Species Diversity and Seasonal Changes of Dominant Ulva Species (Ulvales, Ulvophyceae) in Mikawa Bay, Japan, Deduced from ITS2 rDNA Region Sequences

doi:2007.22.3.221

Algae > Volume 22(3); 2007 > Article

Algae 2007;22(3): 221-228. doi: https://doi.org/10.4490/algae.2007.22.3.221

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

ABSTRACT

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.

Key words: ITS2, non-indigenous species, trans-ocean introduction, Ulva species