首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
The Continuous Plankton Recorder has been deployed for 70 years. Although modifications to the machine have been relatively minor, there has been a steady increase in the speed at which it is towed, creating a need to quantify what effects this may have had on its sampling characteristics. Additionally, because the CPR database is one of the longest and most geographically extensive biological time series in the world, and scientists are currently focusing on gaining understanding about climate-induced ecological changes, there is increasing pressure to quantify the sampling performance and relate the CPR data to data collected by other plankton samplers. Many of these issues of consistency and comparability have been investigated throughout the decades of the CPR survey. The primary aim of this study is to draw together the results of those investigations, updating or integrating them where applicable. A secondary aim is to use the CPR database to address other previously unexamined issues. We show that the increase in speed of tow has had no effect on the depth of sampling and the mechanical efficiency of the internal mechanism, but that at the highest tow speeds there is some evidence that flow may be reduced. Depth of tow may also be dependent on the ship operating a particular route. We describe the processing procedures used to ensure consistency of analysis and detail the changes in taxonomic resolution that have occurred through the course of the survey. Some consistency issues remain unresolved, such as the effects of adding heavy instrumentation to the attitude of the CPR in the water and possible effects on sampling performance. The reduction of flow caused by clogging of the filtering mesh has now been quantified through the addition of flowmeters and each CPR sample can now be calibrated for measured, or derived, filtered volume. Although estimates of abundances for large areas have been shown to be unaffected by recalibration, absolute quantification of plankton abundance is necessary to enable comparisons with other sampling devices. Several studies have now been undertaken that compare plankton abundances obtained with the CPR with those obtained using vertical nets at specific locations on the European continental shelf. Although catches by the CPR are almost always lower, seasonal cycles are replicated in each comparison, and interannual variability generally agrees between time series. The relative catch rates for an individual species by each device appear to be consistent, probably because of the organisms’ behaviour and attributes of the sampling device. We are now able to develop calibration factors to convert CPR catches to absolute abundances that can be integrated with other data sets where appropriate, which should increase the applicability and utility of CPR data.  相似文献   

2.
Since the beginning of the Continuous Plankton Recorder (CPR) survey in 1931, information on the abundance of a large number of plankton species or taxa has been obtained on a monthly basis in the northern North Atlantic. The many different ecological issues in which the survey has been involved have led to the application of a range of statistical methods. In this paper, we review some of the methods applied to the CPR data by presenting new and up-to-date analyses. Special attention is devoted to multivariate analysis, which has been used extensively to extract information from the CPR database. Results obtained from recently applied geostatistical methods on CPR data are then considered. An example of a time series decomposition by the use of Eigenvector filtering is presented to illustrate time-series analysis.  相似文献   

3.
  相似文献   

4.
Taxonomic information provides a crucial understanding of the most basic component of biodiversity – which organisms are present in a region or ecosystem. Taxonomy, however, is a discipline in decline, at times perceived as ‘obsolete’ due to technical advances in science, and with fewer trained taxonomists and analysts emerging each year to replace the previous generation as it retires. Simultaneously, increasing focus is turned towards sustainable management of the marine environment using an ecosystem approach, and towards conserving biodiversity, key species, and habitats. Sensitive indicators derived from taxonomic data are instrumental to the successful delivery of these efforts. At the base of the marine food web and closely linked to their immediate environment, plankton are increasingly needed as indicators to support marine policy, inform conservation efforts for higher trophic organisms, and protect human health. Detailed taxonomic data, containing information on the presence/absence and abundance of individual plankton species, are required to underpin the development of sensitive species- and community-level indicators which are necessary to understand subtle changes in marine ecosystems and inform management and conservation efforts. Here the critical importance of plankton taxonomic data is illustrated, and therefore plankton taxonomic expertise, in informing marine policy and conservation and outline challenges, and potential solutions, facing this discipline.  相似文献   

