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1.
We have utilized data from a recently developed three-dimensionalvelocity fluctuation meter to compute the dissipation of turbulentkinetic energies (TKE) and the intensity of turbulent mixingin horizontal and vertical planes in the pelagic, epilimnicwater of Lake Kinneret, Israel. These characteristics of wind-inducedturbulent movement have been monitored from January 1992 throughDecember 1996. The turbulence parameters were strongly correlatedto wind energy inputs, calculated daily as 5 day cumulativeinputs. There have been dramatic changes in the annual and seasonaldevelopment of phytoplankton, together with unusually high levelsof primary production in this lake since 1994. We observed differentpatterns of vertical and horizontal turbulent movement and ofTKE dissipation rates during the years when unusualphytoplankton development occurred (19941996) comparedto normal years (1992, 1993). The first appearanceof the filamentous cyanobacterium Aphanizomenon in this lakein AugustSeptember 1994 coincided with a period of markedlylower rates of TKE dispersion and a shift from vertical to horizontaldominance of the turbulent eddy spins. The absence of a regularwinter-spring bloom of the dinoflagellate, Peridinium, in 1996occurred when dissipation rates of TKE were extremely high,while record high amounts of dinoflagellates (1994, 1995) appearedwhen dissipation rates were very low. Correlations were shownbetween phytoplankton parameters (chlorophyll, primary productionand the ratio of primary production to chlorophyll) and boththe dissipation rate of TKE and the intensity of water turbulentmixing in the vertical plane. We suggest that the changes inthe turbulence climate of Lake Kinneret were animportant factor in determining shifts in phytoplankton successionand the population composition of the algal assemblage. 相似文献
2.
Phytoplankton population dynamics in perennially ice-covered Lake Fryxell, Antarctica 总被引:1,自引:0,他引:1
Spaulding Sarah A.; MCKnight Diane M.; Smith Richard L.; Dufford Richard 《Journal of plankton research》1994,16(5):527-541
Phytoplankton were collected over five austral summers (198788through 199192) to examine seasonal and annual fluctuationsin species composition and biovolume in Lake Fryxell, a perenniallyice-covered lake located in the Dry Valleys of South VictoriaLand, Antarctica. Lake Fryxell has perennial gradients of salinity,dissolved oxygen and nutrients. We found that algal speciesdiversity was low (56 taxa were collected), confirming the resultsof previous short-term studies. The phytoplankton consistedprimarily of cryptophyte and chlorophyte flagellates, and filamentouscyanobacteria. The presence of filamentous cyanobacteria, whichhave not been reported as abundant in this lake by previousworkers, may represent a significant ecological change. Eachaustral summer, one dominant species contributed >70% ofthe total biovolume; Chroomonas lacustris was dominant in 198788,while Cryptomonas sp. dominated the phytoplankton in the remaining4 years. No species succession occurred during the austral summer.Some common taxa were vertically stratified (Oscillatoria limnetica,Phormidium angustissimum, Pyramimonas sp., Oscillatoria sp.),while others showed no distinct vertical stratification (Chlamydomonassubcaudata, Cryptomonas sp.). The stratification of the phytoplanktonreflects the gradients of nutrients and light, and the stabilityof the water column. 相似文献
3.
Diel patterns of photosynthate biosynthesis by phytoplankton in permanently ice-covered Antarctic lakes under continuous sunlight 总被引:3,自引:0,他引:3
Priscu J.C.; Priscu L.R.; Howard-Williams C.; Vincent W.F. 《Journal of plankton research》1988,10(3):333-340
Diel patterns of photosynthate biosynthesis by Antarctic freshwaterphytoplankton growing under the variable but continuous sunlightof summer were found to be similar in many respects to thosereported from other aquatic environments where light/dark periodsalternate. Lipid synthesis by freshwater phytoplankton in LakesVanda and Fryxell predominated during periods when solar radiationand photosynthesis were most intense; the inverse was generallytrue of the protein and polysaccharide fractions. The majorphotosynthetic end-products in both lakes were protein and polysaccharide,which together accounted for 6081% of the total cellularcarbon incorporation. Less than 4% of the carbon was incorporatedinto lipid in Lake Vanda; >12% appeared in the lipid fractionin Lake Fryxell. The Lake Fryxell populations showed evidenceof photoinhibition of complete photosynthesis during middaywhen irradiance was most intense. Ik values, computed from thephotosynthesis irradiance relationships in Lake Fryxell, corroborateother studies suggesting that the phytoplankton populationsin permanently ice-capped Antarctic lakes are among the mostshade-adapted yet reported. 相似文献
4.
