RESUMO
Human-induced nutrient inputs to global coastal waters are leading to increasing nutrients and escalating eutrophication. However, how aquatic ecosystem functioning responds to these changes remains insufficiently studied. Here we report the long-term changes in the nutrient regime and planktonic ecosystem functioning in the Daya Bay, a typical subtropical semi-enclosed bay experiencing rapid economic and social development for several decades. Time-series (from 1991 to 2018) data with a mostly quarterly resolution were collected to depict long-term changes in dissolved inorganic nutrients and plankton abundances, based on which we constructed simplified abundance size spectra (SASS) and plankton abundance ratios to describe the functioning of the planktonic ecosystem. The results revealed a long-term increase in system productivity but a decrease in integrated energy transfer efficiency of the planktonic ecosystem, with rising concentrations of dissolved inorganic nitrogen (DIN). Shifts in the nutrient regime and planktonic ecosystem functioning were detected at a tipping point or threshold around 2006-2007. The shifts were characterized by abrupt changes in the trends of nutrient (phosphate, ammonia, nitrite) concentrations, nutrient ratios (DIN/phosphate, silicate/phosphate), plankton abundance, and total plankton biomass. Compared to the nutrient regime, the planktonic ecosystem functioning shifted several years later. Overall, this study indicates that the pelagic ecosystem regime can shift significantly in response to long-term increasing input of human-induced nutrients in coastal waters such as the Daya Bay. The regime shifts may have profound implications for fishery production, and ecosystem management in the bay.
Assuntos
Ecossistema , Eutrofização , Plâncton , Humanos , Nitrogênio , Nutrientes , Biomassa , Monitoramento Ambiental , BaíasRESUMO
Currently, the lack of protein source feed has become a pressing issue. Moringa oleifera leaf powder (MOLP) has good potential for the development of protein-derived feeds due to its good protein quality and abundance, but little is known about its effects on broiler growth performance and cecal microbiota. In this study, the chickens were fed different rates of MOLP (1%, 3%, 5%, 7%, and 9%) instead of the rape seed cake, and the effects of different levels of MOLP on growth performance, carcass characteristics, and cecal microbiota of the broilers were evaluated at two different growth stages (day 28 and day 56). In terms of growth performance, the best results were obtained at the 3% MOLP level in the early stages (p < 0.05). In terms of carcass characteristics, in the early stage, the level of 5% MOLP had the best effect; in the later stage, 5% MOLP also had the best effect. In terms of cecal microbial changes, the alpha diversity analysis revealed that 5% MOLP enhanced the richness and diversity of broiler intestinal flora. At the phylum level, the addition of 5% MOLP adjusted the relative abundance of Firmicutes and Bacteroidetes to a level close to that of the A1 group on day 28, while 5% MOLP significantly reduced the relative abundance of Bacteroidetes (p < 0.05) compared to the A2 group on day 56, and the relative abundance of Firmicutes was still higher in the D2 group than in the A2 group (p < 0.05). At the genus level, MOLP addition consistently and significantly increased the relative abundance of Bacteroides (p < 0.05), except for 3% on day 28 and 1% on day 56. For Oscillospira, increasing MOLP levels in the pre- and post-period resulted in a significant decrease in the relative abundance of Oscillospira (p < 0.05). In conclusion, MOLP helps to enhance growth performance and carcass characteristics and improve the cecal microbial structure of broilers. The recommended rate of MOLP addition for broilers is 5% in both the early and late stages.
RESUMO
Seahorses have a circum-global distribution in tropical to temperate coastal waters. Yet, seahorses show many adaptations for a sedentary, cryptic lifestyle: they require specific habitats, such as seagrass, kelp or coral reefs, lack pelvic and caudal fins, and give birth to directly developed offspring without pronounced pelagic larval stage, rendering long-range dispersal by conventional means inefficient. Here we investigate seahorses' worldwide dispersal and biogeographic patterns based on a de novo genome assembly of Hippocampus erectus as well as 358 re-sequenced genomes from 21 species. Seahorses evolved in the late Oligocene and subsequent circum-global colonization routes are identified and linked to changing dynamics in ocean currents and paleo-temporal seaway openings. Furthermore, the genetic basis of the recurring "bony spines" adaptive phenotype is linked to independent substitutions in a key developmental gene. Analyses thus suggest that rafting via ocean currents compensates for poor dispersal and rapid adaptation facilitates colonizing new habitats.
