南海北部海域Synechococcus和Prochlorococcus生长率和被摄食消亡率——变化范围及其与环境因子的关系

2004年首次在南海北部海域使用选择性代谢抑制剂技术进行了Synechococcus和Prochlorococcus生长率和被摄食消亡率的研究.研究结果表明,ynechococcus高丰度值出现在次表层（15 m或20m）,位于温跃层之上,高生长率往往出现在丰度最大值水层上方;Prochlorococcus丰度在夏季出现次表层最大值,与温跃层深度基本一致,表层生长率高于真光层底部.Synechococcus真光层平均生长率为0.11～1.18 d^-1,被摄食消亡率为0.11～0.76 d^-1,分布格局均为从沿岸向外海方向升高.Prochlorococcus真光层平均生长率为0.23～0.49 d^-1,存在较明显的季节变化,夏季近岸略高于外海,而冬季的趋势正好相反;真光层平均被摄食消亡率为0.12～0.33 d^-1,冬夏两季均是近岸高于外海。温度、营养盐和光是影响Synechococcus生长率变化的重要因子.Synechococcus和Prochlorococcus丰度与群落生长率之间不存在相关关系,而与被摄食消亡率之间则存在显著的指数相关.根据Synechococcus和Prochlorococcus的生长率估算了它们的生产力及其对Pico-生产力的贡献.     

Abundance,growth and grazing loss rates of picophytoplankton in Barguzin Bay,Lake Baikal

The abundance, growth, and grazing loss rates of picophytoplankton were investigated in August 2002 in Barguzin Bay, Lake Baikal. Water samples for incubation were taken once at a near-shore station and twice at an offshore station. Contributions of picophytoplankton to total phytoplankton were high (56.9–83.9%) at the offshore station and low (5.8–6.8%) at the near-shore station. The picophytoplankton community in the offshore station comprised mainly phycoerythrin (PE)-rich cyanobacteria, with eukaryotic picophytoplankton being less abundant. In contrast, as well as PE-rich cyanobacteria and eukaryotic picophytoplankton, phycocyanin (PC)-rich cyanobacteria were found in the near-shore station. At the offshore station, growth and grazing loss rates on 25 August were 0.56 and 0.43 day⁻¹, respectively, and on 29 August, 0.69 and 0.83 day⁻¹, respectively. At the near-shore station, growth and grazing loss rates were 1.61 and 0.70 day⁻¹, respectively. These results show that there is a difference in the abundance, composition, and ecological role in the microbial food web of picophytoplankton between the near-shore and the offshore areas in Barguzin Bay.     

Detection of marine birnavirus genome in zooplankton collected from the Uwa Sea,Japan

Marine birnaviruses (MABVs) infect a wide range of fish and shellfish, yet their mode of transmission is still unclear. To determine whether marine plankton serve as a vector for MABVs, we examined plankton collected from the Uwa Sea, Japan. The phytoplankton and zooplankton were collected monthly, at depths of 0 and 40 m, from May to November 2001. Detection of the MABV genome was carried out using 2-step PCR and virus isolation. Viral genome was detected in zooplankton collected at 0 m depth in September and at 40 m depth in November. The virus could not be isolated in the PCR-positive samples. These results suggest that zooplankton may act as a vector of MABVs, although the infective and/or accumulated virus titer in zooplankton was low.     

