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1.
Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific 总被引:3,自引:0,他引:3
The total number of planktonic bacteria in the upper mixed layerof the Bering Sea during the late spring-early summer periodranged between 1 and {small tilde}4 x 106 ml1 (biomass1040mg C m3). In the northern Pacific, along 47526N,the corresponding characteristics of the bacterioplankton densityin the upper mixed water layer were: total number 12x 106 cells ml1 and biomass 1546mg C m3Below the thermocline at 50100 m, the density of bacterioplanktonrapidly decreased. At 300 m depth, it stabilized at 0.10.2x 106 cells ml1. The integrated biomass of bacterioplanktonin the open Bering Sea ranged between 1.2 and 3.6 g C m2(wet biomass 618 g m2) Its production per dayvaried from 2 to 23 mg C m3 days1 in the upper0100 m. The numerical abundance of planktonic ciliatesin this layer was estimated to be from 3 to l0 x 103 cells l1,and in the northern Pacific from 0.4 to 4.5 x 103 l2.Their populations were dominated by naked forms of Strombidium,Strombilidium and Tontonia. In some shelf areas, up to 40% ofthe total ciliate population was represented by the symbioticciliate Mesodinium rubrum. The data on the integrated biomassof basic groups of planktonic microheterotrophs are also presented,and their importance in the trophic relationships in pelagiccommunities of subarctic seas is discussed. 相似文献
2.
Results are presented of size-fractionated primary productionstudies conducted in the vicinity of the Subtropical Front (STF),an adjacent warm-core eddy, and in Sub-antarctic waters duringthe third South African Antarctic Marine Ecosystem Study (SAAMESIII) in austral winter (June/July) 1993. Throughout the investigation,total chlorophyll (Chl a) biomass and production were dominatedby small nano- and picophytoplankton. No distinct patterns intotal Chl a were evident. At stations (n = 7) occupied in thevicinity of the STF, total integrated biomass values rangedfrom 31 to 53 mg Chl a m2. In the vicinity of the eddy,integrated biomass at the eddy edge (n = 3) ranged from 24 to54 mg Chl a m2 and from 32 to 43 mg Chl a m2 inthe eddy (n = 2). At the station occupied in the Sub-antarcticwaters, total integrated biomass was 43 mg Chl a m2.Total daily integrated production was highest at stations occupiedin the vicinity of the STF and at the eddy edge. Here, totalintegrated production ranged from 150 to 423 mg C m2day1 and from 244 to 326mg C m2 day1, respectively.In the eddy centre, total integrated production varied between134 and 156 mg C m2 day1. At the station occupiedin the Sub-antarctic waters, the lowest integrated production(141 mg C m2 day1) during the entire survey wasrecorded. Availability of macronutrients did not appear to limittotal production. However, the low silicate concentrations duringthe survey may account for the predominance of small nano- andpicophytoplankton. Differences in production rates between theeddy edge and eddy core were related to water column stability.In contrast, at stations occupied in the vicinity of the STF,the control of phytoplankton production appears to be relatedto several processes, including water column stability and,possibly, iron availability. 相似文献
3.
Composition and distribution of the pelagic and sympagic algal assemblages in the Laptev Sea during autumnal freeze-up 总被引:5,自引:0,他引:5
Tuschling Kirsten; Juterzenka Karen v.; Okolodkov Yuri B.; Anoshkin Andrej 《Journal of plankton research》2000,22(5):843-864
The phytoplankton and ice algal assemblages in the SiberianLaptev Sea during the autumnal freeze-up period of 1995 aredescribed. The spatial distribution of algal taxa (diatoms,dinoflagellates, chrysophytes, chlorophytes) in the newly formedice and waters at the surface and at 5 m depth differed considerablybetween regions. This was also true for algal biomass measuredby in situ fluorescence, chlorophyll (Chl) a and taxon-specificcarbon content. Highest in situ fluorescence and Chl a concentrations(ranging from 0.1 to 3.2 µg l1) occurred in surfacewaters with maxima in Buor Khaya Bay east of Lena Delta. Thealgal standing stock on the shelf consisted mainly of diatoms,dinoflagellates, chrysophytes and chlorophytes with a totalabundance (excluding unidentified flagellates <10 µm)in surface waters of 35133 660 cells l1. Highestalgal abundance occurred close to the Lena Delta. Phytoplanktonbiomass (phytoplankton carbon; PPC) ranged from 0.1 to 5.3 µgC l1 in surface waters and from 0.3 to 2.1 µg Cl1 at 5 m depth, and followed the distribution patternof abundances. However, the distribution of Chl a differed considerablyfrom the distribution pattern shown by PPC. The algal assemblagein the sea ice, which could not be quantified due to high sedimentload, was dominated by diatom species, accompanied by dinoflagellates.Thus, already during the early stage of autumnal freeze-up,incorporation processes, selective enrichment and subsequentgrowth lead to differences between surface water and sea icealgal assemblages. 相似文献
4.