Assuntos
Adaptação Fisiológica/genética , Distribuição Animal , Evolução Molecular , Smegmamorpha/genética , Animais , Sequência de Bases , DNA/genética , Ecossistema , Geografia , Filogenia , Smegmamorpha/classificação , Smegmamorpha/fisiologia , Especificidade da EspécieRESUMO
Syngnathids (seahorses, pipefishes and seadragons) exhibit an array of morphological innovations including loss of pelvic fins, a toothless tubular mouth and male pregnancy. They comprise two subfamilies: Syngnathinae and Nerophinae. Genomes of three Syngnathinae members have been analyzed previously. In this study, we have sequenced the genome of a Nerophinae member, the Manado pipefish (Microphis manadensis), which has a semi-enclosed brood pouch. Comparative genomic analysis revealed that the molecular evolutionary rate of the four syngnathids is higher than that of other teleosts. The loss of all but one P/Q-rich SCPP gene in the syngnathids suggests a role for the lost genes in dentin and enameloid formation in teleosts. Genome-wide comparison identified a set of 118 genes with parallel identical amino acid substitutions in syngnathids and placental mammals. Association of some of these genes with placental and embryonic development in mammals suggests a role for them in syngnathid pregnancy.
RESUMO
Pigmented bacteria cells, including aerobic anoxygenic phototrophic (AAP) bacteria, contribute significantly to secondary production and aquatic carbon cycling but their distribution in the deep sea is still not well understood, especially in the South China Sea. In this study, microscopic, flow cytometric, and molecular analyses were carried out to investigate the abundance and diversity of AAP bacteria at seven stations in the South China Sea. The results revealed the existence of bacteriochlorophyll-containing bacteria below 500 m from two of seven stations. Flow cytometric analysis detected red and infra-red fluorescence under blue (488 nm) light excitation from fluorescent cells. Blue light-excited red fluorescence of these cells from the 1000 m depth at station E403 were verified using epifluorescence microscopy. Based on fluorescence and side scatter features, fluorescent cells were sorted and subjected to molecular analysis. DNA was extracted from these sorted cells from both stations for PCR amplification using 16S rDNA primers. Sequencing of the PCR products showed that the sorted cells from the 1000 m depth at station E403 belonged to the genus Porphyrobacter. The cell population sorted from 500 m at station E703 contained Sphingomonas and a Methylobacterium-like taxon. All these three taxa belong to aerobic anoxygenic phototrophic alpha-proteobacteria. Using flow cytometric analysis, we found that the abundance of Porphyrobacter sp. at 1000 m was 2.71-2.95×104 cells mL-1 whereas cell counts of Sphingomonas sp. and Methylobacterium at 500 m were about 3.75-4.12×105 cells mL-1. These results indicate that albeit not ubiquitous in deep water, bacteriochlorophyll-containing bacteria can be abundant in the deep-sea aphotic zone.
