Abstract
The deep sea and its inhabitants are often perceived as isolated from human society. However, this vast and largely unexplored environment—the largest living space on Earth—is vulnerable to human impacts and provides key services that sustain our planet and society. Diel vertical migration (DVM), a behavioral adaptation to living in the deep sea and the largest migration on Earth, occurs every night when organisms ascend to the surface ocean to feed before swimming back to the deep sea to hide from predators. DVM plays a vital role in sustaining ocean food webs and the marine carbon cycle, facilitating deep-sea carbon storage (sequestration). To engage students in exploring the deep sea and vertical migration, we developed a lesson plan styled as a “murder mystery investigation.” Designed for middle and high school students, this lesson immerses learners in the process of scientific discovery, transforming them into investigators tasked with solving an open-ocean mystery involving marine organisms, including deep-sea species. Students explore deep-sea habitats and biological adaptations, analyze environmental data and ecological information, and explain key concepts such as vertical zonation in the ocean, adaptations to living in different depth zones, and DVM. Class discussions, challenge questions, and handouts allow students to apply critical thinking and demonstrate their comprehension of scientific principles. Beyond content knowledge, this lesson has students think like scientists, encouraging skill development in data interpretation, hypothesis testing, and collaborative inquiry.