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 31 毫秒
1.
During late winter and spring of 2002 and 2003, 24 two- to three-day cruises were conducted to Dabob Bay, Washington State, USA, to examine the grazing, egg production, and hatching success rates of adult female Calanus pacificus and Pseudocalanus newmani. Here, we discuss the results of our grazing experiments for P. newmani. Each week, we conducted traditional microzooplankton dilution experiments and “copepod dilution” experiments, each from two different layers. Grazing was measured by changes in chlorophyll concentration and direct cell counts. Clearance rates on individual prey species, as calculated by cell counts, showed that Pseudocalanus are highly selective in their feeding, and may have much higher grazing rates on individual taxa than calculated from bulk chlorophyll disappearance. The grazing rates of the copepods, however, are typically an order of magnitude lower than the grazing rates of the microzooplankton community, or the growth rates of the phytoplankton. P. newmani ingested diatoms, but, at certain times fed preferentially on microzooplankton, such as ciliates, tintinnids, and larger dinoflagellates. Removal of the microzooplankton may have released the other phytoplankton species from grazing pressure, allowing those species’ abundance to increase, which was measured as an apparent “negative” grazing on those phytoplankton species. The net result of grazing on some phytoplankton species, while simultaneously releasing others from grazing pressure resulted in bulk chlorophyll-derived estimates of grazing which were essentially zero or slightly negative; thus bulk chlorophyll disappearance is a poor indicator of copepod grazing. Whether copepods can significantly release phytoplankton from the grazing pressure by microzooplankton in situ, thus causing a trophic cascade, remains to be verified, but is suggested by our study.  相似文献   

2.
As one of the important microzooplankton in marine pelagic habitats, tintinnids are classified as neritic genera,oceanic genera and cosmopolitan genera. Until now, we know little about the interaction between neritic and oceanic genera in continental shelves. Low species richness area was found in the mixing area between neritic and oceanic genera in the East China Sea. In this study, we investigated the spatial distribution of tintinnid community throughout the entire Bohai Sea in May(spring) of 2014 to find out:(1) whether the tintinnid assembalges differed in the three major bays bordering this shallow inland sea;(2) whether there was low species richness area in the Bohai Sea. Three genera and 11 species attributed to neritic and cosmopolitan taxa were reported from this region. Tintinnid abundance averaged(81±216) ind./L(0–1 234 ind./L). Tintinnid community differed within the three major bays, with each characterized by different tintinnid taxa. Referring to the average abundance of three bays, tintinnids were most abundant in the Laizhou Bay((328±445) ind./L), and least abundant in the Liaodong Bay((34±57) ind./L). A low species richness area occurred in the central Bohai Sea(20–40 m isobaths), in some stations of which no tintinnid was recorded. Our study demonstrates that tintinnid community varied greatly over small spatial scales, and low species richness area was found in the mixing area between neritic and oceanic genera within this inland sea.  相似文献   

3.
2009年1月在南海北部海域的5个站位,采用稀释法和显微分析技术研究了浮游植物生长率及微型浮游动物对浮游植物的摄食压力,同时测定了微型浮游动物的丰度及类群组成.结果表明:南海北部微型浮游动物类群主要以无壳纤毛虫为主,南海北部微型浮游动物类群细胞丰度为33～529个/dm3.南海北部浮游植物生长率为0.45～1.83 d-1,微型浮游动物摄食率为0.44～1.76 d-1,摄食压力占浮游植物现存量的42.6%～82.8%,占初级生产力的97.3%～225.1%.近岸区摄食压力比陆架区高,表明冬季南海近岸区微型浮游动物摄食能够有效的控制浮游植物的生长,而陆架区浮游植物生长率大于摄食率,浮游植物存在着现存量的积累,微型浮游动物并不能完全控制浮游植物的生长.  相似文献   