Laybourn-Parry Johanna; Ellis-Evans J.Cynan; Butler Helen 《Journal of plankton research》1996,18(4):495-511
The dynamics of bacterioplankton and protozooplankton in twomaritime Antarctic lakes (Heywood Lake and Sombre Lake, SignyIsland, South Orkneys) were studied during the phase of icebreak-out (December and early January 1994/95). The lakes aresuffering animal-induced (fur seal) eutrophication, though HeywoodLake is most severely affected. Both lakes had morphologicallydiverse bacterial communities which increased during the studyperiod, reaching maxima of 80 x 108 l1 in Heywood Lakeand 31.8 x 108 l1 in Sombre Lake. Heterotrophic nanoflagellates(HNAN) reached a peak in late December with maxima of 40.6 x108 l1 in Sombre Lake and 174 x 105 l1 in HeywoodLake. Phototrophic nanoflagellates (PNAN) peaked in late Decemberafter ice loss in Heywood Lake (63 x 105 l1), which coincidedwith a peak in a bloom of Chroomonas acuta which reached abundancesof 1.0 x 108 l1. In Sombre Lake, ice persisted for alonger period and here PNAN reached their highest density atthe end of the study period (around 70.0 x 105 l1). Ciliateabundance reached high levels in Heywood Lake (>600011),while in Sombre Lake maximum abundance was 568l1. Protozooplanktondiversity was greater in the less-enriched Sombre Lake. Grazingrates of ciliates averaged 70.6 bacteria indiv.1 h1in Heywood Lake and 119.3 bacteria indiv.1 h1in Sombre Lake. The difference was a reflection of the differenttaxonomic make-up of the community in the lakes. HNAN grazingrates varied between 0.51 and 0.83 bacteria indiv.1 h1in Sombre and Heywood Lakes, respectively. Specific growth rates(r) h1 in Sombre Lake were 0.028 for ciliates and 0.013for HNAN, and in Heywood Lake 0.010 for ciliates and HNAN 0.012.These growth rates result in doubling times ranging between38 and 69 h for ciliates and around 55 h for HNAN.HNAN grazingon bacteria was curtailed in Heywood Lake in early January asa result of predation by microcrustacean larvae feeding on theplankton. Thus, for a short phase top-down control was apparentin the dynamics of Heywood Lake, a feature uncommon in Antarcticlake ecosystems. The impact of natural eutrophication on thesesystems is discussed in relation to other unaffected Antarcticlakes. 相似文献
5.
Bacterial dynamics and distribution during a spring diatom bloom in the Hudson River plume, USA 总被引:6,自引:0,他引:6
Bacterial abundance and [3H]thymidine incorporation rates wereused to characterize bacterial distributions and dynamics duringa spring diatom bloom in the coastal plume of the Hudson Riverduring March, 1981. Bacterial abundance did not decline significantlyaway from the plume or across the continental shelf. However,a pronounced gradient was observed for [3H]thymidine incorporation. Following a northeast gale, a bloom of Skeletonema costatumdeveloped in response to coastal upwelling. As the plume becamesaltier, warmer and larger, bacterial abundance averaged 1.3x 109 cells 11. Bacterial incorporation of [3H]thymidineinto cold 5% TCA insoluble materials, bacterial production andspecific growth rates averaged 80120 pmol 11 d1,1.42.0 x 109 cells 11 and 1.21.5 d1.respectively. The mean density of bacteria in the plume didnot change even though growth rates were higher than expectedlosses from sinking, mixing and export. The abundance and production levels of attached bacteria inthe plume were significantly higher than they were in coastalwater outside the plume. In contrast, free bacterial levelswere similar in all regions of the shelf and plume. Bacterialparameters in the plume were not correlated with phytoplanktonpigment concentrations, while significant positive correlationswere found in shelf waters >33 salinity. Thus bacteria werecoupled to phytoplankton in shelf waters but not in the plumewhere allochthonous dissolved matter was probably supportingthe bacteria.
