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1.
Community structure, biomass and productivity of size-fractionated summer phytoplankton populations in lower Narragansett Bay, Rhode Island 总被引:1,自引:0,他引:1
Seventeen size-fractionation experiments were carried out duringthe summer of 1979 to compare biomass and productivity in the< 10, <8 and <5 µm size fractions with that ofthe total phytoplankton community in surface waters of NarragansettBay. Flagellates and non-motile ultra-plankton passing 8 µmpolycarbonate filters dominated early summer phytoplankton populations,while diatoms and dinoflagellates retained by 10 µm nylonnetting dominated during the late summer. A significant numberof small diatoms and dinoflagellates were found in the 108µm size fraction. The > 10 µm size fraction accountedfor 50% of the chlorophyll a standing crop and 38% of surfaceproduction. The <8 µm fraction accounted for 39 and18% of the surface biomass and production. Production by the< 8 µm fraction exceeded half of the total communityproduction only during a mid-summer bloom of microflagellates.Mean assimilation numbers and calculated carbon doubling ratesin the <8 µm (2.8 g C g Chl a1 h1; 0.9day1)and<5 µm(1.7 g C g Chl a1h1; 0.5day1)size fractions were consistently lower than those of the totalpopulation (4.8 g C g Chl a1 h1; 1.3 day1)and the <10 µm size fraction (5.8 g C g Chl a1h1; 1.4 day 1). The results indicate that smalldiatoms and dinoflagellates in fractionated phytoplankton populationscan influence productivity out of proportion to their numbersor biomass.
1Present address: Australian Institute of Marine Science, P.M.B.No. 3, Townsville M.S.O., Qld. 4810, Australia. 相似文献
2.
Joaquim-Justo Celia; Pirlot Samuel; Viroux Laurent; Servais Pierre; Thome Jean-Pierre; Descy Jean-Pierre 《Journal of plankton research》2006,28(9):857-870
Trophic interactions within the plankton of the lowland RiverMeuse (Belgium) were measured in spring and summer 2001. Consumptionof bacteria by protozoa was measured by monitoring the disappearanceof 3H-thymidine-labelled bacteria. Metazooplankton bacterivorywas assessed using 0.5-µm fluorescent microparticles (FMPs),and predation of metazooplankton on ciliates was measured usingnatural ciliate assemblages labelled with FMPs as tracer food.Grazing of metazooplankton on flagellates was determined throughin situ incubations with manipulated metazooplankton densities.Protozooplankton bacterivory varied between 6.08 and 53.90 mgC m3 day1 (i.e. from 0.12 to 0.86 g C1bacteria g C1 protozoa day1). Metazooplankton,essentially rotifers, grazing on bacteria was negligible comparedwith grazing by protozoa (1000 times lower). Predation of rotiferson heterotrophic flagellates (HFs) was generally low (on average1.77 mg C m3 day1, i.e. 0.084 g C1 flagellatesg C1 rotifers day1), the higher contribution ofHF in the diet of rotifers being observed when Keratella cochleariswas the dominant metazooplankter. Predation of rotifers on ciliateswas low in spring samples (0.56 mg C m3 day1,i.e. 0.014 g C1 ciliates g C1 rotifers day1)in contrast to measurements performed in July (8.72 mg C m3day1, i.e. 0.242 g C1 ciliates g C1 rotifersday1). The proportion of protozoa in the diet of rotiferswas low compared with that of phytoplankton (<30% of totalcarbon ingestion) except when phytoplankton biomass decreasedbelow the incipient limiting level (ILL) of the main metazooplantonicspecies. In such conditions, protozoa (mainly ciliates) constituted50% of total rotifer diet. These results give evidence thatmicrobial organisms play a significant role within the planktonicfood web of a eutrophic lowland river, ciliates providing analternative food for metazooplankton when phytoplankton becomesscarce. 相似文献
3.