Structure and seasonal trophodynamics of picophytoplankton in sevastopol bay and adjacent waters (the Black Sea)

Abundance and seasonal trophodynamics (specific growth rate, daily production, and grazing mortality) of the major picophytoplankton components, Synechococcus cyanobacteria (Syn) and picoeukaryotes (Pico-E), were studied at three stations in Sevastopol Bay and adjacent coastal waters (the Black Sea) in 2014 by flow cytometry and the dilution method. Pico-E abundance was shown to increase along the nutrient and pollution gradient from the coastal waters outside the bay (annual average of 7.3 ± 5.4 × 10³ cells mL^–1) to the eastern corner of the bay (28.7 ± 11.4 × 10³ cells mL^–1), while no relation was found between the water pollution status and Syn abundance (9.9 ± 8.7 × 10³ cells mL^–1; at all the stations, n = 27). Matter flows through the communities (daily production for Syn and Pico-E 0^–16.6 and 0^–19.3 µg C L^–1 day^–1, respectively; grazing mortality for Syn and PicoE 0–3.6 and 0–21.2 µg C L^–1 day^–1, respectively) were comparable to or even exceeded their biomass stocks (>0.05–6.8 and 0.9–26.5 µg C L^–1 for Syn and PicoE, respectively), indicating high biomass turnover rates. The highest flow-to-stock ratio (up to 6 for Syn) and a significant imbalance between daily production (P) and grazing mortality (G) were observed in the most polluted and eutrophic waters of the bay in spring (Pico-E: P/G < 1) and late summer (Syn: P/G > 1). Black River inflow to the bay was hypothesized to be among the mechanisms maintaining this pronounced and long-term imbalance in the open system without any negative consequences for the picophytoplankton assemblages.     

Growth and grazing mortality rates of phylogenetic groups of bacterioplankton in coastal marine environments

Dilution culture experiments were conducted in western North Pacific coastal regions to determine growth and grazing mortality rates of bacterial phylogenetic groups (alpha-, beta-, and gamma-proteobacteria and the Cytophaga-Flavobacter cluster) detected by fluorescent in situ hybridization. Growth rates varied greatly (1.2- to 4.0-fold) among different groups, and they were related to environmental variables (chlorophyll a concentrations and temperature) in a group-specific fashion. Growth rates of alpha-proteobacteria, the most abundant group in all the samples examined, were generally lower than those of less abundant groups, including the Cytophaga-Flavobacter cluster and gamma-proteobacteria. Grazing mortality rates and mean cell volumes varied little among different groups. These results provide insights into factors that affect distributions of different groups, but growth and grazing mortality alone did not fully explain bacterial community compositions at a broad phylogenetic level.     

Growth and annual production of the brown alga Laminaria japonica (Phaeophyta, Laminariales) introduced into the Uwa Sea in southern Japan

The brown alga Laminaria japonica is distributed from southern Hokkaido to the northeastern Honshu in Japan. Recently, aquaculture of L. japonica has expanded to the southern coast of Japan and to China along the East China Sea. In order to elucidate the growth, biomass and productivity of L. japonica in a subtropical area, we cultivated and examined it in the Uwa Sea, in southwestern Japan over a period of 2 years. The seawater temperature ranged from 13.8 to 26.8 °C in 2001/2002 and from 13.1 to 27.2 °C in 2002/2003. In 2001/2002, the maximum density, maximum mean length and maximum mean wet wt. of L. japonica were 59.7 ± 28.0 ind. 50 cm^− 1 (mean ± S.D.), 187.5 ± 82.7 cm (360 cm in the largest individual) and 130.1 ± 94.6 g wet wt., respectively. In 2002/2003, these values were 94.7 ± 22.2 ind. 50 cm^− 1, 159.3 ± 74.4 cm (300 cm in the largest individual) and 95.2 ± 69.5 g wet wt., respectively. Thus, the length and weight increased when the density was low (2001/2002), and the length and weight decreased when the density was high (2002/2003). The maximum biomass was estimated to be 7200 ± 3400 g wet wt. 50 cm^− 1 in 2001/2002 and 7300 ± 2000 g wet wt. 50 cm^− 1 in 2002/2003. Annual production was estimated to be 33.3 kg wet wt. m^− 1 year^− 1 in 2001/2002 and 34.0 kg wet wt. m^− 1 year^− 1 in 2002/2003. The present study indicates that the annual production of L. japonica per rope of 1 m at Uwajima Bay, the Uwa Sea corresponded to 1.1-2.2 m² of that of Hokkaido in their native area. Thus, the present study indicates that L. japonica is highly adaptable because it is able to keep a high level of productivity when grown in water with a high temperature.     

