Our planet’s surface is 71% water — with five vast oceans that span a range of temperatures and shades of blue. Humans have long loved and feared these oceans. They sustain us and other animals, help regulate our climate, and offer endless opportunities for awe and joy. But our relationship hasn’t always been smooth. The ocean can be a threat to us, and we — with our expanding environmental footprint — can be a threat to it. On this episode of The Pulse, we dig into the science of our oceans: Their connection to our survival, the threats they face, and the secrets they hide.

We hear about the mystery of the great jellyfish boom, and why seaweed might just be the next hot (and sustainable) food trend. We also explore recent discoveries about the fate of plastic in our oceans — and why the impact goes deeper than we once thought.

Also heard on this week’s episode:

• Some scientists are calling it an invasion — across the world, jellyfish are swarming the coasts, leading to beach closures, and even several deaths in Australia and the Philippines. Gisele Regatao reports on what researchers are saying is behind this unprecedented boom.
• You may know Ellen Horne from her years working at Radiolab. But before that, she had another vocation — marine conservationist. Her passion for the field withered with the arrival of aquaculture, a method of seafood farming that she saw as an insurmountable threat to ocean ecosystems. But now, a lifetime later, Horne takes a second look, and explains why that could be changing. We also talk to Amy Novogratz, one of the founders of spark.nl/">Aqua-Spark, a global firm that’s trying to reinvent aquaculture in a more sustainable way.
• Before her death at 25, writer Mallory Smith spent years documenting her life and battle with cystic fibrosis in a series of raw and eloquent journal entries that comprise the newly published memoir, “Salt in My Soul: An Unfinished Life.” We talk with her mother, Diane Shader Smith, who assembled the book, about Mallory and her deep connection with the ocean.
• Marine biologist Rick Stafford, who’s based at Bournemouth University in southwest England, introduces us to underwater soundscapes and explains how our human sounds affect fish.