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1.
Primary and bacterial production compared to growth and food requirements of Daphnia longispina in Lake Kvernavatnet, west Norway 总被引:1,自引:0,他引:1
B{phi}rsheim Knut YUngve; Andersen Sissel; Hele Johnsen Geir; Eva {phi} Kambestad; Norland Svein 《Journal of plankton research》1988,10(5):921-939
Primary production, and bacterial production as measured byincorporation of [3H-methyl]thymidineinto ice cold TCA insolublematerial were investigated during 1984 in Lake Kvernavatnet,west Norway. Primary production averaged 222 mg C m2day1 and bacterial production averaged 163 mg C m2day1. The bacterial production in the euphotic pelagiczonecontributed -60% of the total pelagic bacterial production.The zooplankton was dominated byDaphnia longispina. From growthexperiments with animals fed only natural food in coarse filteredlake water, the population daily growth increments were calculated.The average production of D.longispina was 151 mg C m2day1 during the period investigated. The estimated primaryproduction was too low to sustain both the bacterial productionand the zooplankton food requirements. These results imply thatthe carbon cycle of the lake is dependent on the supply of allochtonousmaterial, or that the current methods for measuring productionrates in aquatic environments are systematical erratic. 相似文献
2.
Oikopleura longicauda occurred throughout the year in ToyamaBay, southern Japan Sea, and analysis of its size compositionand maturity revealed that reproduction was continuous overtheyear. Somatic growth production (Pg) varied with season from0.03 to 103 mg carbon (C) m2day1 (annual Pg 4.5g C m2), and house production (Pe) from 0.11 to 266 mgC m2 day1 (annualPe 11.3 g C m2). The annualPg/B ratio was 176. Compared with production data of some predominantzooplankton species in Toyama Bay, it is suggested that despitetheir smaller biomass, appendicularians are an important secondaryproducer. 相似文献
3.
Plankton composition and cycling of carbon during the rainy season in a tropical coastal ecosystem, Zanzibar, Tanzania 总被引:3,自引:0,他引:3
Lugomela Charles; Wallberg Petra; Nielsen Torkel Gissel 《Journal of plankton research》2001,23(10):1121-1136
Biomass, species composition and production of the planktoniccommunity were investigated during the rainy season in May andJune 1999 outside Zanzibar Island, Tanzania. In general, theplankton biomass of different organisms was uniform betweendepths as well as over time. The integrated water column primaryproduction ranged from 204 to 4142 mg C m2 day1.Bacterial production varied between 10 and 72 mg C m2day1, comprising ~5% of the total bacterial standingstock. The data obtained from these experiments are summarizedin a carbon budget. At the most 77% of the total primary productionchannelled through the heterotrophic flagellates, ciliates andheterotrophic dinoflagellates to higher trophic levels. Of theestimated carbon demand for mesozooplankton, 28% could potentiallybe met by ciliates and heterotrophic dinoflagellates. 相似文献
4.
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
5.
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
6.
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
7.
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
8.
Neomysis mercedis, an important invertebrate predator in somelakes and estuaries in North America, occurred at high densities(>2 mysids m-3) in Lake Washington in the early 1960s, aperiod when Daphnia were scarce in the lake. Because Neomysisfeed selectively on Daphnia, it was hypothesized that mysidpredation contributed significantly to the scarcity of Daphnia.To evaluate this hypothesis, mysid abundance was monitored inthe lake (July 1989February 1992), and whole lake predationimpacts on Daphnia were estimated. Mysid abundance varied from319 million, 0.1 mysids m-3 (February 1992) to 4276 million,1.7 mysids m-3 ( June 1991), and mysid biomass ranged from 1153(October 1991) to 4700 kg dry weight (November 1990). A peakin Daphnia consumption was noted during autumn, when total mysidbiomass was high. In late autumn/winter mysid consumption month-1accounted for 2895% of Daphnia biomass and 1338%of production. Mysid densities in this study were 18x and 5xlower than in 1962 and 1975, respectively. By extrapolation,at a density of 3.5 mysids m-3 observed in the early 1960s,total Neomysis consumption demand month-1 exceeded 100% of Daphniabiomass (late autumnearly spring), and 100% of Daphniaproduction (late autumnwinter). Estimates of the totalmysid consumption demand in this study are thus in accord withthe hypothesis that Neomysis could control Daphnia abundancein Lake Washington. 相似文献
9.
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
10.
