Plentiful, prodigious plankton!

Many animals in the ocean begin their life as drifters, or plankton. The word plankton comes from the Greek work planktos, meaning to wander. Some plankton wander their entire lives—they’re called holoplankton and include diatoms, dinoflagellates, krill and copepods. Others, called meroplankton, wander for a short time until they grow up and settle to the bottom or grow into a free-swimming form—these include most larval forms of echinoderms, crustaceans, and most fish.

Plankton are generally divided into three groups: zooplankton, phytoplankton and bacterioplankton. Zooplankton are animals; sometimes the eggs or larvae of larger animals. Phytoplankton are plants; they live near the water’s surface where there’s enough light to support photosynthesis. And bacterioplankton are, simply, bacteria: one-celled organisms that live their whole lives as plankton.

Survival is the key to success

Most zooplankton are very small but have adapted many ways to survive. Some have transparent bodies, bright colors or bad tastes. Scientists have also discovered that many tiny larval fish and crustaceans quickly become excellent swimmers with incredible endurance.

Plankton on the move

Many types of zooplankton migrate deeper into the water during the day (maybe to avoid predators and lower metabolism in colder water to save energy) and come up at night—to feed on phytoplankton. Plankton are heavier than seawater and depend on locomotion to stay in the water column. Some move through action of cilia, antennae, jointed appendages, muscle contractions and/or jet propulsion.

Making a living

Phytoplankton produce their own food through photosynthesis. Sunlight allows phytoplankton to bloom, which is then a major food source for zooplankton. Barnacle nauplii (larvae) use appendages to sieve particles from water. The young of clams and snails (veligers) use cilia to filter food particles into a “food groove” that leads to the mouth. Some developing echinoderms, such as sea urchin and sand dollar larvae, use well-developed arms to sweep food into their mouths. Some larvae may not feed at all while living as plankton, such as the blood star, which relies on energy stored in the egg.

Strength in numbers and diversity

A teaspoon of seawater can contain millions of plankton. The smallest (called picoplankton) measures less than two micrometers (micrometer = one millionth of meter) and the largest (called siphonophore) can grow 130 feet long (40 meters).

We’re all connected to plankton

Copepods, perhaps the most abundant type of animal in the world’s oceans, sustain many marine fish populations. Baleen whales, such as the humpback whale, consume 1.5 tons of planktonic animals and small fish each day.


This photo of a microscopic image shows a barnacle molt with mites crawling around inside the empty legs.

Want to learn what other animals depend on plankton? Visit the Seattle Aquarium! And learn more by reading our plankton fact sheet.

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Meet us on the beach this summer!

Stroll along almost any Seattle beach during low tide on a summer weekend and you’ll see that the shore is alive! Not only will you witness Puget Sound’s multitude of marine plants and animals, you’ll also see Beach Naturalist program volunteers: advocates for these living wonders sharing their knowledge with beachgoers.

Seattle Aquarium beach naturalists are local citizens who care about Puget Sound beaches and want to help protect them. More than 100 have volunteered to help people learn about and enjoy area shorelines. Beach naturalists know their beaches: they can help you enjoy the habitat without harming it; tell you what sea stars eat; explain why barnacles stand on their heads; describe how moon snails lay their eggs; and so much more. “The enthusiasm and excitement of our beach naturalists transfers directly to the public—it’s a wonderful, infectious thing!” beams Janice Mathisen, community outreach coordinator at the Seattle Aquarium. “To be able to meet a family and educate them on what a treasure we have here in Puget Sound is amazing,” she adds.

New beach naturalist guest blog series! 

Follow the Seattle Aquarium blog this summer season for a new guest blog series, titled “Know your beach–this week from the beach.” Guest bloggers and Aquarium beach naturalists Bobby Arispe and Jen Strongin will share with us their findings from local beaches during summer low tides.

Get to know our beach naturalists:

Bobby Arispe

Bobby is new to the Beach Naturalist program, joining after encouragement from a co-worker who is a seasoned volunteer.

