Coastal Waters Of Southern China Research Articles

Diversity of life history and population connectivity of threadfin fish Eleutheronema tetradactylum along the coastal waters of Southern China

Understanding the diversity of life history, life stage connectivity and population is essential to determine the spatial scale over which fish populations operate. Otolith microchemistry analysis is a powerful tool to elucidate the life history and population connectivity of fish, providing important insights to the natal origin and population structure. In this study, we used laser ablation inductively coupled plasma mass spectrometry to analyze the chemical composition of otoliths throughout the entire lifetime of endangered fourfinger threadfin species, Eleutheronema tetradactylum. We reconstructed the life history of E. tetradactylum from Southern China collected from different locations over a spatial scale of 1200 km. Sr:Ca and Ba:Ca ratios profiles from otolith core-to-edge analysis suggested two contrasting life history patterns. Based on the differences in early life stages, we identified some fish spending their first year in an estuarine environment with subsequent movement to marine coastal systems, while some fish remaining in the coastal systems throughout their entire early life history stages. The non-metric multi-dimensional scaling showed a strong overlap in otolith core elemental composition, indicating a large-scale connectivity in the life history of E. tetradactylum. The immature fish from different natal origins mixed to a large extent when they fed and overwintered in the extensive offshore waters. Clustering of near core chemistry pointed to three possible sources of nursery for the threadfin fish. This study demonstrated the diversity of life history patterns of E. tetradactylum in Southern Chinese waters. Restoration in egg and larvae densities in coastal waters and estuaries may enhance their population abundances.

Taxonomy and Phylogeny of Two Tintinnid Ciliates of Leprotintinnus (Protista, Ciliophora, Choreotrichida) Combining the Loricae, Cytological, Ontogenetic Features, and Barcoding Genes

Tintinnid ciliates are a highly diverse and essential group in the marine planktonic microbial loop. However, most of the known tintinnids were recorded only by the lorica characters and very few of them had been studied on their cytological features. In this study, the morphological characters of the lorica, ciliary pattern, nuclear apparatus, ontogenesis, and the molecular phylogeny of two poorly known tintinnid ciliates, Leprotintinnus nordqvisti (Brandt, 1906) Kofoid and Campbell (1929) and L. simplexSchmidt (1902), isolated from coastal waters of southern China, were investigated based on living observation, silver staining, three nuclear ribosomal DNA markers (18S, ITS1-5.8S-ITS2, and 28S genes) and one mitochondrial DNA marker (CO1 gene). For the first time, the somatic ciliary pattern of the genus Leprotintinnus was disclosed, viz., comprising a ventral, a dorsal, and a posterior kinety as well as a right, a left, and a lateral ciliary field. The diagnoses of both Leprotintinnus species were improved and the neotype was assigned. The ontogenesis of L. nordqvisti was in enantiotropic division mode with the new dorsal and posterior kineties generated de novo. The molecular phylogeny confirmed that Leprotintinnus species are closely related to some species of Tintinnopsis, Stylicauda, Rhizodomus, and Climacocylis. The anterior extending of the ventral kinety together with some of the lateral kinety is likely to be a distinguishing feature to determine their systematic relationships. This study also revealed that (i) the lorica of L. nordqvisti is polymorphic or plastic; (ii) Leprotintinnus tubulosusRoxas (1941) might be a synonym of L. nordqvisti; (iii) Leprotintinnus neriticus sensu Yoo et al. (1988) might be a misidentification of L. simplex.

Novel Contributions to the Taxonomy of the Ciliates Genus Euplotes (Ciliophora, Euplotida): Redescription of Two Poorly Known Species, With a Brief Note on the Distributions of This Genus in Coastal Waters of Southern China

As the typical periphytic ciliate, the genus Euplotes Ehrenberg, 1830 is highly diversified and commonly observed in marine water. In this study, the living morphology, infraciliature and silverline system of two poorly known Euplotes species, E. neapolitanusWichterman, 1964 and E. antarcticusFenchel and Lee, 1972, isolated from coastal water of southern China, were investigated. The original description of these two species were brief, and thus we provided detailed redescription based on our Chinese population. Their diagnoses were improved by adding some morphology characteristics and their detailed illustrations and photomicrographs were first supplied here. Based on the sufficient justification for identification of our population by morphology, their small subunit ribosomal RNA gene sequences which have been reported were linked to the accurate species name. Phylogenetic analyses showed that these two species cluster with their congeners which shared high morphological similarities with them. In addition, the geographic distribution of the genus Euplotes in coast of southern China was revealed, and the mangrove was considered as the ideal habitat for them by possessing the higher species richness.