The productive and optical status of the oligotrophic waters of the Southern Aegean Sea (Cretan Sea), Eastern Mediterranean 总被引:2,自引:0,他引:2
Primary production, pigment concentrations and spectral measurementsof downwelling irradiance were made at four stations in fourseasons (spring, summer, autumn, winter) during 1994 in thewaters of the South Aegean Sea (Cretan Sea), Eastern Mediterranean.Rates of production were determined using in Situ incubationtechniques and included measurements at the surface microlayer.Depth-integrated values averaged over season were 5.66 mg Cm2 h1 for primary production and the correspondingchlorophyll (Ch1) a and phaeophytin (Phaeo) a values had meansof 4.87 and 1.21 mg m3 respectively. The assimilationratio remained very low (mean over season: 1.19 mg C mg2Chl a h1 as did the Phaeo a/Chl a ratio (mean over season:0.24). The annual production for the area was estimated to yield24.79 g C m2 year1. Primary production and Chla estimates showed statistically significant seasonal, spatialand depth variations. The spectral values of the attenuationcoefficient Kd ( 相似文献
11.
The Kinetics of Tracheid Development in Tsuga canadensis Carr. and its Relation to Tree Vigour 总被引:1,自引:0,他引:1
Cell counts from samples taken at weekly intervals, from 14May to 22 October 1969, in a T. canadensis stand in Massachusetts,U.S.A., showed that the width of the annual ring was correlatedwith the rate of cell production and that only the least vigoroustrees (c. 20 tracheids year1) had a shorter growing season.The time required for completion of a cell-division cycle inthe cambial zone decreased during the course of the season,from 35 to 20 days for the less vigorous trees (2545tracheids year1) and from 28 to 10 days for the morevigorous trees (45100 tracheids year1). The timerequired for the completion of radial growth of the tracheidsdecreased from 18 to 9 days, with no evidence of any changeswith tree vigour. The actual radial growth-rate of the tracheidswas constant within the range 1.53 um day1. Thetime required for deposition of the secondary cell wall increasedfrom 10 to 50 days, with little evidence of any changes withtree vigour. The actual rate of deposition of cell wall materialwas about 0.15 µ2 µ1 day1 and seemedto show little change during the course of the season. The timeperiod required for lysis of the cytoplasm was about 4 days,with no evidence of any changes with tree vigour and littleevidence of any changes during the course of the season. 相似文献
12.
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
13.
Simulated annual plankton production in the northeastern Pacific Coastal Upwelling Domain 总被引:1,自引:0,他引:1
Robinson Clifford L.K.; Ware Daniel M.; Parsons Timothy R. 《Journal of plankton research》1993,15(2):161-183
A microcomputer simulation model is presented that describesthe generalized plankton production dynamics, in the surfacemixed layer, of the Juan de Fuca Eddy located on the southwesternBritish Columbia continental shelf. The Juan de Fuca Eddy simulationmodel evaluates how the annual biomass production of diatoms,copepods and euphausiids is forced by plankton feeding interactions,seasonal variability in upwelling, water temperature and solarradiation, and generalized fish predation. The model estimatesannual primary production of 345 g C m2 year1and secondary production of 19.4 g C m2 year1for copepods and 6 g C m2 year1 for euphausiids,during 198589; -90% of the annual plankton productionwas generated during the April-October upwelling season. Perturbationsof 22 abiotic and biotic parameters, one at a time by ±10%of nominal values, indicated that oceanic variability (e.g.upwelling rate) most strongly affected primary production. Conversely,zooplankton production was most sensitive to variability inbiological parameters describing zooplankton grazing potentialand growth (e.g. gross growth efficiency). Simulated seasonalbiomass patterns of diatoms, copepods and euphausiids were foundto closely match empirical data. However, euphausiid biomassproduction in the Juan de Fuca Eddy alone was unable to meetthe demands of estimated pelagic fish consumption. Local Eddyeuphausiid populations had to be supplemented, from regionaleuphausiids. by a mechanism that is proposed to be linked tothe seasonal pattern and intensity of positive Ekman transport(upwelling). 相似文献
14.