His passion for the Salish Sea started when he and his wife moved to Seattle three years ago from San Antonio, Texas.

Bobby is an avid photographer and enjoys capturing his adventures of the Pacific Northwest. During the week you will find him biking to work where he leads a creative team at a local marketing agency.


Jen Strongin

Jen writes:

“I ventured westward from Albany, NY and fell madly in love with our city from the moment I arrived. It was 21 years ago this August when Seattle first charmed me with its lush, forested parks, beautiful beaches, and water and mountain views (when the skies are clear enough) all around.

I spent the first half of my 21 years here immersed in Seattle’s wonderful coffee culture. My husband and I owned and operated Victrola Coffee on Capitol Hill until 2008. We sold our business that year to spend more time with our newborn son and I have been a stay-at-home, homeschooling mama and budding photographer and naturalist ever since! It started with me taking my young son to the beach, gazing into tide pools and wanting to know more about what we were looking at. Soon, I was going to the beach by myself, every low tide I could, and following the Seattle Aquarium beach naturalists around asking questions. :)

I signed up to be an interpretive volunteer at the Seattle Aquarium in 2013, became a beach naturalist volunteer in 2014, and this will be my first year as an official member of the Seattle Aquarium staff as a beach captain. My favorite place to be is on the beach, with my camera, sharing my love and knowledge of our intertidal dwellers with the hope that I will inspire others to love and protect the Salish Sea and the ocean beyond.”

So come and meet us on the beach this summer! For beach locations and accurate directions, visit

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How I wondered my way into the Corps of Ocean Exploration, and you can too!

#1 in a series of guest blog post by Seattle Aquarium Marine Science Interpreter Lindsay Holladay:

Last week I was at Seattle Aquarium giving talks about harbor seals, instructing visitors how to gently touch sea stars in the tide pools, and interacting with scuba divers feeding the fish in the Underwater Dome. This week, I’m over 50 miles off the northeast Pacific coast, as part of a team sending remotely operated vehicles (ROVs) thousands of meters underwater to explore the ocean’s depths. How did I get here?

Image 1 Holladay Blog (002)

Lindsay on the back deck of E/V Nautilus with ROV Argus in the background.

The adventure started several years ago when a coworker introduced me to, the website that live-streams deep-sea explorations of Exploration Vessel (E/V) Nautilus. Watching deep sea research in real-time immediately sparked my sense of wonder! This ship is the ocean exploration and operation platform for Ocean Exploration Trust, founded by Dr. Robert Ballard. He is famously known for discovering the resting place of the Titanic, but far more importantly, he discovered black smokers in the Atlantic and hydrothermal vents off the Galapagos Islands.

While I already have pretty much my dream job at Seattle Aquarium, and I get to scuba dive in Puget Sound, I had very little knowledge about the deeper ocean floor just out our coastal back door. Turns out, there’s still much to be discovered, as less than five percent of our ocean has been explored. So, when I found out the Nautilus was accepting formal and informal educators’ applications to join the ship exploring off the NE Pacific, I jumped at the opportunity. I applied, made it through a rigorous interview process, and was awarded the Science Communication Fellowship!

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Lindsay prepping ROV Argus for a dive with Deck Chief Mark DeRoche and scientist Sarah Seabrook, a researcher from Oregon State University.

Fast forward a few months of training and preparation and I am now sitting in the control van atop the ship, watching the ROVs explore the wreck we only moments before identified as the SS Coast Trader. This is historic because the merchant vessel was torpedoed by a Japanese submarine in 1942. I know the history is significant, but I’m more struck by the hundreds of huge lingcod, yellow-eye rockfish and spiny dogfish sharks living on this unintentional artificial reef. The same species I visit every day in Seattle Aquarium’s Underwater Dome, I’m now observing at 400 feet deep alongside live broadcast viewers around the world. Something I know from my time at the Seattle Aquarium is that rockfish can live over 100 years, so there’s a chance some of those rockfish were alive when the ship sank 74 years ago.

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Lindsay with Hercules, a specialized ROV capable of collecting niskin bottle water samples, sediment cores, and biological and geological specimens.

