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1.
The extent of chlorophyll (Chi) a degradation into colorlessproducts by the copepod Acartia clausi was determined by measuringgut fluorescence prior to fecal pellet production. The efficiencyof pigment degradation of animals fed at different concentrationsof Thalassiosira weiss-fiogii varied between 30.56 and 94.05%,and the quantity of pigments lost during gut passage was directlyrelated to total ingestion. The role of feeding history in pigmentdestruction was tested. The fraction of ingested Chi a degradedby copepods acclimated to a high food concentration (15 ng Chla ml1) was greater than the fraction degraded by thoseacclimated to a low food concentration (1.5 ng Chl a ml1).The percentage of ingested Chl a that A.clausi transformed intofluorometrically undetected compounds was not constant. At present,knowledge of the pigment destruction process indicates thatChi a and Chi --derived pigments are not considered useful quantitativetracers of the feeding activity of copepods. The results ofthis study suggest a reassessment of the application of thegut fluorescence method to evaluate grazing activity of thecopepod A.clausi 相似文献
2.
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
3.
The relative importance of food and temperature to copepod egg production and somatic growth in the southern Benguela upwelling system 总被引:2,自引:0,他引:2
The fecundity and somatic growth rates of Calanus agulhensisand Calanoides carinatus, the dominant large calanoid copepodsin the southern Benguela upwelling system, as well as the fecundityof several other common copepods, were measured between Septemberand March of 1993/94 and 1994/95. Mean egg production of mostcopepods was low at >30 eggs female-1 day-1 {Calanoides carinatus23.7, Calanus agulhensis 19.0, Neocalanus tonsus 16.1 and Rhincalanusnasutus 26.1), whereas the mean fecundity of Centropages brachiatuswas significantly greater (83.6 eggs female1 day-1).This study also presents the first comprehensive field estimatesof the fecundity of Nanno-calanus minor (mean: 26.1 eggs female1day1, range: 0.096.2 eggs female1 day1)and of somatic growth of N6 and all copepodite stages of Calanoidescarinatus (decreasing from 0.58 day1 for N6 to 0.04 day1for C5). Somatic growth rates of Calanus agulhensis also declinedwith age: from 0.57 day1 for N6 to 0.09 day1 for C5. Data ongrowth rates were used to assess the relative importance offood [as measured by total chlorophyll (Chi) a concentration],phytoplankton cell size (proportion of cells >10 µm)and temperature to the growth of copepods. Multiple regressionresults suggested that fecundity and somatic growth rates werepositively related to both Chi a concentration and phytoplanktoncell size, but not to temperature. Although it was not possibleto separate the effects of Chi a concentration and phytoplanktoncell size, data from previous laboratory experiments suggestthat copepod growth is not limited by small cells per se, butby the low Chi a concentrations that are associated with theseparticles in the field. Despite growth not being directly relatedto temperature, a dome-shaped relationship was evident in somespecies, with slower growth rates at cool (<13°C) andwarm (>18°C) temperatures. The shape of this relationshipmirrors that of Chi a versus temperature, where poor Chi a concentrationsare associated with cool and warm temperatures. It is concludedthat the effect of food limitation on growth of copepods outweighsthat of temperature in the southern Benguela region. Sourcesof variability in relationships between growth and Chi a concentrationare discussed. 相似文献
4.
Cohen Jonathan H.; Tester Patricia A.; Forward Richard B. Jr 《Journal of plankton research》2007,29(3):301-315
Apart from grazing interactions, little is known regarding thesublethal effects of Karenia brevis cells on copepod behavior.We conducted grazing and mortality experiments with K. breviscells and brevetoxins (PbTx-2), establishing routes of toxicityfor the copepods Acartia tonsa, Temora turbinata and Centropagestypicus. Subsequent behavioral experiments determined whethercopepod swimming and photobehavior, both behaviors involvedin predator avoidance, were impaired at sublethal K. brevisand PbTx-2 levels. Copepods variably grazed toxic K. brevisand non-toxic Prorocentrum minimum at bloom concentrations.Although copepods accumulated brevetoxins, significant mortalitywas only observed in T. turbinata at the highest test concentration(1 x 107 K. brevis cells L1). Acartia tonsa exhibitedminimal sublethal behavioral effects. However, there were significanteffects on the swimming and photobehavior of T. turbinata andC. typicus at the lowest sublethal concentrations tested (0.15µg PbTx-2 L1, 1 x 105 K. brevis cells L1).Although physiological incapacitation may have altered copepodbehavior, starvation likely played a major role as well. Thesedata suggest that sublethal effects of K. brevis and brevetoxinon copepod behavior occur and predicting the role of zooplanktongrazers in trophic transfer of algal toxins requires knowledgeof species-specific sublethal effects. 相似文献
5.