Overview of the biodiversity and geographic distribution of aloricate oligotrich ciliates (Protozoa, Ciliophora, Spirotrichea) in coastal waters of southern China

Aloricate oligotrich ciliates are important components of marine microplankton. This paper summarizes the results of several biodiversity and faunal studies on this group in typical coastal habitats of southern China that were carried out from 2006 to 2016. The main findings are as follows: (1) a total of 39 species belonging to 17 genera, seven families and four orders of aloricate oligotrich (s. l.) ciliates were identified from coastal waters of Zhanjiang, Guangzhou, Shenzhen, Huizhou, and Hong Kong; among these 16 species, four genera, one family and one order were new to science; (2) the order Oligotrichida represents the most abundant taxon with highest species richness and its members are widely distributed in all coastal habitats; the family Strombidiidae and the genus Strombidium comprise the highest proportion of all oligotrichs at family and genus levels, respectively; (3) based on the results of our taxonomic investigations, the biodiversity of oligotrichs in five typical habitats are compared; mangrove wetland possessing the highest species richness of oligotrich ciliates represents a biodiversity hotspot habitat in the southern coast of China; (4) morphologies of 10 poorly known species, namely Pelagohalteria cirrifera, Strombidium conicum, Spirostrombidium schizostomum, Parallelostrombidium paralatum, Omegastrombidium elegans, Varistrombidium kielum, Spirotontonia turbinata, Pelagostrobilidium simile, Strombidinopsis batos, and Strombidinopsis cheshiri are redescribed based on living and protargol-stained specimens, and some new characters are analysed. Improved diagnoses of Strombidium conicum and Strombidinopsis batos are supplied.

Taxonomy and phylogeny of Pseudovorticella littoralis sp. n. and P. alani sp. n. (Ciliophora: Peritrichia) from coastal waters of southern China

The morphology, infraciliature, and silverline system of two peritrich ciliates, Pseudovorticella littoralis sp. n. and P. alani sp. n., isolated from coastal waters of southern China, were investigated based on both living and silver-stained specimens. Pseudovorticella littoralis sp. n. is characterized by the following combination of characters: cell inverted cone-shaped; contractile vacuole ventral; J-shaped macronucleus; infundibular polykinety 3 with two kinetosome rows of equal length; 19–26 silverlines from peristome to trochal band and 5–14 from trochal band to scopula. Pseudovorticella alani sp. n. is characterized by: cell inverted bell-shaped; contractile vacuole ventral; J-shaped macronucleus recurved almost forming a loop; infundibular polykinety 3 with three kinetosome rows, outer two rows longer than inner one; 48–61 silverlines between peristome and aboral trochal band, and 12–20 between aboral trochal band and scopula. The SSU rDNA sequences of both new species are reported and their genetic distances with congeners and phylogenetic relationships are investigated. Pseudovorticella and Epicarchesium cluster into two subclades with low support values. One subclade contains nearly all the available sequences of Pseudovorticella and Epicarchesium. Another one contains P. monilata and E. pectinatum. This calls on the need of a generic re-classification of Pseudovorticella and Epicarchesium based on more morphological and molecular data.

Corrigendum to "Morphology and Phylogenetic Placement of Three New Zoothamnium species (Ciliophora: Peritrichia) from Coastal Waters of Southern China by Shen etal".

Corrigendum to "Morphology and Phylogenetic Placement of Three New Zoothamnium species (Ciliophora: Peritrichia) from Coastal Waters of Southern China by Shen etal".

Abundance and molecular diversity of thraustochytrids in coastal waters of southern China.