4.
研究了2005年4个季度用浅海Ⅲ型网在长江口40个站位采集的浮游生物样品,发现砂壳纤毛虫11种:Codonellopsis ostenfeldi,C.parva,Eutintinnus tenuis,Favella panamensis,Leprotintinnus nordqvisti,Leprotintinnus sp.,Tintinnopsis japonica,T. karajacensis,T. mortensenii,T. radix,T. schotti.Leprotintinnus sp.,最大丰度可达32 400个/m3,有的种的最大丰度不足200个/m3,如Codonellopsis parva,E. tenuis和T.mortensenii.冬季T.japonica主要分布于长江口外,Leprotintinnus sp.在春、夏、秋季都主要分布于长江口外,其他种的分布没有明显规律.在4个季度长江口内都没有发现砂壳纤毛虫.  相似文献   

5.
Laboratory experiments were conducted to determine the feeding performances of Uca zoeae and the estuarine copepods Acartia tonsa and Tortanus setacaudatus when these zooplankton preyed upon the co-occurring tintinnids Favella panamensis (length 265 μm) and Tintinnopsis tubulosa (length 148 μm). Predation by Favella on Tintinnopsis was also studied. Over the range of experimental prey densities used, Acartia ingested Tintinopsis at rates linearly related to prey density. Favella was ingested by Aractia at higher rates than was Tintinnopsis. Tortamus ingested Favella more readily than did Acartia, but Tortanus did not ingest Tintinnopsis. Uca ingested both Tintinnopsis and Favella while Tintinnopsis was also ingested by the larger tintinnid Favella. Comparisons of Acartia predation on tintinnids with published data on ingestion of nauplii and phytoplankton showed that when the phytoplankton are dominated by small (diameters < 10 μm) species, tintinnids in concentrations exceeding 103 organisms 1?1 can be important items in the diets of Acartia. At lower tintinnid concentrations or when algal species with diameters > 10 μm are present in significant concentrations, tintinnids merely supplement algae in the diet of Acartia. Generally, tintinnids are more important food items for Acartia than are comparably sized nauplii. Only at concentrations exceeding 104 cop. m?3 can Acartia depress tintinid population growth.  相似文献   

6.
汕头沿岸水体沙壳纤毛虫季度变化   总被引：1，自引：0，他引：1  
在2007年枯水期(4月)和丰水期(11月)期间,对汕头沿岸海区沙壳虫进行了采样研究,探讨了沙壳虫的空间分布和种类组成.调查发现,除了表层海水温度以外,表层海水盐度、硝酸盐浓度、硅酸盐浓度均是春季低于秋季.在两个季节的5个采样点共鉴定出7属14种沙壳纤毛虫,其中优势种均为简单薄铃虫Lepmtintinnus simpl...  相似文献   

7.
胶州湾桡足类幼虫和浮游生纤毛虫的丰度与生物量   总被引：8，自引：4，他引：8  
张武昌  王荣 《海洋与湖沼》2001,32(3):280-287
1997年9月，12月，1998年2月，4月，8月，11月以及1999年2月和5大以胶州湾采集桡足类幼虫和浮游生纤毛虫的样品，样品用Lugol‘s试剂固定（最后浓度1％），用显微镜计数桡足类幼虫和浮游生纤毛虫的丰度，并计算总生物量（表层生物量和水体生物量）。桡足类幼虫，无壳纤毛虫和砂壳纤毛虫的最大丰度分别为850ind/L(1998年8月），21300ind/L(1998年8月）和172ind／L(1999年5），表层的总丰度为10－22630ind/L，平均分布湾内比湾外多，表层纤毛虫和桡足类幼虫的总生物量为0．10－380.27ugC/L，水体的生物量为0．20－1426.02mgC/m^2.  相似文献   

