BIOLOGY OF SEAGRASS

Mujizat KawaroeMarine Biology and Biodiversity Laboratory2007Email : ds_biola1@yahoo.com; mujizat@ipb.ac.id

Seagrasses

• A type of submerged aquatic vegetation have evolved from terrestrial plants and have become specialized to live in the marine environment.

• Seagrasses have leaves, roots, conducting tissues, flowers and seeds, and manufacture their own food via photosynthesis.

• Seagrasses do not possess the strong, supportive stems and trunks required to overcome the force of gravity on land.

• Seagrass blades are supported by the natural buoyancy of water, remaining flexible when exposed to waves and currents

Seagrass

• Marine plants with the same basic structure as terrestrial (land) plants.

• They have tiny flowers and strap-like or oval leaves.

• They form meadows in estuaries and shallow coastal waters with sandy or muddy bottoms.

• Most closely related to lilies, they are quite different from seaweeds, which are algae.

Seagrass vs Alga

• Structurally, seagrasses, like terrestrial plants, possess specialized tissues that perform specific tasks within each plant. Algae are relatively simple and unspecialized in structure.

• Algae possess only a tough holdfast that assists in anchoring the plant to a hard substratum, seagrasses possess true roots that not only hold plants in place, but also are specialized for extracting minerals and other nutrients from the sediment.

• All algal cells possess photosynthetic structures capable of utilizing sunlight to produce chemical energy. In seagrasses, chloroplasts occur only in leaves, thus confining photosynthesis to leaves.

• Algae are able to take up minerals and other nutrients directly from the water column via diffusion. Seagrasses however, transport minerals and nutrients in xylem and phloem.

• Algae lack specialized reproductive structures, most seagrasses have separate sexes and produce flowers and seeds, with embryos developing inside ovaries.

Seagrass vs Alga

• Seagrasses produce flowers, fruit and seeds — algae produce spores.

• Seagrasses, have separate roots, leaves and underground stems called rhizomes. These can form an extensive network below the surface. Algae rarely have ‘roots’ below the surface.

• Unlike algae, seagrasses are vascular plants — they have a network of veins to move nutrients and dissolved gases around the plant.

Seagrass vs Alga

How seagrass grows

• Seagrasses need nutrients, often obtained from nearby mangroves, and good light, which means clear water.

• They cannot grow easily where they dry out at low tide. • They therefore thrive in shallow coastal waters where

there is shelter (such as a sand bar) from drying winds and from wave action and strong currents which could create turbulent muddy water.

• Although normally found in shallow water they can grow at depths of 32m and have been found in clear water at 68m

How seagrass survives

• While the roots of seagrasses serve to anchor the plants they are not necessary for water intake. They share the task of nutrient collection with the leaves which can absorb food and water directly from the surrounding water.

• The flowers are very small. • Water carries the pollen from the male to the separate female

flowers. • The resulting fruit are often carried some distance from the

parent plant before the seeds are released. • Flowering, however, is not common for most tropical species

and the spread of seagrasses is largely through vegetative propagation by the growth and branching of rhizomes.

Seagrass

Seagrass Community

Pickled Pickled SyringodiumSyringodium

Classic Oatmeal Raisin Cookies Classic Oatmeal Raisin Cookies with with EnhalusEnhalus seed flour seed flour

A taste of A taste of seagrass…seagrass…

Handicrafts from seagrassHandicrafts from seagrass