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Large-scale Ulva-caused green tides has posed various environmental and ecological problems as well as economic consequences. It is important to identify them accurately and quickly. The current universal markers based on ITS, rbcL, and 5S spacer sequences were defective to distinct closely related species in the genus of Ulva. In this study, by investigating the intergenic regions of chloroplast (cp) genome, a novel marker of c15 (based on ycf3-rps7) were reliable for discrimination of Ulva species. Notably, the resolution of c15 was suitable for resolve the closely related species of U. linza and U. prolifera, which may provide tools for deciphering the blooming mechanisms of green tides. [ABSTRACT FROM AUTHOR]

Qinhuangdao coastal waters have been frequently hitting by nano- and pico-eukaryotic phytoplankton (NPEP) blooms and green tides (macroalgal blooms) in the recent decade. However, understanding about the impacts of environmental factors and the green tides on the NPEP assemblages in this area is limited. In this study, the composition of NPEP assemblages and their variations were analyzed via amplicon sequence variants (ASVs) assay based on amplicon high-throughput sequencing data with the 18S V4 region as a targeted gene in the Qinhuangdao green-tide area during the green tide. Consequently, average NPEP effective sequences and ASVs of 178 000 and 200 were obtained from each sample, respectively. Although there were 25 classes, 110 genera, and 97 species of NPEP were identified and annotated, the proportions of annotated ASVs at genus and species levels were only 44.7% and 17.8%, respectively. The NPEP communities had a seasonal succession from diatom-dominated to dinoflagellate-dominated. During the three investigations, Skeletonema, Karlodinium, and Gonyaulax were the most dominant genera in May, August, and September, respectively. Species diversity and the abundance of NPEP communities could be increased by a high content of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) but inhibited by low dissolved inorganic phosphorus content. The outbreak of green tides could alter the composition and content of nutrients and accelerate the succession of the NPEP communities from diatom-dominated to dinoflagellate-dominated under the background of a seasonal increase in seawater temperature. These results preliminarily revealed the impacts of the recurrent occurrences of green tides on the NPEP assemblages in the Qinhuangdao green-tide area exhibiting high DON content and dissolved inorganic nitrogen/phosphorus ratio. [ABSTRACT FROM AUTHOR]

Algal blooms of haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf, South China Sea (SCS) since 2011. Recent evidence suggests that Type I and Type IV are the two dominant genotypes of P. globosa coexisting in this area, and their marker pigment profiles, colony sizes, and genetic information differ. Two genotype-specific quantitative polymerase chain reaction (qPCR) assays were used to clarify the distribution and dynamics of P. globosa bloom in the Beibu Gulf from November 2018 to February 2019. Results show that the patterns of spatial-temporal distribution of Type I and Type IV were similar, the abundance of Type IV was higher than that of Type I during the algal bloom, and thus Type IV cells dominated the P. globosa bloom in winter 2018. The relationships between environmental factors and P. globosa abundance indicated that temperature and nitrate were critical to the distribution and dynamics of P. globosa blooms in this area. The distribution of P. globosa cells in different water masses before the bloom revealed that the westward water via the Qiongzhou Strait, the SCS bottom water, and the current in the northwestern waters of Hainan Island could transport P. globosa cells into the Beibu Gulf serving as the seed sources triggering the intense blooms in the Beibu Gulf. [ABSTRACT FROM AUTHOR]

Qinhuangdao, a famous coastal resort city in northeastern China, has been affected by the rapid growth of harmful algae. The brown tide induced by Aureococcus anophagefferens (A. anophagefferens) first occurred along Qinhuangdao's coastline in 2009, and it then developed into a harmful alga for the Bohai Sea. Based on MIKE 21, we construct a 2D coupled hydrodynamic and transport model to study the variation and distribution of total nitrogen (TN), and establish the relationship between A. anophagefferens, dissolved organic nitrogen (DON), and TN to provide a fast forewarning system for brown tide in Qinhuangdao. This model considers the decay, diffusion, and settling of TN, and the model results are in good agreement with the measured tidal level, current, and TN, indicating that the model is capable of capturing the observed TN distribution during the brown tide period. The transfer function relating TN to A. anophagefferens leads to a reliable fast forewarning and monitoring system. Moreover, the transferred A. anophagefferens cell density can be used to forecast the regional risk level of brown tide with a specific color indicator. The implementation of national policy relating to marine ecosystems decreases the nearshore concentration of N, P, and other nutrients, and therefore decreases harmful algal blooms. The fast routine assessment of brown tide by the present warning system provides robust guidance for the government to take action. [ABSTRACT FROM AUTHOR]

