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1.
The toxic dinoflagellate Alexandrium tamarense and other dinoflagellatespecies were studied, along with water temperature and nutrientconcentrations, from September 1995 to December 1998 in theGolfo Nuevo, Chubut, Argentina. Nutrient concentrations werelow, showing a peak of high concentration in winter and a phaseof depletion in late spring and summer. Dinoflagellates tendedto be abundant during spring and summer, when Prorocentrum micanswas the most important species. Other dinoflagellates were Pyrophacushorologium and Dinophysis acuminata. Ceratium tripos, C. fususand C. horridum were present during the autumn, and a C. tripospeak up to 5.9 x 103 cell l1 was observed in May 1997.Alexandrium tamarense showed strong interannual variation, thehighest concentration being found in spring (SeptemberOctober)1995, with densities up to 15 x 103 cells l1. The secondA.tamarense peak was observed during OctoberNovember1998 with maximal densities up to 5 x 103 cells l1. Moderatelyhigh A. tamarense cyst densities, up to 300 cysts cm3of sediment, were found in the deep zone of the Golfo Nuevobasin. Among meteorolog-ical variables, increased late winterrain and higher solar radiation during spring may have influencedA. tamarense blooms. 相似文献
2.
Cyst formation: an important mechanism for the termination of Scrippsiella trochoidea (Dinophyceae) bloom 总被引:1,自引:0,他引:1
A sediment trap study was conducted at Daya Bay, South ChinaSea, to investigate the relationships between encystment andpopulation dynamics of Scrippsiella trochoidea from December1999 to January 2001. A dense bloom of S. trochoidea occurredduring the study period from August to September 2000, withthe maximum cell number of 3.18 x 104 cells mL1.Two morphotypes of cysts, one with a thick calcareous wall (calcifiedcyst) and another without the obvious calcareous cover (non-calcifiedcyst), were observed during this investigation. The morphologicaland excystment characteristics of these two cyst types werestudied as well. Mass encystments of S. trochoidea, with themaximum of 3.05 x 105 cysts m2 d1for calcified cyst, and 1.54 x 107 cysts m2 d1for non-calcified cyst, coincided with the maximum abundanceof the vegetative cells. Encystment caused the transfer of atotal of 2.244.49 x 108 cells m2 vegetativecells from the water column to the sea bottom during the bloomand resulted in a considerable loss of the bloom population.High assemblages of cysts of S. trochoidea were detected inthe surface sediments as well. This rich seed bedin the surface sediments caused by the high efficiency of encystmentafter blooms acting as a benthic reservoir for future vegetativepopulation, together with the short dormant period (1526days) and high germination rate (5090%), may explainthe repeated occurrence of S. trochoidea blooms in Daya Bay. 相似文献
3.
The relationships between photosynthesis and photosyntheticphoton flux densities (PPFD, P-l) were studied during a red-tideof Dinophysis norvegica (July-August 1990) in Bedford Basin.Dinophysis norvegica, together with other dinoflagellates suchas Gonyaulax digitate, Ceratium tripos, contributed {small tilde}50%of the phytoplankton biomass that attained a maximum of 16.7µg Chla 1 and 11.93 106 total cells I1.The atomic ratios of carbon to nitrogen for D.norvegica rangedfrom 8.7 to 10.0. The photosynthetic characteristics of fractionatedphytoplankton (>30 µm) dominated by D.norvegica weresimilar to natural bloom assemblages: o (the initial slope ofthe P-l curves) ranged between 0.013 and 0.047 µg C [µgChla]1 h1 [µmol m s1]1the maximum photosynthetic rate, pBm, between 0.66 and 1.85µg C [µghla]1 h1; lk (the photoadaptationindex) from 14 to 69 µ,mol m2 s1. Carbonuptake rates of the isolated cells of D.norvegica (at 780 µmolm2 s1) ranged from 16 to 25 pg C cell1h and were lower than those for C.tripos, G.digitaleand some other dinoflagellates. The variation in carbon uptakerates of isolated cells of D.norvegica corresponded with PBmof the red-tide phytoplankton assemblages in the P-l experiments.Our study showed that D.norvegica, a toxigenic dinoflagellate,was the main contributor to the primary production in the bloom. 相似文献
4.