Thraustochytrids are unicellular fungi-like (heterotrophic) marine protists that have long been considered to play an important role in the biogeochemical cycles of the coastal oceans. However, the significance of their ecological functions and their diversity in marine ecosystems remain largely unknown. In this report, we examined the spatial and temporal variations of planktonic thraustochytrids, their relationship with other environmental factors, and their diversity in the subtropical coastal waters of China. The abundance of planktonic thraustochytrids ranged from 2.56×105 to 17.57×105 cells L-1 with highest abundance detected in polluted coastal water in the Spring (March) season. The thraustochytrid biomass was greater than the bacterial biomass in most seawater samples, ranging from 32.29 to 359.51% that of bacterioplankton. The abundance of thraustochytrids appeared to be largely related to that of bacterioplankton and to chemical oxygen demand in water columns. High-throughput sequencing analyses revealed a total of 105 OTUs (97% similarity), which were members of genera Thraustochytrium, Aplanochytrium, Oblongichytrium, Ulkenia, Labyrinthula and undescribed novel phylotypes. Results of this study indicated unprecedented high diversity of labyrinthulomycetes as well as the presence of novel labyrinthulomycete and thraustochytrid lineages, and also provided new information on the significant role of thraustochytrids in microbial food webs in a coastal marine ecosystem.

Dependence of Hainan medaka, Oryzias curvinotus (Nichols & Pope, 1927), on salinity in the Tien Yen estuary of northern Vietnam

Species of the genus Oryzias are models for studies of adaptation to osmotic environments because they demonstrate inter-species adaptability. Oryzias curvinotus, a fresh and brackish water species, is distributed from the coastal waters of southern China to northern Vietnam. The correlation of O. curvinotus’ distribution with physical water conditions in the Tien Yen estuary of northern Vietnam was recorded during monthly collections for one year. For the current study, a total of 2916 individuals of O. curvinotus were caught, of which 942 were selected to be measured and have their developmental stage recorded: 41 larvae, 749 post-larvae and 152 juveniles or adults. A developmental description and an identification to the species level are also provided. Temperature, salinity and turbidity at collection sites ranged from ca. 17 to 34°C, from ca. 0 to 16 psu and from 0 to 524 NTU, respectively. A peak catch per unit effort was found in April and at the stations at which salinity was about 0.6 to 2.5 psu. In stations where salinity was greater than 17 psu or at 0 psu, few specimens were collected. Examination of distribution indicated a tendency of the species to be present along the estuary, with the center part as the main habitat of this species. The function of an estuarine environment for fishes, which inhabit fresh and brackish waters, is discussed.

Increasing dissolved nitrogen and phosphorus export by the Pearl River (Zhujiang): a modeling approach at the sub-basin scale to assess effective nutrient management

The Pearl River (Zhujiang in Chinese) has been exporting excess of nitrogen (N) and phosphorus (P), causing eutrophication in the coastal waters of southern China for decades. However, sources of these nutrients and their locations are not well studied for the Pearl River basin. As a consequence, it is difficult to formulate effective management options to reduce these nutrients in the river and to prevent further eutrophication. We developed a sub-basin model based onto the Global NEWS-2 (Nutrient Export from WaterSheds) model for the period of 1970–2050 to analyze trends in dissolved inorganic N and P (DIN and DIP) and to identify the main sources of these nutrients and their locations. We validated our model by comparing modeled nutrient fluxes with observed. Future analyses are based on Millennium Ecosystem Assessment scenario that assumes a globalized world with a reactive environmental management. DIN and DIP inputs to the coastal waters are calculated to increase by a factor of 2–2.5 between 1970 and 2050. Over two-thirds of the DIN and DIP inputs to the coastal waters stem from two down-stream basins (Zhujiang delta and Dongjiang), where agriculture and sewage are important drivers of this increase. Agriculture accounts for over 40 % of DIN inputs to coastal waters. Sewage and agriculture account for over 90 % of DIP inputs. Thus nutrient management in agriculture and sewage in down-stream areas is more effective in reducing coastal eutrophication than nutrient management in up- and middle-stream areas of the Pearl River basin.

Diversity and biochemical features of culturable fungi from the coastal waters of Southern China.

Fungi play a major role in various biogeochemical cycles of terrestrial and marine ecosystems. However, fungi in marine environments remain to be one of the most under-studied microbial groups. This study investigates the diversity of planktonic fungi from the coastal habitat off Pearl River Delta (China) using culture-dependent approach. A total of 22 fungi and 9 yeast isolates were recovered from 30 seawater and 2 sediment samples. Microscopic and ITS rRNA gene sequence analyses revealed that most of the fungi belonged to the phylum Ascomycota and Basidiomycota with a very small percentage (3%) of the subphylum Mucoromycotina of the Phylum Zygomycota. Most of these fungal isolates exhibited considerable production of extracellular enzymes, cellulase, lipase and laccase. Fungal isolates of two genera Mucor and Aspergillus sp. demonstrated pelletization capability over a wide range of pH, suggesting them as potential agents towards algae harvesting and wastewater treatment.

