Seaweeds or benthic marine algae are the group of plants that live either in
marine or brackish water environment. Like the land plants, seaweeds contain
photosynthetic pigments and with the help of sunlight and nutrient present in the
seawater, they photosynthesize and produce food.
Seaweeds are found in the coastal region between high tide to low tide and in the
sub-tidal region up to a depth where 0.01 % photosynthetic light is available
(Fig. 1). Plant pigments, light, exposure, depth, temperature, tides and the shore
characteristic combine to create different environment that determine the distribution
and variety among seaweeds.