8.
Ichthyoplankton and microzooplankton were collected twice monthly for one year at a single station in Biscayne Bay, Florida. Based on approximate 10-m3, 333-μm mesh bongo net samples, the mean annual densities were 17·7 m?3 and 1·8 m?3 for fish eggs and larvae, respectively. Ichthyoplankton was most abundant in spring-summer. The most common fish larvae were bay anchovy (Anchoa mitchilli), spotted dragonet (Callionymus pauciradiatus), thread herring (Opisthonema oglinum) and gobies (Gobiidae), which comprised 50% of all larvae collected. A comparison of 35-μm and 333-μm mesh, bongo net collections revealed that mean densities of fish larvae were 8·5 times higher in the smaller mesh. The most abundant microzooplankton, based on 35-μm bongo net collections, were copepod nauplii, <100 μm in width, which averaged 90·41?1 and tintinnids which averaged 168·51?1. The mean density of microzooplankton <100 μm wide, potentially suitable food for first-feeding fish larvae, was 104·91?1, exclusive of tintinnids, and 273·41?1 including tintinninds. Excepting tintinnids, seasonal variability in microzooplankton abundance was low relative to that for ichthyoplankton. High microzooplankton densities, combined with low seasonal variability, indicated that feeding conditions for fish larvae were usually good in Biscayne Bay. Copepods, especially nauplii, were the predominant food of fish larvae (71% of all food items). Only mollusc veliger larvae (18% of all food items) were highly preferred prey but they were a small component of most larval fish diets. Average width of prey eaten by first-feeding larvae was 74 μm. Prey size increased in relation to larval length.  相似文献   

9.
As part of a broader field study examining the potentially deleterious effects of diatoms on planktonic food webs, we examined the abundance, stage composition, diet, and feeding success of the chaetognath, Sagitta elegans, and the abundance and morphometric condition of larval Pacific hake, Merluccius productus. Our objective was to look for a relationship between spring phytoplankton blooms and planktonic predators, as mediated by their copepod prey, with special reference to possible deleterious effects of diatoms. Zooplankton were collected weekly during February–May and in mid-summer of 2002 and 2003 in Dabob Bay, Washington State, USA. S. elegans abundance was high in summer of both years and was higher in spring 2003 than spring 2002. Larval chaetognaths dominated the population in early spring and remained present throughout sampling. S. elegans consumed mostly copepods. The abundance of larval S. elegans was correlated with the abundance of copepodites, although no relationship between chaetognath feeding success and prey abundance was found. Larval Pacific hake abundance was high (1200 larvae per square meter) in late February and early March of 2002 and 2003 and decreased rapidly in late spring. The morphometric condition of M. productus was not significantly related to copepod abundance. These results indicate that any deleterious effects of diatoms on copepod abundance, at the scale seen during spring 2002 and 2003 in Dabob Bay, did not greatly affect the next higher trophic level.  相似文献   

10.
Information on life cycle strategies and reproductive parameters of Metridia pacifica is scarce, despite its importance in the zooplankton of the subarctic Pacific. In many regions it occurs in high abundance, but reproductive rates, when reported, are usually low. This discrepancy was studied in Dabob Bay, Washington, USA, in the context of an investigation of the effect of diatom blooms on the reproductive success of copepod grazers.In situ egg production rates of M. pacifica were measured in spring and mid-summer with standard methods (multi-wells) and a new incubation chamber (spawning towers) that separates the spawning female from its eggs and allows the eggs to develop undisturbed. Many females did not produce eggs, possibly due to a high fraction of immature individuals. Egg production rates were variable, but clutch sizes were higher in spawning towers, and estimates of female egg cannibalism revealed that females consume many eggs shortly after their release. Thus, a separation of females and eggs is mandatory for accurate measurements of M. pacifica egg production rates. The maximum clutch sizes recorded in our study were comparable to measurements for other calanoids. However, unviable eggs were a large fraction of those spawned, independent of incubation method, especially in late winter and early spring. In order to assess whether the diatom effect may be responsible for low viability of embryos and nauplii, we also measured in situ grazing. Adult females were omnivorous, but they ingested some diatoms that rank among the strongest anti-mitotic toxin producers known so far. Although M. pacifica’s vertical migration behavior suggests opportunistic feeding on abundant food during their short stay in the phytoplankton-rich surface, they often ignored the food items that contributed most to microplankton carbon concentrations. Thus, their feeding strategy remains ambiguous. Due to severe reproductive failure early in the season, recruitment was impaired in spring, while the population increased, reaching high abundance in mid-summer when reproductive output was low. While advection and interannual variability in bloom conditions might compensate for the losses described here, the paradox of high Metridia abundance versus low reproductive success still requires further investigation, and methodological constraints need to be ruled out in future studies.  相似文献   

