Tiny, Essential Ocean Creatures

The Ocean's Heart: The Tiny Creatures Essential to Life 

by Jilanne Hoffmann; illus. by Khoa Le 

32 pages; ages 6-10

‎Millbrook Press, 2026

theme: ocean animals, ecology, food web

Far below the ocean’s surface live tiny, restless creatures called zooplankton. They are the ocean’s heart.

Some are so tiny that you need a microscope to see them. Others you can see with your naked eye. The one thing they have in common is they drift along with the ocean’s currents. Like other animals, zooplankton need to eat to survive, and therein lies a problem: to get food, the zooplankton need to rise to the surface where their food supply – tiny plants – thrive. But once in the light, zooplankton are visible to predators! How can these tiny critters eat without being eaten? More importantly, will any of them make it to the end of the book?

What I like love about this book: I love Jilanne’s lyrical language as she takes us on the dangerous journey zooplankton make nightly to get their dinner. And there’s the race – will they get their fill before the larger ocean animals see them and come hunting? Jilanne encourages readers to cheer for the plankton, and to celebrate their success when they make it. There are two perfectly placed book turns where we need vertical pages to see them paddling, rowing, spinning and spiraling up, up, up… and another as they make the return journey, diving and paddling down, down, down to safety. The illustrations bring these tiny creatures to life on the page. And back matter provides more information for curious kids (and adults!) who want to know more about the ocean’s food web. There’s even a list of ways you can help zooplankton! I don't usually give stars, but I'd give this one Five Copepods 

The title of this book is so intriguing that I just had to ask Jilanne One Question:

Me: Can you tell us how you came to view the zoo plankton as the "ocean's heart"?

Jilanne: Great question! I have a tendency to think in metaphor, even when I'm not actively searching for one. My brain suddenly makes a connection and then that metaphor may trigger another one. And sometimes another. This was the case for zooplankton. I had originally written THE OCEAN'S HEART in first person POV from the perspective of the ocean, where Mama Ocean talks about her tiny ones, her children, the ones that are dear to her heart. And I kept that metaphor even as I switched to third person POV, because zooplankton not only form part of the carbon cycle (where they shuttle carbon into the deep ocean after having eating phytoplankton), but those little swimmers (defying their name, they don't just float) also circulate ocean water, sending cold water upward and warm water downward as they migrate each night. 

Scientists now believe that their movement is as important to ocean water circulation (and the circulation of nutrients) as the wind and tides, which is huge! And what does the heart do? It circulates oxygen-rich blood to all parts of the body, and returns carbon dioxide to the lungs that then needs to be exhaled. So, I began thinking of phytoplankton as the ocean's lungs, absorbing that carbon dioxide and releasing oxygen to its waters and the creatures that live there. And then my mind made another leap....whales are like the ocean's muscles...because they pump iron. After eating tons upon tons of zooplankton, effectively concentrating all of the iron from zooplankton in their digestive systems, whales return it to the ocean and to other critters and phytoplankton that need it in the form of poop. The healthier the whale population, the more they pump (poop) iron, the healthier the population of phytoplankton and other critters. So, there you have it, the heart, lungs, and muscles of the ocean. An extended metaphor that will stay with me forever.

Beyond the Books:

Find out more about plankton in this video, The Secret Life of Plankton  and at Woods Hole’s website.

Compare a zooplankton’s nightly migration to your own life. Jilanne compares a zooplankton’s journey to the ocean’s surface to a human swimming 125 miles – and that’s just one way. The zooplankton have to return home, too. Every night! If you traveled 125 miles from your home, where might you end up? For me, that would be close to Russia or Norway – both towns in upstate New York!

How long would it take you to walk 125 miles? The average walking speed of an adult is around 3 miles/hour. Four, if they walk briskly. Think about how far you could walk at a time… and snack breaks. 

Jilanne is a member of the STEAM Team Books group. I reviewed her book, A River of Dust a couple years ago on this very blog. You can find out more about Jilanne and her books at her at her website jilannehoffmann.com. Folks who pre-order her book (before March 3) can get entered in a raffle for amazing prizes. You can preorder a copy here - then direct message her on IG, BlueSky, or Facebook (links at that page) to let her know you'd like to be entered in the raffle. 

 

You can find more about recently released STEM and STEAM at www.steamteambooks.com

Today we’re joining Perfect Picture Book Friday. It’s a wonderful gathering where bloggers share great picture books at Susanna Leonard Hill's website. Review copy provided by the publisher.