Dinoflagellates of the genus Dinophysis are agents of Diarrhetic Shellfish Poisoning (DSP). They occur along the French coast and affect shellfish exploitation during most of the year (during spring, summer and autumn). Because this species is difficult to cultivate, very little is known about this organism. The first problem is the species-delineation within this genus which is sometimes unclear based upon the solely on morphological features, in particular for the complex D. acuminata ( D. cf. acuminata,, D. cf. norvegica, D. cf.sacculus , and D. skagii ) or the complex D. sacculus ( D. sacculus and D. pavillardii ). The second problem is its detection in natural samples. French Dinophysis blooms have been reported to be toxic under 100 cells L−1 , a concentration which corresponds to less than 1 cell 10-mL−1 , as determined by the Utermöhl method of enumeration. Molecular tools may help to resolve these two kind of problems. During one year (spring 1999 to spring 2000), more than 100 fixed samples containing Dinophysis spp. cells were collected along the French coast by the French monitoring network (or REPHY; http://www. ifremer.fr). The genetic diversity of Dinophysis spp. was studied by sequencing and analysis of ribosomal DNA genes. We found that sequences were hightly conserved between species or within the D. acuminata or D. sacculus complex. Two oligonucleotide probes, specific to these complex groups, were designed. Their specificity and sensitivity are actually tested on natural samples by a PCR-based assay. Furthur investigation will include the development of standard molecular diagnostics due to their rapid and sensitive detection in natural samples. 相似文献
5.
Results are presented on the phytoplankton species compositionand abundance from bottle samples collected in September 1989near the confluence of the Brazil and Malvinas currents offArgentina. The phytoplankton assemblages were dominated by diatomsand dinoflagellates. A surface diatom bloom was found alongthe west side of the Brazil Current, and was dominated by Thalassiosiradelicatula Ostenfeld emend. Hasle (cell numbers up to 5.5 x105 cells 11) The bloom was associated with strong temperaturegradients separating Brazil and Malvinas waters, and with thepresence of a cyclonic eddy near the confluence of the currents.These features were detected in satellite imagery coincidentwith the in situ sampling dates. 相似文献
6.
Development and fate of Eutreptiella gymnastica bloom in nutrient-enriched enclosures in the coastal Baltic Sea 总被引:1,自引:0,他引:1
Response of the phytoplankton community to bottom-up (nutrients,organic carbon source) and top-down (fish) manipulations, bothsingly and together, were studied daily during a 3 week periodin July 1993 by using eight 50 m3 mesocosms in the coastal northernBaltic Sea. Nutrient additions (once per week) invoked a seriesof blooms of Eutreptiella gymnastica Throndsen (Euglenophyceae)(up to 13 x 103 cells ml1) which formed the major part(6090%) of the total autotrophic biomass. After rapiddepletion of nutrients (23 days) from the surface layer(06 m) downwards migration and a subsequent peak of E.gymnasticain the lower part of the water columns (612 m) followed.Settled material collected from the bottom of the enclosurescontained a considerable amount of E.gymnastica cells and restingcysts. Nevertheless, sinking loss rates of E.gymnastica wereestimated to be less than 1% day1 of the suspended cellnumbers. The fate of E.gymnastica blooms was estimated to begrazing through mesozooplankton. However, provided the nutrientsare plentiful in the water column, the growth potential of E.gymnasticaappears to exceed the ambient grazing pressure. If the nutrientsbecome depleted, it seems to be effectively controlled by mesozooplanktongrazing, which is probably limiting the likelihood of massiveE.gymnastica blooms in the coastal Baltic Sea. Our study suggeststhat E.gymnastica appears to be a fast-growing fugitive (bloom)species with flexible behavioural (vertical migration) and lifehistory (cyst formation) adaptations which is able to exertdominant role and direct trophic relations similar to otherbloom species adapted for decaying turbulence and high nutrientenvironments. 相似文献
7.
Seasonal dynamics in the abundance of Micromonas pusilla (Prasinophyceae) and its viruses in the Gulf of Naples (Mediterranean Sea) 总被引:2,自引:0,他引:2
To assess the role of viruses in the bloom dynamics of Micromonaspusilla in the Gulf of Naples (Mediterranean Sea), variationsof host and virus abundance were followed over one annual cycleand in late winterspring of three consecutive years.Micromonas pusilla was recorded from autumn to spring, withpeak values up to 6.6 x 103 cells ml1, but was undetectablein summer. Free M.pusilla viruses were detectable in all seasons,with concentrations from 0.02 viruses ml1 to 1.9 x 103viruses ml1, exceeding host abundances only in one case.We found a great intraspecific variability in host susceptibilityto viruses present in natural samples, with viral titres rangingover one or two orders of magnitude for the same samples incubatedon different M.pusilla strains. Over the winterspringperiods, a highly dynamic situation was evident, with wide fluctuationsfor both host and virus abundances from one week to another.In some cases, peak host concentrations were accompanied byan increase in viral numbers, whereas in other cases the respectivefluctuations were uncoupled. Although fluctuations of M.pusillaabundance could be influenced by viral infection, there wasno evidence that viruses were able to terminate host blooms.The summer decline of M.pusilla populations did not appear tobe related to the impact of viral infection. 相似文献
8.