Phaeocystis globosa is an important harmful algal bloom causative species distributing widely in temperate and tropical coastal waters in the world. The morphological, physiological, and biochemical characteristics are different among geographic strains, which can not be distinguished with nuclear ribosomal DNA markers at present. Therefore, the genetic distance and phylogeographic relationships of nuclear 28S rDNA D1–D2 and ITS regions, and three chloroplast intergenic spacers (petN-trnS1, trnM1-psbA, and rbcS-rpl27) were analyzed and compared among 13 strains of P. globosa isolated from the Pacific Ocean and Atlantic Ocean in this study. In addition, the nucleotide polymorphisms of 28S rDNA D1–D2, ITS, and rbcS-rpl27 regions were evaluated in two P. globosa strains. The various levels of nucleotide polymorphism were in the nuclear 28S rDNA D1–D2 region and ITS region, but no polymorphism was in the chloroplast rbcS-rpl27 intergenic spacer. A reasonable intraspecific phylogeographic relationship was presented by rbcS-rpl27 intergenic spacer, which had the strongest distinction to geographic strains compared to those of 28S rDNA D1–D2 and ITS regions. In the phylogenetic tree of rbcS-rpl27 intergenic spacer, the two strains from the North Sea of the Atlantic Ocean were divided firstly from the species of P. globosa, and then formed an independent clade, while the other Atlantic strains and all of Pacific strains joined up to build the other clade. It was implied that at least two genetically distant populations of P. globosa existed in the Atlantic coastal regions. This study provided a high-resolution chloroplast marker to analyze intraspecific phylogeographic populations of P. globosa, and preliminarily clarified the genetic relationships of the Pacific and Atlantic strains of P. globosa. [ABSTRACT FROM AUTHOR]

In recent years, harmful algal blooms (HABs) have occurred frequently along the coast of China, and have been exhibiting succession from diatom- to dinoflagellate-dominated blooms. To examine the effects of different diatom and dinoflagellate HABs, the life history parameters of rotifers ( Brachionus plicatilis Müller) were measured after exposure to different concentrations of HAB species. The HAB species examined included a diatom ( Skeletonema costatum) and four dinoflagellates ( Prorocentrum donghaiense, Alexandrium catenella, Prorocentrum lima and Karlodinium veneficum). Compared with the control treatment (CT), the diatom S. costatum showed no adverse impacts on rotifers. Exposure to dinoflagellates at densities equivalent to those measured in the field resulted in a reduction in all the life history parameters measured. This included a reduction in: lifetime egg production (CT: 20.34 eggs/ind.) reduced to 10.11, 3.22, 4.17, 7.16 eggs/ind., life span (CT: 394.53 h) reduced to 261.11, 162.90, 203.67, 196 h, net reproductive rate (CT: 19.51/ind.) reduced to 3.01, 1.26, 3.53, 5.96/ind., finite rate of increase (CT: 1.47/d) reduced to 1.16, 1.03, 1.33, 1.38/d, and intrinsic rate of population increase (CT: 0.39/d) reduced to 0.15, 0.03, 0.28, 0.32/d, for the dinoflagellates P. donghaiense, A. catenella, P. lima and K. veneficum, respectively. The results showed that the diatom S. costatum had no detrimental consequences on the reproduction and growth of B. plicatilis, however, the four dinoflagellates tested did show adverse effects. This suggests that dinoflagellate HABs may suppress microzooplankton, resulting in an increase in algal numbers. [ABSTRACT FROM AUTHOR]

