The contribution of nano- and micro-planktonic assemblages in the surface layer (0-30 m) under different hydrographic conditions in the upwelling area off Concepción, central Chile

In the highly productive region off central Chile, the structure and temporal and spatial variability of planktonic assemblages, and the factors that determine changes in this structure are poorly understood. In the region, wind-driven upwelling, heating by solar radiation and freshwater inputs are highly seasonal processes, which, together with higher frequency events, can promote changes in the planktonic communities, especially in the upper layer. This study focuses on the structure of nano- through to micro-planktonic assemblages (2-200 μm) of unicellular organisms (protists) in surface waters (0-30 m) during different hydrographic conditions. Samples were taken from a fixed shelf station off Concepción (COPAS time series Station 18) on eight occasions between September 2003 and August 2004. The nano-plankton flagellate-dominated fraction was numerically important during the whole period. Maxima in flagellate abundance and biomass occurred during the upwelling period (November-April samplings) but these maxima appear to be unrelated to the degree of water column stratification. The micro-plankton diatom-dominated fraction was usually the largest component in terms of biomass during the study period and the diatoms made important numerical contributions during the upwelling period, with maxima in abundance and biomass when water column stability was lowest. The dominant genera and morphotypes in each functional group were found throughout the study period, with maxima in abundance and biomass co-occurring under similar environmental upwelling conditions. The mean macro-nutrient concentrations (nitrate and silicate) were relatively high in the top 30 m during both upwelling and non-upwelling periods, and did not explain the maxima in plankton or functional group replacements. The persistence of the dominant taxa in the planktonic assemblages suggests a high degree of flexibility, though probably not at the specific level, to withstand the highly variable environmental conditions in this upwelling area.     

厦门东海域定置网渔获鱼类种类组成及其季节变化

2003年7月～2004年6月对厦门东部海域的定置网渔获鱼类进行采样分析．结果表明厦门东海域至少有鱼类242种，隶属于19个目81科145属，主要是沿岸近底层和底栖的小型鱼类．以鲈形目种类最多，共计127种，占总数的52．5％、经济种类有116种．主要优势种有：青鳞小沙丁鱼、孔鳞小沙丁鱼、斑鲦、马拉邦虫鳗、裸鳍虫鳗、中华须鳗、前鳞鲻、眶棘双边鱼、多鳞鳝、皮氏叫姑鱼、短棘银鲈、列牙垒幸4、黄斑蓝子鱼、褐蓝子鱼、锯塘鳢、锻虎鱼类、褐菖鲇、绿鳍鱼、鳄鲡、卵鳎、中华单角鲍等．渔获种类在秋季及冬初最多，夏季较多，而冬末和春初最少．渔获种类的季节变化比较明显，与海洋表层水温变化有关，种类的月更替率比较高．     

The Continuous Plankton Recorder: concepts and history, from Plankton Indicator to undulating recorders