*Lamont-Doherty Geological Observatory Contribution No. 3459
2Present address: Department of Microbiology, University ofGeorgia, Athens, GA 30602, USA. 相似文献
6.
Bulk-phase viscoelastic properties of seawater relationship with plankton components 总被引:5,自引:0,他引:5
The viscous and elastic moduli at different shear rates, togetherwith various biological oceanographic properties, were determinedin seawater from different hydrological layers in the southernNorth Sea in June. The biological oceanographic parameters includedPhaeocystis and Noctiluca abundances, chlorophyll a level (Chl),bacteria. HNAN and aggregate volume fraction. The plankton wasjointly dominated by Phaeocyslis sp. and Noctiluca scinullans.Noctiluca abundance showed no correlation with any other biologicalor viscoelastic parameter, but Phaeocystis abundance correlatedstrongly. The other biological parameters correlated with Phaeocystisand with each other positively and mostly significantly. Overall,viscoelasticity correlated more strongly with Chl than withany other biological parameter. For non-microlayer samples,the excess complex (viscoelastic) modulus (µ.Pa) G*E =2.0 x Ch113 (Chl in mg m3). Viscous and elasticmoduli also correlated closely with each other. For a givenvalue of Chl. the microlayer samples were 6.5 or 14 times (dependingon the estimation method) more viscoelastic than in bulk-phasesamples. Viscoelasticity in samples of settled benthic fluffwere lower even than bulk-phase samples, but this differencewas not significant. Comparison with Mediterranean data on viscoelasticity(Jenkinson. Oceanol. Acta, 16, 317334, 1993), using publishedvalues for phytoplankton biomass (Wiadnyana, J. Rech. Océanogr.,17, 16, 1992), suggests that the relationship betweenChl (or phytoplankton biomass) and viscoelasticity might begeneral. This apparent biomodification of the viscosity andelasticity of seawater is discussed in relation to its likelyimpact on turbulence and plankton ecology. 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.
Population structure and swarm formation of the cyclopoid copepod Dioithona oculata near mangrove cays 总被引:1,自引:0,他引:1
The cyclopoid copepod Dioithona oculata forms swarms in water>30 on deep among prop roots of red mangroves (Rhizophoramangle) which fringe protected areas of two lagoonal cays, TwinCays, Belize. During 7 of 8 months surveyed by in situ observation,swarms were present but differed in size from small cylindricalswarms (510 cm diameter) to bands extending up to 1200m Swarms were never observed at night Swarms formed at dawnwhen light intensities reached an average value of 13.82 (logioquanta cmAbstract. s1) and dispersed at dusk atsimilar intensities Swarms observed in June formed earlier anddispersed later in the day than swarms observed in January,their swarming behavior followed seasonal changes in light intensityMean dioithonan density in swarms (10 ml1) was much higherthan the mean density (0 15 ml1) of non-swarming dioithonansaround mangrove prop roots. In open water 35 m away fromthe mangroves, mean dioithonan density was 7 9 x 105ml1 during the day, and 2 68 x103 ml1 at nightSwarms were composed predominantly of adults and copepodid stagesIV and V, although younger copepodid stages could be presentNauplii were never present. The average copepodid stagefor all 95 swarms sampled was 5 3, where 6 0 represents a swarmwith only adults In open water 35 m away from the mangroves,the youngest copepodids (stage one) dominated the dioithonanpopulation during the day. At night when swarms dispersed toopen waters, average copepodid stage was higher (3 5) comparedwith the day value (1.2) in open waters. Although densitiesin swarms were higher in June than January, average copepodidstage in June was higher (5 6) than that in January (4.9). Ahigher percentage of adults were females during June than January.Therefore higher densities did not result from increases ofsmaller stages in swarms, but perhaps changes in behavior orpopulation structure. 相似文献
9.