11.
We examined tintinnid (loricate ciliate microzooplankton) diversity using data from 11 stations between the Moroccan upwelling system and the oligotrophic Eastern Mediterranean. Taxonomic and morphological diversity of tintinnids was compared to phytoplankton distribution and size-structure, to the abundance of competitors in the form of oligotrich ciliates, and predators as copepods. Tintinnid taxonomic diversity was estimated as numbers of species and the Shannon Index, H′; morphological diversity was quantified by substituting size classes of lorica dimensions for species. Total chlorophyll was partitioned into micro-, nano- and pico-fractions using pigment data and a size-diversity was estimated by considering the 3 size classes as 3 species. Along a west-to-east gradient, average water column concentrations of most organism groups declined approximately an order of magnitude yielding tight correlations. However, tintinnid diversity, both taxonomic and morphological, increased from the Atlantic upwelling station into the western basin of the Mediterranean, and declined slightly towards the Eastern Mediterranean, paralleling shifts in the chlorophyll size-diversity estimate. Diversity varied with absolute or relative abundance of oligotrich or copepods, but different diversity metrics were significantly correlated only with phytoplankton size-diversity. We conclude that tintinnid diversity more closely reflects resource diversity than competitive interactions or predation.  相似文献   

12.
桑沟湾浮游纤毛虫丰度和生物量分布的季节变化   总被引：1，自引：0，他引：1  
于2011年4、8、10月及2012年1月对桑沟湾进行了浮游纤毛虫丰度和生物量的季节调查。纤毛虫的平均丰度为(7 552±10 979)个/L,范围为408~61 667个/L;纤毛虫的平均生物量(以碳计)为(4.79±5.77)μg/L,范围为0.35~33.09 μg/L。无壳纤毛虫丰度和生物量主要分布在湾内,湾中和湾外丰度相对较低;砂壳纤毛虫丰度和生物量在盐度较高的海区总体较高,呈现朝向外海分布的趋势。纤毛虫丰度和生物量的高值区春季主要出现在湾的西北,夏季向湾中部迁移,秋季主要出现在湾的西南,冬季主要出现在湾的西部,高值区随季节大致呈顺时针迁移的趋势。纤毛虫的丰度春季最高,冬季最低;生物量夏季最高,冬季最低。无壳纤毛虫夏季粒级较大,冬季粒级较小;砂壳纤毛虫壳的平均口径夏季较大,秋季较小。共鉴定出砂壳纤毛虫8属27种,其中拟铃虫属(Tintinnopsis)种数最多。砂壳纤毛虫在纤毛虫总丰度中的比例平均为16.3%±21.9%,夏季最高(36.3%±27.8%),冬季最低(4.9%±5.9%)。纤毛虫丰度与温度、盐度、Chl a浓度及微微型真核浮游生物丰度均没有明显的相关性,但与蓝细菌及异养细菌丰度呈显著的正相关关系。  相似文献   

