Plants grow only in depths to which light penetrates the water. The most common marine plants are algae which form the base of the food chain. They are the primary producers of the marine ecosystem with numerous organisms feeding on them directly or indirectly.
The marine plants can be divided into the following categories.
Green Algae (Chlorophyta) -
These are found in large numbers with the dominant pigment being green chlorophyll. They exist in a variety of shapes, forms and habitats. The calcified leaves of the green algae (Halimeda) are major contributors to the production of marine sediments and the sand cayes. Other green algae include Ulva spp., Acetabularia spp., Caulerpa spp., Udotea spp. and Halimeda spp.
Brown Algae (Phaeophyta) -
This family of plants is almost exclusively marine and prefers cold temperate waters, hence there are a few tropical waters species. Often, this group can be the dominant life form on a reef. The dominant pigment is fucoxanthin and its color is a shade of brown. Examples include Sargussum spp., Turbinaria spp. and Dictyota spp.
Red Algae ( Rhodophyta) -
This is the largest and most diverse of marine plants. It is commonly used in Belize in the preparation of a seaweed drink. In addition, a small quantity is exported to be used as a thickening agent. Its distinguishing feature is a shade of red derived from the pigment phycoerythin. Coralline red algae often contribute greatly to reef structure by holding the corals together hence forming the reefs. For example, Ceramium spp., Hypnea spp., Laurencia spp. and Gracilaria spp.
Diatoms (Chrysophyta) -
These are groups of relatively unknown microscopic plant cells with glassy shell-like structure. They often form chains and are a major component of the plankton.
Blue-green algae (Cyanophyta) -
These consist mainly of microscopic filaments that appear as black patches on rocks or other hard substrates. They are important in converting atmospheric nitrogen into forms available for other marine plants. Common blue-green algae include Schizothriz calcicola and Phormidium corallyticum (black-band disease).
Flowering Plants (Angiosperme) -
These have true roots, stems and leaves as well as small inconspicuous flowers that form spiny seeds. Few marine species exist, though they can be the dominant life form in parts of the Belizean coastal zone. Both Thalassia testudium and Syringodium filiforme are common.