Culturable diversity and biochemical features of thraustochytrids from coastal waters of Southern China

Thraustochytrids are ubiquitous marine osmo-heterotrophic fungi-like microorganisms with only about 40 identified species till now. In this study, a total of 60 thraustochytrid strains were isolated from marine coastal habitats. Analysis of 18S rRNA gene sequences revealed that they belonged to three genera, i.e., Schizochytrium, Aurantiochytrium, and Thraustochytrium. All of the isolates were found to show considerable cellulolytic and lipolytic activities. Strains of Aurantiochytrium sp. and Thraustochytrium sp. were found to produce the highest levels of extracellular polysaccharides (EPS), which reached 345 μg ml(-1) in the growth media. Fourier transform infrared (FTIR) spectra of the EPS samples derived from two thraustochytrids (PKU#Sed1 and #SW1) displayed peaks for carbohydrates, proteins, lipids, uronic acids, and nucleic acids. Fatty acid profiles of four thraustochytrids comprised of palmitic acid (C16:0) and docosahexaenoic acid (DHA) as their major constituents. Schizochytrium sp. demonstrated the highest DHA production at 44 % of total fatty acids (TFA) with biomass and DHA yield of 7.1 and 1.6 g l(-1), respectively, on the fourth day of growth. All the four isolates exhibited considerable production of palmitic acid (16:0) in their fatty acid profiles ranging from 35 to 50 % TFA. This is the first report on extracellular enzymes, EPS, and DHA production from thraustochytrids isolated from the coastal habitats of China.

DNA barcoding reveals cryptic diversity in the peanut worm Sipunculus nudus

Peanut worm (Sipunculus nudus) is a cosmopolitan species mainly distributed in tropical and subtropical coastal waters. Analysis of the mitochondrial cytochrome c oxidase subunit I (COI) gene sequences among S.nudus from GenBank revealed high genetic variation (p-distance, 0.115-0.235; k2p, 0.128-0.297) and paraphyletic relationships. These indicated misidentification and/or cryptic diversity may be present in the genus Sipunculus. To understand the genetic diversity and to manage the recourse of S.nudus, we collected specimens from coastal waters of southern China and Taiwan. In the phylogenetic topology, specimens can be separated into four distinct clades; three of these clades (clade A, B and C) were only represented from this region (southern China and Taiwan), but the clade D grouped with individuals from Central America (Atlantic coast). Furthermore, individuals of clades A and D were collected at the same location, which does not support the hypothesis that this genetic break reflects contemporary geographical isolation. The four distinct clades observed among coastal waters of southern China and Taiwan indicated underestimated diversity. It is noteworthy that the cryptic diversity is vulnerable under high pressure of human activity.

Cadmium and copper accumulation and toxicity in the macroalga Gracilaria tenuistipitata

The macroalga Gracilaria tenuistipitata is widely distributed in the coastal waters of southern China, and is extensively used as the main food source in abalone aquaculture. However, it also possesses a high ability to accumulate trace metals in its tissues. This study investigated the accumulation of cadmium (Cd) and copper (Cu) in this macroalga under various temperatures and salinities, and the subsequent influences on growth rate, lipid peroxidation, and total energy reserve. The accumulation of both Cd and Cu was enhanced with increasing temperature and decreasing salinity. The bioaccumulation factor of Cu was ~10 times higher than that of Cd. Changes in temperature, salinity and accumulated metals all affected the tested biomarkers to some extent. We demonstrated that growth rate, lipid peroxidation level and total energy reserve were all significantly correlated with the accumulated tissue Cu concentrations, suggesting that Cu accumulation in the tissue can be used as a proxy for measuring Cu toxicity in G. tenuistipitata under various environmental conditions. In contrast, among the 3 toxic endpoints, only growth rate was inversely related to the Cd tissue concentrations. Cu exerted a greater toxic effect on G. tenuistipitata than Cd, largely due to its different toxicological mechanisms and biological accumulation potentials. Cd appeared to have no profound influence on the production of reactive oxygen species. A higher Cd accumulation at lower salinity did not cause a stronger growth inhibition as compared to Cu. Given the commercial value of the macroalga as a main food source in abalone aquaculture, Cu contamination and high temperature should be avoided in the culture of G. tenuistipitata, because they can reduce its energy reserves.

