Marine Microalgae

Chen+Changping

Blue-green algae:

let the earth breathe freely

Todays atmosphere contains rich in oxygen, however, the atmosphere-marine systems on the early earth lacked this kind of free state oxygen. 2.7 billion years ago, the blue-green algae which appeared earliest on the earth gradually changed the condition of lack of oxygen in the atmosphere and ocean through photosynthetic oxygen evolution, which had great influences on the early environment on the earth. During the Precambrian period 2.5 billion years ago, the ocean was a ecosystem consists of primary producers such as pronucleus blue-green algae, who had simple structures, rare species but large amounts. The period was also called ” blue-green algae era”. Now, though the blue-green algae loses the ancestors brilliant, its still the microalgae of the largest amounts and the only pronucleus photoautotroph living in the ocean relying on its technique of “ biological fixation of nitrogen”.

The eukaryotic algae:

the risen of

“ the three families”

The situation of the nucleus algaes “domination” in the ocean kept for about 1 billion years. By 1.6 to 1.8 billion years ago, the appearance of eukaryotic algae broke such a situation. The risen of modern eukaryotic algae started from about 230 million years ago, the middle Triassic. In the whole Mesozoic ocean, the blue-green algae is gradually replaced by another three kinds of microalgae, which are diatom, dinoflagellate and coccolithophorid. As the saying goes “big fish swallows little fish, small fish eats shrimp”, then what does the shrimp eat? It eats microalgae. Therefore, the amount of microalgae directly influences the marine industry, several of the big fish farms in China are all sea areas rich in microalgae.

Macroalgae

There are also macroalgae such as red alga, green alga and brown alga in the ocean, colors are their identity cards. For example, the kelp we eat in usual is brown alga, the nori is red alga, while the “ Green laver” enteromorpha popular in Japan is green alga. Then where do they live in the sea? The green alga could reflect green light as the land plants, they live in the high tide zone and intertidal zone clearest to the land in the sea; the red alga reflects red light, they live in the subtidal zone or deeper water; the brown alga reflects yellow light, it lives at the zone between the green alga and the red alga.