13.
几个试验因子对细巧华哲水蚤清滤率和滤食率的影响   总被引：6，自引：0，他引：6  
以象山港浮游桡足类优势种细巧华哲水蚤（Sinocalanus tenellus) 成体为试验动物投喂以大溪地等鞭金藻（Isochrysis galbona)，对其清滤率F（ml/个.h)和滤食率G（细胞／个.h)进行了实验测定，结果表明，温度，海水比重，食物浓度及试验动物密度的变化对细巧华哲水蚤清滤率和滤食率均有显著影响，水温15度，比重1．－1－，食物浓度150000个细胞／ml和试验动物密度．25个／ml的条件下，细巧华哲水蚤滤食率达到最大。  相似文献   

14.
While numerous laboratory studies in the last decade have shown that diatoms can induce reproductive failure in copepods, field evidence for a negative diatom effect is equivocal. To unambiguously elucidate the effects diatoms have on copepod reproduction in situ, we undertook a study of the abundance, distribution, grazing rates, and reproductive success of Calanus pacificus in Dabob Bay, Washington, USA, during two spring bloom periods. We simultaneously measured the phytoplankton composition, abundance, and distribution. Here we present results for the reproductive success of C. pacificus using four measurements: egg production rate, clutch size, egg hatching success, and naupliar survival (to the first feeding stage). Egg production rate was positively correlated with chlorophyll a concentration, and egg hatching success and naupliar survival were usually greater than 80%. However, in February 2002 and 2003 – during blooms of diatoms of the genus Thalassiosira – either egg hatching success, naupliar survival, or both were significantly depressed compared to other times in spring and summer. These effects, combined with evidence that C. pacificus was grazing aldehyde-producing Thalassiosira at the time of their blooms, indicate that diatoms can negatively affect copepod reproduction in the field, albeit only under specific circumstances and for brief periods.  相似文献   

15.
《Journal of Sea Research》2000,43(3-4):345-356
During spring blooms 1998 and 1999, three complementary methods were used to evaluate the in situ feeding activities of the dominant copepod species of the Belgian coastal zone: gut pigment content analysis using HPLC, the 14C tracer method, and cell count experiments. The results obtained by all three methods consistently showed that Phaeocystis globosa is not an adequate food source for the spring copepods in the Belgian coastal zone. Our results demonstrated that, among the potential prey, copepods strongly selected diatoms and microzooplankton, and that these types of prey accounted for the major part of the ingested carbon. However, diatoms and microzooplankton ingestion did not always seem sufficient in terms of carbon to avoid food limitation. Comparison of clearance rates exerted on different potential prey types during the P. globosa peak with those before and after the P. globosa peak showed that the copepods' feeding pressure on diatoms was reduced during the P. globosa peak while that on microzooplankton was not. The low grazing pressure on P. globosa, together with the preferential grazing on diatoms, which reduces the competition for nutrients, and the predation on microzooplankton organisms, which reduces the microzooplankton grazing pressure on P. globosa cells, are likely to favour the P. globosa bloom in the Southern Bight of the North Sea.  相似文献   

16.
Mesozooplankton abundance, community structure and copepod grazing on phytoplankton were examined during the austral spring 1997 and summer 1998 as part of the US JGOFS project in the Pacific sector of the Antarctic polar front. Mesozooplankton abundance and biomass were highest at the polar front and south of the front. Biomass increased by 1.5–2-times during the course of the study. Calanoides acutus, Calanus propinquus, C. simillimus, Rhincalanus gigas and Neocalanus tonsus were the dominant large copepods found in the study. Oithona spp and pteropods were numerically important components of the zooplankton community. The copepod and juvenile krill community consumed 1–7% of the daily chlorophyll standing stock, equivalent to 3–21% of the daily phytoplankton production. There was an increased grazing pressure at night due to both increased gut pigment concentrations as well as increases in zooplankton numbers. Phytoplankton carbon contributed a significant fraction (>50%) of the dietary carbon for the copepods during spring and summer. The relative importance of phytoplankton carbon to the diet increased south of the polar front, suggested that grazing by copepods could be important to organic carbon and biogenic silica flux south of the polar front.  相似文献   