Biomass, feeding and production of Noctiluca scintillans in the Seto Inland Sea, Japan 总被引:1,自引:0,他引:1
The abundance and biomass of the large heterotrophic dinoflagellateNoctiluca scintillans, together with the changes in its potentialprey items, were monitored in the Seto Inland Sea, Japan, duringsummer 1997 (17 July-11 August). Growth and grazing rates ofNscintillans fed natural plankton populations were also measuredeight and seven times, respectively, during the survey period.The abundance and biomass of N scintillans averaged over thewater column (19 m) were in the range 1345 cells 11(temporalaverage = 93 cell11) and 0.149.6 µg C l1(temporalaverage = 13.8 µg C l1; three times higher thanthat of calanoid copepods during the same period). Noctilucascintillans populations followed the changes in phytoplankton:N.scintillans biomass was increasing during the period of diatomblooms and was at a plateau or decreasing during periods oflow chlorophyll a. The growth rates of N.scintillans (µ)were also consistent with the wax and wane of the N.scintillanspopulation: N.scintillans showed highest growth rates duringdiatom blooms. A simple relationship between µ and chlorophylla concentration was established, and the production of N.scintillanswas estimated using this relationship and the measured biomass.The estimated production averaged over the water column wasin the range >0.15.2 µg C l1 day1(temporalaverage = 1.4 µg C l1 day1; 64% of the productionof calanoid copepods during the same period). Diatom clearancerates by N.scintillans were in the range 0.100.35 mlcell1 day1, and the phytoplankton population clearanceby N.scintillans was >12% day1. Thus, although thefeeding pressure of N.scintillans on phytoplankton standingstock was low, N.scintillans was an important member of themesozooplank-ton in terms of biomass and production in the SetoInland Sea during summer. 相似文献
4.
Takahashi Mikio; Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko 《Journal of plankton research》1995,17(5):1017-1025
Measurement of the photosynthetic production rate in Lake Biwawas camed out from May 1985 to September 1987. In the light-saturatedlayer, the seasonal variation in the photosynthesis rate perchlorophyll a was regulated by water temperature. The depth-integratedphotosynthetic production rate was 0.21-1.48 g C m2 day1and the maximum value was observed in midsummer when the watertemperature of the mixed surface layer was highesL The criticalnutrient for photosynthesis may be dissolved reactive phosphorus,which was generally <1 µg P 11 throughout theobservation period. In the trophogenic layer, respiratory organiccarbon consumption, estimated from measurement of respiratoiyelectron transport system activity, was 0.35-1.07 (mean 0.66)g C m1 day1 and corresponded, on average, to 79%of the photosynthetic carbon production rate. This implies thatthe major part of photosynthetic fixed organic matter mightbe recycled in the trophogenic layer. The estimated settlingorganic carbon flux at 20 m depth, from calculation of theseparameters and changes in the particulate organic carbon concentration,was 0.01 (-0.09 to 0.13) g C m1 day1 The meansettling organic carbon flux measured by sediment trap at 20m was 0.19 (0.09-0.31) g C m1 day1 higher thanthe estimated value. It seemed that organic matter collectedby sediment trap may contain allochthonous matter and resuspendedepilimnetic sediment matter. 相似文献
5.
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
6.
Rees A.P.; Owens N.J.P.; Heath M.R.; Plummer D.H.; Bellerby R.S. 《Journal of plankton research》1995,17(6):1307-1324
Carbon (C) fixation and nitrogen (N) assimilation rates havebeen estimated from 14C and 15N techniques for a 12 month periodin a Scottish sea loch. The maximum rate of nitrogen assimilated(29.92 mmol N m2 day1) was in April at the mostseaward station; similar high rates were experienced duringMay at the other stations. Carbon fixation rates were maximal(4884047 mg C m2day1) at the time of highphytoplankton biomass (maximum 8.3 mg m3 chlorophylla) during May, whilst nitrate concentrations remained >0.7µ.mol l1. C:N assimilation ratios suggest nitrogenlimitation only during the peak of the spring bloom, althoughat times nitrogen (nitrate and ammonium) concentration fellto 0.2 µmol l1 in the following months. The verticalstability of the water column, influenced by tidal and riverineflushing, varied along the axis of the loch, resulting in markeddifferences between sampling stations. Although ammonium waspreferentially assimilated by phytoplankton, >50% of productionwas supported by nitrate uptake and only during the summer monthswas the assimilation of ammonium quantitatively important. 相似文献
7.
Growth rates of two freshwater diatoms and three chlorophyteswere compared under 3 h days at 10 µmol m2 s1.Specific growth rates ranged between µ=0.03 day1and µ=0.055 day1 for the different species andwere in every species independent of temperature between 8 and16°C. 相似文献
8.
