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Phaeocystis globosa has formed intensive blooms in the South China Sea and even around the world, causing huge social economic losses and environmental damage. However, little is known about the formation mechanism and dynamics of P. globosa blooms. 19′-Hexanoyloxyfucoxanthin (hex-fuco) is often used as the pigment proxy to estimate Phaeocystis biomass, while this is challenged by the giant-colony-forming P. globosa in the Beibu Gulf, which contains only 19′-butanoyloxyfucoxanthin (but-fuco) but not hex-fuco.

The giant-colony-forming haptophyte Phaeocystis globosa has caused several large-scale blooms in the Beibu Gulf since 2011, but the distribution and dynamics of the blooms remained largely unknown. In this study, colonies of P. globosa, as well as membrane-concentrated phytoplankton samples, were collected during eight cruises in the Beibu Gulf from September 2016 to August 2017. Pigments were analyzed by high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD). The pigment 19′-hexanoyloxyfucoxanthin (hex-fuco), generally considered a diagnostic pigment for Phaeocystis, was not detected in P. globosa colonies in the Beibu Gulf, whereas 19′-butanoyloxyfucoxanthin (but-fuco) was found in all colony samples. Moreover, but-fuco in membrane-concentrated phytoplankton samples exhibited a similar distribution pattern to that of P. globosa colonies, suggesting that but-fuco provided the diagnostic pigment for bloom-forming P. globosa in the Beibu Gulf. Based on the distribution of but-fuco in different water masses in the region prior to the formation of intensive blooms, it is suggested that P. globosa blooms in the Beibu Gulf could originate from two different sources. IMPORTANCE Phaeocystis globosa has formed intensive blooms in the South China Sea and even around the world, causing huge social economic losses and environmental damage. However, little is known about the formation mechanism and dynamics of P. globosa blooms. 19′-Hexanoyloxyfucoxanthin (hex-fuco) is often used as the pigment proxy to estimate Phaeocystis biomass, while this is challenged by the giant-colony-forming P. globosa in the Beibu Gulf, which contains only 19′-butanoyloxyfucoxanthin (but-fuco) but not hex-fuco. Using but-fuco as a diagnostic pigment, we traced two different origins of P. globosa blooms in the Beibu Gulf. This study clarifies the development process of P. globosa blooms in the Beibu Gulf, which provides a basis for the early monitoring and prevention of the blooms.

A shorted-patch antenna (SPA) towards dual-band and circularly-polarization (CP) is proposed. Initially, several modes are selected to require the orthogonal electric-field components for CP generation. Next, the short pins are inserted below the rectangular patch to turn up TM 0,1/2 mode closely to TM 1,1/2 mode. Besides, a narrow rectangular slot is properly etched on the top-layer of the SPA to move down TM3,3/2 mode in proximity to TM 0,3/2 mode. In addition, an annular slot is properly etched around the feeding port for good impedance matching. Finally, the results illustrate that its effective bandwidth $(\vert S_{11}\vert and $\text{AR} ) is held around 1.19% (2.684-2.716 GHz) in low frequency band and 1.05% (5.683-5.743 GHz) in high frequency band. Additionally, the proposed SPA achieves CP radiation performances in dual bands, while keeping low-profile, single feeding and single-element properties.

Cultural eutrophication caused by nutrient over-enrichment in coastal waters will lead to a cascading set of ecosystem changes and deleterious ecological consequences, such as harmful algal blooms (HABs) and hypoxia. During the past two decades since the late 1990s, recurrent large-scale HABs (red tides) and an extensive hypoxic zone have been reported in the coastal waters adjacent to the Changjiang River estuary. To retrieve the history of eutrophication and its associated ecosystem changes, a sediment core was collected from the “red-tide zone” adjacent to the Changjiang River estuary. The core was dated using the 210Pb radioisotope and examined for multiple proxies, including organic carbon (OC), total nitrogen (TN), stable isotopes of C and N, and plant pigments. An apparent up-core increase of OC content was observed after the 1970s, accompanied by a rapid increase of TN. The concurrent enrichment of δ13C and increase of the C/N ratio suggested the accumulation of organic matter derived from marine primary production during this stage. The accumulation of OC after the 1970s well reflected the significant increase of primary production in the red-tide zone and probably the intensification of hypoxia as well. Plant pigments, including chlorophyll a, β-carotene, and diatoxanthin, showed similar patterns of variation to OC throughout the core, which further confirmed the important contribution of microalgae, particularly diatoms, to the deposited organic matter. Based on the variant profiles of the pigments representative of different microalgal groups, the potential changes of the phytoplankton community since the 1970s were discussed.