17.
The dynamics, composition and grazing impact of microzooplankton were studied during the in situ iron fertilisation experiment EisenEx in the Antarctic Polar Frontal Zone in austral spring (November 2000). During the 21 day experiment, protozooplankton and small metazooplankton were sampled from the mixed layer inside and outside the patch using Niskin bottles. Aplastidic dinoflagellates increased threefold in abundance and biomass in the first 10 days of the experiment, but decreased thereafter to values twofold higher than pre-fertilisation values. The decline after day 10 is attributed to increasing grazing pressure by copepods. They also constrained ciliate abundances and biomass which were higher inside the fertilised patch than outside but highly variable. Copepod nauplii abundance remained stable whereas biomass doubled. Numbers of copepodites and adults of small copepod species (<1.5 mm) increased threefold inside the patch, but doubled in surrounding waters. Grazing rates estimated using the dilution method suggest that microzooplankton grazing constrained pico- and nanoplankton populations, but species capable of feeding on large diatoms (dinoflagellates and small copepods including possibly nauplii) were selectively predated by the metazoan community. Thus, iron fertilisation of a developing spring phytoplankton assemblage resulted in a trophic cascade which favoured dominance of the bloom by large diatoms.  相似文献   

18.
The distribution of ciliate plankton was compared between inner and outer areas of a harbor divided by an artificial breakwater in Kuryongpo, on the eastern coast of Korea, from February 2001 to October 2003. Less dissolved oxygen and higher concentrations of nitrogenous nutrients and phosphate were observed in the inner area. The abundance of oligotrich ciliates peaked in February 2001, when nanoflagellates bloomed in the inner area. The photosynthetic ciliate Mesodinium rubrum showed differing population dynamics annually, with blooming peaks in October 2001 in the inner area and in February 2003 in the outer area. The tintinnid species Tintinnopsis beroidea and Helicostomella subulata were generally more abundant in the outer area. Total ciliates were significantly related to oligotrich abundance in the inner area, and to tintinnid abundances in the outer area. Ciliate distribution showed quantitative and qualitative differences between the inner and outer areas in connection with the distribution of other plankton communities: oligotrich ciliate abundance increased with nanoflagellate blooms; dominance of M. rubrum was consistent with blooming of micro-sized phytoplankton (diatoms and dinoflagellates); large-sized tintinnids concurred with small dinoflagellates; and ciliate abundances decreased with mesozooplankton increases. The results indicate that the breakwater induces eutrophication in the inner area and provides suitable conditions for nanoflagellate blooms, which serially trigger opportunistic increases in oligotrich ciliates.  相似文献   

19.
The effects of irradiance on the excystment of tintinids from marine sediments were examined by incubating sediment samples in filtered seawater under various light levels. The total incidence of tintinnid excystment over five days was significantly less at low irradiance at and less than 2.5 E m–2sec–1 comparing to that at higher irradiance, at and more than 6.9 E m–2sec–1 (p<0.01), indicating that excystment of tintinnids is inhibited under low irradiance conditions. These results imply that water depth, disturbance of surface sediments and vertical mixing of water influence the excystment of tintinnids in coastal areas because these factors determine the light levels to which the tintinnid cysts are exposed.  相似文献   

20.
Abstract. The grazing of Acartia hudsonica and Acartia tonsa was observed on cultures of Olisthodiscus luteus and Dunaliella tertiotecta presented alone and in combination. Feeding on D. lertiolecla by both Acartia species increased directly with concentration but was always lower at equivalent food concentrations when O. luteus was present. In mixed phytoplankton cultures, A. hudsonica fed on both species at low O. luteus concentration, only on D, lertiolecla at intermediate levels and stopped feeding at highest O. luteus concentrations. A. tonsa showed a variable but similar result. These studies indicate the possible role of these dominant herbivores on the dynamics of O. luteus 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