The effect of detrital addition on the development of nanoflagellates and bacteria in Lake Kinneret 总被引:1,自引:0,他引:1
Hadas O.; Pinkas R.; Albert-Diez C.; Bloem J.; Cappenberg T.; Berman T. 《Journal of plankton research》1990,12(1):185-199
The effect of adding dissolved substrates derived from algalcells on the patterns of nutrient cycling and growth of bacteria,heterotrophic nanoflagellates (HNAN) and photoautotrophs wasdetermined in samples of near-surface waters from Lake Kinneret.Supplementation of substrates always resulted in an increasedpeak of HNAN numbers and had little effect on bacterial numbers.HNAN-mediated nutrient remineralization of nitrogen and phosphoruswas also stimulated. In light-incubated samples the remineralizednutrients were taken up by photoautotrophic cells. Maximum growthrates observed for HNAN ranged from 0.03 to 0.11 h1,clearance rates for bacteria 1.17.3 nl HNAN1 h1and remineralization rates 6.48.4 µg N mg dry wt1h1 and 0.370.99 µg P mg dry wt1 h1. 相似文献
10.
The dynamics of heterotrophic nanoflagellates and bacterioplankton in a large ultra-oligotrophic Antarctic lake 总被引:4,自引:0,他引:4
Laybourn-Parry Johanna; Bayliss Peter; Ellis-Evans J.Cynan 《Journal of plankton research》1995,17(9):1835-1850
The abundance of both heterotrophic nanoflagellates (HNAN) andbacterioplankton in a large (9km2) ultraoligotrophic Antarcticlake (Crooked Lake) were investigated from December 1992 untilNovember 1993. HNAN abundance peaked in spring, summer and autumn,falling to lowest numbers during the winter. Numbers rangedbetween 0 and 50.9x104 l1. Bacterioplankton abundancewas highest during the late summer and then fell progressivelytowards winter and autumn (range 1.194.46x106 l1)In contrast to numbers, mean cell volumes (MCV) of the bacteriareached their highest in spring, and consequently highest bacterialbiomass occurred at this time. MCV ranged between 0.052 and0.224µm3. Bacterial production measurements followingthe incorporation of [3H] thymidine into DNA and [14C] leucineinto protein using a doubling-labelling procedure were undertakenin January, June, August, October and November. Rates variedbetween 2.8 and 52 ng C l1 h1. On occasions, a significant differencein production rates based on the uptake of leucine and thymidinewas observed, suggesting unbalanced growth. Highest rates ofproduction coincided with times of high dissolved organic carbonlevels in the water column and lowest production with low levelsof DOC. HNAN grazing rates were measured by following the uptakeof fluorescently labelled bacteria and averaged 4.8 bacterialcells individual1 day1 at 2 and 4°C. Specific growth rates(h1) ranged around 0.000700.00077 in both the field andlaboratory, giving doubling times of 37.3 and 41.0 days, respectively.These low rates of grazing and growth indicate that there isno adaptation to low temperatures in these freshwater protists.Based on these data, the gross production efficiency is 24%.HNAN removed between 0.1 and 9.7% of bacterial production perday. 相似文献
11.
