Zongling Wang’s research while affiliated with First Institute of Oceanography and other places

Introduction Mercury (Hg) and its organic forms can accumulate in marine organisms, undergoing biomagnification as they transfer through food chains. However, the factors affecting such Hg biomagnification are not fully understood. Methods This study analyzed the biomagnification of total mercury (THg) and methylmercury (MeHg) in marine food chains represented by invertebrates and fish from the offshore waters of Changshan Archipelago, grouped into continuous trophic level (TL) ranges based on nitrogen stable isotopic analysis. Results Concentrations of THg and MeHg ranged from 4.8 ng/g to 115.4 ng/g and 1.8 ng/g to 47.3 ng/g in invertebrates, and from 3.7 ng/g to 102.1 ng/g and 0.5 ng/g to 67.6 ng/g in fish, with TL ranges for invertebrates and fish of 1.27–2.70 and 1.97–3.60, respectively. Hg concentration increased with increasing TLs in both fish and invertebrates. Combined with nitrogen stable isotopic analysis, trophic magnification factors (TMF) were 1.51 and 1.16 for THg and MeHg in fish, and 1.95 and 1.71 for THg and MeHg in invertebrates, respectively, indicating the biomagnification of THg and MeHg in the study area. Further analysis of Hg biomagnification showed higher TMF values of Hg in both invertebrate and fish groups with higher δ¹³C values, suggesting that food sources influenced Hg biomagnification in marine organisms. Discussion Food sources with lower δ¹³C values might reduce biomagnification efficiency of both THg and MeHg within marine fauna. These results aided understanding of Hg biomagnification in marine food chains and provided a reference for developing ways to harness Hg pollution.

Harmful macroalgal blooms caused by Ulva prolifera and Sargassum horneri are increasing in the Yellow Sea and East China Sea. However, our understanding of macroalgal blooms before 2008 is fragmented and unclear. Using time-series Landsat imagery from 1984 to 2008, we examined macroalgal bloom events and their evolutionary patterns. The results suggest that no macroalgal blooms were observed before 1999. Ulva blooms could be traced back to 1999 and occurred on a small scale in 2000, 2004 and 2005, before escalating into large green tides in 2007 and 2008. Notably, these Ulva blooms were confined to the southern Yellow Sea from May to August. In comparison, Sargassum blooms were first detected in the East China Sea in March 2000 and occurred almost every year thereafter, although the size of the blooms showed significant interannual variation. The distribution areas generally moved northwards from March until the bloom dissipated in May or June, suggesting the influence of the monsoon and currents. Our investigation provided some insight into the bloom history of these two harmful macroalgal blooms in the Yellow Sea and East China Sea.

Modern stalked crinoids, an important group of echinoderms, represent the ancestral mode of crinoids, and studying their evolution is key to understanding the evolution of echinoderms. In this study, we selected Metacrinus rotundus, a species of modern stalked crinoids, for investigation. We generated M. rotundus transcripts using Pacific Biosciences single-molecule real-time (SMRT) long-read sequencing technology. A total of 160,849 full-length (FL) transcripts were captured by Iso-Seq, with a mean length of 2,470 bp. Of these FL transcripts, 110,859 were well-annotated based on public database. A portion of transcripts remained unannotated, representing potential novel genes for M. rotundus. Additionally, we identified 71,740 long-noncoding RNA (LncRNAs), 57,548 simple sequence repeats (SSRs), and 3,486 hypothetical transcript factors (TFs). By comparing Holothuroid and Echinoid, M. rotundus have a higher proportion of zf-CCCH and TF_Otx within TFs, as well as trinucleotide SSRs within SSRs. Notably, transposable elements (TEs) make up a large proportion of the full-length transcriptome of M. rotundus, with RNA transposons being the largest class of annotated TEs. Our study enhances understanding of the characteristics of M. rotundus transcriptome and provides a valuable genetic resource for further studies on adaptive evolution in this species, as well as in other crinoids.

