Marine Plants: a Unique and Unexplored Resource*

The seas provided a suitable site for the early evolution of all life. Ever since plants and animals developed structures and mechanisms that enabled them to survive on land, terrestrial and aquatic plants have been exposed to different abiotic and biotic selective pressures. Marine plants, which, unlike terrestrial plants, have evolved and adapted to life in a largely stable but saline environment, have developed many unique chemical structures not found in terrestrial plants. The photosynthetic plants in the sea represent the foundation of the marine food web. The oceans occupy 70 percent of the Earth’s surface, and the marine plants are known to provide at least the same percentage of available oxygen through photosynthesis. Marine plants are represented both by seaweeds, macroscopic forms largely inhabiting the shallow-water coastal zones, and by phytoplankton, free floating, widely distributed unicellular marine plants. Although a few flowering plants (angiosperms) are abundant in shallow waters, the majority of marine plants are algae, typified by their lack of a vascular system which serves for nutrient transport. Although all are classified as algae, these plants have an amazing taxonomic diversity. Marine algae have been subdivided into at least 12 distinct phyla (16): Macroscopic forms Rhodophyta . . . the Phaeophyta . . . the Chlorophyta . . . the Cyanophyta . . . the Chrysophyte . . . . the Haptophyta . . . . * Xanthophyta . . . . * Microscopic, red seaweeds brown seaweeds green seaweeds blue-green algae yellow-green algae