Nippon Suisan Gakkaishi 78 (4), 692-704 (2012)

Phenology and photosynthetic characteristics of a Japanese seagrass Zostera marina at the southern end of its distribution in the northwestern Pacific

TAKASHI KAWANO,1 GREGORY N. NISHIHARA2 AND RYUTA TERADA1*

1Department of Fisheries, Faculty of Fisheries, Kagoshima University, Shimoarata, Kagoshima 890-0056, 2Institute for East China Sea Research, Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, Taira-machi, Nagasaki 851-2213, Japan

The phenology and photosynthetic characteristics of a Japanese seagrass Zostera marina were examined from April 2010 to September 2011 at Yamagawa, Ibusuki City, Kagoshima Prefecture, which is near the southern distributional limit in the northwestern Pacific. A line-transect survey conducted to elucidate its community structure showed that it is distributed at depths of 2-2.5 m. The biomass of this species showed a peak in May accompanying maturation; meanwhile, it disappeared from the substratum from August to October, suggesting that this population has an annual life history. Photosynthesis in this species was determined over a range of temperatures (12-32℃) by dissolved oxygen sensor, and revealed that the net photosynthetic rate was highest at 20℃. An ANOVA analysis indicated that there were no significant differences from 12℃ to 24℃. Pulse-amplitude modulated fluorometry was used to demonstrate that the relative electron transport rate (rETR) of photosystem II (water/plastoquinone oxido-reductase) increased quickly with increasing PAR, was highest at 611 μmol photons m−2 s−1, and decreased as PAR further increased. Summer seawater temperature was around 28-31℃ in the natural habitat of the community examined, suggesting that respiration and photosynthetic activity might be influenced by the natural conditions.


  [BACK]  [TOP]