Microbial communities within animals provide nutritional foundation and energy supply for the hydrothermal ecosystem. The peltospirid snail Gigantopelta aegis forms large aggregation in the Longqi vent field on the Southwest Indian Ridge. This endemic species is characterized by a changeable diet and morphology, especially reflected in internal organs such as remarkably enlarged esophageal glands. Here, 16S full-length rRNA gene analysis was performed to compare the variations in esophageal gland microbiota between two body size groups (small and large) of G. aegis. Phyla Proteobacteria and Bacteroidetes were the dominant featured bacteria contributing to the microbial community. No significant differences between the small and large groups were revealed by the diversity index and principal component analysis (PCA) clustering. The differences were in the relative abundance of bacteria. Compared with small-sized snails, the larger ones housed more Thiogranum (9.94% to 34.86%) and fewer Sediminibacterium (29.38% to 4.54%). Functional prediction for all of the microbiota showed that the pathways related to metabolism appeared highly abundant in smaller G. aegis. However, for the larger ones, the most distinctive pathways were those of environmental information processing. Facultative symbiotic Sulfurovum was marked as a core node in the co-occurrence network and suggested an influence on habitat selection of G. aegis in hydrothermal fields. In summary, variations in bacteria composition and potential functions possibly reflected changes in the anatomical structure and dietary habits of G. aegis. These dominant bacteria shared capabilities in nutritional supplementation and ecological niche expansion in the host, potentially a key adaptation for hydrothermal survival. IMPORTANCE Dominant in the Longqi hydrothermal vent Southwest Indian Ridge, Gigantopelta aegis was observed to undergo unique and significant morphological changes and diet shifts known as cryptometamorphosis. During this process, G. aegis developed a specialized bacteria-housing organ, the esophageal gland, in the later life stages. Our research discovered variations in esophageal gland microbes between different body size groups of snails. These bacteria were closely related to the development and health of G. aegis. Full-length 16S rRNA gene analysis revealed more Thiogranum and fewer Sediminibacterium, suggesting a potential association with environmental adaptation. In the small-sized group, the potential functions were enriched in metabolism, while in larger G. aegis individuals, predictions indicated adaptive functions such as environmental information processing. Also, symbiotic Sulfurovum could be one of the factors influencing the habitat selection of G. aegis. Understanding the complex relationship between benthic macrofauna and microbes helps us describe the mechanisms of survival in extreme environments.

Deep-sea corals are critical to global exploration of deep-sea biodiversity, but research on them in the Indian Ocean is very limited. In this study, we report the first discovery of two new species of red corals at a depth of 1697 m in the western Indian Ocean. The species were identified through detailed morphological analysis, including microscopic examination of colony structure, branches and autozooids (assessing size, abundance and spacing), as well as scanning electron microscopy (SEM) of sclerite morphology and quantity. Two species for the genus Hemicorallium Gray, 1867 were found as new species, designated Hemicorallium indicodensumsp. nov. and Hemicorallium jiaolongensissp. nov.H. indicodensumsp. nov. is characterised by densely branched structures and numerous globular double-club sclerites, distinguishing it from other species. Meanwhile, H. jiaolongensissp. nov. features yellowish-white colonies with short rods with sharp, large radial projections in the tentacles. Four mitochondrial regions were used to reveal the phylogenetic relationship in Coralliidae, supporting the taxonomic placement of these two new species. This study provides significant new insights into the biodiversity of deep-sea corals in the Indian Ocean, enriching the known species pool. Additionally, a more comprehensive key to the genus Hemicorallium is provided, further enhancing our understanding of the group’s taxonomy.

Green tides caused by Ulva prolifera occur annually in the Yellow Sea of China, and the massive amount of biomass decomposing during the demise stage of this green tide has deleterious ecological effects. Although microorganisms are considered key factors influencing algal bloom demise, an understanding of the microbial-algae interactions within the phycospheric microenvironment during this process is still lacking. Here, we focused on the variations in phycospheric microbial communities during the late stage of the green tide in three typically affected areas of the Yellow Sea via metagenomic sequencing analysis. In total, 16.9 million reads obtained from 18 metagenome samples were incorporated into the assembled contigs (13.4 Gbp). The phycosphere microbial community composition and diversity changed visibly during the demise of U. prolifera. The abundances of algae-lysing bacteria, Flavobacteriaceae at the family level and Alteromonas, Maribacter, and Vibrio at the genus level increased significantly in the phycosphere. In addition, the levels of glycoside hydrolases (GHs) and polysaccharide lyases (PLs) enzymes, which decompose U. prolifera polysaccharides in the phycosphere, were greater. Therefore, the degradation of algal polysaccharides can increase the efficiency of carbon metabolism pathways in the phycospheric microenvironment. Most of the genes detected in the phycosphere, especially norC, nrfA, and nasA, were associated with nitrogen metabolism pathways and showed dynamics related to the demise of the large amount of organic matter released by a green tide. Therefore, the demise of green tide algae may affect the potential carbon and nitrogen cycles of the phycospheric microenvironment by driving changes in the structure and diversity of microbial communities. Our research provides a novel perspective to better understand the ecological impact of U. prolifera during the green tide demise stage.