Spectral absorption coefficient of phytoplankton and its relation to chlorophyll a and remote sensing reflectance in coastal waters of southern China

The spectral absorption coefficient of phytoplankton in coastal waters of southern China is investigated. Large variations in the absorption coefficient of phytoplankton are found. The absorption coefficient of phytoplankton at 443 nm ranged from 0.006 m−1 to 0.484 with an average value of 0.067 m−1 The chlorophyll-specific absorption coefficient of phytoplankton is also a bio-optical variable, with a spectrally averaged value of 0.025 m2˙mg−1. The variations of chlorophyll-specific absorption coefficient are mainly attributed to pigment composition of phytoplankton and package effect. The chlorophyll-specific absorption coefficient of phytoplankton decreases with the increasing of chlorophyll a concentration. This relationship can be described by a power law function, with the parameters and the coefficient of determination r2 as functions of wavelength, but the parameters describing the relationships in present study differed from that in Case 1 waters, thus the regional adjustment of model parameters was of particular significance for improving the accuracy of bio-optical algorithms for estimation of Chl-a concentration and primary production from remotely sensed data. Regression analysis of reflectance (Rrs) ratio and absorption coefficient of phytoplankton (aph) indicates a close correlation between them, which means that it is possible to sretrieve absorption coefficient of phytoplankton using ocean color remote sensing data in optically complex coastal waters.

Toxin composition variations in cultures of Alexandrium species isolated from the coastal waters of southern China

The composition of the paralytic shellfish toxins (PSTs) of five Alexandrium tamarense strains isolated from the coastal waters of southern China and one Alexandrium minutum strain from Taiwan Island were investigated. A. tamarense CI01 and A. tamarense Dapeng predominantly produced C2 toxin (over 90%) with trace amounts of C1 toxin (C1), gonyautoxin-2 (GTX2) and GTX3; two strains of A. tamarense HK9301 maintained in different locations produced C1-4 toxins and GTX1, 4, 5 and 6; no PSTs were found in A. tamarense NEW, while A. minutum TW produced only GTX1-4. The toxin compositions of cultured A. tamarense strains did not vary as much during different growth phases as did the toxin composition of A. minutum TW. The toxin compositions of A. tamarense HK9301-1 did not change significantly under different salinity, light intensity, and nitrate and phosphate levels in the culture medium, although the toxin productivity varied expectably. Another strain HK9301-2 maintained in a different location produced much less toxins with a considerably different toxin composition. Under similar culture maintenance conditions for 3 years, the toxin profiles of A. tamarense HK9301-1 did not change as much as did A. tamarense CI01. Our results indicate that toxin compositions of the dinoflagellate strains are strain-specific and are subject to influence by nutritional and environmental conditions but not as much by the growth phase. Use of toxin composition in identifying a toxigenic strain requires special caution.

Toxin composition variations in cultures of Alexandrium species isolated from the coastal waters of southern China

Toxin composition variations in cultures of Alexandrium species isolated from the coastal waters of southern China

Interactions of paralytic shellfish toxins with xenobiotic-metabolizing and antioxidant enzymes in rodents

Paralytic shellfish toxins (PSTs) are neurotoxins known to block voltage-gated sodium channels in intoxicated animals and humans. Their metabolism in mammalian systems and their effects on other receptors are not as well understood. In this study, we investigated the in vitro metabolism of two classes of PSTs, gonyautoxin 2/3 (GTX2/3) and C1/2 toxins (C1/2), using rat and mouse liver enzyme preparations. We also analyzed the effects of these toxins on several antioxidant and xenobiotic-metabolizing enzymes in mice. These toxins were selected for their prevalence in the coastal waters of Southern China. When the toxins were incubated with liver preparations containing Phase I and Phase II xenobiotic metabolizing enzymes and appropriate co-factors, no transformation of the toxins was detectable. When mice were given sub-lethal doses of GTX2/3, a loss of activity was observed in hepatic ethoxyresorufin- O-deethylase, penthoxyresorufin- O-deethylase, glutathione peroxidase and superoxide dismutase, but not in glutathione S-transferase, catalase and glutathione reductase. Exposure to the same mouse units of C1/2 caused only a slight reduction in the activity of penthoxyresorufin- O-deethylase and glutathione peroxidase. Our results indicated that these toxins may not be metabolized readily in mammals and that they may cause adverse effects other than sodium channel blocking.

Distribution and biology of marine cladocerans in the coastal waters of southern China

Distribution and biology of marine cladocerans in the coastal waters of southern China