After nearly 20 years of exploration, various areas of the seafloor with hydrocarbon seepage have been discovered in the South China Sea (SCS). Through linking subsurface and seafloor biospheres, seeps have become natural laboratories to enhance our knowledge on the processes of hydrocarbon migration and associated hydrocarbon-based ecosystems in the marine environment. This review summarizes the distribution of macrofauna in the active seep areas of the SCS and describes the physiological characteristics of three groups of representative macrofauna (bathymodioline mussels, pliocardiine clams, siboglinid tubeworms). In addition, a comparison is made between the seep macrofauna of the SCS and the Northwest Pacific Ocean. Modes of energy transfer and microbial processes are elucidated by integrating trace element, stable isotope, and lipid biomarker data of macrofaunal soft tissues. Our aims are to provide an overview of the macro-ecology of the SCS seeps and to underscore aspects which desire more research efforts in the future. 

Macro-ecology of cold seeps in the South China Sea

Mussels in the subfamily Bathymodiolinae are common inhabitants of deep-sea chemosynthetic habitats, but in many places their diversity remains unknown. Here we describe Nypamodiolus samadiae n. gen. et n. sp. (Mytilidae: Bathymodiolinae) based on samples collected from the Haima cold seep in the South China Sea. Phylogenetic analyses based on fragments of three mitochondrial ( cox1 , 16S rRNA and nad4 ) and three nuclear ( 18S rRNA , 28S rRNA and histone H3 ) genes show that this new species belongs to a new genus, Nypamodiolus , which includes three named species ( Myrina longissima Thiele and Jaeckel, 1931 , Myrina simpsoni Marshall, 1900 , Idasola japonica Habe, 1976 ) and a few undescribed species. Nypamodiolus n. gen. is characterized by small-sized, modioliform to fan-shaped shells with the umbones in a non-terminal position, and by robust anterior and posterior byssal retractor muscles arranged in roughly one plane. Most closely related to Nypamodiolus samadiae n. sp. is an undescribed species from northern Papua New Guinea, to which it has a Kimura-2-parameter genetic distance of 11.8% for cox1 . Sequencing the V3–V4 region of the microbial 16S rRNA gene reveals two dominant gill-associated symbionts in the new species, including one sulfur-oxidizing Gammaproteobacteria (relative abundance: 43.8–58.8%) and one unclassified Spirochaetes (relative abundance: 23.9–28.1%). Morphologically, N. samadiae n. sp. is similar to N . simpsoni , while can be distinguished by a larger maximum shell size (45.0 mm vs. 40.0 mm), larger length/height ratio (2.6–2.9 vs. 2.1–2.4), broader posterior end, slightly curved dorsal margin, and more anterior umbones. • A new deep-sea mussel, Nypamodiolus samadiae new genus and species, is described. • It is phylogenetically most closely related to a species from Papua New Guinea. • Morphologically it is most similar to Nypamodiolus simpsoni. • It harbors both Gammaproteobacteria and Spirochaetes in its gill epithelial cells. 

Phylogenetic placement, morphology and gill-associated bacteria of a new genus and species of deep-sea mussel (Mytilidae: Bathymodiolinae) from the South China Sea

Bioaccumulation of emerging persistent organic pollutants in the deep-sea cold seep ecosystems: Evidence from chlorinated paraffin.

Knowledge about community structure and genetic diversity can help assess the potential for change in the loss and restoration of biodiversity, thereby facilitating effective management and ecosystem protection. Macroinvertebrate communities are an important biotic component of deep sea cold seep ecosystems. As Haima cold seep is increasingly being assessed for its potential gas hydrate mineral wealth, knowledge of community characteristics and genetic diversity of macrobenthos is needed to anticipate the potential impacts on biodiversity. In this study, we examined species diversity and community structure at five sites in the Haima cold seep using a remote-operated vehicle (ROV) for in situ surveying. The results identified 12 macrobenthic species from 5 phyla and 12 families. The macrobenthos community could be divided into two communities (H1 and H2=mussel bed community, and H3 and H4= vesicomyid clams community) based on CLUSTER and NMDS analyses. Gigantidas haimaensis (Mollusca), Branchipolynoe pettiboneae (Annelida), and Histampica haimaensis (Echinodermata) were most dominant within their respective phyla, with values of the dominance of 0.160, 0.021 and 0.114, respectively. The genetic diversity of these three typical macrobenthic species in the Haima cold seep was evaluated using the mitochondrial cytochrome c oxidase subunit I ( COI ) gene, haplotype, and nucleotide diversity values were 0.651 to 0.912 and 0.00148 to 0.00812, respectively, representing high haplotype diversity but low nucleotide diversity. Finally, mitochondrial concatenated dataset (MCD) sequences from three mitochondrial genes ( ATP6 , COI , and NAD4 ) and 294,734 genome-wide single nucleotide polymorphisms (SNPs) from restriction site-associated DNA-sequencing (RAD-seq) data were obtained from 60 individuals from two sites (H1 and H2), providing deep insight into the genetic diversity and structure of G. haimaensis , the engineer species in Haima cold seep. No significant genetic differentiation between G. haimaensis in H1 and H2 was detected based on MCD sequences. Nevertheless, when using SNP datasets, a small but clear genetic subdivision between G. haimaensis in the two sites as revealed by STRUCTURE and principal component analysis (PCA). The results comprehensively illuminate macrobenthos biodiversity in the Haima cold seep ecosystem and provide a baseline against which population dynamics may be assessed in the future. 