Occurrence of viable photoautotrophic picoplankton in the aphotic zone of Lake Biwa, Japan 总被引:1,自引:0,他引:1
Eguchi Mitsuru; Oketa Takemi; Miyamoto Nobukazu; Maeda Hiroto; Kawai Akira 《Journal of plankton research》1996,18(4):539-550
The distribution and abundance of photoautotrophic picoplankton(PPP. Synechococcus group) in the aphotic bottom sediments ofLake Biwa were investigated by direct counting and viable counting(most probable number, MPN) methods. In the surface layer ofbottom sediments (01 cm). where large PPP blooms occurredin the past 5 years, >105 cells cm3 of PPP were foundto be viable throughout the year. Furthermore, the density ofPPP deposited on the sediment surface (00.1 cm) was oneorder of magnitude higher (MPN = 1.3 x 106 cells cm3.direct count = 9.9 x 106 cells cm3) than that of bulkedsurface sediments (01 cm). Even in the deeper layer (1314cm) of bottom mud, viable PPP were still found (101 cells cm1.In winter, viable PPP in the aphotic bottom sediments were 104105times greater per Unit volume than those in the euphotic lakewater. Since the aphotic bottom sediments have high levels ofPPP, as well as high growth potential (high ratio of viablecount/total direct count), they are likely to seed PPP bloomsin the North Basin of Lake Biwa. 相似文献
9.
In a coastal area of southern Chile (41° S), the major ammoniumassimilating enzyme glutamine synthetase (GS) was detected ina green dinoflagellate bloom during April 2003. High chlorophylla concentrations (1000 µg L1) attributable to Gymnodiniumcf. chlorophorum in surface waters were associated with highand very low nitrate reductase activities. Coincident with thebloom, dissolved inorganic nitrogen concentrations were nearthe detection limit (NO3 + NH4+ <0.5 µM). SinceGS correlates with the use of ammonium as an external nitrogensource, we suggest that GS activity seems to be a good indicatorof ammonium utilization in a period dominated by a single dinoflagellatespecies. 相似文献
10.
Carrias Jean-Francois; Amblard Christian; Bourdier Gilles 《Journal of plankton research》1994,16(5):471-485
Seasonal population dynamics and the vertical distribution ofciliates were studied in relation to the particular food resourcesoccurring in a humic and moderately acidic lake (Lake Vassivière).The abundance (1.4 x 10320.4 x 103 cells l1 mean= 4.8 x 103 cells l1) and biomass (0.534.6 µgC l1, mean = 6.0 µg C l1) of ciliated protozoawere low and close to values reported for oligotrophic environments.The species composition of the population varied greatly withdepth. Whereas large-sized species of oligotrichs, some of whichwere mixotrophic, dominated at the surface, haptorids were bestrepresented in deep waters. The spatial distribution of thevarious groups of ciliates was largely determined by light andthe vertical distribution of microbial food resources (detritus,bacteria, algae) within the water column of this brown-coloredlake. 相似文献
11.
During the spring of 1994, we determined the factors responsiblefor the decline of the seasonal diatom bloom in the Gullmarfjord, on the west coast of Sweden. Four species constituted>75% of the biomassDetonula confervacea, Chaetocerosdiadema, Skeletonema costatum and Thalassiosira nordenskioeldiireachingconcentrations of 4900, 350, 8200 and 270 cells ml1,respectively. Growth of phytoplankton was exponential (growthrate = 0.12 day1) from 3 to 21 March, after which a galewith winds >15 m s1 caused massive aggregation. Amaximum of 130 p.p.m. (v/v) of marine snow aggregates was observedby in situ video at the peak of the bloom. Critical concentrations(Jackson, Deep-Sea Res., 37, 11971211, 1990) were similarto observed showing that coagulation theory could explain thesudden decline of the bloom. The heterotrophic dinoflagellateGyrodinium cf. spirale increased exponentially after the peakof the bloom with maximum (temperature-adjusted) growth rates.After the rapid aggregation and sedimentation of the bloom,they were able to control any further growth of diatoms. Nitrateand silicate were never depleted, but phosphate may have beenlimiting by the end of the study period. We conclude that massaggregation during a gale marked the end of the bloom, and thatintense grazing by heterotrophic dinoflagellates prevented anysubsequent increase of diatoms. 相似文献
12.