Novel lineages of Prochlorococcus and Synechococcus in the global oceans

Picocyanobacteria represented by Prochlorococcus and Synechococcus have an important role in oceanic carbon fixation and nutrient cycling. In this study, we compared the community composition of picocyanobacteria from diverse marine ecosystems ranging from estuary to open oceans, tropical to polar oceans and surface to deep water, based on the sequences of 16S-23S rRNA internal transcribed spacer (ITS). A total of 1339 ITS sequences recovered from 20 samples unveiled diverse and several previously unknown clades of Prochlorococcus and Synechococcus. Six high-light (HL)-adapted Prochlorococcus clades were identified, among which clade HLVI had not been described previously. Prochlorococcus clades HLIII, HLIV and HLV, detected in the Equatorial Pacific samples, could be related to the HNLC clades recently found in the high-nutrient, low-chlorophyll (HNLC), iron-depleted tropical oceans. At least four novel Synechococcus clades (out of six clades in total) in subcluster 5.3 were found in subtropical open oceans and the South China Sea. A niche partitioning with depth was observed in the Synechococcus subcluster 5.3. Members of Synechococcus subcluster 5.2 were dominant in the high-latitude waters (northern Bering Sea and Chukchi Sea), suggesting a possible cold-adaptation of some marine Synechococcus in this subcluster. A distinct shift of the picocyanobacterial community was observed from the Bering Sea to the Chukchi Sea, which reflected the change of water temperature. Our study demonstrates that oceanic systems contain a large pool of diverse picocyanobacteria, and further suggest that new genotypes or ecotypes of picocyanobacteria will continue to emerge, as microbial consortia are explored with advanced sequencing technology.     

Growth and grazing rates of Protoperidinium hirobis Abe, a thecate heterotrophic dinoflagellate

Growth and feeding rates of a laboratory-reared small thecateheterotrophic dinoflagellate, Protoperidinium hirobis Abè,grown on the diatom Leptocylindrus danicus, were measured inbatch cultures. Ingestion rates were determined directly bythe enumeration of empty diatom frustules produced by dinoflagellatefeeding. Both growth and feeding rates saturated at diatom concentrationsof {small tilde} 10⁴ cells ml^–1, and reached maximum valuesof 1.7 divisions day^–1 and 23 diatoms grazer^–1 day^–1,respectively. This rate of cell division is notably high comparedto photosynthetic dinoflagellates, which seldom grow fasterthan 1 division day^–1. A maximal clearance rate of 0.5µl h^–1 was measured. Mean cell size varied proportionallywith food abundance, with food-saturated cells having doublethe mean volume of food-depleted cells. Tuning of cell divisionand grazing rate patterns were also examined; while mitosisoccurred chiefly during the dark period, no diel variationsin feeding rate were detected. These rates represent the firstdirect growth and ingestion measurements to be made for a thecateheterotrophic dinoflagellate. They serve to underscore one functionthese dinoflagellates perform within the microzooplanktonicfood web: that of transforming large diatoms into particlesmore easily ingested by microzooplankters.     

Genomic and structural analysis of Syn9, a cyanophage infecting marine Prochlorococcus and Synechococcus