/pdf/community-characteristics-and-genetic-diversity-of-h1kvruvx.pdf

Community Characteristics and Genetic Diversity of Macrobenthos in Haima Cold Seep

﻿Abstract Gastropods in the family Provannidae are characteristic members of deep-sea chemosynthesis-based communities. Recently, surveys of hydrothermal vents and hydrocarbon seeps in the western Pacific have revealed a high diversity of provannids, with new discoveries continuing to be made. Here, we report and describe a further new species, Provannaexquisitasp. nov., discovered from the Northwest Eifuku volcano on the Mariana Arc. This new species is distinguished from all other described Provanna species by its exaggerated sculpture characterised by two to three sharply raised, flange-like keels on the teleoconch whorls. The status of P.exquisitasp. nov. is also supported by a molecular phylogeny reconstruction using the mitochondrial cytochrome c oxidase subunit I (COI) gene, which suggested that it is most closely related to a clade of three species described from Okinawa Trough vents including P.clathrata, P.subglabra, and P.fenestrata. Despite being one of the better-explored regions of the world in terms of hydrothermal vent biodiversity, new discoveries like P.exquisitasp. nov. continue to remind us that we are nowhere near fully documenting the species diversity in these unique ecosystems—despite the species being threatened from imminent anthropogenic impacts such as deep-sea mining.

/pdf/a-new-provannid-snail-gastropoda-abyssochrysoidea-discovered-1z4a5gyu.pdf

﻿A new provannid snail (Gastropoda, Abyssochrysoidea) discovered from Northwest Eifuku Volcano, Mariana Arc

The macrofaunal community in the Haima cold seeps of the South China Sea was investigated, and trophic relationships were evaluated using carbon and nitrogen stable isotope signatures (δ13C and δ15N). A total of 30 macrofaunal species were identified in this study, most of which were collected from the Gigantidas haimaensis mussel beds. Only four macrofaunal species were collected from the Calyptogena marissinica clam beds, where the environment may not be suitable for the survival of most macrofauna. The bush of slim tubeworms (Sclerolinum sp.) might be an important nursery ground for mussels. G. haimaensis was the predominant species, and its average δ13C and δ15N values were −52.7‰ and 0.6‰, respectively. Compared with the stable isotope signatures of particulate organic matter (POM), it suggested that the food source of macrofauna in the Haima cold seeps was mainly originated from chemosynthetic autotrophs. In the mussel bed, most of the macrofauna had a large δ13C isotopic distance compared with G. haimaensis, suggesting that G. haimaensis was not a direct food source for most cold-seep macrofauna in the mussel bed. The variation in stable isotope signatures of macrofauna might be attributed to different proportions of methanotrophic and thiotrophic endosymbionts. Neolithodes brodiei and Bathynomus jamesi showed the highest δ13C and δ15N values. However, the large isotopic distance indicated that N. brodiei and B. jamesi might just occasionally visit the cold-seep ecosystem and their food sources were mainly from the upper ecosystem relying on photosynthesis. Overall, our results suggested that there was no significant predator-prey relationship among these macrofaunal species in the Haima cold seeps. This study provided important baseline data of stable isotope signatures for further studies to elucidate the trophic interaction among seep organisms. 

A preliminary study of macrofaunal communities and their carbon and nitrogen stable isotopes in the Haima cold seeps, South China Sea

Until now, no completely effective parasite‐specific drugs or vaccines have been approved for the treatment of cryptosporidiosis. Through the separation and identification of the sporozoite membrane protein of Cryptosporidium parvum (C. parvum), 20 related proteins were obtained. Among them, a calmodulin‐like protein (CML) has a similar functional domain‐exchange factor hand (EF‐hand) motif as calmodulin proteins (CaMs), so it may play a similarly important role in the invasion process. A 663 bp full gene encoding the C. parvum calmodulin‐like protein (CpCML) was inserted in pET28a vector and expressed in Escherichia coli. An immunofluorescence assay showed that CpCML was mainly located on the surface of the sporozoites. Three‐week‐old female BALB/c mice were used for modelling the immunoreactions and immunoprotection of recombinant CpCML (rCpCML) against artificial Cryptosporidium tyzzeri infections. The results indicated a significantly increased in anti‐CpCML antibody response, which was induced by the immunized recombinant protein. Compared to rP23 (recombinant P23), GST6P‐1 (expressed by pGEX‐6P‐1 transfected E. coli), GST4T‐1 (expressed by pGEX‐4T‐1 transfected E. coli), glutathione (GSH), adjuvant and blank control groups, rCpCML‐immunized mice produced specific spleen cell proliferation in addition to different production levels of IL‐2, IFN‐γ, TNF‐α, IL‐4 and IL‐5. Additionally, immunization with rCpCML led to 34.08% reduction of oocyst shedding in C. tyzzeri infected mice faeces which was similar to rP23. These results suggest that CpCML may be developed as a potential vaccine candidate antigen against cryptosporidiosis.

Yu Chen

Papers

A preliminary study of macrofaunal communities and their carbon and nitrogen stable isotopes in the Haima cold seeps, South China Sea

Isolation and identification of sporozoite membrane protein of Cryptosporidium parvum and evaluation of calmodulin‐like protein immune protection

Fibrillarin RNA methylase is an interacting protein of Cryptosporidium parvum calmodulin-like protein (CpCML).