The Life Cycle of Fishers Island Eelgrass
We have all seen it. Eelgrass leaves are washed up on the beach, and we wonder, “Is this okay for the environment?” We get it! Wrack from eelgrass might not look the best, but it signifies a healthy, well-functioning marine ecosystem. Why? Because the life cycle of eelgrass includes regularly shedding its leaves. Let’s discover more about how Fishers Island eelgrass grows throughout the year!
Detritus that washes up on shore from the ocean is called wrack. The area where the wrack gathers is called the wrack line.
Fast Facts
Eelgrass is a perennial plant that grows quickly in the spring until the summer heat decreases productivity. When the seasons change from summer to fall, eelgrass starts a second growth spurt before slowing to a dormant state in the winter.
During the growing season, a new eelgrass plant grows every 10-14 days.
Eelgrass has an unusually high light requirement - 15-30% of the light available at the surface to photosynthesize [1].
Nutrients are primarily absorbed through the plant’s roots, but the leaves can absorb and utilize some nutrients.
The Life Cycle
We like to envision the eelgrass life cycle as a spiral rather than a circle. A spiral better represents how the rhizome becomes the heart of the plant and can keep it growing for generations - here is how it works:
An eelgrass seed germinates through the late fall and winter - it will be visible in spring.
The sea temperatures rise, and the days become longer, creating more favorable conditions for the seedling.
The seedling enjoys rapid growth up to 5 feet tall - on Fishers Island, seedlings are distinguished by their shorter stature since mature eelgrass is considerably longer.
The plant leaves shed monthly as they are damaged by epiphyte overgrowth and bruised by currents, waves, and tides.
The rhizome grows horizontally under the sediments as the primary shoot grows vertically. As it spreads, it produces 2-12 lateral shoots, forming new eelgrass clones.
The sea temperatures continue to rise, and the days get even longer. These conditions force the eelgrass plants into unproductive rates of respiration. Plant growth slows.
Sea temperature declines with shorter days, and eelgrass enjoys a second growth spurt if there is time before winter sets in.
Winter temperatures and limited sunlight create conditions for eelgrass to become dormant. Growth slows, and the plants are nearly invisible from the surface. The long leaves shed from the shoot as the plant goes dormant.
The eelgrass plant enters its second growing season in the spring. It starts growing rapidly upwards with its shoots and outwards from its rhizomes.
in early spring to summer, the primary shoot creates a reproductive shoot and a flower for reproduction. The pollen from other plants in the meadow fertilizes the flower as it floats in the water.
After fertilization, eventually, the seed pod breaks off and floats with the current up to 150 km before it sinks to the bottom and is buried. [4]
The primary shoot dies at the end of the second growing season. The plant lives on through the rhizome and its cloned shoots.
The rhizome branches out in the third growing season, creating more lateral shoots. Each shoot grows up to 5 feet tall.
When winter comes, the plant goes dormant, only producing tiny blades.
Steps 12 - 14 are repeated year after year. Shoots only live for two years, but the rhizome can live for over 1000 years! [5]
When you see eelgrass in the wrack line this year, remember that these plants work hard to sequester carbon, provide marine habitat, and prevent coastal erosion. We thank these washed-up leaves for all they have done for us on Fishers Island!
