Thermal and Sub-thermal Cyanopycean Algae from Beppu

Abstract

The thermal and sub-thermal representatives of Cyanophycean algae from Beppu are numerous and include of all three orders. In the previous study I had found 73 species and varieties, and more four species have been found in the subsequent investigation. Thus I have found 27 genera and 77 species and varieties in all, and six of them are believed new t science. The most abundant genera are mastigocladus and Phormidium. At some sites the plants of these genera form extravagant strata of up to several centimeters thick. The species of Oscillatoria are exceedingly numerous in number and widely distributed in this region, but their significance in thermal flora is less than the former two genera. The species of Synechococcus, Chroococcus and Lyngbya are not uncommon ; while it is notable that those of Gloeocapsa, Calothrix, and Schizothrix are observed only a few. The hot springs of Beppu are divergent in chemical nature. Most of them, however, are simple or carburreted springs, and in such waters the thermal flora flourish most. Synechococeus, Mastigocladus, Oscillatoria and Phormidium are found most frequently in simple springs, while the species of Lyngbya, very few. In carburreted springs Chroococcus, Synechococcus, Mastigocladus, Oscillatoria, Phormidium and Lyngbya are found abundantly. In acidic springs Chroococcns, Oscillatoria grow abundantly, but Phormidium, very poorly. In hot water of particular nature only a few members of algae are found. The thermal Cyanophyceae of Beppu generally occur in waters neutral or slightly acidic. In this study the total range which the algae can thrive is pH 5,0-9,2. They occur most abundantly at about pH 6,0-7,0. The majority of the species are restricted to a range of 2,0 units or less, very few grow through a range of 3,0 units. The members of thermal blue-green algae occur abundantly at temperature 30-50 _. Above 60_ the abundance abruptly decreases. Several species such as Oscillatoria formosa, O. princeps, etc., show a wide temperature range. In this study the upper temperature limit is noted for O. formosa at 75_. Typical thermal forms which are found abundautly are as follows : Mastigocladus laminosus, Oscillatoria amphibia, O. animalis, O. formosa, O. geminata, O. Okeni, O. princeps, O. tenuis, Phormidium laminosum, Ph. tenue, Ph. valderianum. It is interesting that the species known from the tropics are found from the thermal springs of this region. They are Stichosiphon regularis, Nostochopsis Wichmannii, Calothrix brevissima, and Oscillatoria Lemmermannii.