Institutional Repository of South China Sea Institute of Oceanology, CAS
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Carbonate sedimentary characteristics of the beach rocks around Qilian Islets and Cays, Xisha Islands: Implication for coral reef development and decline
No full textBeach rocks, developed on the coast of Qilian Islets and Cays, Xisha Islands, China, represent carbonate sedimentary formation on a typical biogenic coast adjacent to coral reef areas. The subaerial and submarine distribution and natural outcrop sections of beach rocks around three islets were surveyed, traced, measured and mapped to determine their development and depositional successions. Carbonate sedimentary characteristics of the beach rocks show that more than 95% of sediments are sourced from adjacent reef flat and reef crest, and are dominated by reef-building coral skeletal fragments and detritus, calcareous algae, and other skeletal grains of reef dwellers. Bioclastic content, algal and microbial content, sorting and roundness of skeletal grains and porosity in depositional successions change with sediment source, sediment accumulation rate, grain characteristics and textures of sediments, hydrodynamic intensity and cementation features. Cementation of the beach rocks is characterized by the binding action of algae and microbes, the micritization caused by boring of endolithic algae and microbes, the early marine cementation, and the early meteoric cementation. Algal and microbial activity played a major role in micritization of skeletal grains of beach rocks. The beach rock formation is mainly affected by the algal and microbial content in beach sediments, the sediment supply from reef flat, the grain characteristics of beach sediments, cementation and diagenesis process, the hydrodynamic intensity driven by wind and monsoons, and sea-level changes. The developmental dimensions and spatial extent of coral reef architecture, the flourishing and extinction of reef-building organisms in reef ecosystem, the abundance of algae and microbes and the diversity of reef dwellers may influence wave energy dissipation and sediment transport patterns in reef flat, thus alter the carbonate sediment budget of the coastal environment. (C) 2016 Elsevier B.V. All rights reserved
Coexisting invasive gobies reveal no evidence for temporal and trophic niche differentiation in the sublittoral habitat of Lake Erhai, China
No full textNiche differentiation facilitates the coexistence of species within a community through avoidance of competition via mechanisms involving spatial, temporal and/or trophic dimensions. Where invasive species coexist in their non-native range, niche differentiation could allow their persistence at higher levels of abundance. Here, we tested whether there was temporal and/or trophic niche differentiation between two congeneric invasive goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) in the sublittoral habitat of Lake Erhai (south-west China) through quantifying their diel and seasonal rhythm of locomotion activities, feeding activities and diet composition. Both species displayed two similar diel peaks in activity and two main feeding periods (6:00-10:00 and 18:00-22:00), with rhythms of locomotion and feeding activity not differing significantly between the species in each season. Their diets had a high degree of overlap, being primarily composed of macrozooplankton, aquatic insects and shrimp larvae, with no diel changes across the seasons. Thus, in this habitat, there was no clear temporal or trophic niche differentiation between the invasive congeners, indicating their coexistence with high temporal and trophic overlap. In conjunction with data from the littoral and profundal habitats, the gobies revealed different strategies across the habitats (e.g. spatial segregation, trophic niche differentiation) that minimised their competitive interactions and promoted their coexistence. This suggests that the interactions of invasive fishes during the integration into native communities can be context dependent, varying according to factors including habitat and the availability of food resources
Interactive effects of nitrogen and light on growth rates and RUBISCO content of small and large centric diatoms
No full textAmong marine phytoplankton groups, diatoms span the widest range of cell size, with resulting effects upon their nitrogen uptake, photosynthesis and growth responses to light. We grew two strains of marine centric diatoms differing by similar to 4 orders of magnitude in cell biovolume in high (enriched artificial seawater with similar to 500 A mu mol L-1 A mu mol L-1 NO3 (-)) and lower-nitrogen (enriched artificial seawater with < 10 A mu mol L-1 NO3 (-)) media, across a range of growth light levels. Nitrogen and total protein per cell decreased with increasing growth light in both species when grown under the lower-nitrogen media. Cells growing under lower-nitrogen media increased their cellular allocation to RUBISCO and their rate of electron transport away from PSII, for the smaller diatom under low growth light and for the larger diatom across the range of growth lights. The smaller coastal diatom Thalassiosira pseudonana is able to exploit high nitrogen in growth media by up-regulating growth rate, but the same high-nitrogen growth media inhibits growth of the larger diatom species
