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[D-4.1.1 Effects of Environmental Stresses on the Zooxanthellae(Final Report)]

[Contact Person]

Tomoko Sakami
Researcher
Biotic Environmental Section, Division of Environmental Management
National Research Institute of Aquaculture, Fisheries Agency
Nansei, Mie, 516-01, Japan
Phone:+81-6-1830, Fax:+81-6-1962
E-mail:sakami@nria.affrc.go.jp

[Total Budget for FY1994-1996]

6,100,000 Yen (FY1996 2,209,000 Yen)

[Abstract]

　Effects of main environmental factors, temperature, irradiation salinity and inorganic nitrogen concentration on the growth or photosynthetic activities of two strains of zooxanthellae cultures were investigated. The algal growth rates were reduced greatly when the irradiation reduced from 6 to 3μE/m²/s.
　The algae had maximum growth rate at 32℃ but the photosynthetic activities were higher at 28℃ than at 32℃. The optimum salinity for these algae were 30 but they had comparable activities at 25 as much as at 35. Temperature and irradiation influenced the algal tolerance against low salinity.
　Effects of nitrogen enrichment on the growth rate and photosynthetic activities of two strains of zooxanthellae culture were investigated. A low concentration DIN enrichment (2μM/day as NH₄⁺) increased their growth rates and cellular chlorophyll a contents but it had no effect on their photosynthetic activity. Cellular chlorophyll a contents increased as the increasing DIN concentration up to 20mM/day but photosynthesis per cell did not increase over 5μM/day DIN enrichment.

[Key Words]

Coral, Zooxanthellae, Environmental stress, Eutrophication