Common Eelgrass, Zostera marina
Common Eelgrass, Zostera marina. Underwater photograph taken in coastal waters off San Diego, California, September 2019. Photograph and identification of Bob Hillis, Ivins, Utah.
Common Eelgrass, Zostera marina. Underwater photograph taken in coastal waters off San Diego, California, September 2019. Photograph and identification of Bob Hillis, Ivins, Utah. Photo illustrating leaves, stem, and roots.
Phylogeny: Common Eelgrass, Zostera marina (Linnaeus, 1753) is a member of the Zosteraceae Family of Eelgrasses. They are also known as Seawrack or Tapegrass. Plants in the Zosteraceae Family are perennial flowering marine plants. The Zostera Genus is one of two genera in this family. The genus name Zostera comes from the Greek word for belt or girdle, referring to the strap-like form of these plants. There are two subgenera and fifteen species in the Zostera Genus.
Morphology: Like other eelgrasses, Common Eelgrass is an angiosperm and not an algae. It has true leaves, stems, and roots. It is a monocot, like tulips or orchids. Common Eelgrass varies in appearance based on environmental conditions such as substrate, depth, water movement, light, and nutrient availability. The leaf blades are long and narrow, but wider then grasses in the Phyllospadix genus of Sea Grasses. The leaf tips are rounded. The bright green leaves grow from creeping, underground, stems (rhizomes). The rhizomes have hair-like roots. The leaves vary in width from 2 mm (0.1 inch) to 12 mm (0.4 inch) and can reach a maximum of 1.2 m (3 feet 11 inches) in length.
Habitat and Distribution: Common Eelgrass grows in mud and sand substrates. It is most commonly found in large beds, in protected waters such as bay and lagoons. It lives in the intertidal zone and to depths of around 12 m (39 feet). It is a temperate to subtropical northern Pacific and northern Atlantic species. In Mexican waters it is limited to north of the San Ignacio Lagoon, Baja California Sur, along the central and northwest coasts of the Baja Peninsula, and from Bahía Kino, Sonora to Topolobampo, Sinaloa in the Sea of Cortez. Common Eelgrass is adversely affected by warm water temperatures and impacted by seasonal and other water temperature changes.
Predators: Common Eelgrass is preyed upon by crabs, ducks, geese, mollusks and sea urchins.
Reproduction: Common Eelgrass is monecious (each plant having male and female reproductive organs {hermaphrodites}). They reproduce sexually through flowers, seeds, and pollen, just like most terrestrial plants. Pollen drifting in the water fertilizes the flowers. The seeds grow on reproductive shoots called spathes. The spathes break off and drift with the currents, establishing new colonies. They also reproduce asexually through the elongation of the rhizomes, which maintains established beds.
Ecosystem Interactions: Common Eelgrass provides shelter and structure and nurery habitat for various species of crustaceans, fish, mollusks, and other invertebrates.
Human Interactions: Historically, Common Eelgrass was used to mattress stuffing and housing insulation, until it was replaced by synthetic materials. Most Eelgrass populations are declining from poor water quality, dredging, and coastal development. From a conservation perspective Common Eelgrass is currently considered to be of Least Concern.
Synonyms: Zostera angustifolia, Zostera hornemanniana, and Zostera marina var. angustifolia.