Settlement of vegetative fragments of Ulva prolifera confirmed as an important seed source for succession of a large‐scale green tide bloom

Abstract

Ulva prolifera green tides in the Yellow Sea of China in the past 3 yr are among the largest macroalgal blooms ever recorded. Satellite images, as well as wind and current patterns, provide a clear picture of the formation of these green tides; however, their place of origin remains unclear. Terrestrial investigation along the coastline of the Jiangsu Province and two shipboard surveys in the Yellow Sea in 2009 showed that filamentous Ulvaceae algae were prevalent in various environments in Jiangsu Province including floating rafts for Porphyra cultivation, landbased bivalve culturing ponds, estuaries, embankments, intertidal stones, wharfs, and hard muddy coasts. Vegetative fragments in sediment samples were found in both shipboard surveys during the bloom and postbloom periods, and all of the samples were U. prolifera. Phylogenetic analysis of 5S spacer sequences showed that the green tide in the Yellow Sea was not of terrestrial origin. However, settled vegetative fragments of U. prolifera were an important seed source for the successive and more serious green tide blooms.

Re-evaluation of green tide-forming species in the Yellow Sea

“…Massive floating green mats covered about 1,200 km 2 of coastal water, and the Qingdao shoreline on the northeastern coast of China. This phenomenon reoccurred in the same region in July 2009, covering much of the same area as the previous year (Zhang et al 2011). It has subsequently become an annual phenomenon.…”

“…U. linza and U. compressa occurred on both sides of the YS (the east coast of China and the southwest coast of Korea), whereas U. prolifera only occurred along the east coast of China. The green tide-forming species in the YS have been regarded as U. prolifera in many studies (e.g., Wang et al 2010, Zhang et al 2011. However, U. linza was the dominant species, and it was mixed with some other Ulva spp.…”

“…Leliaert et al (2009) concluded that the species from 2008 Qingdao was part of the Ulva linza-proceraprolifera (LPP) complex, whereas Wang et al (2010) concluded that the alga was U. prolifera. Zhang et al (2011) reported that the blooming species forming the floating mats in the YS in 2008 and 2009 was U. prolifera based on a 5S rDNA spacer sequence analysis. (Choi et al 2010).…”

The yellow sea green tides were dominated by one species, Ulva (Enteromorpha) prolifera, from 2007 to 2011

“…AJ002301 represents 70 identical free-floating samples in 2008 [26]. HM031186, HM046595, and HM046600 represent 21 free-floating samples in 2009 [12,14].…”

“…Liu et al [12,13] proved that the dominant free-floating Ulva species in 2008 and 2009 possibly belonged to a single strain of the LPP clade, and the dominant bloom-forming alga was unlikely able to survive in the coastal waters in the winter conditions of Qingdao. Zhang et al [14] demonstrated that the ITS and 5S spacer sequences of the algae covering the large area of the Yellow Sea in 2008 and 2009 exhibit high similarities, and the bloom-forming algae were identified as U. prolifera.…”