5.
The Continuous Plankton Recorder (CPR) survey was conceived from the outset as a programme of applied research designed to assist the fishing industry. Its survival and continuing vigour after 70 years is a testament to its utility, which has been achieved in spite of great changes in our understanding of the marine environment and in our concerns over how to manage it. The CPR has been superseded in several respects by other technologies, such as acoustics and remote sensing, but it continues to provide unrivalled seasonal and geographic information about a wide range of zooplankton and phytoplankton taxa. The value of this coverage increases with time and provides the basis for placing recent observations into the context of long-term, large-scale variability and thus suggesting what the causes are likely to be. Information from the CPR is used extensively in judging environmental impacts and producing quality status reports (QSR); it has shown the distributions of fish stocks, which had not previously been exploited; it has pointed to the extent of ungrazed phytoplankton production in the North Atlantic, which was a vital element in establishing the importance of carbon sequestration by phytoplankton.The CPR continues to be the principal source of large-scale, long-term information about the plankton ecosystem of the North Atlantic. It has recently provided extensive information about the biodiversity of the plankton and about the distribution of introduced species. It serves as a valuable example for the design of future monitoring of the marine environment and it has been essential to the design and implementation of most North Atlantic plankton research.  相似文献   

6.
Traditional methods for determining spatial distributions of planktonic taxa involve net, pump, and bottle collections followed by the tedious and time-consuming task of plankton sample analysis. Thus, plankton ecologists often require months or even years to process samples from a single study. In this paper, we present a method that allows rapid visualization of the distribution of planktonic taxa while at sea. Rapid characterization of plankton distributions is essential in the dynamic physical environment, where biological and physical patterns can change quickly. Such a “sample-and-observe” capability is necessary for mapping ephemeral features (such as patches, eddies, jets, plumes) and determining appropriate locations to conduct more localized sampling, including in situ observational studies. We describe the techniques used in imaging the plankton, analyzing the video, and visualizing the data. We present an example of at-sea data analysis conducted aboard R.V. Columbus Iselin on Georges Bank in May 1994 and visualizations of the 3-dimensional distribution of selected planktonic taxa in a 2 × 2 km × 90 m volume of seawater. A video of the image processing and visualization is included on the CD-ROM accompanying this volume and is an essential part of this paper.  相似文献   

7.
《Journal of Sea Research》2002,47(2):161-184
Benthic community data collected between 1938 and 1950 by N.S. Jones were compared with modern samples from seven sites in the Irish Sea. Multivariate and univariate methods were used to compare community change over time and examine the possible impact of scallop dredging over the 60 year time period. A conservative approach to data analysis ensured that observed differences in faunal composition between time periods were not due to differences in sampling methodologies or taxonomic identification. The community composition changed at all sites, though to different degrees. The amount of change was related to how long a site had been fished, rather than fishing intensity. Mobile, robust and scavenging taxa have increased in abundance, while slow-moving or sessile, fragile taxa have decreased. Differences between historical and modern samples were greater than could be accounted for by the natural variability of the system (as indicated by spatial and temporal replication at three sites) and indicate real long-term change. This study emphasises that, in the absence of good-quality data series and experiments, the use of ‘fuzzy’ historical data is often the only possible way to judge long-term change and can yield valuable results.  相似文献   

8.
Zooplankton sampling has been carried out by the Continuous Plankton Recorder (CPR) survey since the 1930s enabling the study of long-term changes in plankton populations, the elucidation of seasonal patterns of abundance, and more recently providing zooplankton biomass estimates for ecosystem models. Data for zooplankton abundance collected by CPR tows in the Western English Channel (between 1988 and 1998) were compared to vertically integrated samples collected from station L4 off Plymouth, UK. Comparisons were made for locally abundant copepods (including Acartia, Calanus, Para/Pseudocalanus, Centropages, Oithona and Temora) collected by CPR and WP-2 nets. All dominant species recorded at L4 were also common to the CPR data. However, the position of the taxa in the two datasets was not equivalent. Seasonal cycles revealed by CPR data were significantly similar to those recorded throughout the water column at L4 for most taxa. However, absolute levels of abundance differed for the two datasets: abundances were underestimated by CPR samples when compared to those of vertically integrated samples by a factor of between 2 and 35, with the exception of Centropages. The differing mesh sizes (200 and 270 μm) of the WP-2 net and CPR mesh could only partially explain these differences in abundance, implying that the behaviour of individual taxa and their depth in the water column also influenced the abundance recorded.  相似文献   