Gocke Klaus; Hernandez Carlos; Giesenhagen Hanna; Hoppe Hans-Georg 《Journal of plankton research》2004,26(12):1429-1439
The seasonal development of bacteria was studied in the hypertrophiccoastal lagoon Ciénaga Grande de Santa Marta (Caribbeancoast of Colombia). This large but only 1.5 m deep lagoon issubject to strong seasonal variations of salinity from almostfully marine (April/May) to brackish conditions in October/November.Chlorophyll ranged from 6 to 182 µg L1, and grossprimary production amounted to 1690 g C m2 per year.Total bacterial number (TBN) ranged from 6.5 to 90.5 x 109 cellsL1 and bacterial biomass (BBM) from 77 to 1542 µgC L1, which are among the highest ever reported for naturalcoastal waters. Neither TBN nor BBM varied significantly withsalinity, phytoplankton or seston concentrations. Only the bacterialmean cell volume showed a significant relation to salinity,being highest (0.066 µm3) during the period of increasingand lowest (0.032 µm3) during decreasing salinity. Bacterialprotein accounted for 24% (1926%) and phytoplankton proteinfor 57% (5371%) of total seston protein. The ratio (annualmean) of bacterial carbon to phytoplankton carbon was 0.44 (range0.041.43). At low phytoplankton abundance [chlorophylla (Chl a) < 25 µg L1], bacterial carbon wasalmost equal to phytoplankton biomass (i.e. the mean ratio was1.04). In contrast, at Chl a > 100 µg L1, BBMwas low compared to phytoplankton biomass (the mean ratio was0.16). In general, BBM varied less than phytoplankton biomass.Most probably, the missing correlation between bacterial andphytoplankton variables was due to (i) organic material partlyderived from allochthonous sources serving as food resourcefor bacteria and (ii) a strong resuspension of bacteria fromthe sediment caused by frequent wind-induced mixing of the veryshallow lagoon. 相似文献
12.
Savenkoff Claude; da Silva Nadja Lins; Lefevre Dominique; Denis Michel; Rassoulzadegan Fereidoun 《Journal of plankton research》1992,14(6):835-850
Spatial and size distribution of micro-organisms and their ETSactivity has been investigated in Ligurian Sea surface watersalong the Nice-Calvi transect across frontal areas from 18 to37 km offshore (TOMOFRONT 1 and 2 cruises, April 1988 and April-May1989 respectively). Aplastidic and plastidic nanoflagellatesand aplastidic picoflagellates were present in numbers closeto 0.25 x 104 cells ml1, whereas plastidic picoflagellatesaccounted for about half this number. Correlations have beenevidenced between plastidic and aplastidic micro-organisms withinthe same size group, suggesting that they belong to a well-definedecosystem. The highest correlation between total ETS activityand abundance of the considered size groups was observed fornanoflagellates (r = 0.94, n = 22, and r = 0.90, n = 22 foraplastidic and plastidic cells respectively). The importanceof the role of nanoflagellates in surface waters, with respectto the overall ETS activity, was supported by results from sizefractionation which assigned to the 310 µm sizerange a 73.3% contribution to overall ETS activity. Resultsemphasize analysing global ETS activity of natural samples inorder to derive relationships between the different populationspresent in the sampled water. It is suggested that couplingflow cytometry to the ETS approach should be very helpful inthat respect. 相似文献
13.
Published data on the biomass and specific respiration ratesof mesozooplankton in the oceans across all latitudes were combinedto assess their community respiration on a global basis. Mesozooplanktonbiomass was higher in boreal/anti-boreal and polar waters, intermediatein equatorial waters and lowest in the subtropical gyres. Specificrespiration rates were the highest in equatorial waters anddecreased rapidly poleward. Global community respiration ofmesozooplankton in the upper 200 m of the oceans integratedover all latitudes was 10.4 ± 3.7 (SE) Gt C year1(n = 838). Below the epipelagic zone, mesozooplankton respirationliving in the mesopelagic (2001000 m) and bathypelagic(below 1000 m) zones was estimated as 2.2 ± 0.4 (n =57) and 0.40 ± 0.2 (n = 12) Gt C year1, respectively.Thus, global depth-integrated mesozooplankton respiration was13.0 ± 4.2 Gt C year1 (1732% of globalprimary production), which is 38-fold higher than thevalues assigned to mesozooplankton respiration in recent estimatesof total respiration in the ocean. Thus, it appears that mesozooplanktonrepresent a major, but neglected component of the carbon cyclein the ocean. 相似文献
14.