Gut clearance rates of starving and continuously feeding Acartiatonsa were estimated. During the initial 30 min the rates weresimilar (0.045 and 0.048 min1, respectively; 14°C)but thereafter starving animals expelled the remains of theirgut contents at half the rate (0.019 min1) of fed ones(0.048). Pigment destruction was estimated by (i) incubationexperiments over 34 days, (ii) silica to pigment ratioin algae and faeces and (iii) by gut filling experiments. Theincubations showed that 8% of the ingested pigments were destroyedto nonfluorescent residues during gut passage. The silica topigment ratio method gave an average of 11 % (1 24) destructionand gut-filling experiments showed no systematic differencebetween ingestion measured as gut filling rate (fluorescence)and particle reduction.
1Present address: Kristineberg Marine Biological Station, S-45034 Fiskebäckskil, Sweden 相似文献
6.
We examined the relationship between egg production rate (E)and pigment ingestion rate (I, from gut content corrected for33% loss) for adult female Temora longicornis in Long IslandSound on 47 occasions. Linear regression of E on I [both variablesexpressed in mass of nitrogen (N) female1 day1]was: EN = 0.0016 + 0.770 x IN. The slope, 0.77, is the apparentgross efficiency of egg production, equivalent to the grossgrowth efficiency (GGE) assuming that females partition allnitrogen for growth into egg production. Published work suggeststhat a GGE of 0.37 would be expected for herbivorous copepods.The discrepancy between the expected value of 0.37 and observedvalue of 0.77 could result from unquantified losses of gut pigmentor because T.longicomis ingested a significant amount of nitrogenby feeding as a carnivore. We suggest that if T.longicomis femalesderive all of their nitrogen for growth by feeding on phytoplankton,and if no correction for pigment loss is employed, then thegut pigment method underestimates pigment ingestion by no morethan a factor of two. 相似文献
7.
Mesozooplankton grazing under conditions of extreme eutrophication in Guanabara Bay, Brazil 总被引:1,自引:0,他引:1
Schwamborn R.; Bonecker S. L. C.; Galvao I. B.; Silva T. A.; Neumann-Leitao S. 《Journal of plankton research》2004,26(9):983-992
The objective of the present study was to quantify mesozooplanktongrazing in the eutrophic waters of Guanabara Bay. Mesozooplankton(>200 µm) was dominated by the copepods Acartia lilljeborgi,Acartia tonsa, Parvocalanus crassirostris and Paracalanus furcatus.Dinoflagellates, specifically the species Prorocentrum triestinum,were an important group for mesozooplankton nutrition, beingingested in significant amounts during all experiments. On average,12.3 ± 2.9 P. triestinum cells were ingested copepod1min1 (other dinoflagellates: 11 ± 8 cells copepod1min1). Filamentous cyanophyceae and nanoplankton wereingested in one experiment each, but the mesozooplankton communitygenerally preferred dinoflagellates to these groups, which werealways abundant in the water column. Euglenophyceae were notingested, although they dominated in one experiment. Mesozooplanktoningested, on average, only 0.2% of the nano- and microplanktonbiomass per day. The results suggest that grazing was not acontrolling process for the nano- and microplankton communityin the study area. Addition of zoeae larvae of Chasmagnatusgranulata (Decapoda: Brachyura: Grapsidae) in one experimenthad a significant effect on the mortality of adult copepods,probably due to a predatorprey relationship. 相似文献
8.
