What is a seagrass?


Seagrass Halodule uninervis” by Wikimedia Commons licensed by CC by 2.0

Many of us make think a seagrass is seaweed, but it is not. Seagrasses belong to a group of plants called monocotyledons. This group contains plants like grasses, lilies, and palms. Seagrasses have leaves, roots, veins, produce seeds and flowers just like a regular flowering plant like you see on land. Chloroplasts are in the tissues of sea grasses and use the suns energy to convert carbon dioxide and water into sugar and oxygen for growth via photosynthesis.  The veins of seagrasses carry nutrients and water throughout the plant. These plants have pockets called lacunae that keep the leaves buoyant and exchange oxygen and carbon dioxide throughout the plant. Seagrasses lack a stomata. Stomata is the tiny the pores that open and close to control water and gas exchange. Instead seagrass has a cuticle layer which allows grasses and nutrients to diffuse directly into and out of the leaves from sediment.

Where are they found?

Seagrasses can be found in salty and semi salty waters around the world. Seagrasses depend on light for photosynthesis so they are typically found in shallow waters so the plant can get the nutrients and the sunlight they need for survival.



Green Sea Turtle grazing seagrass” by Wikimedia Commons licensed by CC by 3.0

There are 72 species of seagrasses!  They are dived into four main groups: Zosteraceae, Hydrocharitaceae, Posidoniaceae and Cymodoceaceae. More commonly known as eelgrass, turtle grass, tape grass, shoal grass, and spoon grass. Seagrasses range from species that have long flat blades that look ribbons or to fern and paddle shaped leaves. They also can range in cylindrical or spaghetti blades, or branching shoots. Zostera caulescens is the tallest seagrass species; it is found growing up to 35 feet in japan.


Why are they important?


Syringodium filiforme (manatee grass) (southeastern Graham’s Harbour, San Salvador Island, Bahamas) 1” by James St. John licensed by CC by 2.0

When areas of the ocean are free of seagrasses, they are vulnerable to intense wave action from currents and storms. Their roots grow both horizontally and vertically, this helps stabilize the sea bottom in a way similar to the way land gasses prevent soil erosion. Seagrasses also provide food, shelter, and nursery grounds to fish. Manatee’s and sea turtles directly eat the grass; others use the seagrasses to directly to provide nutrients. Detritus from bacterial decomposing of dead seagrasses plants provide foods for worms, sea cucumbers, crabs, and filter feeders like anemones and ascidians.  Seagrasses also provide an ideal location for juvenile and small fish to escape from larger predators. Some species use sea grasses is a buffer from currents. Some of these species are starfish, clams, worms, sea cucumbers, and sea urchins. Sea grasses also help with the water quality. They trap sediments and particles suspended in the water column, which helps increase water clarity


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3 Responses to Seagrass

  1. haleyzanga says:

    Thanks for this post! Do you know if there are any common features with seagrass and seaweed? Its crazy to think how seagrass is so little but is such an important part of ecosystem playing so many roles.

    Liked by 1 person

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