Assuntos
Bactérias/classificação , RNA Ribossômico 16S/genética , Água do Mar/microbiologia , Análise de Sequência de DNA/métodos , Bactérias/genética , Bactérias/metabolismo , Bacterioclorofilas/metabolismo , China , DNA Bacteriano/genética , DNA Ribossômico/genética , Citometria de Fluxo , Processos Fototróficos , FilogeniaRESUMO
Previous field investigations implied a potential phosphorus (P)-limitation on the growth of phytoplankton in Daya Bay, a mesotrophic bay in the northern South China Sea. Using a total of 15 mesocosms (3 × 3 × 1.5 m, with ~10.8 m3 natural seawater containing phytoplankton assemblages for each), we found P-enrichment caused no obvious effect on phytoplankton (Chl a) growth across 8-day's cultivation in neither winter nor summer, while nitrogen (N)-enrichment greatly increased Chl a in both seasons. N plus P-enrichment further increased Chl a content. The N- or N plus P-enrichments increased the allocation of nano-Chl a but decreased micro-Chl a in most cases, with no obvious effect by P-alone. Coincided with nutrients effect on Chl a content, N- or N plus P-enrichments significantly enhanced the maximum photochemical quantum yield of Photosystem II (FV/FM) and maximum relative electron transport rate (rETRmax), but declined the non-photochemical quenching (NPQ), as well as the threshold for light saturation of electron transport (EK); again, P-enrichment had no significant effect. Moreover, the absorption cross section for PSII photochemistry (σPSII) and electron transport efficiency (α) increased due to N- or N plus P-enrichments, indicating the increased nutrients enhance the light utilization efficiency through promoting PSII light harvesting ability, and thus to enhance phytoplankton growth. Our findings indicate that N- or N plus P-enrichments rigorously fuel phytoplankton blooms regardless of N:P ratios, making a note of caution on the expected P-deficiency or P-limitation on the basis of Redfield N:P ratios in Daya Bay.
Assuntos
Monitoramento Ambiental , Fósforo/metabolismo , Fitoplâncton/crescimento & desenvolvimento , Poluentes Químicos da Água/metabolismo , Baías , China , Eutrofização , Nutrientes/metabolismo , Fitoplâncton/efeitos dos fármacosRESUMO
The influence of anthropogenic nutrient loading on the stable isotopic signatures (δ13C and δ15N) in the suspended particulate organic matter (SPOM) is still not fully understood. Water quality and the values of δ13C and δ15N in the SPOM were investigated in the surface water of Daya Bay during the spring of 2016 and 2017. The results indicated that the Dan'ao River is the main point source of nutrient pollution in Daya Bay. The δ15NPOM was very low in the Dan'ao River. The distribution pattern for this parameter in Daya Bay was determined chiefly by Dan'ao River discharge. Variations in δ15NPOM were ascribed mostly to the input of 15N-depleted DIN assimilated by the estuarine phytoplankton in Daya Bay. Extremely high NH4+ level in the river discharge should be responsible for the low δ15NPOM in the river water. The distribution of δ13CPOM in Daya Bay was regulated mainly by the input of 13C-depleted riverine SPOM. In the present study, the influence of phytoplankton growth on the δ13CPOM was not significant. Moreover, episodic rain events significantly influenced the temporal and spatial variations in water quality and isotopic signature in Daya Bay. The relatively depleted SPOM 15N in 2016 may have been correlated with the strong El Niño events of 2015-2016. Increases in the frequency and volume of rainfall associated with El Niño may have enhanced nutrient loading and the risk of algal red tide in the Daya Bay. In general, significant 15N depletion in SPOM could be the characteristic of hypereutrophic riverine waters. This study suggested that δ15NPOM may be an effective indicator of the strength of riverine nutrient loading in Daya Bay.
Assuntos
Baías/química , Monitoramento Ambiental , Substâncias Húmicas/análise , Isótopos de Nitrogênio/análise , Esgotos/análise , Poluição da Água/análise , Baías/microbiologia , China , Fitoplâncton , Poluição da Água/estatística & dados numéricosRESUMO
Aluminum (Al) is widespread in the environment including the ocean. The effects of Al on marine organisms have attracted more and more attention in recent years. However, the mechanisms of uptake of Al by marine organisms and the subcellular distribution of Al once assimilated are unknown. Here we report the uptake and subcellular distribution of Al in a marine diatom Thalassiosira weissflogii. Short-term (<â¯120â¯min) uptake experiments showed that the Al uptake rate by the diatom was 0.033⯱â¯0.013 fmol-1 cell-1 min-1 (internalization flux normalized to the exposure Al concentration of 2⯵Mâ¯=â¯0.034⯱â¯0.013â¯nmolâ¯m-2 min-1 nM-1). Subcellular fractionation experiments showed that the internalized Al was partitioned to subcellular components in the following order: granules (69⯱â¯5%) >â¯debris (17⯱â¯4%) >â¯organelles (12⯱â¯2%) >â¯heat-stable peptides (HSP) (~2%) >â¯heat-denaturable proteins (HDP) (<â¯1%), indicating that the majority of intracellular Al was detoxified and stored in inorganic forms. The subcellular distribution of Al in the diatom is different from that of Al in freshwater green algae, in which most of the internalized Al is partitioned to organelles. We also evaluated an artificial seawater-based EDTA rinse solution to remove Al adsorbed on the diatom cell surface. Overall, our study provides new information to understand the mechanisms of uptake of Al by marine diatoms, and the mechanisms responsible for the biological effects (both toxic and beneficial) of Al on the growth of marine phytoplankton, especially diatoms.