The total and heterotrophic bacterial microflora of gut andfecal pellets of the copepod Temora stylifera was studied inthe coastal zone of the northwestern Mediterranean basin. Digestivetracts and feces were always found to contain bacteria. Withmean values close to 1011 cells ml1and 1010 colony-formingunits (CFU) ml1, both total and heterotrophic communitiesfound in fecal pellets largely exceeded the corresponding bacterialmicroflora observed in surrounding seawater (105 cells ml1 and103 CFU ml). In the same way, the frequency of dividingcells and mean cell volumes increased, respectively, from 3%and 0.12µm3 in seawater to >6% and 0.24 µm3 infecal pellets. The bacterial community structure was investigatedby carrying out 29 morphological and biochemical tests on 147isolated strains. Although Pseudomonas was always the most frequentlyencountered genus, the bacterial communities found in copepodfecal pellets clearly differ from those inhabiting seawater.Vibrio species, which were not detected in seawater microflora,were always present in fecal pellet communities. The close correspondenceobserved between the potential metabolic characteristics ofthe fecal bacterial communities isolated from a subantarcticdeposit feeder (Mytilus edulis) and from zooplankton in thisMediterranean study suggests that the fecal community differentiationis an even more general feature. 相似文献
15.
Pakhomov E.A.; Perissinotto R.; Froneman P.W.; Miller D.G.M. 《Journal of plankton research》1997,19(4):399-423
Measurements of adult Antarctic krill (Euphausia superba) gutcontents, evacuation and egestion rates, as well as digestiveefficiency, were carried out during February-March 1994 in thevicin ity of South Georgia to estimate in situ daily ration.These were combined with acoustically derived biomass data tocalculate the grazing impact of Antarctic krill and its contributionto the carbon flux in the region. Individual levels of gut pigmentconcentrations and evacuation rates ranged from 27 to 1831 ngchlorophyll a-eq. ind.1 and from 0.133 to 0.424 h1,respectively. Losses of pigment fluor escence during digestionwere very high, ranging from 58 to 98% of the total pigmentdigested. Daily carbon consumption estimated using the gut fluorescencemethod varied from 0.234 to 0.931 mg C ind.1 day1(or 0.41.7% of body carbon), compared to {small tilde}2.73mg C ind.1 day1 (or {small tilde}5% of body carbon)using the faecal pellet production data. The 3-fold higher dailyration estimated using egestion rate data may be explained bypredation on micro-and mesozooplankton. Maximum krill grazingimpact ranged from 0.4 to 1.9% of the total phytoplankton stockor from 10 to 59% of the total daily primary production. However,grazing impact on the microphytoplankton (>20 µm) wassubstantially higher, at times exceeding 100% of the daily microphytoplanktonproduction. It is suggested that to meet its energetic demands,kriil must consume a substantial proportion of heterotrophiccarbon.
3Present address Zoology Department, University of Fort Hare,P/Bag X1314, Alice, 5700, South Africa 相似文献
16.
Growth and ingestion rates of larval fish populations in the coastal waters of Israel 总被引:1,自引:0,他引:1
Clupeoid larvae were collected on eight cruises between February1984 and February 1985 in the coastal waters of Israel. Fromanalysis of daily growth increments of otoliths, growth ratesof the abundant clupeoids, Engraulis encrasicolus, Sardina pilchardusand Sardinella aurita were found to be 0.55 mm day1,0.67 mm day1 and 0.60 mm day1, respectively, duringthe first month after hatching. Ingestion rates were estimatedusing an equation from the literature relating ingestion andgrowth of larval fish. Ingestion calculated for populationsof fish larvae in pelagic waters ranged from 0 to >23 mgC m2 day1 with maximum rates observed in April.Annual ingestion by larval fish at a pelagic station near Haifawas calculated to be 2.2 g C m2 year1, 1020%of annual primary production estimated from 14C uptake. 相似文献
17.
