It's a Jungle Down There!

LIFE ON THE EDGE
by Nancy Sefton

Just offshore, throughout our Puget Sound saltwater labyrinth, there’s a special shallow-water world that few people are aware of: miniature green jungles full of creatures locked in a life-and-death struggle to survive.

The ribbon-like Kelly-green leaves of perennial eelgrass, a flowering plant, grow to a half inch wide and four feet long, creating meadows beneath the shallows near shore, undulating with the tidal currents like prairie grasses in the wind. The residents are diverse. Seafood lovers take note: much of our Dungeness and red crab harvests, and even the health of our salmon runs, depends on the health of these eelgrass jungles.

This diagram shows the variety of marine species that depend on eelgrass beds.

They’re breeding grounds for fish of many species, and an important sheltering nursery as well. Herring lay their eggs right on the blades; juvenile salmon feed on the eggs, and more mature salmon feed on the live herring.

As an important player in the marine food chain, eelgrass is eaten directly by some animals, such as waterfowl, sea urchins and snails. Other creatures may feed on the microorganisms and algae thriving on the surfaces of the leaves.

But first and foremost is eelgrass’ contribution of detritus, small particles of decaying leaves and stems. These serve as habitat for diatoms, bacteria, fungi and algae, the base of the food chain. Carried on currents, eelgrass detritus travels great distances, nourishing sea creatures well beyond the meadow boundaries.

This tiny brooding anemone attaches to a single 1/4" blade of grass.

Eelgrass plants prefer sandy or muddy bottoms in areas with little water movement. Light levels in the murky, polluted waters of Puget Sound limit the growth of eelgrass to depths less than 30 feet. But in areas with clear water, it grows much deeper. Where eelgrass thrives, it protects the bottom from erosion by waves and currents, thanks to its extensive root network.

Like the canary in the coal mine, eelgrass is an indicator of our regional waters’ overall health. Pollution and other human impacts have resulted in the loss of 33 % of the eelgrass beds in Puget Sound, since studies began. Wisely, those who manage our natural resources have today adopted a “no net loss” policy as they try to restore lost beds and prevent more from disappearing.