Massive green tides of Ulva prolifera have been recorded consecutively since 2007 in the Yellow Sea (YS). It has been proposed that the floating green algae in the YS are originally from the culture rafts of Porphyra yezoensis in the Subei Shoal. However, there is still much debate about this, mainly due to the difficulty in rapid and accurate identification of U. prolifera. In this study, a developed fluorescence in situ hybridization (FISH) method was adopted to identify U. prolifera and assess its relative abundance in the green algal community. Using this method, several processes related to the formation of green tides were studied, including: (1) variation of the relative abundance of U. prolifera in the green algal community attached to Porphyra rafts in the Subei Shoal; (2) contribution of the microscopic propagules in seawater to the U. prolifera population attached to the rafts; and (3) variation of the proportion of U. prolifera in the floating green algae in the YS. U. prolifera were detected in the green algae attached to Porphyra rafts from March to May 2012, where its relative abundance increased rapidly from 10% at the end of April to 40 -60% in mid-May. Microscopic propagules of U. prolifera, which could be detected from seawater and sediment, contributed significantly to the dramatic increase of the attached U. prolifera on the Porphyra rafts. After the attached green algae were removed from the rafts, U. prolifera rapidly demonstrated dominance in the floating green algal community, and the proportion of U. prolifera increased gradually from south to north. Our conceptual model is that the germination of U. prolifera microscopic propagules on Porphyra rafts promotes the proliferation of attached U. prolifera on the rafts, which release more microscopic propagules into seawater and sediments after they became mature. This positive feedback enhances the dominance of U. prolifera in the attached green algal community in late May, which leads to the formation of green tides after the attached plants are removed from the rafts during Porphyra harvest. The proportion of U. prolifera then increases rapidly in the resuspended and floating green algal community due to its unique structure, making it the most dominant species of floating green algae. The application of the FISH method clearly depicted the early development of green tides in the Subei Shoal and greatly helped to solidify the proposed linkage between Porphyra culture rafts and the formation of green tides in the YS. (C) 2014 Elsevier Ltd. All rights reserved.

Large-scale green tides have occurred consecutively since 2007 in the Yellow Sea (YS), China. The dominant causative species of the green tides has been identified as Ulva prolifera. The origin of green tides in the YS has been traced back to the Subei Shoal based on the results of remote-sensing, numerical simulations and field investigations. However, it is difficult to study the early development of green tides in the Subei Shoal because of the mixture of multiple green algae and the morphological diversity of U. prolifera when under variable environmental conditions. In this study, a rapid and accurate fluorescence in situ hybridization (FISH) method was developed to detect U. prolifera from the community of green algae targeting the 5S rDNA spacer region of U. prolifera. Two specific probes, 5S-1 and 5S-2, were designed based on the sequences of the 5S rDNA spacer regions of U. prolifera, Ulva linza and Ulva flexuosa. Specificity of the FISH method was tested using the six species of green algae commonly occurring in the Subei Shoal, including U. prolifera, U. linza, U. flexuosa, Ulva compressa, Ulva pertusa and Blidingia sp. The results showed that only U. prolifera could be labeled with both probes. Probe 5S-1, which showed a much higher labeling efficiency on U. prolifera, was ultimately selected as the probe for the FISH detection. The sample preparation method was optimized, particularly for the mature green algae, by the addition of cellulase and proteinase K in the pre-hybridization solution. Labeling efficiency with the probe 5S-1 reached 96% on average under the optimized conditions. The successful development of the FISH method has been applied to qualitative and quantitative analysis of field samples collected from the YS, and the results indicate a potential use in future green algae studies. (C) 2014 Elsevier Ltd. All rights reserved.

Some dinoflagellate species within the genera Alexandrium, Gymnodinium and Pyrodinium are well-known producers of paralytic shellfish toxins (PST), which led to many poisoning incidents around the world. In the northern Yellow Sea, an important mariculture zone for scallop Patinopecten yessoensis, PST have been frequently detected from scallops. However, there is little knowledge concerning PST-producing microalgae in this region so far. In cruises carried out in 2011 and 2012, scallop and phytoplankton samples were collected from the northern Yellow Sea. PST were detected from scallops by high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Toxin content and profile were remarkably different among the four tissues, i.e. viscera, adductor muscle, mantle and gonad, suggesting apparent toxin transfer and transformation in scallops. Viscera always had the highest content of PST dominated by low-potency N-sulfocarbamoyl toxins C1 and C2, which closely resembled the toxin profiles of net-concentrated phytoplankton samples in spring. Based on the morphological features, cells of Alexandrium spp. in net-concentrated phytoplankton samples were picked out and a partial sequence of the large subunit ribosomal RNA gene (LSU rDNA) was amplified using a single-cell polymerase chain reaction (PCR) method. Cells of both toxic A. tamarense species complex and non-toxic A. affine were identified from the phytoplankton samples based on the partial LSU rDNA sequence information. According to these findings, it is implied that A. tamarense species complex is the major toxic species related to PST contamination in scallops of the northern Yellow Sea. The presence of both toxic and non-toxic Alexandrium spp. in this region requires for a species-specific method to monitor the distribution and dynamics of A. tamarense species complex.

The identification of core genes involved in the biosynthesis of saxitoxin (STX) offers a great opportunity to detect toxic algae associated with paralytic shellfish toxins (PST). In the Yellow Sea (YS) in China, both toxic and nontoxic Alexandrium species are present, which makes it a difficult issue to specifically monitor PST-producing toxic algae. In this study, a quantitative PCR (qPCR) assay targeting sxtA4 , a domain in the sxt gene cluster that encodes a unique enzyme involved in STX biosynthesis, was applied to analyze samples collected from the YS in spring of 2012. The abundance of two toxic species within the Alexandrium tamarense species complex, i.e., A. fundyense and A. pacificum , was also determined with TaqMan-based qPCR assays, and PSTs in net-concentrated phytoplankton samples were analyzed with high-performance liquid chromatography coupled with a fluorescence detector. It was found that the distribution of the sxtA4 gene in the YS was consistent with the toxic algae and PSTs, and the quantitation results of sxtA4 correlated well with the abundance of the two toxic species ( r = 0.857). These results suggested that the two toxic species were major PST producers during the sampling season and that sxtA -based qPCR is a promising method to detect toxic algae associated with PSTs in the YS. The correlation between PST levels and sxtA -based qPCR results, however, was less significant ( r = 0.552), implying that sxtA -based qPCR is not accurate enough to reflect the toxicity of PST-producing toxic algae. The combination of an sxtA -based qPCR assay and chemical means might be a promising method for monitoring toxic algal blooms.