The present study deals with structure and functioning of threeareas of Himalayan oak forest. Low- and mid-altitude oaks, namelyQuercus leucotrichophora, and Quercus floribunda, form predominantevergreen forests in Central and Western Himalaya. The totaltree basal cover ranged between 33·89 m2 ha1 (Q.floribunda site) to 36·83 m2 ha1 (Q. leucotrichophorasite). The density ranged between 570 and 760 individuals ha1.Allometric equations relating biomass of different tree componentsto GBH (girth at breast height) were significant with the exceptionof leaf biomass in Q. leucotrichophora and Rhododendron arboreum.Total vegetation biomass (29·40467·0 tha1) was distributed as 377·1 t ha1 intrees, 5·40 t ha1 in shrubs and 1·23 tha1 in herbs. Total forest floor biomass ranged between4·6 and 6·2 t ha1. Of the total annuallitter fall (4·74·8 t ha1), 77·5% was contributed by leaf litter, 17·8 % by wood litterand 4·7 % by miscellaneous litter. Turnover rate of treelitter varied from 0·66 to 0·70. Net primary productionof total vegetation ranged between 15·9 and 20·6t ha1 yr1, of which the contribution of trees,shrubs and herbs was 81·2 %, 8·6 % and 10·2%, respectively. A compartment model of dry matter on the basisof mean data across sites was developed to show dry matter storageand flow of dry matter within the system. Quercus leucotrichophora forest, Q. floribunda forest, Q. lanuginosa forest, biomass, litter fall, net primary production, compartmental transfer 相似文献
18.
Temporal variability of diversity and biomass of tintinnids (Ciliophora) in a southwestern Atlantic temperate estuary 总被引:2,自引:0,他引:2
Seasonal variations in diversity and biomass of tintinnids (Ciliophora:Tintinnida) were investigated at two fixed stations in the innerpart of the Bahía Blanca Estuary (38°42' S, 61°50'W) during an annual cycle. The variations were analysed in relationto surface temperature, salinity, transparency, solar radiationand chlorophyll a (Chl a)concentration. Biomass was calculatedin terms of biovolume and carbon units. Diversity was estimatedas the number of species and the Shannon Index (H', ln based).Density of tintinnids ranged from 100 to 7800 individuals L1H' ranged from 0 to 1.81. The biomass varied from 0.3 to 127.78x 106 µm3 L1 (0.0239.4 µg C L1).Density was significantly related to temperature, solar radiationand Secchi distance (P < 0.01); diversity was significantlyrelated to temperature (P < 0.01) and solar radiation (P< 0.05). Biomass was significantly related only to temperature(P < 0.01) in one of the stations. According to principalcomponents analysis (PCA) tintinnids exhibited a segregationof three groups: winter, springsummer and autumn forthe most internal station and winter, spring and summerautumnfor the most external station. H' values were lower than thoseobserved in other coastal systems found at about the same latitudein the northern hemisphere. 相似文献
19.
Picoplankton community structure along the northern Iberian continental margin in late winter-early spring 总被引:1,自引:0,他引:1
Calvo-Diaz Alejandra; Moran Xose Anxelu G.; Nogueira Enrique; Bode Antonio; Varela Manuel 《Journal of plankton research》2004,26(9):1069-1081
The surface distribution of autotrophic and heterotrophic picoplanktonwas assessed in 24 transects perpendicular to the coast alongthe N and NW Iberian peninsula shelf in late winter and earlyspring 2002. Community structure was analyzed by flow cytometry(FC) and found to be strongly influenced by hydrography. Typicallate winter conditions were found during the survey, characterizedby the presence of the poleward Portugal coastal counter current(PCCC) in the west and an increasing stratification eastwards.Cyanobacteria (mostly Synechococcus) dominated at low chlorophylla (Chl a) concentration whereas both the total and relativeabundance of picoeukaryotes generally increased with total phytoplanktonbiomass. Differences in the cell size of most FC-defined picoplanktonicgroups were also observed along the longitudinal and coastaloffshoregradients. The presence of Prochlorococcus (<103 cells mL1)coincided with the core of the PCCC and its significant correlationwith salinity suggests its possible use as a tracer of thiscurrent. Two groups of heterotrophic bacteria were distinguishedaccording to their relative DNA content. High DNA bacteria dominatedthe community (60 ± 1% SE of total numbers), reachingmaximum values in areas under riverine influence with presumedhigher inputs of organic matter. Picoplankton biomass was dominatedby heterotrophic bacteria in the western region (58 ±3%) while autotrophic groups contributed on average 66 ±2% in the southern Bay of Biscay. The heterotrophic bacteriato phytoplankton biomass ratio decreased significantly alongthe measured range. Yet showing regional differences, the estimatedcontribution of picophytoplankton to total algal biomass washigh (mean 59 ± 4%), indicating the important role ofsmall cells at the onset of the spring bloom in these temperateshelf waters. 相似文献
20.
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