Assuntos
Alumínio/metabolismo , Diatomáceas/efeitos dos fármacos , Água do Mar/química , Poluentes Químicos da Água/metabolismo , Adsorção , Alumínio/análise , Alumínio/toxicidade , Diatomáceas/metabolismo , Fitoplâncton/efeitos dos fármacos , Fitoplâncton/metabolismo , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidadeRESUMO
Estuarine oxygen depletion is one of the worldwide problems, which is caused by the freshwater-input-derived severe stratification and high nutrients loading. In this study we presented the horizontal and vertical distributions of dissolved oxygen (DO) in the Pearl River estuary, together with temperature, salinity, chlorophyll a concentration and heterotrophic bacteria abundance obtained from two cruises during the summer (wet) and winter (dry) periods of 2015. In surface water, the DO level in the summer period was lower and varied greater, as compared to the winter period. The DO remained unsaturated in the summer period if salinity is <12 and saturated if salinity is >12; while in the winter period it remained saturated throughout the estuary. In subsurface (>5m) water, the DO level varied from 0.71 to 6.65mgL-1 and from 6.58 to 8.20mgL-1 in the summer and winter periods, respectively. Particularly, we observed an area of ~1500km2 low DO zone in the subsurface water with a threshold of 4mgDOL-1 during this summer period, that located at the fresh- and saline-water intersection where is characterized with severe stratification and high heterotrophic bacteria abundance. In addition, our results indicate that spatial DO variability in surface water was contributed differently by biological and physio-chemical variables in the summer and winter periods, respectively.
Assuntos
Estuários , Oxigênio/análise , Bactérias/isolamento & purificação , Clorofila/análise , Clorofila A , Monitoramento Ambiental , Água Doce/microbiologia , Rios , Salinidade , Estações do Ano , Água do Mar/microbiologia , TemperaturaRESUMO
Compared to extensive studies reporting the aluminum (Al) toxicity to terrestrial plants and freshwater organisms, very little is known about how marine phytoplankton responds to Al in the field. Here we report the marine phytoplankton responses to Al enrichment in the South China Sea (SCS) using on-deck bottle incubation experiments during eight cruises from May 2010 to November 2013. Generally, Al addition alone enhanced the growth of diatom and Trichodesmium, and nitrogen fixation, but it inhibited the growth of dinoflagellates and Synechococcus. Nevertheless, Al addition alone did not influence the chlorophyll a concentration of the entire phytoplankton assemblages. By adding nitrate and phosphate simultaneously, Al enrichment led to substantial increases in chlorophyll a concentration (especially that of the picophytoplankton<3µm), and cell abundances of diatom and photosynthetic picoeukaryotes. These results indicate varied responses of phytoplankton in different size fractions and taxonomic groups to Al enrichment. Further, by simultaneously adding different macronutrients and/or sufficient trace metals including iron, we found that the phytoplankton responses to Al enrichment were relevant to nutrients coexisting in the environment. Al enrichment may give some phytoplankton a competitive edge over using nutrients, especially the limited ones. The possible influences of Al on the competitors and grazers (predators) of some phytoplankton might indirectly contribute to the positive responses of the phytoplankton to Al enrichment. Our results indicate that Al may influence marine carbon cycle by impacting phytoplankton growth and structure in natural seawater.