The pelagic harpacticoid copepod Macrosetella gracilis usesthe colonial cyanobacterium Trichodesmium not only as a physicalsubstrate for juvenile development, but also as a food source.By associating itself with a buoyant colonial cyanobacterium,M.gracilis has developed a successful mode of life for existencein the plankton. Further evidence of M.gracills' dependenceon Trichodesmium as a physical substrate is demonstrated bypreviously undescribed microscopic observations of a gravidM.gracilis female attaching eggs to a Trichodesmium colony.Shipboard experiments investigating the ingestion and assimilationof Trichodesmium carbon (C) were conducted in September 1991and January/February 1992 in waters of the Bahamas and the Caribbean,respectively. Macrosetella gracilis not only ingested, but rapidlyincorporated, cyanobacterial organic matter into its own cellularmaterial. Utilization of ingested Trichodesmium by M.graciliswas investigated by assessing the metabolic partitioning andincorporation of 14C-labelled Trichodesmium into copepod lipids,proteins, polysaccharides and low-molecular-weight (LMW) compoundsusing sequential biochemical fractionation techniques. Despitevariations in grazing rates between the two sites and times(September 1991,0.017 µg C* µg1 C h1;January 1992, 0.134 µg C * µg1 C h1,the partitioning of incorporated C into the different biochemicalfractions was relatively consistent. There was rapid assimilationof ingested C into the LMW ({small tilde}60%) and polysaccharidefractions ({small tilde}30%) in the first few hours, with asubsequent increase in the percent C incorporated into protein.On average, {small tilde}21% of the Trichodesmium C ingestedby M.gracilis was assimilated. Therefore, M.gracilis is an importantsecondary link in the food web of oligotrophic waters whereTrichodesmium is abundant. 相似文献
9.
Ammonium release rates by individual marine copepods (Eucalanuspileatus) were examined kinetically over successive 10-min intervalsafter the animals were exposed to three concentrations of thediatom Thalassiosira fluviatilis as food. Food concentrationsspanned those expected in the natural environment. "Well-fed"(3 mm3 T. fluviatilis l1) copepods released ammoniumsignificantly (p<0.05) faster than those fed zero or lowconcentrations of food, but differences were not dramatic. Meanexcretion rates (± SE) for animals removed from foodfor 18 22 h [30 ± 6 nmol NH4(mg ash free dry weight)1h 1] were 60% of those for "well-fed" animals [49 ±8 nmol NH4 (mg ash free dry weight)1 h1]. Continuedhigh release rates after extended periods without food suggestthat E. pileatus must feed frequently in nature to maintainan adequate nitrogen balance. Depending on food concentration,animals released ammonium at rates ranging from 40 to > 100%of their N ingestion rates over the previous 1822 h.Long-term (46 h) kinetic excretion experiments with "well-fed"animals indicated that, on average, release rates decreasedwith time after food removal, but patterns varied among individualcopepods. In addition to ammonium release, o-phthalaldehydereactive amino acid nitrogen was occasionally released by E.pileatus in large "spurt events" lasting from 20 to 60 min.
1GLERL Contribution No. 283 相似文献
10.
Temporal variability in copepod fecundity during two different spring bloom periods in coastal waters off Plymouth (SW England) 总被引:2,自引:0,他引:2
Bautista Begoa; Harris Roger P.; Rodriguez Valeriano; Guerrero Francisco 《Journal of plankton research》1994,16(10):1367-1377
The temporal variation in egg production of the planktonic copepodsCalanus helgolandicus, Temora longicornis and Pseudocalanuselongatus was studied during two different spring bloom periodsin 1989 and 1990 by weekly sampling at two permanent stationsin coastal waters off Plymouth (SW England). Copepod egg productionwas estimated in situ by incubating individual adult femalesin filtered seawater for 24 h (72 h until hatching for P.elongatus)at the field surface temperature. The relationship between copepodegg production rates and: (i) chlorophyll a concentration (totaland >10 µm size fraction), (ii) temperature and (iii)initial copepod gut pigment content was investigated. The springbloom periods were very different in both years, with the occurrenceof a Phaeocystis sp. bloom in 1990, which negatively affectedthe feeding and fecundity of copepods. Egg production ratesin spring 1989 were significantly correlated with chlorophylla concentration (particularly with the >10 µm fraction),field temperature and copepod gut pigment contents. In spring1990, egg production rates were also correlated with copepodgut pigment contents, but no significant correlations were obtainedwith temperature or with chlorophyll a concentration, as a consequenceof the lower egg production rates obtained during the Phaeocystissp. dominance period. These results show that food availabilityis the factor which mainly affects the fecundity of neriticcopepods in short time periods. 相似文献
11.
