Abstract: To study on morphological characteristics of \textit{Ulva
linza} from floating green algae, we selected specimens with the
typical features of \textit{U. linza. }Only 4 specimens from 25
samples were determined as \textit{U. linza }from the morphological
characteristics results. The molecular biology research by means of
nuclear-encoded ITS sequences analysis was also carried out. Fifteen
floating specimens with characters of \textit{U. linza} clustered
into the LPP (\textit{U. linza-procera-prolifera}) complex group
including the attached species DF05 from Jiangsu Province, QD03 from
Shandong Province and XS01, XS02 from Zhejiang Province. The
floating green algae from Rudong inland river and coastal pool of
Sheyang were included in LPP complex as well. \textit{U. flexuosa}
group included two specimens that just were fixation growth algae
from Fujian Province. \textit{U. compressa} group had four
specimens, and they all were floating green algae. A great disparity
existed between the morphological characteristics and the molecular
results. Identification of \textit{U. linza} and other floating
green algae based on either morphology or ITS sequence unilaterally
was not reliable. Almost all of floating green algae from the same
location had certain morphological types, and they were considered
to be different species by the ITS sequences analysis. The result of
N-J tree and ITS data showed that the species in LPP complex and
\textit{U. compressa} existed in the green tide. But\textit{ U.
flexuosa }did not exist in the floating green algae in this
research.

Key words: green tide, Ulva linza, morphology, ITS, molecular biology