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1.
Retusa obtusa held individually in the laboratory carried largeoocytes in the gonad but did not spawn in December-late January.In late Jan-early Feb, however, the first few individuals producedbatches of 817 eggs and, by early February, most individualswere producing means of 24 eggs d1 and maximain late Feb of <7.9 d1. Spawning declined to low levelsin few individuals in late March. By early April, spawning hadvirtually ceased prior to the drastic loss of adults in thepopulation by May. Larger R. obtusa generally produced more eggs than smaller onesand the few specimens shorter than 3.8 mm produced markedlyfewer than those of 3.85.0 mm shell length. Twenty of the 34 R. obtusa held in the main breeding period(4 sets started 29 Jan-3 Mar) spawned in 3 or more successiveweeks whereas only 6 of them failed to spawn in 2 consecutiveweeks, so indicating that several successive batches of eggsare commonly produced. Yet in virtually all individuals (exceptat the start of breeding) more eggs were produced in the firstweek of captivity than subsequently. These first-week valuesimply total production by individuals in the spawning seasonof some 112-305 eggs comprising about 2.8-7.6 mg dry weightor, by the Forth estuary population, of 26880-73200 eggs m2comprising 0.67-1.83 g dry weight m2. (Received 19 August 1988; accepted 30 September 1988) 相似文献
2.
Napp Jeffrey M.; Hopcroft Russell R.; Baier Christine T.; Clarke Cheryl 《Journal of plankton research》2005,27(5):415-426
Pseudocalanus species are important contributors to the secondaryproduction of the northern hemisphere mid- to high-latitudeoceans. In the coastal Gulf of Alaska, Pseudocalanus are presentyear round and are represented by three species. In 2001, Pseudocalanusmimus was the dominant Pseudocalanus species on the shelf duringspring and summer, comprising 30100% of the total, whilePseudocalanus newmani dominated in Prince William Sound (1090%).Pseudocalanus minutus were only abundant in Prince William Soundduring early spring. Egg production (by number and volume) wasa function of female prosome length and decreased from springto summer; however, significant variability was attributableto regional influences that were independent of size. For thesame sized female, P. newmani produced more eggs per clutchthan P. mimus. Pseudocalanus mimus, however, tended to havea larger mean egg size than P. newmani. Consequently, clutchvolumes of the two species were indistinguishable. Pseudocalanusegg production rates (EPRs) (eggs female1 day1)were lower in July and August (ca. 24) than April andMay (ca. 19), but total egg production by the population(eggs day1) was nearly equivalent for the two time periodsdue to higher female concentrations in summer. 相似文献
3.
Cerastoderma edule is the dominant member of a non-random CerastodermaNephthyscommunity, occupying a physically, homogeneous, submerged sandbankin the Limfjord, Denmark. C. edule is patchily distributed withinthis community, growth rates showing a clear density-dependence.Individual production is about 35%lower in high density patchesthan outside them; at low density annual individual flesh dryweight increment is 295 mg. Seasonal variation in water, ash,lipid, protein and glycogen contents is studied, and a sizedependent(= density-dependent) relationship is shown to exist for someparameters. Population production, estimated by a new graphicalmethod, and taking into account gametic and shell protein production,attains 150 g dry flesh weight, m2.yr1 at meanpopulation density rising to 250 g dry flesh weight. m2.yr1in the high density patches.
1Present address: Institut für Physiologische Chemie, Abt.Zellbiochemie, Universitat Hamburg, Martinistrasse 52, 2000Hamburg 20 (Received 10 March 1980; 相似文献
4.
Biomass and phosphorus distribution and accumulation rates wereestimated for an undisturbed subtropical rainforest in northernNew South Wales. The accumulation rates were estimated overa 16-year period. It is estimated that the steady-state above-groundbiomass for this forest is 35.0 tonne ha1. Most of theannual biomass production was replacing litterfall and mortality.The above-ground forest contained 52 kg P ha1 with agross annual accumulation of about 0.4 kg P ha1/yr1.The forest understorey and forest floor contained 4.7 kg P ha1and 7.9 kg P ha1, respectively. The annual uptake wasapprox. 4 kg P ha1 yr1. The phosphorus utilizationof this stand was compared with that of a Eucalyptus grandisplantation Sub-tropical rainforest, biomass accumulation, phosphorus cycling 相似文献
5.