The purpose of the investigation is the determination of thevolumes and numbers of cells of the meristematic dome and ofeach of the first 7 primordia and internodes at the apex ofthe shoot of Lupinui albus. This system occupies a zone whichis about 0·4 mm. in length. Techniques are describedfor dissecting the region in which the observations are made,for determining the numbers of cells and the volumes of theseveral fragments. From the number of cells and the volume ofeach fragment an average cell volume it calculated. It is shown that in the midphase of the plastochron the domecontains 3,500 cells and has a volume of 1·6 x103mm.3,the first primordium contains 1,630 cells and has a volume of0·38 x103 mm.3, and the first intemode containsabout 700 cells and has a volume of about 1·4 x103mm3The number of cells and the volume of the primordium increaseexponentially with increasing plastochron age, and the seventhprimordium contains 26,000 cells and has a volume of 20·9x 103mm3 The seventh intemode contains about 5,000 cellsand has a volume of 8·6x103mm3 The average cell volume in the dome is 4·7 x 107mm.3in the first primorndium it is 2·3 x 107mm.3 andin the first internode it is 20·9x 107mm.3 Inthe seventh primordium the average cell volume increases to7·9 x 107mm.3 In the internodes there is little,if. any, change in cell volume from the first to the seventhof the series. The significance of these changes is discussed. 相似文献
13.
A persistent and unusual bloom of Dinophysic acuta Ehrenbergin the RIas Bajas (Northwest Spain) from early July to mid-November1989, was associated with a diarshetic shellfish poisoning (DSP)outbreak that prevented mussel extraction in some areas fromearly August to mid-December. Integrated samples (05,510 and 1015 m) were taken once or twice a weekat six stations. Maximum numbers of D.acuta (up to 2.3 104intheintegratedsamples)andpercentageofobserveddMdingcells(upto3l%),appearedin August, and formed a maximum in the thermodine. Cellnumbers were minimal when upwelling caused a breakdown of stratification.Fligh numbers of D.acuta (up to 1.8 104 cells 11 appearedagain when persistent south winds in late October caused a reversalof the circulation. Thus, the two cell maxima occurred duringtwo distinct hydrographic regimes, but in both cases at temperaturesof 1517C. Numerous cells with one typical D.acuta valve,but the other valve reduced in size, were seen during the bloom,as well as Dinophysts dens Pavillard cells that might be a lifecycle stage of D.acuta. Other observations include double- walled,unwinged forms that are perhaps some kind of cyst, and a hypotheticalfertilizing tube emerging from the larger cellof a D.acuta/D.dens couplet. It is suggested that the maximaduring stratification and during downwelling episodes couldcorrespond to periods with a predominance of in situ growthand physical accumulation, respectively, and that the exceptionalmeteorological conditions during 1989 provided the optimum scenariofor the unusual occurrence of D.acuta. 相似文献
14.
Llewellyn Carole A.; Tarran Glen A.; Galliene Chris P.; Cummings Denise G.; De Menezes Alex; Rees Andy P.; Dixon Jo L.; Widdicombe Claire E.; Fileman Elaine S.; Wilson Willie H. 《Journal of plankton research》2008,30(3):261-273
The microbial dynamics during a spring diatom bloom declinewas monitored in the Northeast Atlantic during a 5-day Lagrangianstudy (8–12 April 2002). Phytoplankton abundance, compositionand health status were related to viral and bacterial abundance,zooplankton abundance and grazing rates, as well as bacterialproduction. Phytoplankton reached maximum concentration on Day3 (Chl a >5 µg L–1) and declined on Day 5 (Chla 2 µg L–1) and was dominated (70% of Chl a) bydiatoms. Bacterial production increased substantially to >20µg C L–1 day–1 on Day 3 and concomitantlylarge viruses decreased in number by half to <10 x 103 mL–1.This was followed by a 5-fold increase in large viruses on Day5, indicating infection and subsequent lysis on Days 3 and 5,respectively. Micro- and mesozooplankton grazing were not theprincipal cause for the decline of the bloom and pheophorbide-ashowing little variation in concentration from Days 1–4(100 ng L–1) although doubled on Day 5. The poor physiologicalstatus of the diatoms, indicated by the high chlorophyllide-aconcentrations (50–480 ng L–1), likely promoteda series of closely interrelated events involving bacteria andviruses leading to the demise of the diatom bloom. 相似文献
15.