Biochemical basis for hydrolysis of organophosphorus by a marine bacterial prolidase
No full textExtensive application of synthesized organophosphorus compounds (OPs) leads to pollutant accumulation and enhanced eco-toxicity. Hydrolysis of phosphotriester bonds catalyzed by evolved microbial enzymes is a key step for detoxification of OPs. Here, a new marine bacterial prolidase OPAA4301 exhibiting promiscuous phosphotriesterase activity was isolated and systematically characterized. The homo-tetrameric enzyme OPAA4301 can catalyze the hydrolysis of both amido bond and phosphotriester bond. Manganese ions were observed to be essential for its catalytic integrity, and in vitro substitution of manganese ions by different metal cofactors led to decreased activity. We also revealed cooperation pattern of metal ligands and substrate-binding residues on OP hydrolysis by mutational analysis. Metal-binding sites together with Arg418 in the large-binding pocket of the enzyme were found to be indispensable for catalytic ability. Substitution mutation of small- and large-binding pocket residues caused significant variation in phosphotriesterase activity, and leaving group sites appeared to be involved in the catalytic process as substrate affinity regulators. Our study gave an overall biochemical understanding on the organophosphorus hydrolysis pattern of the newly identified marine bacterial prolidase and provided ideas for protein engineering to expand its application in the bioremediation field. (C) 2016 Elsevier Ltd. All rights reserved
Artificial breeding and culture of the crown-of-thorns starfish Acanthaster planci (Linnaeus, 1758) larvae in China
No full textThough the breeding and the rearing of Acanthaster planci larvae had been reported before, the descriptions of them are not all-around, and there are no clear and detailed pictures indicating the whole process of embryonic and larval development. Besides, some methods described previously for culturing A. planci larvae are troublesome and even not available. In this study, adult A. planci were artificially induced to spawn and fertilized eggs were incubated and cultured indoor with disinfected seawater. A. planci developed from fertilized eggs to early bipinnaria by 50 h. Once a large number of late brachiolaria occurred, the diets were replaced by mixed benthic diatoms on settlement plates. Five-armed juveniles were reached after 23-day rearing when enough live Chaetoceros mueller and oceanic red yeast were supplied. It is critical to prevent infections by protozoa and pathogenic bacteria. The diets used here are universal in larval rearing and easily obtainable, which guarantees constant supply of diets and thus largely increases the successful rate of the rearing. Artificial breeding and culture of A. planci larvae not only enriched the knowledge on the spawning, larval culture, and developmental process of A. planci but also provided abundant materials to facilitate various studies
Dietary change in seabirds on Guangjin Island, South China Sea, over the past 1200 years inferred from stable isotope analysis
No full textQuantifying variation in animals' paleodiet from the fossil record is difficult as a continuous record of their remains is difficult to obtain. Here we assess dietary change in seabirds from Guangjin Island, Xisha Archipelago, South China Sea, by using stable nitrogen isotopes in seabird bones and prey remains collected from a coral sand ornithogenic sediment profile. N-15 of seabird bone collagen varied from 11.7 parts per thousand to 14.1 parts per thousand (averaging 12.8 parts per thousand +/- 0.4 parts per thousand), but that of fish bones and scales showed minor variations. Flying fish and squid are two favorite foods of tropical seabirds, and the average values of muscle N-15 in typical flying fish and squid samples were 9.2 parts per thousand and 10.2 parts per thousand, respectively. Based on nitrogen isotope mass balance calculation, we conclude that flying fish accounts for 80% +/- 40% of seabird diet averaged over the past 1200 years, but this prey accounted for only about 37% +/- 30% during the Little Ice Age' (AD 1400-1850). Flying fish averaged up to 88% +/- 2% during the Medieval Warm Period' (AD 850-1200), close to modern observed value of 89.6%. Thus, it appears that seabirds on Guangjin Island mainly preyed on flying fish during warm periods, and shift to squid during cooler periods. Our results suggest that recent global warming and human activities have likely caused a rapid decrease in tropical seabird population and dietary shift
The simultaneous uptake of dietary and waterborne Cd in gastrointestinal tracts of marine yellowstripe goby Mugilogobius chulae
