Algae. 1989; 4(2): 149-163.
Vertical Distribution and Photosynthetic Pigments of Marine Green Algae
Yasutsuga Yokohama
Shimoda Marine Research Center, University of Tsukuba, Shimoda
There are many green algae growing in coastal deep waters where the illumination is dominated by green light which is regarded to be unfavorable to green thalli. We recognized the difference in thallus color ad absorption spectrum among green algae living in different depths, and found that the green algae niched in deep waters contained siphonaxanthin as a photosynthetic pigment collecting green light. However, this carotenoid and/or another green light-absorbing pigment siphonein, the ester of siphonaxanthin, were detected in all the members examined of eusiphonean orders (the Codiales, Derbesiales, Caulerpales and Dichotomosiphonales) regardless of their habitats. Many species of the Caulerpales are found on sands of shallow lagoon surrounded by reefs, where the water is very calm. They might have originally niched on sands of deep waters so calm as to permit them to inhabit such unstable substratum with their delicate rhizoids. Actually we found some species of eusiphonean orders growing on sans at about 40 m depth in southern part of Japan. On the other hand, some species of the Cladophorales and Siphonocladales growing in deep waters or shaded sites have no green light-absorbing pigments. It was found that they had loroxanthin, the direct precursor of siphonaxanthin. Typical shallow-water green algae and higher plants have abundant lutein, the direct precursor of loroxanthin. The original members of green algae are considered to have niched in deep waters and had abundant sipnonaxanthin since they were not permitted to love in shallow waters in their primitive time, a thousand million years ago, because of strong ultra violet rays. Shallow-water species having abundant lutein might have derived from deep-water ones having siphonaxanthin or loroxanthin by failing to oxidize lutein into loroxanthin.
Keywords : Chlorophyceae, chromatic adaptation, loroxanthin, lutein, siphonaxanthin, siphonein, vertical distribution.