The seasonal abundance of the phototrophic ciliate Mesodinium rubrum in Southampton Water, England 总被引:1,自引:0,他引:1
The abundance of the marine phototrophic planktonic ciliateMesodinium rubrum was monitored throughout an annual cycle attwo stations in the Southampton Water estuary. Seasonal changesin the concentration of nitrate, ammonia and phosphate weremonitored both at the inner estuary station (NW Netley) andouter estuary station (Calshot). Nutrient levels in the winterwere similar at both stations, and were diminished during sequentialdiatom blooms dominated initially by Sketetonema costatum andthen by Rhizosolenia dclicatula. Nitrate was reduced to a seasonalminimum in the outer estuary following these spring diatom blooms,but in the inner estuary was sustained >500 µg I1until the onset of the M.rubrum bloom. During the developmentof a visible red tide of M.rubrum in June/July at NW Netley,nutrient concentrations were considerably reduced. Cell numbersof M.rubrum varied between 2 and 3 cells ml during winterto >400 cells ml1 during the bloom at NW Netley, whereasat Calshot cell abundance did not increase above 25 cells ml1at any time of the year. At NW Netley, dense accumulations ofthe ciliate occurred over restricted depth intervals duringthe bloom and possible factors influencing the observed verticaldistribution of cells are considered.
1Present address: Biology Department, Faculty of Science, AddisAbaba University, PO Box 1176, Addis Ababa, Ethiopia 相似文献
16.
《Harmful algae》2016
Dinophysis acuminata and Dinophysis acuta are recurrent species off NW Iberia but their outbreaks occur under different conditions. A decade (2004–2013) of weekly data for each species at two sentinel stations located at the entrance of Rias de Aveiro-AV (NW Portugal, 40°38.6′ N) and Pontevedra-PO (Galicia, Spain, 42°21.5′ N), were used to investigate the regional synchronism and mesoscale differences related to species detection, bloom (>200 cells L−1) initiation and development. Results highlight the high interannual variability of bloom events and summarize the associated meteorological/oceanographic conditions. D. acuta blooms were observed in 2004–2008 and 2013, and the species highest maxima at AV occurred after the highest maxima of its prey Mesodinium, with a time-lag of 2–3 weeks. D. acuminata blooms were observed every year at both stations. The cell concentration time series shows that the blooms generally present a sequence starting in March with D. acuminata in PO and three weeks later in AV, followed by D. acuta that starts at AV and three months later in PO. Exceptionally, D. acuminata blooms occurred earlier at AV than PO, namely in high spring upwelling (2007) or river runoff (2010) years. A four-year gap (2009–2012) of D. acuta blooms occurred after an anomalous 2008 autumn with intense upwelling which is interpreted as the result of an equatorward displacement of the population core. Numerical model solutions are used to analyze monthly alongshore current anomalies and test transport hypotheses for selected events. The results show a strong interannual variability in the poleward/equatorward currents associated with changes in upwelling forcing winds, the advection of D. acuta blooms from AV to PO and the possibility that D. acuminata blooms at AV might result from inocula advected southward from PO. However, the sensitivity of the results to vertical position of the lagrangian tracers call for more studies on species distribution at the various bloom stages. 相似文献
17.
The theory and practice of applying the thermodynamics of irreversibleprocesses to mass-flow theories is presented. Onsager coefficientswere measured on cut and uncut phloem and cut xylem strandsof Heracleum muntegazzimum. In 0.3 N sucrose + 1 mN KC1 theyare as follows. In phloem, LEE = 5 ? 104 mho cm1,LpE = 9 ? 106 cm3 s1 cm2 volt1 cm,and LPP = 0.16 cm3 s1 cm2 (J cm3)1cm. In uncut phloem strands LEE is about 1 ? 103 mhocm1. In xylem in 2 x 103 N KCI, Lpp = 50 to 225,LPE = 2 ? 104, and LEE = 4 ? 103. The measurementsare tentative since the blockage of the sieve plates is an interferingfactor, but if they are valid they lead to the conclusion thatneither a pressure-flow nor an electro-kinetic mechanism envisaginga long distance current pathway can be the majormotive force for transport in mature phloem. Measurementsof biopotentials along conducting but laterally detached phloembundles of Heracleum suggest, nevertheless, that there may bea small electro-osmotic component of at least 0.1 mV cm1endogenous in the phloem. 相似文献
18.
