe ’17 on a 2019 paper in the IEEE Sensors Journal. These kinds of opportunities for undergraduate research in Anderson’s lab are made possible by the Swezey and Jewell, Moore and MacKenzie funds, and have propelled students to internships and graduate work at schools such as MIT, Princeton, Vanderbilt, the University of Alabama and Boston University.
In addition to Anderson, a number of scientists contributed to the article. They include lead author Brooke E. Flammang, Simone Marras, Abhishek Mukherjee and Haley E. Amplo of New Jersey Institute of Technology; Jeremy A. Goldbogen and David E. Cade of Stanford University; Oriol Lehmkuhl, Guillaume Houzeaux and Mariano Vázquez, Department of Computer Applications in Science and Engineering, AQ1 Supercomputing Center, Barcelona; Michael Beckert and Jason H. Nadler of Georgia Tech Research Institute; John Calambokidis of Cascadia Research Collective; and Ari S. Friedlaender of University of California Santa Cruz.
(Image credit: Stanford University & Cascadia Research Collective)