Cyanobacteriophage Syn9 is a large, contractile-tailed bacteriophage infecting the widespread, numerically dominant marine cyanobacteria of the genera Prochlorococcus and Synechococcus . Its 177 300 bp genome sequence encodes 226 putative proteins and six tRNAs. Experimental and computational analyses identified genes likely involved in virion formation, nucleotide synthesis, and DNA replication and repair. Syn9 shows significant mosaicism when compared with related cyanophages S-PM2, P-SSM2 and P-SSM4, although shared genes show strong purifying selection and evidence for large population sizes relative to other phages. Related to coliphage T4 – which shares 19% of Syn9's genes – Syn9 shows evidence for different patterns of DNA replication and uses homologous proteins to assemble capsids with a different overall structure that shares topology with phage SPO1 and herpes virus. Noteworthy bacteria-related sequences in the Syn9 genome potentially encode subunits of the photosynthetic reaction centre, electron transport proteins, three pentose pathway enzymes and two tryptophan halogenases. These genes suggest that Syn9 is well adapted to the physiology of its photosynthetic hosts and may affect the evolution of these sequences within marine cyanobacteria.     

Abundance of picophytoplankton in the halocline of a meromictic lake, Lake Suigetsu, Japan

Numerous (0.5 to 4.8 × 10⁵ cells/ml), small phytoplankton (smaller than 0.5–1 × 1–2 μm in cell size, picophytoplankton) were distributed in the halocline (depth 2–12 m, 4–14 practical salinity units) of the saline meromictic lake, Lake Suigetsu (35°35′ N, 135°52′ E), located in the central part of the coast of Wakasa Bay along the Japan Sea in Fukui Prefecture, Japan. Vertical distribution of phytoplankton revealed that the maximum number of picophytoplankton was always observed near or a little deeper than the oxic-anoxic boundary layer (depth 5–6 m); they were dominant phytoplankton in the water layer deeper than the oxic-anoxic boundary from July to late September 2005. Spectral analysis of autofluorescence emitted from the particle fractions smaller than 5 μm measured with a spectrofluorometer and from individual cells measured with a microscope photodiode array detector revealed that the major component of picophytoplankton was phycoerythrin-rich, unicellular cyanobacteria (picocyanobacteria). Eukaryotic phytoplankton about 2.5 μm in diameter were also found, but the numbers were low. Fluorescence intensity of chlorophyll a at 685 nm (room temperature) emitted from the particle fractions smaller than 5 μm was increased by the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. These observations indicated that at least some picophytoplankton had a functional photosystem II in the halocline where sulfide, the potential inhibitor of oxygenic photosynthesis, was always present. The large abundance together with their physiological potency suggest that picophytoplankton are one of the important primary producers in the halocline of Lake Suigetsu. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Modelling the vertical distribution of Prochlorococcus and Synechococcus in the North Pacific Subtropical Ocean

A simple model was developed to examine the vertical distribution of Prochlorococcus and Synechococcus ecotypes in the water column, based on their adaptation to light intensity. Model simulations were compared with a 14-year time series of Prochlorococcus and Synechococcus cell abundances at Station ALOHA in the North Pacific Subtropical Gyre. Data were analysed to examine spatial and temporal patterns in abundances and their ranges of variability in the euphotic zone, the surface mixed layer and the layer in the euphotic zone but below the base of the mixed layer. Model simulations show that the apparent occupation of the whole euphotic zone by a genus can be the result of a co-occurrence of different ecotypes that segregate vertically. The segregation of ecotypes can result simply from differences in light response. A sensitivity analysis of the model, performed on the parameter alpha (initial slope of the light-response curve) and the DIN concentration in the upper water column, demonstrates that the model successfully reproduces the observed range of vertical distributions. Results support the idea that intermittent mixing events may have important ecological and geochemical impacts on the phytoplankton community at Station ALOHA.     

Occurrence of Marine Birnavirus Through the Year in Coastal Seawater in the Uwa Sea

This study aims to determine the seasonal occurrence of marine birnavirus (MABV) at a coastal site in the Uwa Sea, Japan, in 1997 and 1998. To detect MABV from seawater, a simple method was developed for concentrating MABV by dialysis and ethanol precipitation. The concentrated virus was used for polymerase chain reaction (PCR), enzyme-linked immunosorbent assay, and virus isolation. Viral genome was detected through the experimental period. The amount of PCR product varied; it was small in summer, but increased from fall to winter. Viral protein was also detected, and the amount in the January sample was equivalent to approximately 10² TCID₅₀ (50% tissue culture infectious dose) of the virus. However, infectious viruses were not isolated. This suggested that MABV was released from hosts to environmental seawater in winter and possibly degraded after release. Received May 7, 1999; accepted September 16, 1999.     