The contribution of ammonia excreted by zooplankton to phytoplankton production in Narragansett Bay 总被引:1,自引:0,他引:1
Ammonia excreted by mixed zooplankton populations over an annual(19721973) cycle in Narragansett Bay varied from 0.04to 3.21 µg at NH3-N dry wt1 day1, exclusiveof two exceptional rates measured one year apart: 11.74 and18.39 µg at NH3-N mg dry wt1 day1. Grossphytoplankton production integrated over the year (19721973)averaged 151 mg C m3 day1 for an 8 m water column;peaks of 332 and 905 mg C m3 day1 occurred duringthe winter-spring and summer blooms, respectively. Excretedammonia, integrated seasonally and annually, contributed only0.2% and 4.9% of the nitrogen required for observed gross productionduring the winter-spring and summer blooms, respectively, and4.4% annually. However, excreted ammonia may be an importantsource of the nitrogen required by Skeletonema costatum, thedominant diatom in Narragansett Bay, during the post-bloom periodwhen 186% of the nitrogen required for its net production wasmet by ammonia excretion. A combination of zooplankton ammoniaexcretion and benthic ammonia flux contributed 22% of the nitrogenrequired for the annual gross production (440 g C m2)while 51% of the nitrogen required for the net production ofSkeletonema was accounted for by regenerated nitrogen.
1This research was supported by NSF grant GA 31319X awardedto Dr.T.J.Smayda. 相似文献
9.
Biomass and productivity of microplankton were measured in theCraternaya Bay (Kurile Islands), which is influenced by hydrothermalactivity and volcanic heating. The hydrothermal fields are situatedaround its shores and underwater within the 020 m depth.A dense bloom of photoautotrophic microplanktonwas observed there, dominated by diatoms, phytoflagellates andthe symbiont-containing ciliate Mesodinium rubrum. The biomassof these ciliates attained 311 g m-3 in the upper waterlayer. The total biomass of the phototrophic microplankton reached3046 g m-3. The primary production in the water columnwas, correspondingly, enormously high: 610 g C m-2 day-1.The depth of the euphotic zone was 7 m. Pelagic photosynthesiswas inhibited in the upper 01 m by the spreading of alayer of low-salinity hydrothermal water. The numerical densityof bacterioplankton in the upper zone of the water column variedfrom 1 x 106 to 2.9 x 106 cells ml-1, and its wet biomass from250 to 750 mg m-3. Its production varied at stations from 70to 390 mg m-3 day-1. Chemosynthesis contributed up to 30% ofthis production in the sites neighbouring the hydrothermal vents.Outside their direct impact however, its share was negligible.The biomass of heterotrophic planktonic ciliates varied from30 to 270 mg m-3. The mechanisms of possible influence of shallowvolcanic activity on development and function of microplanktonin the Craternaya Bay is discussed. 相似文献
10.
Phytoplankton composition, density, vertical distribution andprimary production were investigated in the Sea of Okhotsk andin the adjacent northern north Pacific in JulyAugust1994, together with measurements of density and distributionof planktonic microheterotrophs: bacteria, nanoheterotrophsand ciliates. Different phases of phytoplankton seasonal successionwere encountered during the period of investigation in variousregions of this sea. Primary production measured at 144 stationswas found to be greatest (1.54 g C m-2day-1) in areasof spring-phase succession along the Sakhalin shelf and theKashevarov bank. Periodic relapses of the spring blooms of heavydiatoms during the whole growth season were recorded over thisbank. The summer phase of the phytoplankton minimum prevailedin the central and eastern parts of the sea, manifested by thedominance of nanoflagellates in terms of phytoplankton biomass.Primary production was 0.51 g C m-2 day-1. The earlyautumn phase of succession was typical of the Kurile straitarea and the adjacent north Pacific. Primary production therevaried from 0.7 to 2 g C m-2 day-1. The integrated phytoplanktonbiomass in the water column varied from 912 g m-2 inzones supporting the summer minimum assemblage to 1520g m-2 in zones of early autumn recovery of phytoplankton growth,and up to 4070 g m-2 in areas of remnant or relapseddiatom blooms. The numerical density of bacterioplankton wasbetween 1 x 106 and 3 x 106 cells ml-1 and its wet biomass wasbetween 100 and 370 mg m-3. In deep waters it was 815mg m-3. The integrated bacterioplankton biomass in the upperwater column varied from 6 to 29 g m-2. The numerical densityof zooflagellates varied in the upper layer between 0.8 x 106and 4 x 106 l-1 and their biomass was between 20 and 50 mg m-3.In deep waters they were still present at a density of 0.05x 106 to 0.2 x 106 cells l-1. The biomass of planktonic ciliatesvaried between stations from 20 to 100 mg m-3. The joint biomassof planktonic protozoa in the water column was between 3 and12 g m-3 at most of the stations. 相似文献
11.