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
12.
The relationship between ingestion rate and gut transit timeof the calanoid copepod Acartia clausi was examined in laboratoryexperiments with five different diets: (i) living cells of thediatom Thalassiosira weissflogii, (ii) detrital cells of thesame diatom, (iii) 50:50 mix of the two previous diets on aprotein basis, (iv) dinoflagellate cells of Prorocentrum micansand (v) Prorocentrum minimum. Ingestion followed a Holling type2 response for diets 1 and 4 and a linear one for diets 2, 3and 5. Gut transit time varied with food abundance only whenthe copepods were fed with the living diatom. The gut evacuationrate increased with the concentration of T. weissflogii withvalues of 0.010, 0.020, 0.032, 0.042 min1, correspondingto gut transit time of 97, 50, 31 and 24 min, measured at 50,110, 130 and 275 µg protein L1, respectively. Copepodsfed with dinoflagellates, mixed and pure detrital diets exhibitedlonger and similar gut transit times ranging from 85 to 166min, depending on diet. The coupling between ingestion rateand gut transit time measurements is discussed in the contextof copepod feeding strategies. 相似文献
13.
Jonasdottir Sigrun H.; Trung Nguyen Huu; Hansen Frank; Gartner Sanne 《Journal of plankton research》2005,27(12):1239-1259
Spatial and seasonal egg production rates (Er) and egg hatchingsuccess in the copepods Calanus finmarchicus and Calanus helgolandicuswere measured in the North Sea from March to September. Foodavailability was monitored by chlorophyll and protist concentrationsand three size fractions of seston fatty acids. Seasonal andspatial distribution and production differed between the species.Calanus finmarchicus was found only offshore of the 50-m isobath,with decreasing Er (3728 eggs female1 day1)from March to July. Calanus helgolandicus had two abundancepeaks, in spring and autumn, with a low in May during whichtime the highest Er were observed (38 eggs female1 day1).At other times, Er in C. helgolandicus remained lower than inC. finmarchicus ( 相似文献
14.
Copepod egg production, moulting and growth rates, and secondary production, in the Skagerrak in August 1988 总被引:5,自引:0,他引:5
Peterson William T.; Tiselius Peter; Kiorboe Thomas 《Journal of plankton research》1991,13(1):131-154
Measurements of hydrography, chlorophyll, moulting rates ofjuvenile copepods and egg production rates of adult female copepodswere made at eight stations along a transect across the Skagerrak.The goals of the study were to determine (i) if there were correlationsbetween spatial variations in hydrography, phytoplankton andcopepod production rates, (ii) if copepod egg production rateswere correlated with juvenile growth rates, and (iii) if therewas evidence of food-niche separation among co-occumng femalecopepods The 200 km wide Skagerrak had a stratified water columnin the center and a mixed water column along the margins. Suchspatial variations should lead to a dominance of small phytoplanktoncells in the center and large cells along the margins; however,during our study blooms of Gyrodinium aureolum and Ceratium(three species) masked any locally driven differences in cellsize: 50% of chla was >11 µm, 5% in the 1150µm fraction and 45% <50 µm. averaged for allstations. Chlorophyll ranged from 0.2 to 2.5 µg l1at most depths and stations. Specific growth rates of copepodsaveraged 0.10 day1 for adult females and 0.27 day1for juveniles The latter is similar to maximum rates known fromlaboratory studies, thus were probably not food-limited. Eggproduction rates were food-limited with the degree of limitationvarying among species: 75% of maximum for Centropages typicus, 50% for Calanus finmarchicus, 30% for Paracalanus parvus and 15% for Acartia longiremis and Temora longicornis. Thedegree of limitation was unrelated to female body size suggestingfood-niche separation among adults. Copepod production, summedover all species, ranged from 3 to 8 mg carbon m3day1and averaged 4.6 mg carbon m1 day1. Egg productionaccounted for 25% of the total. 相似文献
15.