In order to obtain information on the assemblage of Protozoain the changing environment in Lake Naini Tal, this study wascarried out for a period of one year from November 1995 to October1996. Samplings were done from the mudwater interfaceat two stations which differed considerably in their magnitudeof pollution. Station I was moderately polluted while StationII was highly polluted. Some physico-chemical parameters ofwater such as temperature, dissolved oxygen, free CO2, pH, nitrate-nitrogen,phosphate-phosphorus and BOD were also measured. A total of23 ciliates were found at the mudwater interface of thetwo stations during the sampling period. The annual mean ofspecies richness at Station I was significantly greater (19species) than that of Station II (13 species). The species compositionwas also different at the two stations. In general, StationI supported larger ciliated species (1249 x 103 µm3 taxon1)than Station II (348 x 103 µm3 taxon1). Among differentfeeding groups of ciliates, the groups Algivore-Bacterivoreand Bacterivore were about twice as common atStation II (116 x 103 cells1) than at Station I (55 x103 cells1). The annual average ciliate community abundancewas more diverse at Station I than Station II. The annual averagebiomass in terms of carbon content for both stations was almostthe same (6.0 mg Cl1 for Station I and 6.1 mg Cl1Station II). However, different species were responsible forthe contribution to the biomass at the two stations. The valuesfor Shannon-Weiner's diversity indices at Staion I were higherthat those for Station II. 相似文献
19.
The development of Anabaena ucrainica blooms in a small agriculturalreservoir was monitored in 1998 and 1999. In the reservoir,numerous Anabaena akinetes were found in all regions of thesediment analyzed, with an average cell density in the uppermostlayer (02 cm) of 1.5 x 104 cm-3. Anabaena ucrainica filamentnumbers began to increase exponentially in mid-May 1998 andin late April 1999, when the water temperature exceeded 15°C.The average in situ net growth rate was 0.18 day-1 as measuredby filament numbers. The effect of temperature on germinationof the akinetes was investigated using Anabaena akinetes takenfrom the reservoir sediment. High germination percentages wereobserved at temperatures between 14 and 23°C; however, theAnabaena akinetes did not germinate without irradiance. Growthexperiments using an axenic culture of A. ucrainica isolatedfrom the reservoir showed that an increase in incubation temperatureto 26°C resulted in a rise in the specific growth rate.Consequently, it was hypothesized that temperature increasescould similarly enhance the growth rate of A. ucrainica duringbloom development. Furthermore, judging from the in situ growthrate of A. ucrainica, initial inocula arising from dense akinetepopulations in the sediment would advance bloom formation andcould enhance the relative probability of Anabaena bloom formation. 相似文献
20.
Turner Jefferson T.; Ianora Adrianna; Esposito Francesco; Carotenuto Ylenia; Miralto Antonio 《Journal of plankton research》2002,24(11):1185-1195
The bloom-forming alga Phaeocystis is ingested by a varietyof zooplankton grazers, but is thought to be a poor source offood. We examined copepod grazing on solitary Phaeocystis cellsby adult females of Temora stylifera, and survival, fecal pelletproduction, egg production and egg hatching success in Calanushelgolandicus and T. stylifera over periods of 15 consecutivedays. Phaeocystis cell concentrations were high (1.23.6x 104 cells ml1 for C. helgolandicus and 2.57.9x 104 cells ml1 for T. stylifera), but within the rangeof maxima recorded for natural blooms. Both copepods survivedwell and continuously produced fecal pellets (indicating continuousgrazing) on a diet of Phaeocystis. However, egg production ratesfor both copepods were low, even though hatching success ofthe few eggs produced was high. Clearance rates for T. styliferawere higher than for most previous measurements of other copepodsfeeding on Phaeocystis solitary cells at lower cell concentrations.We conclude that even though copepods feed well upon Phaeocystis,resulting poor fecundity on this diet may inhibit copepod populationincreases during blooms, thereby contributing to the perpetuationof blooms. However, the high egg hatching success on this dietargues against Phaeocystis containing chemical compounds thatact as mitotic inhibitors reducing copepod egg viability, suchas those found in some other phytoplankters. 相似文献