The impact of grazing by natural assemblages of microzooplanktonwas estimated in an upwelling area (Concepción, Chile)during the non-upwelling season in 2003 and 2004. Seawater dilutionexperiments using chlorophyll a (Chl a) as a tracer were usedto estimate daily rates of phytoplankton growth and microzooplanktongrazing. Initial Chl a concentrations ranged from 0.4 to 1.4mg Chl a m3 and phytoplankton prey biomass and abundancewere numerically dominated by components <20 µm. Phytoplanktongrowth and microzooplankton grazing rates were 0.190.25day1 and 0.260.52 day 1, respectively.These results suggest that microzooplankton exert a significantremoval of primary production (>100%) during the non-upwellingperiod. 相似文献
12.
Photoadaptation in Antarctic phytopfankton: variations in growth rate, chemical composition and P versus I curves 总被引:1,自引:0,他引:1
The response of phytoplankton to variations in the light regimewas studied during the VULCAN and ACDA cruises in the Antarctic.Unenriched batch cultures of 1219 days' duration reachedchl concentrations of 1050 µg1 and exhibitedexponential growth rates, with the maximal rate being 0.41 doubl,day1. Ice edge algae exhibited maximum growth rates atphoton flux densities (PFD) of 30100 µE m2S1and the growth rate was reduced by about 30% at 5001000µE m2S1 The chl/C ratio ranged between 0.004and 0.018, with the lowest ratios at PFDs above 500 µEm2S1 chl/C ratios were also below maximum at PFDsbelow 4050 µE m2S1 The C:N:P ratioswere close to the Redfield ratios; the Si/C ratio averaged 0.16(atoms), and the ATP/C ratio averaged from 0.0024 to 0.0050in different culture senes. When thawed after having been frozenfor 10 days, shade-adapted cultures were in a much better conditionthan sun-adapted ones. P versus I data showed that the maximumassimilation number varied from 0.75 to 4.4 µg C (µgchl)1h1. It varied inversely with the chl/C ratio;therefore the maximum carbon turnover rate varied little betweensamples (0.024/0.035 h1). Low biomass communities exhibitedrelatively high values for (the initial slope of P versus Icurves), low values for 1sat (160330 µE m2S1),and they were susceptible to photoinhibition. In contrast, communitiesdominated by Odontella weissflogii exhibited low values for, a high value for Isat (560 µE m2S1 andthey tolerated high PFDs. The photo-adaptational status of thephytoplankton in natural water samples is discussed relativeto the profile of water column stability and mixing processes. 相似文献
13.
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
14.
The plastochron index (PI) has been compared with leaf growthand biomass accumulation in young soya bean plants of severalcultivars that were grown in controlled environments with differentirradiance levels and durations, temperatures, and nitrogen(N) regimes. Increasing the photoperiod from 10 to 16 h day1 increasedthe plastochron rate (PR) and the proportion of axillary growth.Doubling the photosynthetic photon flux density (PPFD) to 1000µmol m2S1, increased PR and the proportionof roots to total plant weight, but decreased the proportionof stems plus petioles to total. In a series of experiments,the plants were grown in an 8 h photoperiod at constant temperaturesof 17, 20, 26 or 32 °C. As temperature increased, PR increased,but the duration of leaf expansion decreased. Leaves were largestat 20 and progressively smaller at 26, 32 and 17 °C. Biomasswas greatest for a given PI at 20 °C and decreased in theorder of 26, 32, and 17 °C. The proportion of axillary growthalso was greatest at 20 °C. When plants were grown in a15 h photoperiod at temperatures from 17.1 to 26.6 °C, leafsize continued to increase up to the highest temperature. At17 °C, the PR in the 15 h photoperiod (PPFD 390 µmol;m2S1) was about threefold greater than in 8 h(500 µmol m2 S1); biomass accumulation perday was about fivefold greater. Increasing N from 3 to 36 mMincreased PR about 10 per cent, altered biomass partitioningamong plant parts, and increased the biomass of the plants.The NO2 form of N markedly stimulated axillary growth as comparedwith the NH4+ form. Environment or cultivar had little influenceon the duration of leaf expansion in terms of PI. Cultivarsdid not differ consistently in biomass production and allocationin the different environments. Glycine max (L.) Merrill, soybean, soya bean, plastochron index, leaf development, growth analysis, partitioning, light, nitrogen, temperature 相似文献
15.