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
16.
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
17.
Katechakis Alexis; Stibor Herwig; Sommer Ulrich; Hansen Thomas 《Journal of plankton research》2004,26(6):589-603
Selectivity-size spectra, clearance and ingestion rates andassimilation efficiencies of Acartia clausi (Copepoda), Peniliaavirostris (Cladocera) and Doliolum denticulatum (Doliolida)from Blanes Bay (Catalan Sea, NW Mediterranean) were evaluatedin grazing experiments over a wide range of food concentrations(0.028.8 mm3 L1 plankton assemblages from BlanesBay, grown in mesocosms at different nutrient levels). Acartiaclausi reached the highest grazing coefficients for large algae>70 µm (longest linear extension), P. avirostris forintermediate food sizes between 15 and 70 µm, and D. denticulatumfor small sizes from 2.5 to 15 µm. Penilia avirostrisand D. denticulatum acted as passive filter-feeders. Acartiaclausi gave some evidence for a supplementary raptorial feedingmode. Effective food concentration (EFC) decreased linearlywith increasing nutrient enrichment for D. denticulatum andfollowed domed curves for A. clausi and for P. avirostris withmaximum values at intermediate and high enrichment levels, respectively.Clearance rates of crustacean species showed curvilinear responseswith narrow modal ranges to increasing food concentration. Clearancerates of D. denticulatum increased abruptly and levelled intoa plateau at low food concentrations. Mean clearance rates were13.9, 25.5 and 64.1 mL ind.1 day1, respectively.No clearance could be detected for A. clausi at food concentrations<0.1 mm3 L1 and for P. avirostris at food concentrations 相似文献
18.
Miralto A.; Ianora A.; Guglielmo L; Zagami G.; Buttino I. 《Journal of plankton research》1998,20(12):2369-2378
In situ rates of egg production and hatching success are reportedfor Calanus simillimus, one of the most abundant calanoid speciesin peri-Antarctic regions, during the Italian Italicscruise in the Straits of Magellan in March-April 1995. Low fecundity(8.6 eggs female1 day1) and fecal pellet production(0.8 fecal pellets female1 day1) in this periodindicate that the species was feeding very poorly. Sixty-sixof the 126 females sampled did not produce eggs and 80 of thesedid not produce any fecal pellets during the 24 h period ofincubation. Striking abnormal naupliar and embryonic developmentwas recorded in 81.8% of the eggs spawned. Aberrant eggs didnot undergo normal cleavage, and failed to develop to hatching.Deformed nauplii were asymmetrical and presented strong anatomicalanomalies in the total body length and number of swimming appendages.These results are discussed in the light of recent findingson the causes of low hatching success in copepods. 相似文献
19.
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
20.
Egg production, growth and development rates of Oithona similiswere measured in the laboratory as a function of food concentrationand composition. On an optimum diet, development is isochronaland growth is near exponential. The maximum juvenile growthrate at 15C (0.2 day1) is similar to juvenile growthin calanoid copepods. The maximum weight-specific egg productionrate (0.1 day1), on the other hand, is substantiallyless than in free-spawning calanoids, but similar to that inegg-carrying calanoids. In the Kattegat, Oithona spp. egg productionis strongly limited by food during summer and controlled bytemperature during winter. The seasonal signal in fecundityand population biomass is much weaker than in the co-occurringfree-spawning calanoid genera, where fecundity and populationbiomass undergo dramatic seasonal viaration.
1Present address: Instituto Nacional de Investigacin y DesarrolloPesquero, INIDEP, CC 175, Playa Grande, Mar del Plata, Argentina 相似文献