9.
The earliest comprehensive plankton sampling programme in the Southern Ocean was undertaken during the early part of last century by Discovery Investigations to gain a greater scientific understanding of whale stocks and their summer feeding grounds. An initial survey was carried out around South Georgia during December 1926 and January 1927 to describe the distribution of plankton during the summer, and to serve as a baseline against which to compare future surveys. We have reanalysed phytoplankton and zooplankton data from this survey and elucidated patterns of community distribution and compared them with our recent understanding of the ecosystem based on contemporary data. Analysis of Discovery data identified five groups of stations with characteristic phytoplankton communities which were almost entirely consistent with the original analysis conducted by [Hardy A.C., Gunther, E.R., 1935. The plankton of the South Georgia whaling grounds and adjacent waters 1926-1927. Discovery Report 11, 1-456]. Major groupings were located at the western end of the island and over the northern shelf where Corethron spp. were dominant, and to the south and east where a more diverse flora included high abundances of Nitzschia seriata. Major zooplankton-station groupings were located over the inner shelf which was characterised by a high abundance of Drepanopus forcipatus and in oceanic water >500 m deep that were dominated by Foraminifera, Oithona spp., Ctenocalanus vanus, and Calanoides acutus. Stations along the middle and outer shelf regions to the north and west, were characterised by low overall abundance. There was some evidence that groupings of stations to the north of the island originated in different water masses on either side of the Southern Antarctic Circumpolar Current Front, the major frontal system in the deep ocean close to South Georgia. However, transect lines during 1926/1927 did not extend far enough offshore to sample this frontal region adequately. Interannual variability of zooplankton abundance was assessed from stations which were sampled repeatedly during seven recent British Antarctic Survey cruises (1995-2005) to the region and following taxonomic harmonization and numerical standardization (ind. m−3), a subset of 45 taxonomic categories of zooplankton (species and higher taxa) from 1926/1927, were compared with similar data obtained during the BAS cruises using a linear model. Initially comparisons were restricted to BAS stations that lay within 40 km of Discovery stations although a comparison was also made using all available data. Despite low abundance values in 1926/1927, in neither comparison did Discovery data differ significantly from BAS data. Calculation of the percentage similarity index across cruises did not reveal any systematic differences in species composition between 1926 and 1927 and the present. In the light of ocean warming trends, the existence of more subtle changes in species composition is not ruled out, but an absence of finely resolved time-series data make this impossible to determine.  相似文献   

10.
The importance of key taxonomic groups of eukaryotic phytoplankton as contributors to downward particle flux was evaluated near the European time-series station (ESTOC) in the eastern subtropical North Atlantic in March 2005. For the first time, molecular (cloning and sequencing) techniques were used to compare plankton communities from various depths in the euphotic zone with clone libraries from surface-tethered particle traps. Analyses of 18S rDNA clone libraries revealed compositional differences between the phytoplankton assemblages in the photic zone and those retrieved from shallow particle traps below, suggesting that not all phytoplankton contribute equally to particle flux. Contrary to expectations, our study also showed that it is not diatoms, despite their high abundance in the water column, but rather small phytoplankton taxa that dominated sequences recovered from trap material. We provide here first observational evidence that large taxa with mineral tests may not necessarily contribute more to export production than do smaller taxa even if the former are abundant in the water column.  相似文献   

11.
The recognition of the economic value of nature and the services it provides to humanity has become increasingly essential in the context of coastal zone management. In this paper we review the progress to date on both the necessary conceptual framework and empirical valuation studies required to bolster decision support systems (DSS) targeted at integrated coastal zone management goals. We highlight the importance of using an ecosystem services approach and recommend some basic sequential, although overlapping, analytical steps for appropriate environmental valuation and policy assessment: spatial explicitness; marginal changes; double counting; non-linearities; and threshold effects. We illustrate the practical use of the DSS by reviewing an existing UK case study on managed coastal realignment along the Eastern coast of England, and a new UK case study on managed realignment implemented in a southern area on the same coast. Comparing the two studies, the importance of spatial explicitness and the need for a sequential decision support system when dealing with ecosystem services valuation and project policy appraisal become particularly evident.  相似文献   

12.
浮游生物在海洋生态系统中处于基础性地位,为促进我国浮游生物监测工作的发展,文章在现代海洋环境监测体系和海洋管理的背景下,从海洋生态系统保护、全球变化研究和现代海洋管理3个方面,系统梳理和分析浮游生物监测的意义和价值,并对我国相关领域的工作提出启示和展望。研究结果表明:浮游生物的恶性暴发和入侵对海洋生态系统造成严重影响,各类国际公约和政府间协议都将浮游生物监测作为保护海洋生物多样性的重要内容;浮游生物的分类信息以及其分布区和物候学特征对气候变化和海水温度的指示信息,可作为全球变化研究的重要指标;浮游生物监测已被广泛应用于国内外现代海洋管理中,主要包括海洋生态系统服务评价、海洋环境影响评价和海洋生物资源评价3个方面;我国浮游生物监测工作在浮游生物分类和鉴定以及大数据应用方面存在不足,未来应加强相关能力考核、标准化计量认证、数据整合共享和新技术手段运用。  相似文献   