No full textAquatic animals under waterborne metal exposure are also very likely exposed to elevated dietary metals. This study quantified the simultaneous uptake of dietary and waterborne Cd in gastrointestinal tracts (GT) of marine yellowstripe goby using a dual stable isotope tracer method. The Cd spiked diet (10 100 mu g g(-1), Cd-111 as tracers) were fed to the fish as a single meal, and then the fish were exposed to waterborne Cd (0-500 mu g L-1, Cd-113 as tracers) for 48 h, during which the time-course uptake of Cd in the stomach and intestine was determined. The findings revealed that the dietary Cd uptake mainly occurred within 12 h after feeding. The fish exposed to 500 mu g L-1 waterborne Cd showed significantly lower Cd assimilation efficiency (2.07%) than the control group (3.48%) at the dietary Cd of 100 mu g g(-1). Moreover, during 4-12 h when there was chyme in the GT, the waterborne Cd uptake in the intestine was lowest but the stomach showed the highest waterborne Cd uptake rate. The uptake of dietary and waterborne Cd, and the relative importance of dietary vs waterborne Cd was positively correlated with the Cd concentration in the chyme. Overall, this research demonstrated that there was interaction between dietary and waterborne Cd uptake in the GT of marine fish. The simultaneous uptake of metal from two routes is far more complex than the situation of a single route of metal uptake, which should be evaluated in determining metal bioaccumulation and toxicity in both laboratory and field metal exposure scenario. (C) 2016 Elsevier Ltd. All rights reserved
Deciphering the sugar biosynthetic pathway and tailoring steps of nucleoside antibiotic A201A unveils a GDP-L-galactose mutase
No full textGalactose, a monosaccharide capable of assuming two possible configurational isomers (D-/L-), can exist as a six-membered ring, galactopyranose (Galp), or as a five-membered ring, galactofuranose (Galf). UDP-galactopyranose mutase (UGM) mediates the conversion of pyranose to furanose thereby providing a precursor for D-Galf. Moreover, UGM is critical to the virulence of numerous eukaryotic and prokaryotic human pathogens and thus represents an excellent antimicrobial drug target. However, the biosynthetic mechanism and relevant enzymes that drive L-Galf production have not yet been characterized. Herein we report that efforts to decipher the sugar biosynthetic pathway and tailoring steps en route to nucleoside antibiotic A201A led to the discovery of a GDP-L-galactose mutase, MtdL. Systematic inactivation of 18 of the 33 biosynthetic genes in the A201A cluster and elucidation of 10 congeners, coupled with feeding and in vitro biochemical experiments, enabled us to: (i) decipher the unique enzyme, GDP-Lgalactose mutase associated with production of two unique D-mannose-derived sugars, and (ii) assign two glycosyltransferases, four methyltransferases, and one desaturase that regiospecifically tailor the A201A scaffold and display relaxed substrate specificities. Taken together, these data provide important insight into the origin of L-Galf-containing natural product biosynthetic pathways with likely ramifications in other organisms and possible antimicrobial drug targeting strategies
Penicillenols from a deep-sea fungus Aspergillus restrictus inhibit Candida albicans biofilm formation and hyphal growth
No full textPenicillenols (Al, A2, Bl, B2, Cl and C2) were isolated from Aspergillus restrictus DFFSCS006, and could differentially inhibit biofilm formation and eradicate pre-developed biofilms of Candida albicans. Their structure bioactivity relationships suggested that the saturation of hydrocarbon chain at C-8, R-configuration of C-5 and trans-configuration of the double bond between C-5 and C-6 of pyrrolidine-2,4-dione unit were important for their anti-biofilm activities. Penicillenols A2 and B1 slowed the hyphal growth and suppressed the transcripts of hypha specific genes HWP1, ALS1, ALS3, ECE1 and SAP4. Moreover, penicillenols A2 and B1 were found to act synergistically with amphotericin B against C. albicans biofilm formation
Transcriptomic analyses on muscle tissues of Litopenaeus vannamei provide the first profile insight into the response to low temperature stress
No full textThe Pacific white shrimp (Litopenaeus vannamei) is an important cultured crustacean species worldwide. However, little is known about the molecular mechanism of this species involved in the response to cold stress. In this study, four separate RNA-Seq libraries of L. vannamei were generated from 13 degrees C stress and control temperature. Total 29,662 of Unigenes and overall of 19,619 annotated genes were obtained. Three comparisons were carried out among the four libraries, in which 72 of the top 20% of differentially-expressed genes were obtained, 15 GO and 5 KEGG temperature-sensitive pathways were fished out. Catalytic activity (GO: 0003824) and Metabolic pathways (ko01100) were the most annotated GO and KEGG pathways in response to cold stress, respectively. In addition, Calcium, MAPK cascade, Transcription factor and Serine/threonine-protein kinase signal pathway were picked out and clustered. Serine/threonine-protein kinase signal pathway might play more important roles in cold adaptation, while other three signal pathway were not widely transcribed. Our results had summarized the differentially-expressed genes and suggested the major important signaling pathways and related genes. These findings provide the first profile insight into the molecular basis of L. vannamei response to cold stress