Huskin I.; Anadon R.; Woodd-Walker R. S.; Harris R. P. 《Journal of plankton research》2001,23(12):1361-1371
Size-fractionated copepod abundance and ingestion rates wereinvestigated along a 50°S50°Nlatitudinal transect,during the Atlantic Meridional Transect (AMT) 4, 5 and 6 cruises(boreal springautumn 1997, boreal springsummer1998). Copepod abundance was higher at high latitudes in spring,near northwest Africa, in the equatorial and Benguela upwellingsystems, and in the Subtropical Convergence, and lower in oligotrophicgyres. Gut contents were not related to phytoplankton biomassor production. Gut evacuation rate averaged 0.03 min-1, andwas not related to latitude or body size. Conservative estimatesof copepod community total ingestion rates ranged between 3.4and 173 mg C m-2 day-1 for AMT4, 1.6252 mg C m-2 day-1in AMT5 and 10160 mg C m-2 day-1 in AMT6. Maximum valueswere always in the upwelling regions, the subtropical convergenceand high latitudes in the Northern Hemisphere during borealspring. Calculated ingestion rates translate into average dailyminimal consumption values of 2.07%, 1.89% and 2.6% of totalchlorophyll stock, or 8.02%, 14.5% and 12.9% of total primaryproduction ingested daily on AMT4, 5 and 6 respectively. Grazingimpact increases considerably if we consider ingestion of phytoplanktonlarger than 2 µm, especially under the influence of theEquatorial and North African upwellings, where copepod ingestionrepresents up to 30% of the biomass and >100% of productionby large cells. 相似文献
16.
The development of the Daphnia longispina (O. F. Müller)population in a highly humic boreal lake was followed throughoutone growing season, and the amount of secondary production wasestimated in relation to primary production and available foodresources. The growth rate method was applied in the secondaryproduction measurements. Daphnia longispina did not appear inthe water column until 16 May, after which the animals werepresent throughout the growing season. The population showedthree density peaks; the first appeared in early June, and thesecond and third in mid-July and at the beginning of September,respectively. Somatic production followed a seasonal pattern,with highest production rates in midsummer. The maximum valueof 127 mg C m2day1 was recorded at the beginningof July. The total annual net production of D. longispina was7.9 g C m2. During most of the growing season, the primaryproductivity in the lake was well below 100 mg C m2 day1and the total annual productivity of photosynthetic algae was5.0 g C m2. We conclude that in this lake the zooplanktonpopulation did not rely on phytoplankton primary productionas a sole carbon source, but that most of the carbon must haveoriginated from bacterial production either directly or througha microbial loop. 相似文献
17.
Size-fractionated Primary Production in the South Atlantic and Atlantic Sectors of the Southern Ocean 总被引:3,自引:0,他引:3
Results are presented from size fractionated chlorophyll a (Chla) and primary production studies along a transect between Antarcticaand southern Africa during the second South African AntarcticMarine Ecosystem Study (SAAMES II), conducted in late australsummer (January to February) 1993. Total integrated Chl a alongthe transect was highest in the vicinity of the Marginal IceZone (MIZ) and Antarctic Polar Front (APF). At these stations,integrated Chl a biomass was always >25 mg Chl a m2and was dominated by microphytoplankton. Although nominal increasesinChl a biomass were also associated with the Subantarctic Front(SAF) and Subtropical Convergence (STC), total Chl a biomassin these regions was dominated by nanophytoplankton. Withinthe inter-frontal regions, total integrated Chl a biomass waslower, generally <25 mg Chl a m2, and was always dominatedby nanophytoplankton. An exception was found in the AgulhasReturn Current (ARC) where picophytoplankton dominated. Totaldaily integrated production along the transect ranged between60 and 436 mg C m2 day1. Elevated production rateswere recorded at stations occupied in the vicinity of the MIZand at all the major oceanic frontal systems. The contributionsof the various size fractions to total daily production displayedthe same spatial pattern as integrated biomass, with microphytoplanktonbeing the most important contributor in areas characterizedby elevated phytoplankton biomass. Outside these regions, nanophytoplanktondominated the total phytoplankton production. Again, an exceptionwas found in the ARC north of the STC where picophytoplanktondominated total production. There, the lowest production alongthe entire transect was recorded, with total daily integratedproduction always <90 mg C m2 day1. The increasedproduction rates recorded in the MIZ appeared to result fromincreased water column stability as indicated by a shallow mixed-layerdepth. Within the inter-frontal regions, the existence of adeep mixed layer appeared to limit phytoplankton production.Low silicate concentrations in the waters north of the APF mayalso have limited the growth of large microphytoplankton. 相似文献
18.