A large-scale bloom occurred from May to June in 2011 in sea area near Qinhuangdao of the Bohai Sea, leading to huge damage of the scallop culture industry. Similar blooms have been observed in this region for three years. The causative species of the bloom, which dominated the phytoplankton community with the maximum cell density around 10 cell/L, could not be identified with morphological features due to the small cell size (∼2 m m). A pigment analytical method was then adopted to analyze the pigment profile of the phytoplankton samples collected from the blooming sea area. It was found that pico-sized (<2 m m), nano-sized (2-20 m m), and bulk phytoplankton samples had similar pigment profile, representing the pigment signature of the bloom-causative species. The major pigments detected included 19-butanoyloxyfucoxanthin (But-fuco), fucoxanthin (Fuco), diadinoxanthin (Diad) and chlorophyll a (Chl a), and high content of But-fuco was the most significant characteristics of the phytoplankton samples. Based on the pigment composition and content, the bloom-causative species could be tentatively identified as pelagophyte, 'type 8' group of haptophyte, or silicoflagellate. Some unique features of the bloom, such as the extremely high cell density, small-sized and But-fuco containing cells, occurring in early summer, and the feeding-cessation effects on scallops, suggest it be a 'brown tide' event similar to those reported in the east coast of the United States of America. The recurrent 'brown tide' events and their dramatic impacts on the shellfish mariculture industry in Qinhuangdao need close attention in the coming years. [ABSTRACT FROM AUTHOR]

Brown tides caused by the pelagophyte Aureococcus anophagefferens have frequently occurred in the Bohai Sea since 2009 and have led to a dramatic collapse of the local scallop culture. To determine why brown tides occurred in the Bohai Sea rather than in other eutrophic coastal waters of China, phytoplankton communities and nutrients were evaluated and nutrient addition experiments were conducted in the Qinhuangdao coastal area. The concentration of dissolved organic nitrogen (DON) was nearly five times higher than that of dissolved inorganic nitrogen (DIN) during brown tides. High levels of phytoplankton biomass and nutrients were observed in the inshore waters, and the patterns of different nutrients were heterogeneous, which could be due to the uneven distribution of pelagophytes and non-brown tide phytoplankton populations (NBTP). The nutrient enrichment results indicated that the growth of the phytoplankton community was nitrogen-limited. Enrichment of DON, especially urea, could promote the growth of pelagophytes during the development stages of the brown tide. In brief, the results of this study imply that the unique nutrient profile (rich in DON but deficient in DIN) could support the outbreak of brown tides in the inshore waters of Qinhuangdao. • Brown tides have plagued the coastal waters of Qinhuangdao, Bohai Sea. • We performed field investigations and nutrient addition experiments in 2012 and 2013. • The Qinhuangdao coastal water is rich in DON but deficient in DIN. • Enrichment of DON, especially urea, could promote the growth of the pelagophyte. • The unique nutrient profile supports the outbreak of brown tides. [ABSTRACT FROM AUTHOR]

Four cruises were carried out in the southern Yellow Sea from May to June of 2012 with the aim of observing the development of green tides. Free-floating patches of green algae dominated by Ulva prolifer a occurred in early May in coastal waters of the southern Yellow Sea with an average biomass of 0.05 g m −2 . The average biomass of free-floating green algae developed rapidly and reached 3.20 gm −2 in mid-May, and the affected area reached 8.7 × 10 3 km 2 with a total biomass of 1.37 × 10 5 tons. In late May, the average biomass reached 5.81 gm −2 , and the affected area reached 3.2 × 10 4 km 2 with a total biomass of 2.5 × 10 5 tons. In early June, the average biomass reached 8.47 gm −2 , the affected area covered 3.6 × 10 4 km 2 , and the total biomass of floating green algae was 3.64 × 10 5 tons. The affected areas of green tide in our observed data were higher than those estimated from remote sensing images in the early two cruises, and basically matched the remote sensing data in the last two cruises. With the increased biomass and the expansion of the affected area, the free-floating algal patches moved progressively northward. They first appeared in coastal water of middle Jiangsu province, gradually reached 35°N in early May, and finally drifted to the southern coast of the Shandong Peninsula (36°N) after one month. This work can offer help for the early prediction and warning of a green algal bloom and provide decision-making bases for governmental departments. [ABSTRACT FROM AUTHOR]