The abundance, life span, growth and production of the mud snailsHydrobia minoricensis, H. ulvae and H. ventrosa in a semi-naturallagoon system were studied by taking monthly samples at threesites during 1991 and 1992. The most abundant species, H. minoricensisoccurred at mean densities of 12834 to 26264 snails m2(10.7 to 25.8g dry weigh m2), depending on the site.The least abundant species, H. ulvae, occurred at mean densitiesof 185 to 353 snails m2 (3.2 to 2.2g dry weight m2).The numerical abundance and biomass of the three Hydrobia specieswere positively related to the biomass of benthic macroalgae(P<0.01). Although H. ulvae egg capsules were recorded throughoutthe year, newly hatched snailsof this species were not observed,in contrast to the other two species. The early spring and summercohorts of H. minoricensis and H. ventrosa seemed to be themost numerous. The average life spans of these two species wereestimated to be about 18 and 13 months respectively. Annualproduction estimates for the whole lagoon system were 29.0 (6.3),5.5 (0.8) and 5.2 (1.0)g dry weight (ash-free dry weight) m2yr1 for H. minoricensis, H. ulvae and H. ventrosa respectively.The annual P/B ratio was about 2 for H. minoricensis and H.ventrosa. (Received 5 July 1994; accepted 5 October 1994) 相似文献
6.
Loliun perenne L. (cv.S. 23) was grown on vermiculite in winterin a heated greenhouse for 8 weeks under factorial combinationsof two potassium regimes (nominally 6 parts/106 and 156 parts/106in Hewitt's solution) and three densities of artificially supplementedvisible radiation flux (36.1, 7.3, and 2.2 W m2). Growthand potassium uptake were studied through the calculation ofvarious growth functions from fitted curves. There was little effect of potassium treatment but the experimentalmaterial responded markedly to light. Leaf-area ratio in thethree treatments showed extreme plasticity in increasing from23 x 102 through 6 x 102 to 89 x102 m2 g1 as light intensity decreased. Correspondingdecreases in unit leaf rate, however, caused over-all reductionsin relative growth rate. Specific absorption rates for potassium (AK, dry-weight basis)were strongly reduced at the lower light intensities but alsodisplayed complex ontogenetic drifts. Values of the allometricconstant, k (the ratio of root and shoot relative growth rates),decreased from c. 0.7 at 36.1 W m2 through c. 0.3 at7.3 W m2 to a value not significantly different fromzero (P < 0.05) at 2.2 W m2. In material grown under the two higher light intensities a constantinverse relationship was found between the mass ratio of rootand shoot and the corresponding activity ratio. The resultsconform to this model: Mass ratio = 0.001+45.0 (1/activityratio) where activity ratio is expressed as specific absorptionrate for potassium (in µg g root1 h1)/unitshoot rate (rate of increase of whole-plant dry weight per unitshoot dry weight, in mg g shoot1 h1). The implicationsof this relationship are discussed. 相似文献
7.
Grande Karen D.; Bender Michael L.; Irwin Brian; Platt Trevor 《Journal of plankton research》1991,13(1):1-16
In vitrorates of gross and net oxygen production were measuredas a function of light intensity in some plankton communitiescollected from Bedford Basin, Nova Scotia, and in a monoclonalculture of Synechococcus. The rate of gross oxygen productionwas measured by a technique in which the stable oxygen isotope,18O, serves as a photosynthetic tracer Net oxygen productionwas measured by automated Winkler technique. The rate of communityrespiration in the light was then determined by the differencebetween gross and net rates of oxygen production. In the naturalpopulations examined, neither gross nor net oxygen productionrates were significantly inhibited at the highest light intensitymeasured (500800 µE m2 s1) In a samplein which the dark respiration rate was small relative to themaximal rate of production [Pmax;sensu Platt et al (1980) JMar. Res., 38, 687701] the rates of lightrespiration were 3 times greater. In two other communities,with high rates of dark respiration relative to Pmaxthe ratesof light respiration were closer to rates of darkrespiration. In the Synechococcus clone, both gross and netoxygen production rates were inhibited at high light intensities.Rates of light respiration were found to varyas a function of light intensity. The greatest rates of respirationwere measured in samples incubated at light intensities thatwere just saturating (100 µE m2 s1). Therates of 14C production were also measured as a function oflight intensity The photosynthetic quotients, based on 14C productionrates and gross oxygen production rates, average 1 9 相似文献
8.