A comparison of performance of WP2 and MOCNESS 总被引:1,自引:0,他引:1
Gjosater Harald; Dalpadado Padmini; Hassel Arne; Skjoldal Hein Rune 《Journal of plankton research》2000,22(10):1901-1908
Zooplankton biomass in the Barents Sea was monitored during198897 using WP2 and MOCNESS plankton nets. These twosampling gears differ in their size and mode of operation. Theplankton samples were size fractionated into three categoriesand the dry weight per square metre was calculated. The smallestand the medium size fractions (< 2000 µm) representedmainly copepods, and the larger size fraction (> 2000 µm)consisted mainly of macrozooplankton such as krill and amphipods.WP2 biomass values were higher for the smallest size fraction,whereas the MOCNESS tended to give higher values for the largestsize fraction However, the total amount of zooplankton biomass(g m1) obtained by these two methods was not significantlydifferent. 相似文献
19.
Fonda Umani S.; Beran A.; Parlato S.; Virgilio D.; Zollet T.; De Olazabal A.; Lazzarini B.; Cabrini M. 《Journal of plankton research》2004,26(5):545-561
The first bloom of Noctiluca scintillans in theNorthern Adriatic Sea was recorded in 1977. The organism causedseveral red tides in the whole basin during the late 1970s,a period characterized by increasing nutrient loads. Duringthe 1980s and early 1990s, there was no red tide,but the species was an almost constant summer presence, associatedwith high temperatures. Noctiluca scintillans was almost completelyabsent from 1994 until May 1997, concurrent with a general planktondecrease. From summer 1997, N. scintillans was recorded againin the whole basin, although there was no other signal of increasingeutrophication. In contrast to all previous observations, duringwinter 20022003, N. scintillans was continuously sampledin the Gulf of Trieste. We estimated experimentally growth andgrazing rates of the dinoflagellate at 910°C in cultureand consuming the natural assemblage. Noctiluca scintillanswas able to reproduce actively at low temperatures, showingsimilar growth rates in both experiments (k = 0.2 day1).The values found were close to those reported in the literaturefor higher temperatures. The natural diet was mainly composedof phytoplankton (ingestion = 0.008 µg C Noctiluca 1day1), microzooplankton (ingestion = 0.008 µg CNoctiluca 1 day1) and bacteria (ingestion = 0.005µg C Noctiluca 1 day1) with an average carboncontent of 0.138 ± 0.020 µg C Noctiluca cell1. 相似文献
20.
Copepod abundance in the western Irish Sea: relationship to physical regime, phytoplankton production and standing stock 总被引:1,自引:0,他引:1
Gowen R.J.; McCullough G.; Dickey-Collas M.; Kleppel G.S. 《Journal of plankton research》1998,20(2):315-330
The distinct patterns of stratification in the North Channeland stratified region of the western Irish Sea influence theseasonal abundance of phytoplankton. The 34 month productionseason in the stratified region was characterized by productionand biomass peaks in the spring (up to 2378 mg C m2 day1and 178.4 mg chlorophyll m2) and autumn (up to 1280 mgC m2 day1 and 101.9 mg chlorophyll m2).Phytoplankton in the North Channel exhibited a short, late productionseason with a single summer (June/July) peak in production (4483mg Cm2 day1) and biomass (160.6 mg chlorophyllm2). These differences have little influence on copepoddynamics. Both regions supported recurrent annual cycles ofcopepod abundance with similar seasonal maxima (182.8241.8103ind. m2) and dominant species (Pseudocalanus elongatusand Acartia clausi). Specific rates of population increase inthe spring were 0.071 and 0.048 day1 for the North Channel andstratified region, respectively. Increased copepod abundancein the stratified region coincided with the spring bloom, andwas significantly correlated with chlorophyll standing stock.Increased copepod abundance preceded the summer production peakin the North Channel. This increase was not correlated withchlorophyll standing crop, suggesting that a food resource otherthan phytoplankton may be responsible for the onset of copepodproduction prior to the spring bloom. Hetero-trophic microplanktonas an alternative food source, and advection of copepods fromthe stratified region, are proposed as possible explanationsfor copepod abundance increasing in advance of the summer peakin primary production. 相似文献