Module 12

OHT 7

Seaweed

Algae

Many varieties

Float free (phytoplankton) or attach to hard surface

Look something like plants on the land

Usually slippery to touch

Do not have roots, leaves or flowers

Can break off and grow new plants

May reproduce by eggs and sperm

Colours

Blue Green (most are very tiny)

Green (live nearest the surface where purest light is)

Brown (live a little deeper where some light has been absorbed by water)

Red (live deeper down to where the last light bands reach)

Smelly when rotting on the beach

Begin the food chain on the surface and edges of the ocean

Seagrasses

Few varieties

Are like land plants (they returned to the sea sometime in the past)

Do have roots, leaves and flowers

Only grow in shallow waters

Are significant nursery areas for many animals

Control erosion and fix substrate

Sensitive to changes in sedimentation and nutrients