Tracking the algal origin of the Ulva bloom in the Yellow Sea by a combination of molecular, morphological and physiological analyses

Abstract

In 2008, Qingdao (36 degrees 06'N, 120 degrees 25'E, PR China) experienced the world largest drifting macroalgal bloom composed of the filamentous macroalga Ulva prolifera. No convincing biologic evidence regarding the algal source is available so far. A series of field collections of both Ulva sp. and waters in various sites along Jiangsu coasts were conducted in March to May of 2009. Density of microscopic Ulva germlings in the waters sampled from different sites ranged from 7 to 3140 individuals L(-1), indicating the wide-spreading and long-term existence of the algae in the investigated region. Morphological and the nuclear ribosomal internal transcribed spacer ITS nrDNA and the chloroplast-encoded rbcL gene comparisons of 26 algal samples revealed that the algae collected from land-based animal aquaculture ponds mostly resembled the dominating blooming alga in 2008. Mismatch of Porphyra farming period with the occurrence of the green tide bloom, as well as the negative identification results of the sampled green algae from the Porphyra rafts eliminated Porphyra rafts as the principal and original source of the dominating blooming alga.

Inter- and intra-annual patterns of Ulva prolifera green tides in the Yellow Sea during 2007–2009, their origin and relationship to the expansion of coastal seaweed aquaculture in China

“…Thus, tides are likely to play an important role in transporting the U. prolifera biomass offshore from this location into the Yellow Sea. Pang et al (2010) presented a contrary view to that of , suggesting that the source of the blooms were microscopic germlings of U. prolifera produced in coastal aquaculture ponds used for crab and shrimp farming situated along the coast near Lianyungang (Fig. 8b) near to the area where the 2008 bloom was first observed on 14 May 2008 (Figs.…”

“…Since that time, various news reports and scientific articles have described the event, discussed the causes, evaluated the consequences and studied the biology of U. prolifera. Fu et al (2008), , Leliaert et al (2009), Li et al (2009), Liu et al (2010a,b) and Pang et al (2010) studied aspects of its biology and genetics. The scale of the bloom and its movement was described using satellite tracking methods by Hu and He (2008), Hu (2009), , Shi and Wang (2009) and Hu et al (2010).…”

“…The scale of the bloom and its movement was described using satellite tracking methods by Hu and He (2008), Hu (2009), , Shi and Wang (2009) and Hu et al (2010). A variety of possible causes were advanced by , ), Pang et al (2010, Xu et al (2009), Zhang et al (2010) and Hu et al (2010). predicted that blooms would recur annually and Liu et al (2010a) have described the subsequent 2009 green-tide event, which was similar in magnitude to that in 2008.…”

“…Zhang et al (2010) suggested somatic cells in marine sediments provided a propagule bank for U. prolifera. Pang et al (2010) also compared the genetics of U. prolifera in the 2008 Qingdao green tide with that from other coastal locations in Jiangsu province and attributed the 2008 bloom to a supply of U. prolifera thalli and germlings in the effluent of onshore aquaculture ponds used for shrimp and crab aquaculture. concluded either aquaculture ponds or Porphyra aquaculture could be responsible for the seed biomass for the bloom.…”

“…Thus, the objectives of this study were to: (1) determine the novelty of the bloom that lead to the 2008 Yellow Sea green-tide; (2) examine the oceanographic influences on the evolution of the 2008 and 2009 green tides and (3) track the origin of blooms and consider the relevance of this to hypotheses proposed by ), Xu et al (2009) and Pang et al (2010 which nominate different point sources to explain the cause of the blooms.…”