Alister Hardy conceived the Continuous Plankton Recorder (CPR) survey in the 1920s as a means of mapping near-surface plankton in space and time, interpreting the changing fortunes of the fisheries and relating plankton changes to hydrometeorology and climatic change. The seed he planted has grown to become the most extensive long-term survey of marine organisms in the world and the breadth of his vision becomes ever more apparent. The survey has now run for over 70 years and its value increases with every passing decade. Operating from ‘ships of opportunity’ the machines used are robust, reliable and easy to handle. Wherever possible, all the sampling and analytical methods have not been changed to maintain the consistency of the time series. Computerisation and the development of new statistical approaches have increased our ability to handle the large quantities of information generated and enhance the sensitivity of the data analyses. This overview, based on almost 900 papers, recounts the various phases in the history of the survey. It starts with the Indicator Survey (1921–1934), the deployment of the first CPR on the Discovery Expedition (1924–1927) and the early CPR survey in the North Sea (1931–1939). The survey reopened in 1946 after the Second World War and expanded across the North Atlantic to North America from 1959. Taxonomic studies were initiated and an emphasis was placed on patterns of distribution, which were seen to reflect the varying oceanographic conditions. The years 1968–1976 saw further expansion with operations even in the American Great Lakes, publication of a Plankton Atlas and initial evidence for a downward trend in plankton biomass. At about this time electronic instrumentation was attached to CPRs to make additional measurements and work was started on the development of a new generation of undulating Continuous Plankton and Environmental Recorders (CPERs). In 1976 the survey moved to Plymouth. Scientific priorities in the UK changed in the subsequent decade and funding became more difficult to secure even though some of the CPR papers being published at the time are now regarded as classics in plankton ecology. In 1988 the UK Natural Environment Research Council (NERC) decided to close the survey. An international rescue operation led to the creation of the Sir Alister Hardy Foundation for Ocean Science (SAHFOS) in 1990, which has continued with consortium funding from a number of countries, and from 1999 again included NERC. The scientific rationale of the survey has gained credibility as concern over climate change and other anthropogenic effects has grown and as the key role that plankton plays as an indicator of large-scale environmental conditions becomes ever more apparent. Recently, the survey became an integral component of the Global Ocean Observation System (GOOS) and expanded into the North Pacific. It plays a complementary role in many large international and multidisciplinary projects and is providing inspiration, advice and support to daughter surveys elsewhere in the world. At the start of a new millennium, Hardy’s vision from the 1920s is a powerful driving force not just in international biological oceanography, but in global environmental science.     

Industry participation in stock assessment: the New Zealand SNA1 snapper (Pagrus auratus) fishery

We describe industry funded contributions to the assessment of the SNA1 snapper (Pagrus auratus) fishery during the 1990s and discuss the advantages and disadvantages of industry funded research. We also provide background on the history of fisheries management in New Zealand, on the current assessment and management processes, and on the SNA1 snapper fishery. In the SNA1 fishery, the contributions of industry and the cooperation with Government scientists has resulted in high quality assessments. In our opinion, the advantages of industry funded research out weigh the disadvantages and suggest that industry funded assessments are highly desirable and should be an integral part of any management system.     

皱纹盘鲍三倍体生长的初步研究

将用低温休克法和细胞松弛素B诱导法,获得的皱纹盘鲍(Haliotis discus hannai Ino)三倍体诱导群与二倍体的个体,在室内同样条件下饲育,对其生长情况进行了比较,结果表明:(1)三倍体与二倍体的当年稚鲍在壳长和体重的增长上无明显差异。(2)三倍体与二倍体的2龄鲍,在第二年前期生长无明显差异,但从第二年后期开始,三倍体的壳长、体重增长逐渐优于二倍体。(3)统计学分析表明,三倍体与二倍体的3龄鲍在体重、软体部和足肌的增长方面,存在着明显差异。(4)在室内饲育19个月的鲍,三倍体诱导群的壳长比二倍体大10.2％,体重比二倍体大20.1％,足肌湿重比二倍体大17.6％。     