Production of Penilia avirostris in Kingston Harbour, Jamaica 总被引:2,自引:0,他引:2
The cladoceran Penilia avirostris is one of the more abundantand widespread members of the crustacean zooplankton in nearshoretropical and subtropical waters. Its abundance, biomass, fecundity,development rate and production were estimated in Kingston Harbour,Jamaica, during an 18 month period. Mean annual abundance ofPenilia was 1821 m3, while biomass (excluding eggs/embryos)was 2.87 mg ash-free dry-weight (AFDW) m3 (43.1 mg AFDWm2), accounting for 13% of the copepod community biomass.Fecundity increased with body size. There was no clear seasonalpattern of abundance, size or fecundity, nor were physical orbiological variables correlated to these variations. Developmenttime averaged 20.5 h for juveniles and 41.4 h for adult femalesduring incubations; there was no clear evidence of a diel patternto molting. Growth rate appeared to be exponential, with correspondingsomatic growth rates, averaging 0.27 day1 for juveniles,and 0.34 day1 for somatic plus reproductive growth inadult females. Annual production was estimated as 173 kJ m2year1, 相似文献
15.
Community respiration (R) was determined in Bransfield Straitfrom oxygen changes in water samples incubated in borosilicatebottles maintained at in situ temperature. The respiratory electrontransport system (ETS) activity of seawater communities wasalso measured from the same samples. Both data sets were relatedby the regression equation: log R (mg O2 m3 day1)=0.462+0.730xlogETS activity mg O2 m3 day1) (r=0.80, n=23). Fromthis equation and 37 ETS activity depth profiles, we calculatedthe integrated (0100 m) community respiration as beingin the range 1.24.5 g O2 m2 day1 (mean=2.2).These values do not differ significantly from other publishedresults for the Arctic and Antarctic Oceans. Assuming a respiratoryquotient of unity, the areal respiration ranges between 0.45and 1.69 g C m2 day1 (mean=0.8). This would representan important sink for the primary production reported for BransStrait. The spatial distribution of community respiration showedhigher values associated with the warmer and phytoplankton-richwaters outflowing from Gerlache Strait into Bransfield Strait,and with the front that separates Bellingshausen Sea watersfrom Weddell Sea waters. We suggest that this pattern of distributionmay be related to the transport of organic matter by the BransfieldCurrent along the front. 相似文献
16.
The geographical distribution, seasonal life cycle, biomassand production of a copepod Calanus sinicus were investigatedin and around Kii Channel of the Inland Sea of Japan. The distributioncenter of the population was located in Kii Channel. The patternof the seasonal variation in abundance of copepodites and adultsdiffered geographically within the study area. In Kii Channel,for example, they were most abundant in June-July and leastabundant in October. Over the study area, the reproduction ofC.sinicus took place throughout the year, indicating the absenceof diapause phase. In adults, females usually outnumbered males.The prosome length of late copepodites and adults was inverselycorrelated with water temperature. The annual mean biomass washighest (4.87 mg C m3 or 231 mg C m2) in Kii Channel.The potential production rate of the population exhibited aseasonal variation more or less similar to that of the biomassand the annual potential production rate was 358 mg C m3year1 (14.1 g C m2 year1) in Kii Channel.Daily production and biomass (P/B) ratios in Kii Channel increasedfrom 0.11 at 11.8°C to 0.26 at 20°C. 相似文献
17.
Factors controlling production of phytoplankton and bacteria under ice in a humic, boreal lake 总被引:1,自引:0,他引:1
Tulonen Tiina; Kankaala Paula; Ojala Anne; Arvola Lauri 《Journal of plankton research》1994,16(10):1411-1432
The factors controlling pelagic primary and bacterial productionof a humic, boreal lake in winter were investigated, combininglaboratory and field experiments where some of the predictedconsequences of the climate change, i.e.the increased load ofphosphate-phosphorus and dissolved organic matter (DOM), weresimulated. In situ incubations were performed in eight acrylictubes lowered underneath the ice cover for 14 months.In the lake, production of phytoplankton (0.030.33 µgC l1 day1) was lower than that of bacteria (0.22.3µg C l1 day1) from the end of January tomid-April. Later in spring, the light conditions improved dueto the disappearance of snow and finally ice itself, and primaryproduction was revived. The importance of light as the factorcontrolling primary production in winter was confirmed in laboratoryexperiments where additions of phosphorus and DOM did not enhancethe primary production. These same enrichments resulted in highergrowth rates and production of bacteria. However, bacterioplanktonwas simultaneously controlled by heterotrophic flagellates,as in the laboratory experiments the exclusion of flagellatesalways resulted in higher yields of bacteria of increased cellsize. There was also some evidence that the quality of substratesis of importance for microbial activities. The importance oftemperature was highlighted with the significant correlation(r2 = 0.59) between bacterial production and temperature withinthe range 0.62.1C. Thus, on the boreal zone the possiblewarming of climate may lead to enhanced activities in winter,but under unchanged light conditions no effects on primary productionwill be expected. 相似文献
18.