The effects of a population of the boring gastropod Natica tectaon the bivalve Choromytilus meridionalis were investigated atBailey's Cottage, False Bay, South Africa. In July 1979 theN. tecta density on the mussel bed averaged 69 m2 andthe population consisted mainly of reproductively mature individualsbetween 2033 mm shell width. Laboratory experiments on N. tecta showed that prey size selectionis an increasing function of predator size. The prey size rangetaken by large N. tecta is also greater than that taken by smallindividuals. The position of the borehole on the mussel shellis a function of the way in which the shell is held by the footduring the boring process. Consumption rates measured in thelaboratory showed an increase from approximately 1 kJ per weekin 18 mm N. tecta to 4.5 kJ per week in 28 mm individuals. Populationconsumption in the field was calculated as 663 kJ m2month1. It was estimated that at this rate the standingcrop of mussels in the pool would be eliminated within 10 months.Field measurements showed significant depletion after 6 months. New spat settlement of mussels occur every 46 years.The growth curve shows that after one year the population meansize exceeds 30 mm shell length, which is beyond the prey selectionsize range of small N. tecta. It was concluded that at the timeof a new mussel settlement a niche is provided for the simultaneoussettlement and growth of juvenile N. tecta in high densities.However, within one year the increase in prey size, togetherwith depletion due to over-exploitation, limits population growthand density in N. tecta. (Received 14 March 1980; 相似文献
9.
Hydrococcus brazieri and Arthritica semen on a sandflat at Coodanup,Peel Inlet, Western Australia, accounted for 89.5% of totalmollusc numbers. The mean density of H. brazieri was 9487 m2and A. semen averaged 8105 m2. H. brazieri grew at 0.5mm month1 and reached maturity in 4 months; A. semengrew at 0.3 mm month1 and reached maturity in 6 months.Somatic production in the Peel-Harvey estuarine system was estimatedto be 0.5 g m2yr1for H. brazieri and 4.1 g m2yr1for A. semen. The positions of these two species in the estuarinefoodweb is discussed. (Received 26 June 1981; 相似文献
10.
Rates of ingestion and their variability between individual calanoid copepods: direct observations 总被引:1,自引:0,他引:1
Paffenhofer G.-A.; Bundy M.H.; Lewis K.D.; Metz C. 《Journal of plankton research》1995,17(7):1573-1585
The goals of this study were to determine rates of ingestionand fecal pellet release, and their variability, for individualplanktonic copepods over extended periods of time (>20 min).Ingestions and rejections of individual cells of the diatomThalassiosira eccentrica by adult females of the calanoid Paracalanusaculeatus were directly quantified by observing individual copepodscontinuously at cell concentrations ranging from 0.1 toli mm3l1.Average ingestion rates increased with increasing food concentration,but were not significantly different between 0.3 and 1.0 mm3l1(9.8 and 32.7 µg Cl1) of T.eccentrica. Rates ofcell rejections were low and similar at 0.1 and 0.3, but weresignificantly higher at 1.0 mm3 l1. The coefficientsof variation for average ingestion rates of individual copepodshardly differed between food concentrations, ranging from 17to 22%, and were close to those for average fecal pellet releaseintervals which ranged from 15 to 21%. A comparison betweenindividuals at each food concentration found no significantdifferences at 1.0; at 0.1 and 0.3 mm3l1, respectively,ingestion rates of four out of five females did not differ significantlyfrom each other. Average intervals between fecal pellet releaseswere similar at 0.3 and 1.0 mm3l1 of T.eccentrica, butsignificantly longer at 0.1 mm3 l1. Fecal pellet releaseintervals between individuals were significantly different ateach food concentration; these significant differences wereattributed to rather narrow ranges of pellet release intervalsof each individual female. Potential sources/causes of variabilityin the sizes and rates of copepods in the ocean are evaluated.
3Present address: Great Lakes Environmental Research Laboratory,2205 Commonwealth Boulevard, Ann Arbor, Ml 48105, USA 相似文献
11.
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
12.
The data of chlorophyll amounts in diverse bio-communities arecompiled and discussed with reference to matter production. The chlorophyll amount in euphotic zone of lakes and oceanswas less than 1 g/m2, mostly less than 0.1 g/m2. In phytoplanktonblooms it was ca. 0.11 g/m2. Large values of 520g/m2 were obtained in the outdoor mass cultures of Chlorella,in which the high population density and chlorophyll contentof the alga were observed. In terrestrial higher plant communitiesthe chlorophyll amount (ca. 110 g/m2) was usually higherthan in aquatic phytoplankton communities. The largest (13.3g/m2) was obtained with an evergreen gallery forest in Thailand.The chlorophyll amount of desert bio-community could be expectedto be as high as that in water blooms. The maximum chlorophyll amount in bio-communities seems to attainup to 20 g/m2 when the conditions are favorable.