Assuntos
Alumínio/toxicidade , Fixação de Nitrogênio/efeitos dos fármacos , Fitoplâncton/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Ciclo do Carbono/efeitos dos fármacos , China , Diatomáceas/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/metabolismo , Dinoflagellida/efeitos dos fármacos , Dinoflagellida/crescimento & desenvolvimento , Dinoflagellida/metabolismo , Resistência a Medicamentos , Farmacorresistência Bacteriana , Nitratos/metabolismo , Concentração Osmolar , Oceano Pacífico , Fosfatos/metabolismo , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/metabolismo , Análise Espaço-Temporal , Especificidade da Espécie , Synechococcus/efeitos dos fármacos , Synechococcus/crescimento & desenvolvimento , Synechococcus/metabolismo , Oligoelementos/metabolismo , Trichodesmium/efeitos dos fármacos , Trichodesmium/crescimento & desenvolvimento , Trichodesmium/metabolismoRESUMO
Phosphorus (P) is an essential nutrient for marine phytoplankton as for other living organisms, and the preferred form, dissolved inorganic phosphate (DIP), is often quickly depleted in the sunlit layer of the ocean. Phytoplankton have developed mechanisms to utilize organic forms of P (DOP). Hydrolysis of DOP to release DIP by alkaline phosphatase is believed to be the most common mechanism of DOP utilization. Little effort has been made, however, to understand other potential molecular mechanisms of utilizing different types of DOP. This study investigated the bioavailability of glucose-6-phosphate (G6P) and its underlying molecular mechanism in the dinoflagellate Karenia mikimotoi. Suppression Subtraction Hybridization (SSH) was used to identify genes up- and down-regulated during G6P utilization compared to DIP condition. The results showed that G6P supported the growth and yield of K. mikimotoi as efficiently as DIP. Neither DIP release nor AP activity was detected in the cultures grown in G6P medium, however, suggesting direct uptake of G6P. SSH analysis and RT-qPCR results showed evidence of metabolic modifications, particularly that mitochondrial ATP synthase f1gamma subunit and thioredoxin reductase were up-regulated while diphosphatase and pyrophosphatase were down-regulated in the G6P cultures. All the results indicate that K. mikimotoi has developed a mechanism other than alkaline phosphatase to utilize G6P.
Assuntos
Dinoflagellida/metabolismo , Glucose-6-Fosfato/metabolismo , Fosfatase Alcalina/metabolismo , DNA Complementar/genética , Dinoflagellida/efeitos dos fármacos , Dinoflagellida/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Ontologia Genética , Anotação de Sequência Molecular , Fósforo/farmacologia , Análise de Sequência de DNARESUMO
To understand the variations of picoplankton (Prochlorococcus, Synechococcus, picoeukaryotes, and heterotrophic bacteria) abundances during diatom bloom, the distribution of picoplankton in the Taiwan Bank, South China Sea was investigated using flow cytometry during a Thalassiosira diporocyclus bloom in March 2016. The results indicated an abrupt abundance decrease for Prochlorococcus, Synechococcus, and picoeukaryotes within the bloom area while the abundance of heterotrophic bacteria showed no significant difference between the bloom and non-bloom areas. We found two sub-groups of heterotrophic bacteria: high- and low-nucleic acid content (HNA and LNA) bacteria with HNA dominated in the bloom area whereas LNA dominated in the non-bloom area. Among the picoplankton components, HNA represented the highest (61.1%) carbon biomass in the bloom area while picoeukaryotes represented the highest (37.6%) in the non-bloom area. Our findings implied that heterotrophic bacteria, especially HNA, played an essential role during the diatom bloom.
Assuntos
Diatomáceas/isolamento & purificação , Eutrofização , Processos Heterotróficos , Plâncton/isolamento & purificação , Água do Mar/microbiologia , Bactérias/isolamento & purificação , Ácidos Nucleicos/análise , Prochlorococcus/isolamento & purificação , Estações do Ano , Synechococcus/isolamento & purificação , TaiwanRESUMO
Stable isotopic signatures (δ13C and δ15N) and C/N ratios of suspended particulate organic matter (POM) were investigated from the surface water of Daya Bay during summer and winter of 2015. The relatively high δ13CPOM values suggested the input of 13C-depleted terrigenous organic matter was low in Daya Bay. There were significant correlations between δ13CPOM values and chlorophyll a concentrations both during summer and winter, suggesting the δ13CPOM values were mainly controlled by the phytoplankton biomass in the surface water. The distribution of δ15NPOM values was more complicated than that of δ13CPOM and displayed low values in the outer bay and the Dan'ao River estuary. 15N-depleted ammonia originating from industrial wastewater might have strongly influenced the water quality and stable isotopic signatures of POM near the Dan'ao River estuary. The δ13CPOM and δ15NPOM values strongly reflect the influences of anthropogenic activity and eutrophication in Daya Bay.