Cauchie Henry-Michel; Hoffmann Lucien; Thome Jean-Pierre 《Journal of plankton research》2000,22(12):2263-2287
The seasonal dynamics of metazooplankton biomass was monitoredin an aerated waste stabilization pond during three consecutiveyears (19941996). The pond showed a low diversity ofplanktonic metazoans because of elevated pH, relatively highconcentration of free dissolved ammonia and low oxygen concentration.The planktonic community was composed of the anomopod branchiopodDaphnia magna, and the cyclopoid copepods Cyclops vicinus andCyclops strenuus. Both predation by cyclopoids and competitionwith D.magna excluded rotifers from the pond, except duringa short period in spring 1996. Daphnia magna was the dominantorganism from a biomass point of view. In parallel with biomass,demographic parameters, secondary production and the spatialdistribution of D.magna were studied. A significant seasonaland interannual variation in the density, biomass and productionof D.magna was observed. The maximum density of daphnids variedfrom 264 x 103 to 686 x 103 individuals m2 and the maximumbiomass from 4 to 30 g dry weight (DW) m2. The annualnet production was high compared with the production of Daphniain natural environments, ranging from 288 to 593 g DW m2year1. The annual net production of exuviae accountedfor ~25% of the total annual net production. Harvesting of daphnidsfor commercial applications that took place during the productiveperiod did not have any discernible effect on the populationdynamics of D.magna. Sexual reproduction was not observed duringthe three studied years. Negative mortality rates, occurringduring early spring, however, indicated that recruitment fromephippia was effective in the pond of Differdange and that sexualreproduction took place before 1994. Swarming was regularlyobserved in relation to high densities. 相似文献
19.
Chlorophyll standing crop and phytoplankton production in the western Irish Sea during 1992 and 1993
Chlorophyll standing crop and phytoplankton production werestudied in the western Irish Sea over a 21 month period during1992 and 1993. For both years, the start of the production seasonwas first observed in Dundalk Bay and occurred progressivelylater in more northerly coastal and offshore waters. Standingcrop and production exhibited marked spatial heterogeneity with12.5- to 19-fold differences in crop observed over distancesof 2030 km. Distinct regional differences in the lengthof the production season were apparent. The longest season,67 months with a production of 194 g C m2, occurredin Dundalk Bay. The season lasted 34 months in the summerstratified region with a production of 140 g C m2. Northerly,offshore mixed waters and coastal waters of Northern Irelandsupported a short (23 months) season and production of194 and 140 g C m2, respectively. The similarity in seasonalproduction between Dundalk Bay and coastal waters of NorthernIreland, and between the summer stratified and northern mixedregions, is attributed to the intensity of production duringthe summer. Between 59 and 79% of seasonal production in thenorthern mixed region and coastal waters of Northern Irelandtook place during June and July, compared to 2940% inDundalk Bay and the summer stratified region. Lower summer productionin the latter two may be due to nutrient limitation and thishas implications for the sensitivity of these two regions toanthropogenic nutrient enrichment. 相似文献
20.
Feeding on natural plankton populations and respiration of thesmall cyclopoid copepod Oithona similis were measured duringthe warm season in Buzzards Bay, Massachusetts, USA. AlthoughO.similis did not significantly ingest small autotrophic andheterotrophic flagellates (28 µn), this copepodactively fed on >10 µm particles, including autotrophic/heterotrophic(dino)flagel-lates and ciliates, with clearance rates of 0.030.38ml animal1 h1. The clearance rates increased withthe prey size. O.similis also fed on copepod nauplii (mainlycomposed of the N1 stage of Acartia tonsa with a clearance rateof 0.16 ml animal1 h1. Daily carbon ration fromthe combination of these food items averaged 148 ng C animal1day1 (41% of body C day1), with ciliates and heterotrophicdino-flagellates being the main food source ({small tilde}69%of total carbon ration). Respiration rates were 0200.23µl O2 animal1 day1. Assuming a respiratoryquotient of 0.8 and digestion efficiency of 0.7, the carbonrequirement for respiration was calculated to be 125143ng C animal1 day1, close to the daily carbon rationestimated above. We conclude that predation on ciliates andheterotrophic dinoflagellates was important for O.similis tosustain its population in our study area during the warm season. 相似文献