13.
生物发光现象在海洋中广泛存在,基于微光成像技术对深海发光浮游生物的发光现象进行视觉捕获是一种先进的原位观测手段,但目前缺乏有效的方法对获取的生物发光影像资料进行自动分析。针对此问题,本文提出一种基于多特征匹配跟踪的发光浮游生物自动计数方法,基于同一目标在连续帧间的运动具有连续性的思想,首先采用帧间质心差小于一定阈值的原则进行初始粗匹配,然后针对目标过近造成的误匹配问题再进一步进行运动方向的匹配,提高帧间匹配精度,从而准确计数。采用所提出的方法对深海发光浮游生物的真实视频数据进行了自动分析,实验结果证明该计数方法具有较好的准确率,对生物发光区域的尺度变化、发光目标间距过近等情况具有较好的鲁棒性,能达到较好的计数效果。  相似文献   

14.
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.  相似文献   

15.
The plankton abundance data of the Continuous Plankton Recorder (CPR) route from Bergen or Rotterdam to Weather Station Mike (6444′N, 2E) from 1949 to 1981 were analysed for long-term trends and seasonal production cycles, and were related to environmental data. The data were explored using the canonical correlation analysis and nonparametric techniques like the Nadaraya–Watson regression. While large copepods such as Calanus spp. and Metridia lucens did not show any temporal trends, a sharp decrease in the abundances of smaller copepods and phytoplankton was observed after 1960. The temporal trends were not related to the NAO, but did show a correlation with the wind direction. Seasonal abundance curves showed that production of both phytoplankton and zooplankton taxa started earlier in coastal water compared to Atlantic water. From the 1950s to the 1970s most taxa showed a delay in the start of the seasonal production cycles, indicating a reduction in the length of the productive cycle. This may to some extent explain the reduced abundance of smaller copepods, phytoplankton and other species during the 1960s and 1970s.  相似文献   

16.
The Continuous Plankton Recorder (CPR) Type I was first used in Antarctic waters during the 1925–1927 Discovery Expedition, and has been used successfully for 70 years to monitor plankton in the North Sea and North Atlantic Ocean. Sixty-five years later the CPR as a Type II version returned to Antarctic waters when the Australian Antarctic Division initiated a survey of the Southern Ocean on RSV Aurora Australis south of Australia and west to Mawson. The objectives are to study regional, seasonal, interannual and long-term variability in zooplankton abundance, species composition and community patterns, as well as the annual abundance and distribution of krill larvae. The survey covers a large area from 60°E to 160°E, and south from about 48°S to the Antarctic coast—an area of more than 14 million km2. Tows are conducted throughout the shipping season, normally September to April, but occasionally as early as July (midwinter). The large areal and temporal scale means that it is difficult to separate temporal and geographical variation in the data. Hence, CPRs are now also towed on the Japanese icebreaker Shirase in collaboration with the Japanese Antarctic programme. Shirase has a fixed route and time schedule, travelling south on 110°E in early December and north on 150°E in mid-March each year, and will serve as an important temporal reference for measuring long-term interannual variability and to help interpret the Australian data. Since 1991, over 90 tows have been made, providing over 36,000 nautical miles of records. The most successful seasons to date have been the 1997/1998, 1999/2000 and 2000/2001 austral summers with 20, 31 and 26 tows, respectively. The 1999/2000 season included a unique, nearly simultaneous three-ship crossing of the Southern Ocean along 25° 30’E, 110°E and 157°E. Typical CPR tows show very high abundance of zooplankton in the uppermost 20 m of the permanently open ocean zone between the sea-ice zone and the Sub-Antarctic Front; this is an area thought to be oligotrophic. Appendicularians and small calanoid and cyclopoid copepods dominate the plankton. By comparison the surface waters of the sea-ice zone have low species diversity and abundances. Zooplankton data, and hence distribution patterns, can be time- and geo-coded to GPS data and environmental data collected by the ships’ underway monitoring system (e.g. fluorescence, water temperature, salinity, and meteorological data).  相似文献   

