Morphology and molecular identification of Ulva forming green tides in Qingdao, China

Abstract

Green tides are caused by the proliferation of chlorophytes under suitable hydrographic conditions. These blooms lead to environmental degradation and negatively impact the waters and seagrass beds, as well as fishing and other recreational activities in the bay. A comprehensive ecological understanding of the bloom dynamics, including the origin and persistence, is needed to foster management decisions. The algae in the great majority of green tide blooms usually belong to two genera of Ulvophyceae, Ulva and Enteromorpha. Ulva has been observed more often in recent years. In China, green tides occurred for the first time in the middle area of the Yellow Sea in 2007, and a large-scale algae blooming broke out in the middle and southern areas of the Yellow Sea in late May 2008. We identified them as Ulva prolifera by comparative analysis of the rDNA internal transcribed spacer 1 (ITS1), 5.8S and ITS2 sequences in combination with microscopic observation. Morphological differences were found between the free-floating algae and the attached thalli. Various reproduction patterns of the free-floating algae include sexual, asexual and vegetative propagations, which played important roles in the long-term green tide persistence in China. The ITS sequences of the blooming algae were identical to those of the samples from the Lianyungang sea area but were different from the attached samples from the Qingdao sea area. The results infer that the blooms are originated from other sea areas rather than from the local attached populations.

Genetic analyses of floating Ulva prolifera in the Yellow Sea suggest a unique ecotype

“…Most remarkably, the bloom-forming thalli exhibited denser branches, which facilitated the long-time and far-distance drifting of them, than the attached thalli (Kong et al, 2011). And the morphological characteristics displayed continuously through several generations cultured in the laboratory (Hiraoka et al, 2011).…”

Differentiation between some Ulva spp. by morphological, genetic and biochemical analyses

“…The genus Ulva was first identified by Linnaeus in 1753 (Kong et al, 2011). Since many taxonomists and phycologists have been involved in the identification of Ulva species (Wolf et al, 2012) which are notoriously difficult to classify due to the morphological plasticity expressed by many members as well as the few reliable characters available for differentiating taxa (Heech et al, 2009;Wolf et al, 2012).…”

A Molecular Survey of Ulva (Chlorophyta) in Temperate Australia Reveals Enhanced Levels of Cosmopolitanism

“…, Kong et al. ), but review of recent publications also points to the diverse range of positive applications. For example, Ulva spp.…”