The structure and dynamics of the phytoplankton assemblages in Lake Kinneret, Israel 总被引:3,自引:0,他引:3
The phytoplankton of Lake Kinneret, a warm monomictic lake,is dominated by a Pyrrhophyta-Chlorophyta assemblage. Four stagesof succession of planktonic algae occur in the lake, startingwith thermal and chemical destratification and ending with stratification. The index of diversity of the phytoplankton communities is highduring the destratification and mixed periods. The index reachesminimal values during late summer, when the ecosystem is subjectto strong physical, chemical and biological stresses. The diversityin Lake Kinneret increases with the increase in nutrients andnot with the increase in temperature. During most of the year, the nanoplanktonic forms are in greaternumbers than the netplankton species. This fact is correlatedwith the amounts of available nutrients in the lake. The annual averages of the wet autotrophic biomass in Lake Kinneretare very high in comparison with other warm lakes. The contributionof the nanoplanktonic species to the total algal biomass isvery small during the Peridinium bloom, but represents approximatelyhalf of the total algal biomass during the rest of the year. The concentration of nutrients in the water, together with theadverse competitive effect of Peridinium on other algae, areto a large extent responsible for the composition, successionand abundance of the phytoplankton assemblages in Lake Kinneret. 相似文献
5.
Importance of intermediate disturbances for the species composition and diversity of phytoplankton in two very different Berlin lakes 总被引:2,自引:2,他引:0
Species composition and diversity of phytoplankton were studied for several years in two lakes which differ with respect to mixing conditions and nutrient limitation: Schlachtensee regularly stratifies very stably. In contrast, size and wind-exposure predispose Lake Tegel to deeper mixing; additionally, stratification is artificially destabilized by aeration. As the duration of aeration was varied, the study period includes interannual changes in mixing conditions. For both lakes, it also covers trophic change due to restoration; this was especially pronounced in Schlachtensee.Results show that mixing conditions affect species composition on two levels: on a superordinate level, lake morphology or hydrology govern stability of stratification and susceptibility to perturbation, and hence the extent to which motile species can develop. In Schlachtensee, species with some means of actively seeking preferred depths usually dominated during summer stratification: Planktothrix agardhii during the hypertrophic phase, and flagellates since restoration. In contrast, in Lake Tegel deeper mixing as a generally prevailing condition favored non-motile species. Their seasonal pattern was remarkably constant from year to year. Although changes in the extent of mixing were pronounced during the four years studied (1987–1990), these were within a range that affected species composition only slightly: in summer, cyanobacteria and diatoms represented climax species whose dominance was not offset by additional, weather-induced increases of turbulence.On a subordinate level, and within the constraints set by nutrient limitation as well as by grazing pressure, small-scale changes in mixing conditions caused by meteorological cycles were shown to strongly affect species composition and in consequence diversity: Results for the fouryear post-restoration study period at Schlachtensee show that considerable interannual variations of species composition and diversity can be attributed to variations in the frequency of meteorological changes. In accordance with the intermediate disturbance hypothesis (IDH), diversity was lowest during 1989, the year with the longest and most pronounced cycles of fair weather (14 to 27 fair days on end). However, the mechanism for this was rarely a decline of diversity caused by competitive exclusion within single long phases of stable conditions, as conceived by the intermediate disturbance hypothesis. Instead, diversity responded to changes in mixing conditions with a variety of patterns — often with low values during phases of increased mixing and with high values under quiescent conditions, especially during the first calm days just after increased mixing. Thus, not disturbance as such, but rather the rate of change between phases of disturbance and quiescence appears to determine the frequency of high diversity indices.In Lake Tegel, high diversity indices were somewhat more frequent in 1989, the year during which thermal stratification was most stable. For species adapted to frequent or continuous mixing, interjected calm phases with unusually high stability of thermal stratification may represent a disturbance of accustomed conditions. Thus, in turbulent Lake Tegel, meteorological cycles appear to act in reversal to the IDH, in a sense which may be termed intermediate quiescence hypothesis.Phosphorus limitation due to successful restoration was found to decrease winter and vernal diversity in Schlachtensee. Presumably, without nutrient constraints, new populations could grow more rapidly in response to the rapid changes of physical parameters during this season. In contrast, restoration has increased summer diversity, as phosphorus concentrations no longer allow the virtual monocultures of Planktothrix agardhii which prevailed previously. In Lake Tegel, the reduction of phosphorus concentration down to 60 µg/l P in 1989 limited biomass, but this level was still too high to significantly alter species composition or diversity. 相似文献
6.