Assuntos
Baías/química , Clorofila/análise , Monitoramento Ambiental , Material Particulado , Poluentes da Água/análise , China , Estuários , Eutrofização , Fitoplâncton , Rios , Estações do Ano , Qualidade da ÁguaRESUMO
Seahorses have a specialized morphology that includes a toothless tubular mouth, a body covered with bony plates, a male brood pouch, and the absence of caudal and pelvic fins. Here we report the sequencing and de novo assembly of the genome of the tiger tail seahorse, Hippocampus comes. Comparative genomic analysis identifies higher protein and nucleotide evolutionary rates in H. comes compared with other teleost fish genomes. We identified an astacin metalloprotease gene family that has undergone expansion and is highly expressed in the male brood pouch. We also find that the H. comes genome lacks enamel matrix protein-coding proline/glutamine-rich secretory calcium-binding phosphoprotein genes, which might have led to the loss of mineralized teeth. tbx4, a regulator of hindlimb development, is also not found in H. comes genome. Knockout of tbx4 in zebrafish showed a 'pelvic fin-loss' phenotype similar to that of seahorses.
Assuntos
Evolução Biológica , Proteínas de Peixes/genética , Genoma/genética , Smegmamorpha/anatomia & histologia , Smegmamorpha/genética , Nadadeiras de Animais/anatomia & histologia , Nadadeiras de Animais/metabolismo , Animais , Sequência Conservada/genética , Proteínas de Peixes/deficiência , Deleção de Genes , Genômica , Membro Posterior/anatomia & histologia , Membro Posterior/metabolismo , Masculino , Anotação de Sequência Molecular , Família Multigênica/genética , Taxa de Mutação , Filogenia , Reprodução/fisiologia , Proteínas com Domínio T/deficiência , Proteínas com Domínio T/genética , Fatores de Tempo , Proteínas de Peixe-Zebra/deficiência , Proteínas de Peixe-Zebra/genéticaRESUMO
Protist-alga symbiosis is widespread in the ocean, but its characteristics and function in situ remain largely unexplored. Here we report the symbiosis of the ciliate Mesodinium rubrum with cryptophyte cells during a red-tide bloom in Long Island Sound. In contrast to the current notion that Mesodinium retains cryptophyte chloroplasts or organelles, our multiapproach analyses reveal that in this bloom the endosymbiotic Teleaulax amphioxeia cells were intact and expressing genes of membrane transporters, nucleus-to-cytoplasm RNA transporters, and all major metabolic pathways. Among the most highly expressed were ammonium transporters in both organisms, indicating cooperative acquisition of ammonium as a major N nutrient, and genes for photosynthesis and cell division in the cryptophyte, showing active population proliferation of the endosymbiont. We posit this as a "Mesodinium-farming-Teleaulax" relationship, a model of protist-alga symbiosis worth further investigation by metatranscriptomic technology.
Assuntos
Cloroplastos/genética , Cilióforos/genética , Criptófitas/genética , Simbiose/genética , Agricultura , Compostos de Amônio/metabolismo , Cilióforos/crescimento & desenvolvimento , Criptófitas/crescimento & desenvolvimento , Regulação da Expressão Gênica , Proliferação Nociva de Algas/fisiologia , Proteínas de Membrana Transportadoras/genética , Fotossíntese/genética , Plastídeos/genética , Transporte de RNA/genéticaRESUMO
In order to evaluate the levels and the influence on phytoplankton productivity of dissolved nutrients, concentrations and distribution of N, P and Si were studied in coastal areas profoundly influenced by human activities in Guangdong Province, South China. Generally, concentrations of dissolved inorganic nitrogen were high in wet periods because of the inputs from strong seasonal land runoff. Si and P concentrations were generally low in summer due to the consumption by phytoplankton growth. Dissolved organic N and P were important in study area. Chl a and primary productivity (PP) were relatively high and showed seasonal and geographical variations. Concentrations of Chl a were the highest in summer, and the high water temperature and sufficient illumination accelerated the growth of phytoplankton, especially in surface water. Additionally, water stratification in summer decreased mixed layer depth and trapped PP in upper layer.