17.
浮游生物光学计数器（Optical Plankton Counter,OPC）能够在现场和实验室内对浮游动物、鱼卵和其它水生生物进行实时的数量统计和粒径划分,可以有效地替代繁琐的传统人工计数,快速获得丰度和生物量（体积）谱数据。但在实际应用中会存在很多问题,特别是如何进行标定和消除由于操作方法而引起的误差,这些问题的存在与解决,直接影响到观测数据的准确性和可靠性,以及能否利用此仪器进行快速、有效的浮游生物长时间序列监测与分析。本研究中作者针对计数过程中气泡干扰和样品重叠的问题,对进样系统进行了改良,通过大量实验研究了准确率与进样速度、生物形状之间的关系,探讨了如何通过速度控制有效提升准确率。通过改进循环水系统并加装相应的外围设施,使气泡问题得以解决。通过一系列的对比试验发现,控制Dmax（最大测样速度）在11个／s以内,可以使重合率维持在5％以下;控制Dmax在7个／s以内,可以使重合率降低到2％以下。同时发现生物的形状也会影响测量精度。结果表明,无论在何种测样速度下,随着长宽比（L/W）的增加,ESD（Equivalent Spherical Diameter,遮挡相同数量光线的球的直径）均值准确度均出现“V”形变化,先降低后增加,在L／W为4或6时准确度达到最低。本研究中作者有效解决了气泡干扰的问题,根据所确定的参数和目标种群体型相结合,选择合理的进样速度,完全能够达到98％以上的数量准确度和95％的ESD均值准确度。  相似文献   

18.
  相似文献   

19.
Fishermen, scientists, national policy makers, and staff of environmental NGOs (ENGOs) hold different perceptions about temporal patterns in fish stocks. Perception differences are problematic in multi-stakeholder settings, because they elicit controversies and unbalanced disputes. These hinder effective participation, a prerequisite for ‘good governance’ and effective management of sustainable fisheries. This study shows that perceptions of change (‘does the stock increase or decrease?’) and of current status of a fish stock (‘is it doing well or not?’) are influenced by the capturing and processing of information, rather than by interests alone. We focused on the Dutch North Sea fishery on plaice and sole and examined (1) availability and accessibility of information on temporal patterns of these stocks and (2) perception differences between all parties. A first explanation for these differences is the use of different parameters as a measure for stock size. Fishermen focus on catch rates or catch-per-unit-effort (relative stock size), whereas scientists, policy makers, and ENGO-staff mainly use scientific assessments of spawning stock biomass (absolute stock size). Between-group perception differences are further explained by spatial aggregation levels of information, lengths of time series evaluated, and by modes of comparison to qualify the current status of fish stocks. Awareness of information differences and the development of shared information use and processing may release some of the tensions in multi-stakeholder settings debating fisheries management. However, comprehension problems amongst all parties on how spawning stock biomass is reconstructed and how it relates to catch rates in the fishery may pose an enduring barrier.  相似文献   

20.
Vertical and horizontal distribution patterns of larval and juvenile fishes were described from five offshore petroleum platforms in the north-central Gulf of Mexico. Light traps and passively-fished plankton nets were used nocturnally between 1995–2000 to collect fishes in surface and deep (15–23 m depth) waters within the platform structure, and light traps were also used in surface waters directly down-current of the platforms. Light traps fished at the surface, as opposed to at-depth, collected greater CPUEs and greater diversity of larval and juvenile fishes. Of the dominant taxa collected by light traps, clupeids, engraulids, synodontids, and presettlement blenniids were most common in surface waters within the platform, while postflexion scombrids and settlement-size blenniids and pomacentrids were most common in surface waters down-current of the platforms. Deep plankton nets collected greater densities of non-clupeiform larval fishes, although surface plankton nets collected greater numbers of taxa. The vertical distribution patterns described for dominant larval fish collected by plankton nets were generally consistent with those from other studies, i.e. clupeid, carangid, sciaenid and scombrid larvae more abundant in surface waters at platforms, and synodontid, bregmacerotid, gobiid and bothid larvae more abundant in deeper waters. Oil and gas platforms likely impact larval and juvenile fish populations, particularly considering their proliferation in the Gulf (i.e., over 4000 platforms). The results from this study provide valuable baseline information for future research investigating how platforms impact the life history stages of fish populations.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号