Finding and surveying this wreck is just one of our varied expedition goals over the next three weeks. Dr. Robert Embley, senior researcher at NOAA/PMEL and lead scientist on this expedition, explained today, “We have a real potpourri of scientific objectives,” including mapping methane seeps, collecting sediment cores as geologic and biologic samples, exploring a rare deep-water sponge reef, and cataloging deep-sea coral DNA from water. My role in the expedition team is to help communicate the science, engineering and excitement of ocean exploration out to a global network of viewers. What is so amazing is that whether observers are tuned in from their offices, classrooms, or from the Nautilus control van, we are all seeing the ROV footage together for the first time. My watch is from 8 to 12 morning and night when ROVs are active. If I’m on watch, you can hear my voice along with my teammates in the control van—type in your questions for us, and follow along with real-time deep-sea discoveries. So tune in to and explore along!

About Lindsay:
Lindsay Holladay is a marine science interpreter at Seattle Aquarium and a 2016 Science Communication Fellow with the Ocean Exploration Trust. She is currently spending three weeks aboard the E/V Nautilus, exploring methane seeps and deep-sea ecosystems along the Cascadia Margin.


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What are those gray toilet plungers on the beach?

It’s a question often asked of our beach naturalists when they volunteer on local shorelines during low-tide days each summer. The photo below offers a great hint. The animal is a moon snail, and the gray “plunger” is the snail’s egg case. They’re a common sight on Seattle beaches in the summertime, and they are commonly mistaken for litter. They look like rubber, but they are actually made of sand, with a middle jelly layer that contains the snail’s eggs. The mother moon snail turns upside down to lay her egg mass, and as it emerges, the mother’s mucous adheres sand to the outside of the egg mass, and the collar shape forms as she moves her shell and foot. The eggs (roughly 500,000 of them) take about six weeks to hatch.

moon snail 01

In the photo below, you can see a microscopic peek inside that egg collar (for a chance to check out the microscope that captured the image, visit the Aquarium for Family Science Weekend, May 28-30!).

moon snail 02

Another common sight on the beach that invites questions? Clamshells, like the one pictured below, with sunken holes near the hinges. How do the holes get there? Perhaps you guessed it—they’re the work of moon snails. They use their radula (or rasp-like structure of tiny teeth) to drill holes in clamshells—then it’s clam on the half shell for lunch!

moon snail 03

Interested in learning more about the amazing creatures on local beaches during low tide? Join Seattle Aquarium beach naturalists this summer! They’ll be stationed at a dozen Puget Sound shorelines on low-tide days throughout the summer. Click here for the complete schedule, locations and accurate directions.

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Spotted seahorses now at the Seattle Aquarium

Five spotted seahorses (Hippocampus kuda) are now on display in our Tropical Pacific exhibit! They join our one lined seahorse (Hippocampus erectus).

The Seattle Aquarium has traditionally displayed lined seahorses—but we made the decision to switch to spotted seahorses because they’re found in the tropical Pacific (and are thus a good match for the theme of the exhibit), while lined seahorses are native to the Western Atlantic and Caribbean.

Spotted seahorses prefer sea grass habitats in sheltered bays and estuaries. They feed on small invertebrates such as shrimp. This species can be nearly 12 inches in length, but animals often appear shorter due to the way their tail curls up. They are variable in color, despite their alternate common name: yellow seahorse.

Our sole remaining lined seahorse is not the only fish at the Aquarium that mixes with a school of a different species. Look for the following loners in our exhibits the next time you visit!

pile perch

Pile perch with blue striped perch in the Underwater Dome

Look for pile perch’s more deeply forked tail and the dark, vertical bar on the side of this fish’s body. In contrast, the blue striped perch has many thin horizontal stripes.

yelloweye rockfish

Yelloweye rockfish with canary rockfish in the Octopus Exhibit

The juvenile yelloweye has a deep red-orange color and two prominent white horizontal stripes, which fade away as the fish matures. Canary rockfish have only one prominent white stripe, along their lateral line.

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