Assuntos
Nitrogênio , Fósforo , Fitoplâncton/crescimento & desenvolvimento , Silício , China , Atividades Humanas , Estações do AnoRESUMO
In the present study, the complete mitogenome sequence of the Cyprinid fish Squalidus argentatus (Cypriniformes, Cyprinidae) was determined. The mitogenome, consisting of 16,609 base pairs (bp), was characterized by the typical vertebrate mitochondrial gene arrangement, including 13 protein-coding, 22 transfer RNAs, 2 ribosomal RNAs genes and a noncoding control region. Control region (CR), of 931 bp in length, was located between tRNA(Pro) and tRNA(Phe). The overall base composition of S. argentatus was 30.45% for A, 16.70% for G, 25.62% for T and 27.24% for C, with a slight AT bias of 56.07%.
Assuntos
Cyprinidae/genética , DNA Mitocondrial/genética , Genoma Mitocondrial , Animais , Composição de Bases/genética , Códon/genética , Fases de Leitura Aberta/genética , RNA de Transferência/genéticaRESUMO
Bacterial metabolism plays a dual role [bacterial production (BP) and bacterial respiration (BR)] in the aquatic ecosystem and potentially leads to hypoxia in the coastal eutrophic area. Bacterial growth efficiency (BGE) is an important index showing the contribution of bacterial metabolism to marine biological production and carbon budget in the pelagic ecosystem. In this study, the spatial and seasonal variety as well as diurnal variation dynamics of BGE and associated ecological characteristics were investigated in a partly eutrophicated subtropical bay (the Daya Bay) located in the northern South China Sea. Furthermore, the relationship between bacterial metabolism and potential hypoxia event was analyzed. The average BGE was 0.14 and 0.22 in summer and winter, respectively, which was lower than the mean value ever reported in other coastal and estuarine waters. The diurnal variations of BGE and BP were widely fluctuated in the Daya Bay, with approximately 3-8 fold variation of BP and 2-3 fold variation of BR in different seasons, suggesting the importance of short-term ecological dynamics on evaluating the long-term ecological processes in the coastal waters. BR was the predominant contributor to the bacterial carbon demand; however, the variation of BGE was controlled by BP in both seasons. BGE was always high in the near-shore waters with higher eutrophic level and more active BP and BR. The bacterial metabolism could deplete dissolved oxygen (DO) in the Daya bay within about 9 days when the water body was enclosed and photosynthesis was prohibited. Therefore, low DO concentration and potential hypoxia was more likely to be found in the near-shore waters of the Daya Bay in summer, since the water was stratified and enclosed with poor water exchange capacity in this area. While in winter, hypoxia seldom occurred due to vertical mixing throughout the water column. Further biological-physical coupling research is recommended to find out the detailed formation mechanism of hypoxia in the bay, and to predict the potential hypoxia events and their environmental impacts in the future.
Assuntos
Bactérias/crescimento & desenvolvimento , Baías/microbiologia , Eutrofização , Anaerobiose , Bactérias/efeitos dos fármacos , China , Ecossistema , Estações do AnoRESUMO
The complete mitochondrial genome sequence of the lined seahorse Hippocampus erectus was first determined in this article. The total length of H. erectus mitogenome is 16,529 bp, which consists of 13 protein-coding genes, 22 tRNA and 2 rRNA genes and 1 control region. The features of the H. erectus mitochondrial genome were similar to the typical vertebrates. The overall base composition of H. erectus is 31.8% A, 28.6% T, 24.3% C and 15.3% G, with a slight A + T rich feature (60.4%).