1 Dedicated to Prof. H. TAMIYA on the occasion of his 60th birthday. (Received December 25, 1962; ) 相似文献
13.
The specific respiration rates of nodulated root systems, ofnodules and of roots were determined during active nitrogenfixation in soya bean, navy bean, pea, lucerne, red clover andwhite clover, by measurements on whole plants before and afterthe removal of nodule populations. Similar measurements weremade on comparable populations of the six legumes, lacking nodulesbut receiving abundant nitrate-nitrogen, to determine the specificrespiration of their roots. All plants were grown in a controlled-environmentclimate which fostered rapid growth. The specific respiration rates of nodulated root systems ofthe three grain and three forage legumes during a 714-dayperiod of vegetative growth varied between 10 and 17 mg CO2g1 (dry weight) h1. This mean value consistedof two components: a specific root respiration rate of 69mg CO2 g1 h1 and a specific nodule respirationrate of 2246 mg CO2 g1 h1. Nodule respirationaccounted for 4270 per cent of nodulated root respiration;nodule weight accounted for 1240 per cent of nodulatedroot weight. The specific respiration rates of roots lackingnodules and utilizing nitrate nitrogen were generally 2030per cent greater than the equivalent rates of roots from nodulatedplants. The measured respiratory effluxes are discussed in thecontext of nitrogen nitrogen fixation, nitrate assimilation. Glycine max, Phaseolus vulgaris, Pisum sativum, Medicago sativa, Trifolium pratense, Trifolium repens, soya bean, navy bean, pea, lucerne, red clover, white clover, nodule respiration, root respiration, fixation, nitrate assimilation 相似文献
14.
Zooplankton growth rates: the larvaceans Appendicularia, Fritillaria and Oikopleura in tropical waters 总被引:1,自引:0,他引:1
Hopcroft Russell R.; Roff John C.; Bouman Heather A. 《Journal of plankton research》1998,20(3):539-555
The growth rates of Appendicularia sicula, Fritillaria borealissargassi, Fritillaria haplostoma, Oikopleura dioica and Oikopleuralongicauda were determined from microcosms incubated in situat 23C in Jamaican waters. Experiments were conducted fromoligotrophic offshore waters, through mesotrophic Lime Cay andeutrophic Kingston Harbour in both natural and nutrient-enhancedphytoplankton communities. Length-weight relationships werecalculated for two of these species: O.longicauda log W=2.47log TL 6.10 and F.haplostoma log W=2.44 log TL 7.37,where weight (W) is in micrograms and trunk length (TL) is inmicrometres. Instantaneous growth rates averaged 1.72.5day1 for the five species and were observed as high as3.3 day1 These instantaneous rates are equivalent todaily specific growth rates averaging 4.611.4 and rangingup to 28. In larger genera, growth rates were related positivelyto picoplankton and nanoplankton concentration, and negativelyto the biomass of larvaceans, but in the smallest species growthwas unrelated to these factors. However, because the variabilityin these two factors within microcosms exceeded their naturalrange of variability, growth rates of larvaceans may normallybe unlimited by resources or population density effects.
1Present address :Monterey Bay Aquarium Research Institute 7700Sandholdt Road, Moss Landing, CA 95039-0628, USA
2Present address :Bedford Institute of Oceanography PO Box 1006,Dartmouth, Nova Scotia B2Y 4A2, Canada 相似文献
15.
