Algae. 2007; 22(3): 221-228.
Species Diversity and Seasonal Changes of Dominant Ulva Species (Ulvales, Ulvophyceae) in Mikawa Bay, Japan, Deduced from ITS2 rDNA Region Sequences
Hiroshi Kawai1*, Satoshi Shimada2, Takeaki Hanyuda1, Teruaki Suzuki3 and Gamagori City Office4
1Kobe University Research Center for Inland Seas, Rokkodai, Nadaku, Kobe 657-8501, Japan 2Creative Research Initiative ‘Sousei’, Hokkaido University, Sapporo, 060-0810 Japan 3Aichi Fisheries Research Institute, Gamagori 443-0021, Japan 4Asahimachi, Gamagori 443-8601, Japan
Frequent occurrences of green tides caused by Ulva species (Ulvales, Ulvophyceae) associated with eutrophication along enclosed coasts are currently causing environmental problems in coastal ecosystems. In addition, increasing intercontinental introductions of coastal marine organisms, including Ulva, are also a serious issue. However, due to the considerable morphological plasticity of this genus, the taxonomy of Ulva species based on morphological studies is problematic. Therefore, in order to elucidate the species diversity and seasonal changes of the dominant Ulva species in Mikawa Bay, central Honshu, Japan, we made seasonal collections of Ulva species at seven localities, and identified the dominant species using the ITS2 rDNA region sequences. We identified the following nine taxa as common Ulva species in the area: 1) Ulva pertusa Kjellman; 2) U. ohnoi Hiraoka et Shimada; 3) U. linza L.; 4) U. californica Wille; 5) U. flexuosa Wulfen; 6) U. fasciata Delile; 7) U. compressa L.; 8) U. armoricana Dion et al.; 9) U. scandinavica Bliding. Among the species, U. pertusa was most common and dominant from spring to summer, and U. ohnoi from autumn to winter. Ulva californica and U. scandinavica have not been reported before from Japan.
Keywords : ITS2, non-indigenous species, trans-ocean introduction, Ulva species