The decadal changes in the Ahnfeltia bed in the Peter the Great Bay (Sea of Japan): possible causes

The decadal changes (from 1992 to 2005) of a community of unattached red algae in the Sea of Japan dominated by Ahnfeltia tobuchiensis were studied for the first time. The most important changes were an increase in species richness and significant changes in the stock of dominant species in the Ahnfeltia bed accompanied by a drastic decrease in the stock and biomass of the cold-temperate-water species Chondrus armatus, which coincided with a significant increase in the stock and biomass of Ahnfeltiopsis flabelliformis, an alga with warm-temperate-water affinity, while the stock and biomass of A. tobuchiensis did not change considerably. These changes led to the alteration of the algal community. The association co-dominated by A. tobuchiensis and C. armatus was noted in 1992, and by 2005, this association was replaced by the A. tobuchiensis and A. flabelliformis co-dominated association. Possible causes for these changes are discussed. It was concluded that warmer waters may be the basic environmental stress factor playing the central role in changing the community structure of the studied Ahnfeltia bed.