Survival and cause-specific mortality rates of female sika deer in eastern Hokkaido, Japan

Survival and cause-specific mortality rates of female sika deer (Cervus nippon) were studied using radio telemetry in eastern Hokkaido, Japan. We captured and radio-collared 18 female deer, and monitored their survival from April 1993 to May 1996. Estimated annual survival rate for adult females was 0.779 (95% confidence interval was 0.609–0.997). The harvest mortality rate of adult females was higher than the natural mortality rate. Experimental female hunting during 1994–1996 contributed to an increase in the mortality rate for females and was useful in the control of the sika deer population.     

Global phylogeography of marine Synechococcus and Prochlorococcus reveals a distinct partitioning of lineages among oceanic biomes

Marine cyanobacteria of the genera Prochlorococcus and Synechococcus are important contributors to global primary production occupying a key position at the base of marine food webs. The genetically diverse nature of each genus is likely an important reason for their successful colonization of vast tracts of the world's oceans, a feature that has led to detailed analysis of the distribution of these genetic lineages at the local and ocean basin scale. Here, we extend these analyses to the global dimension, using new data from cruises in the Pacific, Indian and Arctic Oceans in combination with data from previous studies in the Atlantic Ocean, Arabian Sea, Red Sea and a circumnavigation of the southern hemisphere to form a data set which comprises most of the world's major ocean systems. We show that the distribution patterns of Prochlorococcus and Synechococcus lineages are remarkably similar in different ocean systems with comparable environmental conditions, but producing a strikingly different 'signature' in the four major ocean domains or biomes (the Polar Domain, Coastal Boundary Domain, Trade Winds Domain and Westerly Winds Domain). This clearly reiterates the idea of spatial partitioning of individual cyanobacterial lineages, but at the global scale.     

The importance of phytoflagellate, heterotrophic flagellate and ciliate grazing on bacteria and picophytoplankton sized prey in a coastal marine environment

The uptake of bacteria and picoplankton sized fluorescentlylabelled beads was measured off the west coast of the SouthIsland of New Zealand in winter. Phytoflagellates and heterotrophicflagellates showed similar grazing rates on 0.49 µm beads,with mean clearance rates of 1.1 and 1.8 nl ind.^–1 h^–1,respectively. Clearance rates for 1.09 µm beads were 0.9nl ind.^–1 h^–1 for heterotrophic flagellates and0.5 nl ind.^–1 h^–1 for phytoflagellates. Non-loricateciliates had clearance rates of 1.5 µl ind.^–1 h^–1for the picoplankton sized particles. The heterotrophic flagellatesshowed no significant difference between clearance rates of0.49 and 1.09 µm particles. Phytoflagellates, however,showed an apparent preference for the smaller particles. Themeasurement of significant grazing by phytoflagellate populationsin the marine environment is important and indicates that weneed to reassess our concepts of food web structure.     

Growth and Longevity of the Gastropod Nucella heyseana in Vostok Bay,Sea of Japan

Features of the morphology, longevity, and growth of the gastropod mollusk Nucella heyseana collected in different seasons in 2000–2001 in Vostok Bay (Sea of Japan) were investigated. Shell surface features such as grooves and spurs of the axial sculpture have proven to be unhelpful in the estimation of individual age and growth rate of this species. Concentric rings on the outside of the operculum formed yearly in the cold season are useful for these purposes. The longevity of N. heyseana in southern Primorye is 10 years; this value is similar to the life span of mollusks from the southern Kuril Islands. Local differences in longevity, growth allometry, and age changes in the body size and mass of N. heyseana in relation to habitat conditions are discussed.