Fisheries Farming Laboratory, Fisheries Experimental Station, Wakayama Research Center of Agriculture, Forestry and Fisheries, Tanabe, Wakayama 646-0058, Japan
An investigation to demonstrate seasonal changes of communities of Zostera japonica was conducted at intertidal sampling points in Tanabe Bay, the Pacific Coast of middle Japan, from May 2004 to August 2005. The biomass at Takinai and Uchinoura changed between 26.8 and 218.5 g/m2, 51.8 and 386.3 g/m2, respectively. Total biomass reached a peak in early summer (June-July). The largest proportion of the biomass was rhizome (including roots), which comprised 94% of total biomass as the maximum value. With these results, the seasonal changes are classified into seven periods. In the latter growth period, leaf lengths lengthen and biomass of Z. japonica increases. In the ripening period, flowering shoots begin to form and leaf lengths reach their maximum values. The next period, when leaf lengths begin to shorten and the increase of biomass ends, is called the latter luxuriant period. The decrease of biomass begins gradually in the last luxuriant period. In the negative growth period, aboveground biomass rapidly decreases, while belowground biomass slowly decreases. In the last negative growth period, biomass reaches the minimum value. Gradual growth of Z. japonica begins in the former growth period.