The Undersea Meadow

Life in an Eelgrass Bed

The edge of Puget Sound, where the water and the land meet, is a very beautiful place. In some places big trees grow right to the water’s edge. In others there are rocky ledges or beaches. Many birds live where the land and water meet.

From January to May, flocks of Black Brants are coming to the Puget Sound from Mexico to rest in estuaries where they can find their primary food: eelgrass.

Eelgrass grows in salt water, just a little below the surface of the water at low tide. It grows where there is a muddy or sandy bottom.

The yellow arrow points to a piece of sea lettuce (algae) that is growing on the eelgrass.

Black Brant are smaller cousins of the Canada Goose. Brants have a white neck band to compliment their smoky brown coloring. They are dabblers. They harvest eelgrass from shallow waters by tipping forward into a bottoms up position. Brants are so dependent on eelgrass that in the 1930’s when there was a widespread dieback of the plant along the east coast, Brants populations were wiped out.

Eelgrass beds are important habitats for many species of small fish as well as the young of larger fish. There is plenty to eat and abundant cover in which to hide from one’s predators. Shiner Perch are about 2 inches long at birth. They are born tail first, one at a time, and swim away. Shiner Perch grow to be 6 inches in length in about six years.

Here is a sculpin that lives, eats and reproduces in the eelgrass beds.. All sculpins have rather large heads that taper to a narrow tail. Most are a drab gray or brown color and mottled. Most do not exceed 5 inches in length when full grown. Sculpins feed on plankton, aquatic insects, small mollusks, and small fish.

The Orange Spotted (Clown) Nudibranch has a white body with orange bumps. The orange bumps are small retractible gills. They retract their gills if they are disturbed. They feed on sponges, hydroids and various other animals. Hydroids are plant-like animals that attach to floats, rocks, shells and other various things.

This is a sea slug. Another name for a sea slug is a nudibranch. This one is very easy to see on the green eelgrass. It’s orange color gives a message to predators that it tastes bad.

Nudibranchs are related to snails and slugs. They feed by rasping away at their food with file like tongues.

Here is the Hooded Nudibranch, about 4 inches long. Part of its head is a large hood with slender tentacles around the edge. It throws the hood out like a net to catch zooplankton floating by in the water. On its back are leaf-shaped appendages that are thought to aid in respiration. It moves through the water in a thrashing motion.

Above you will see nudibranch eggs.

These fish are Tube-snouts. They are bout 7 inches long. At the end of their long, thin snout is a tiny mouth with a hinged upper jaw, which bears tiny teeth directed inward. Tube-snouts eat plankton and the larvae of fish, including their own! They build nests in seaweed. The female lays the eggs, which begin hatching in about 2 weeks. The male defends the nest as the eggs develop.

Also found lurking around the eelgrass leaves are the perfectly camouflaged Pipefishes. They are relatives of Seahorses. Their tiny mouths have no teeth; they inflate their cheeks to suck in plankton. They often assume a vertical position in the water, sometimes twining their bodies around eelgrass leaves. Like the seahorse, the male Pipefish has a brood pouch in which the fertilized eggs are deposited and develop until the young hatch and swim out. The adults are about 13 inches long. The newly hatched young are less than an inch long.

Phytoplankton are microscopic plants that float in the seawater and are moved about by the currents.

Zooplankton are microscopic animals that float in the seawater. Some have appendages that provide a method of movement. Larvae of crustaceans (Crab Family), Fish and Mollusks are types of Zooplankton.

Eelgrass bed always have large amounts of detritus, decaying organic matter. It is composed mostly of eelgrass plants but may include other plants and animals as well.

This detritus is a source of great quantities of food in a complicated food web of decomposers, producers and consumers.

Gunnels are elongated, eel-like fishes that are often found mixing in with the bottom debris and marine plants.  The Penpoint Gunnel blends in well with its green body.  This fish is a predator in the eelgrass bed, eating small crustaceans and mollusks. It can get up to 18 inches long.

Can you spot the fish? On soft-bottom surfaces, there are few crevices within which to hide. Many species of flatfish have chromatophores that permit rapid adjustments of surface color and pattern to the background sediment. Here, a fish has adjusted its color to a mottled sand environment.

Here is a C-O Sole, a fish that spends it’s life on the sand or mud at the base of the plants. Newly hatched flat fish look like any other fish, but as they develop, one eye, usually the left one, migrates over to join the other eye on the fish’s right side. After this, the fish settle down to the bottom with their blind side down. This C-O Sole has very prominent eyes, it can look both forward and backwards at once!

Dungeness crabs often come to eelgrass beds to molt and lay eggs. The larvae of the crab grows much faster in an eelgrass bed that in the open water.

The female crab carries about 2 million eggs under a flap on her abdomen.

A much enlarged picture of crab larvae.

The Sunflower Star can cruise along the floor of the Eelgrass bed at the fantastic speed of 9 yards a minute! It is a large, soft sea star with 20 or more arms. Its underside carries a hidden army of tube feet. Although it is soft and floppy in our hands, it is a powerful predator.

Sitting on the bottom, or burrowing just below the surface, is the Heart Cockle. It is the prey of the Sunflower Star. If it detects the Sunflower Star coming close, it will stick out its foot and dig down into the sand or use its foot to flip it away from the predator.

On protected sandy beaches and mud flats, you may sometimes in spring or summer sea something that looks like an old rubber ring.

It is about 6 inches across and made up of grains of sand stuck together.

What looks like an old inner tube is the egg case of this snail. This is a moon snail, the biggest snail in this area. It glues its eggs and the sand together on the outside of its big, soft body. Then it crawls out from underneath. The egg case sits on the beach until a high tide comes and covers it. The sand then falls apart and the eggs are hatched at sea.

This is a young salmon. The young salmon may stay for a summer in an eelgrass bed. They need a lot of food and a place to hide from their predators so they can grow bigger before they head out to sea.

Eelgrass beds are important places for young fish to grow up. They provide abundant food, increased oxygen levels and a place to hide. Within this Eelgrass estuary, the young salmon make the changes they need to move from fresh water to salt water.

Eelgrass Beds

• Eelgrass is one of the few flowering aquatic plants in Puget Sound. It is not seaweed.

• Eelgrass beds provide a rich habitat for a lot of different organisms with interesting adaptations.

• Eelgrass beds provide the necessary protection and food for the young of many organisms.

• The food web in an eelgrass bed is very dependent on decaying organic matter; detritus.