Primary production in the eastern tropical Pacific: A review

The eastern tropical Pacific includes 28 million km² of ocean between 23.5°N and S and Central/South America and 140°W, and contains the eastern and equatorial branches of the north and South Pacific subtropical gyres plus two equatorial and two coastal countercurrents. Spatial patterns of primary production are in general determined by supply of macronutrients (nitrate, phosphate) from below the thermocline. Where the thermocline is shallow and intersects the lighted euphotic zone, biological production is enhanced. In the eastern tropical Pacific thermocline depth is controlled by three interrelated processes: a basin-scale east/west thermocline tilt, a basin-scale thermocline shoaling at the gyre margins, and local wind-driven upwelling. These processes regulate supply of nutrient-rich subsurface waters to the euphotic zone, and on their basis we have divided the eastern tropical Pacific into seven main regions. Primary production and its physical and chemical controls are described for each.Enhanced rates of macronutrient supply maintains levels of primary production in the eastern tropical Pacific above those of the oligotrophic subtropical gyres to the north and south. On the other hand lack of the micronutrient iron limits phytoplankton growth (and nitrogen fixation) over large portions of the open-ocean eastern tropical Pacific, depressing rates of primary production and resulting in the so-called high nitrate-low chlorophyll condition. Very high rates of primary production can occur in those coastal areas where both macronutrients and iron are supplied in abundance to surface waters. In these eutrophic coastal areas large phytoplankton cells dominate; conversely, in the open-ocean small cells are dominant. In a ‘shadow zone’ between the subtropical gyres with limited subsurface ventilation, enough production sinks and decays to produce anoxic and denitrified waters which spread beneath very large parts of the eastern tropical Pacific.Seasonal cycles are weak over much of the open-ocean eastern tropical Pacific, although several eutrophic coastal areas do exhibit substantial seasonality. The ENSO fluctuation, however, is an exceedingly important source of interannual variability in this region. El Niño in general results in a depressed thermocline and thus reduced rates of macronutrient supply and primary production. The multi-decadal PDO is likely also an important source of variability, with the ‘El Viejo’ phase of the PDO resulting in warmer and lower nutrient and productivity conditions similar to El Niño.On average the eastern tropical Pacific is moderately productive and, relative to Pacific and global means, its productivity and area are roughly equivalent. For example, it occupies about 18% of the Pacific Ocean by area and accounts for 22–23% of its productivity. Similarly, it occupies about 9% of the global ocean and accounts for 10% of its productivity. While representative, these average values obscure very substantial spatial and temporal variability that characterizes the dynamics of this tropical ocean.     

Application of Atomic Force Microscopy to Observation of Marine Bacteria

The atomic force microscopy (AFM) is a recently developed, bench-top instrument that can image the surface structures of biological specimens at high resolution with simultaneous measurement of their size. This paper describes the application of AFM to marine bacteria. Both natural and cultured bacteria were retained on a filter or placed on glass, washed, air-dried and observed by AFM. The instrumental condition, the choice of suitable filter, effect of fixation and filtration, comparison with epifluorescent microscopic (EFM) count, and the size and shape of bacterial cells were investigated. An Isopore filter was best for concentration and subsequent observation because of its surface flatness. Cross section images showed that both rod and coccoid cells were flattened, the former usually having a two-humped shape. Bacterial cells were differentiated from non-living particles based on their cross section shape and size. Bacterial counts by AFM and EFM showed good agreement. Although size measurement is easily done by the instrument, AFM tends to overestimate the size of microspheres. More work is thus needed on the size measurement of living organisms. Because AFM easily provides images of natural bacterial cells at high magnification, it can be used as a new tool to study the fine structures of marine bacteria. This revised version was published online in July 2006 with corrections to the Cover Date.     

State Estimation of the North Pacific Ocean by a Four-Dimensional Variational Data Assimilation Experiment

A four-dimensional variational data assimilation system has been applied to an experiment to describe the dynamic state of the North Pacific Ocean. A synthesis of available observational records and a sophisticated ocean general circulation model produces a dynamically consistent dataset, which, in contrast to the nudging approach, provides realistic features of the seasonally-varying ocean circulation with no artificial sources/sinks for temperature and salinity fields. This new dataset enables us to estimate heat and water mass transports in addition to the qualification of water mass formation and movement processes. A sensitivity experiment on our assimilation system reveals that the origin of the North Pacific Intermediate Water can be traced back to the Sea of Okhotsk and the Bering Sea in the subarctic region and to the subtropical Kuroshio region further south. These results demonstrate that our data assimilation system is a very powerful tool for the identification and characterization of ocean variabilities and for our understanding of the dynamic state of ocean circulation. This revised version was published online in July 2006 with corrections to the Cover Date.