The calanoid copepod, Eudiaplomus graciloides, was reared fromegg to adult on uni-algal diets (0.1. 0.5 and 2.5 mg dry wt11) using the green alga, Chlamydomonas reinhardtii,as food, or on a mixed diet consisting of Lake Esrom water filteredthrough a plankton net with pore size 45 µm and supplementedwith C. reinhardtii (2.5 mg dry wt 11). On the mixeddiet at 21.0°C growth in body dry wt (W, µg dry wt)was exponential, and the growth constants were 0.21 day1in the early to mid juvenile stage (N1 - C4) and 0.11 day1in the late juvenile to early adult stage (C4-A). At 14.5°Cthe corresponding growth rate constants were 0.10 and 0.08 day1.Similar growth rates were found at uni-algal concentrationsof 0.5 and 2.5 mg dry wt I1, and it was argued that thethreshold concentration for growth in Eudiaptomus was closeto 0.1 mg dry wt I1. The clearance (C, ml h1)of copepodites was measured on the uni-algal diets. The constantsof the regression (C = aWb) were: a = 0.125, b = 0.858 (2000C. reinhardtii ml1), a = 0.068, b = 0.849 (10 000), a= 0.028, b = 0.875 (50 000). Ingestion rates were calculatedfrom the clearances and the average algal concentrations. Atthe three food levels the average daily rations were 30, 67and 125% of body dry wt. The respiration rate (R, nl O2 h1)was measured in individuals reared on the mixed diet. The constantsof the regression (R = aWb) were: a = 4.82, b = 1.07 (nauplii,14.5°C), a = 4.17, b = 0.904 (copepodites and adults, 14.5°C),a = 6.87, b = 0.757 (copepodites and adults, 21.0°C). Nosignificant difference in the respiration rate of copepoditesreared on uni-algal diets and the mixed diet could be demonstrated.Energy budgets were calculated. The assimilation efficiencyand the gross growth efficiency of copepodites decreased markedlywith increasing food concentration, the net growth efficiencyvaried from an average of 0.44 at the lowest algal concentrationto 0.60 on the mixed diet. The results are discussed in relationto previous findings with both freshwater and marine copepods. 相似文献
16.
Summer coastal zooplankton biomass and copepod community structure near the Italian Terra Nova Base (Terra Nova Bay, Ross Sea, Antarctica) 总被引:7,自引:0,他引:7
Pane Luigi; Feletti Mirvana; Francomacaro Barbara; Mariottini Gian Luigi 《Journal of plankton research》2004,26(12):1479-1488
The structure of the zooplankton biotic community and of copepodpopulation in the coastal area of Terra Nova Bay (Ross Sea,Antarctica) was investigated during the 10th Italian AntarcticExpedition (1994/1995). Zooplankton biotic community consistedmainly of pteropods (Limacina helicina and Clione antarctica),Cyclopoid (Oithona similis), Poecilostomatoid (Oncaea curvata)and Calanoid (Ctenocalanus vanus, Paraeuchaeta antarctica, Metridiagerlachei and Stephos longipes) copepods, ostracods, larvalpolychaetes and larval euphausiids. Zooplankton abundance rangedfrom 48.1 ind m3 to 5968.9 ind m3, and copepodabundance ranged from 45.2 ind m3 to 3965.3 ind m3.The highest peak of zooplankton abundance was observed between25 m and the surface and was mainly due to the contributionof O. similis, O. curvata and C. vanus. Zooplankton biomassranged from 5.28 mg m3 to 13.04 mg m3 dry weight;the maximum value was observed between 25 m and the surface.Total lipid content varied from 216.44 to 460.73 mg g1dry weight. 相似文献
17.
Planktonic primary production in the German Wadden Sea 总被引:8,自引:0,他引:8
By combining weekly data of irradiance, attenuation and chlorophylla concentrations with photosynthesis (P) versus light intensity(E) curve characteristics, the annual cycle of planktonic primaryproduction in the estuarine part of the Northfrisian WaddenSea was computed for a 2 year period. Daily water column particulategross production ranged from 5 to 2200 mg C m2 day1and showed a seasonal pattern similar to chlorophyll a. Budgetcalculation yielded annual gross particulate primary productionsof 124 and 176 g C m2 year1 in 1995 and 1996,respectively. Annual amounts of phytoplankton respiration, calculatedaccording to a two-compartment model of Langdon [in Li,W.K.W.and Maestrini,S.Y. (eds), Measurement of Primary Productionfrom the Molecular to the Global Scale. International Councilfor the Exploration of the Sea, Copenhagen, 1993, pp. 2036],and dissolved production in 1996, were both in the range of2439 g C m2 year1. Annual total net productionwas thus very similar to particulate gross production (127 and177 g C m2 year1 in 1995 and 1996, respectively).Phytoplankton growth was low or even negative in winter. Inspring and summer, production/biomass (Pr/B) ratios varied from0.2 up to 1.7. Phytoplankton growth during the growth seasonalways surpassed average flushing time in the area, thus underliningthe potential of local phytoplankton bloom development in thispart of the Wadden Sea. The chlorophyll-specific maximum photosyntheticrate (PBmax) ranged from 0.8 to 9.9 mg C mg1 Chl h1and was strongly correlated with water temperature (r2 = 0.67).By contrast, there was no clear seasonal cycle in B, which rangedfrom 0.007 to 0.039 mg C mg1 Chl h1 (µmolphotons m2 s1)1. Its variability was muchless than PBmax and independent of temperature. The magnitudeand part of the variability of PBmax and B are presumably causedby changes in species composition, as evidenced from the rangeof these parameters found among 10 predominant diatom speciesisolated from the Wadden Sea. The ratio of average light conditionsin the water column (Eav) to the light saturation parameterEk indicates that primary production in the Wadden Sea regionunder study is predominantly controlled by light limitationand that nutrient limitation was likely to occur for a few hoursper day only during 5 (dissolved inorganic nitrogen) to 10 (PO4,Si) weeks in the 2 year period investigated. 相似文献
18.
