At low tide, beachgoers may catch a small glimpse of the underwater world. Divots in rocks allow for water to become trapped and serve as a mini ecosystem for small creatures like snails, hermit crabs, green anemones, and juvenile fish like sculpins. This is just a small fraction of the life that lives below the surface.

Life in the tidepools must be extremely robust. Due to high wave action, direct exposure to sun and air, and limited food availability, the animals and algae that live in these pools are specially adapted to overcome these challenges. For example, barnacles close themselves into their shells to prevent drying out. Anemones, filled with watery gelatinous substances, stay moist through the heat of the day.

It can be concerning when you see an animal like a sea star out of the water during low tide, but don’t worry! It is best to avoid touching these creatures and let nature take its course. Remember that these intertidal species are adapted to surviving without water for extended periods of time.

The sand flats uncovered by the low tide makes for a great beach walk. When the tide rises, it’s a temporary ecosystem for sand-dwelling creatures like burrowing anemones and flatfish. There’s no place for animals to hide from predators in this wide open area. They must take another approach and use camouflage. The sand-colored flatfish are nearly impossible to notice until they move because they look exactly like the sand. Their bodies are thin with two bulging eyes on one side of their body so they can stay alert for predators. When they are not hiding, they are hunting for worms, shrimp, and other small creatures that live in the sand. When the tide flows out again, the mobile animals flee to the safety of shallow eelgrass beds. The sessile organisms brace themselves to survive in the air until the tide rises again.

Eelgrass is a flowering marine plant that serves one of the most important roles in the ocean ecosystem. Most of what you can see of the eelgrass is the long ribbon-like blades which flow with the current. Their hidden roots are just as important, though. These roots can connect one organism for over a mile long and sequester carbon. This means they can remove CO2 from the atmosphere and trap it and turn it into organic carbon. With the increase in atmospheric CO2, this is incredibly important. Seagrasses, including eelgrass, act as “carbon sinks”—a term scientists use for areas that are natural reservoirs which store organic carbon. Carbon is an important element, as all organisms need it to grow, but is harmful when too much organic carbon is converted to carbon dioxide.

Seagrass beds offer protection for juvenile organisms like young fish and crabs. Many animals also choose to spawn here, like Pacific herring and salmon. Herring play crucial roles in the ecosystem at every stage of life, supporting the food web and the animals that feed on them. Some of our favorite marine mammals, like the Southern Resident orca whales unique to the Salish Sea, rely heavily on Chinook salmon as a source of food.

Since seagrasses grow in shallow water to be able to absorb sunlight, much of the construction that happens on land near the shore affects seagrass communities. In order to form ports for boats, seagrass communities are dredged and removed. This is devastating to animals that rely on the meadows for safety and to the soil that has worked to trap carbon for so long. Even runoff from the land can harm seagrass ecosystems because of the algal blooms they cause, making it harder for photosynthesizing blades to receive sunlight.

In the winter, the bottom of Edmonds Underwater Park is sandy and bare, with flatfish darting about. In the summer, sea lettuce algae grows like a thick blanket to cover the sandy bottom. The layers of algae serve as a great hiding spot for many juvenile fish, crabs, and shrimp. Turning over the delicate leaves might reveal a helmet crab, kelp crab, or a white lined dirona nudibranch. Sea lettuce is unique from other algaes because it serves as a bioindicator of pollution. Many species of algae do not tolerate high levels of nutrients, which come from waste runoff and other sources of pollution. Sea lettuce, however, can withstand high nutrients and can therefore indicate when the water may be polluted. It is normal for sea lettuce to be present in the summer months, but researchers keep a close eye on the density of this algae to make sure pollution does not influence its growth.

Edmonds Underwater Park is home to many human-made rocky reef structures, including the jetty and underwater rock cairns. While most of the underwater area is flat, structures are essential for drawing life. Animals flock to these structures for protection and to find food. Rockfish thrive on the rocky reef, hence their name. Crevices between rocks serve as hiding spots for smaller rockfish, while the larger ones swim above and hunt for small crustaceans, other fish, and algae growing on the rocks. 

There are many structures and diver reefs at Edmonds Underwater Park. Just like the rock reefs, structure attracts life to the park. Boats receive a second life underwater as they become a hotspot for creatures to live and grow. From the giant Lopez Pontoon at the western edge of the park, to the smaller ships scattered throughout, these structures provide great hiding places for all sorts of animals and schooling fish.

Many people wonder about the buoys floating above the Edmonds Underwater Park. They are not crab pots, as this is a protected area. The buoys mark an underwater grid system used by divers to navigate, and also serve as safety devices. The buoys help keep boats out of the park and serve as a rest stop for divers. As a diver descends down a buoy line, they must watch out for marine life covering the ropes. Sea anemones, barnacles, crabs, and algae thrive on the rope. Fish also gather around these lines looking for food and protection. If you notice an orange-tan leathery mass growing on a rope, look closer and you might find that this mass is a population of colonial Didemnum tunicates. While tunicates are an important food source for many small invertebrates, this specific species of tunicate is invasive to Puget Sound and the park. When invasive species enter an ecosystem, they do not have a natural role in the food web—they have no natural predators, and are successful because they outcompete local species. The invasive tunicates in the park overgrow buoy lines and sides of wrecks, taking away space from the local organisms that usually make their homes here. The can also grow right over already-established sessile organisms. In an effort to protect the park, Bruce and his team are keeping an eye out for these tunicates and removing the colonies.

Pelagic animals exist freely in open water. The most essential organisms to the entire world, called plankton, live in the pelagic zone. Plankton consists of phytoplankton, zooplankton, and animals floating in the currents. They can be as big as the lion’s mane jellyfish or microscopic. Despite their size, they serve one of the most important roles in the global food web and carbon cycle. Phytoplankton are primary producers and create up to 70% of the oxygen our planet needs. 

Phytoplankton function similarly to photosynthetic plants converting sunlight to oxygen. In this process, they also sequester carbon from the atmosphere. One major group of phytoplankton known as diatoms, a marine algae, are responsible for producing almost half of Earth’s oxygen! They are made of silicon and are beautiful to look at under a microscope. Since phytoplankton need sunlight, they are found in the top portion of the water column.

Zooplankton is another kind of tiny organism, and they are the primary consumers of phytoplankton. Many animals, including whales, feed on zooplankton. Animals that have a pelagic larval life stage are a type of zooplankton. Baby crabs have a planktonic life stage and move throughout the ocean as such until they are able to settle and grow into their full form.