Peterson William T.; Painting Suzanne J.; Hutchings Laurence 《Journal of plankton research》1990,12(2):259-281
The gut fluorescence technique was used to estimate ingestionand filtration rates of the adult female copepods Paracalanusparvus, Cenlropages brachiatus and Calanus austrails, and copepoditestages 3, 4 and 5 of C.australis in the southern Benguela upwellingregion. During the study period chlorophyll concentrations withinthe upper 20 m of the water column were high, 5 µg I1in mid-shelf waters and 1530 µg I1 in innershelf waters. Copepod gut pigment content was low and constantduring the day then increased sharply during the first 2 h aftersunset. Gut pigment content was 26 times higher duringthe night compared with daytime values. Small non-migratingcopepods (Paracalanus parvus) showed the smallest diel differencein gut pigment content and large migrating copepods (Centropagesbrachiatus and Calanus australis) the largest difference. Eggproduction rates were 20 and 50% of maximum at the mid-shelfand inner shelf stations respectively, suggesting food-limitation.Comparison of ingestion rates calculated from egg productiondata with ingestion rates calculated from gut pigment data suggestedthat the copepods were feeding omnivorously at the inner shelfstations but herbivorously at the mid-shelf stations. Assumingthat all of the phytoplankton was available as food, the nearshorecopepod assemblage grazed {small tilde}1% of the standing cropeach day, and the mid-shelf assemblage grazed 5% day1.Because of errors and uncertainties associated with the gutfluorescence technique, the feeding impact could be underestimatedby 24-fold. We discuss several approaches which couldlead to more precise estimates of feeding rates.
3Present address: Marine Sciences, SUNY, Stony Brook, NY, 11794-5000,USA 相似文献
19.
In the stoichiometric study of phytozooplankton interactions,a controversy exists about how Daphnia species regulate theirfeeding rate when submitted to low-quality food (i.e. high dietarycarbon:phosphorus [C:P] ratio). In this study, we gathered dataover 3 years on in situ clearance rates of a Daphnia galeatapopulation, by conducting grazing experiments from April 1998to October 2000 in the Esch-sur-Sûre reservoir (Grand-Duchyof Luxembourg). Observed clearance rates (2.513.5 mLindividual1 day1, mean 7.0 mL individual1day1) were correlated with population and environmentalvariables. Mean body size of Daphnia individuals was the bestpredictor of clearance rate (r2 = 0.639), followed by watertemperature (r2 = 0.262) and P concentration in the seston (r2 相似文献
20.
COMPARATIVE LIFE-CYCLE, BIOMASS AND SECONDARY PRODUCTION OF THREE SYMPATRIC FRESHWATER GASTROPOD SPECIES 总被引:1,自引:0,他引:1
The life cycles, biomass and secondary production of three sympatricfreshwater basommatophoran snails, Lymnaea palustris (MÜller),Physa fontinalis Linnaeus and Anisus rotundatus (Poiret) werestudied during two years in a freshwater ditch. L. palustrisexhibited an iteroparous life-cycle whereas the two other speciespresented a semelparous life-cycle, adults died just after oviposition.L. palustris secondary production (dry weight) value was higher(P = 11 298.4 mg 0.1 m1 yr1) than those of P.fontinalis (P = 846.3 mg 0.1 m2 yr1) and A. rotundatus(P = 1192 mg 0.1 m2 yr1). (Received 16 March 1992; accepted 30 June 1992) 相似文献