Hansen B.W.; Hygum B.H.; Brozek M.; Jensen F.; Rey C. 《Journal of plankton research》2000,22(3):569-588
The significance of nauplii versus copepodite stage V of Calanusfinmarchicus grazing and their effects on the structure of thefood web were investigated during two sampling periods of 78days in March and April in experimental mesocosms held in aNorwegian fjord over a 2 month period. The mesocosms were manipulatedby the addition of two different levels of inorganic nutrients(control versus enriched). During the naupliarperiod in March, the phytoplankton was characterized by a diatombloom while during the copepodite period in April,it was in a post-bloom phase characterized by small-celled species,mainly Phaeocystis pouchetii. Phytoplankton, bacterial and protozooanbiomass and production rates were measured in addition to copepodbiomass. Copepod grazing was estimated by three different methods:(i) gut fluorescence; (ii) chlorophyll clearance from the water;and (iii) growth method measured as body carbon increase. Thetwo latter methods gave similar results for nauplii, but allthree gave different results for the copepodites. Independentsomatic growth, based on changes in abundance and individualcarbon content, and grazing estimates revealed an overall growthefficiency of 0.66 ± 0.20 (mean ± S.E.) for copepodites.Empirical carbon flow models were constructed, which indicatedthat the nauplii could not control either phytoplankton or protozoangrowth in either the control or in the enriched system. Ignoringrecycling and sedimentation, the fate of the primary productionfor the nauplii-dominated community was to be grazed by a diverseand abundant protozooplankton community. In the copepodite-dominatedcommunity, the copepods grazed >100% of the daily primaryproduction, and also grazed heavily on a protozooplankton communityof low biomass and diversity and presumably on detritus. Thefate of the primary production in the two different copepodscenarios followed predicted routes for low meso-zooplanktonand for high meso-zooplankton biomass systems,as suggested by Wassmann (Wassmann, 1998). 相似文献
7.
The Changes in the Composition of the Diatom Assemblages Found in the Surface Sediments of Blelham Tarn in the English Lake District During 1973 总被引:1,自引:0,他引:1
A study has been made of the accumulation of diatom frustulesin the surface layers of lake sediments, taking advantage ofthe appearance of a new diatom bloom in Blelham Tarn in theEnglish Lake District. Results from monitoring the top 5 cmof sediment and seston trap material, and comparison with phytoplanktonrecords show that there is good agreement between all threeand that sediment diatom assemblages change in response to theliving populations so that the record of large bloomscan be quickly diluted. The centric diatom, Stephanodiscus astraeavar. minutula appeared to sink out of the phytoplankton quicklyand mix down into older sediments fairly readily, circumstanceswhich may be assisted by the compact shape of its frustule. 相似文献
8.
Effect of large- and of small-bodied zooplankton on phytoplankton in a eutrophic oxbow 总被引:1,自引:0,他引:1
Grigorszky Istvaan; Nagy Saandor; Tooth Albert; Maathee Csaba; Muuller Zoltaan; Borbeely Gyoorgy 《Journal of plankton research》1998,20(10):1989-1995
Macrozooplankton and microzooplankton effects on the phytoplanktonwere measured in situ in a eutrophic lake. Indigenous phytoplanktonwere incubated for 5 days in 301 mesocosms with either the macro-and microzooplankton (complete), microzooplankton only (micro)or no zooplankton (none). Changes in phytoplankton biovolumewere investigated. Rotifer densities became significantly higherin the micro treatment than in the completeand none treatments. Total algal biovolume changedlittle in the complete and nonetreatments, but increased significantly in the microtreatment. The results suggest that macrozooplankton (Daphniamagna) suppressed it and microzooplankton (Keratella cochlearis)enhanced it. They had opposite net effects on the phytoplankton.Suppression of microzooplankton by Daphnia probably had an indirectnegative effect on the phytoplankton. 相似文献
9.
Phytoplankton succession and diversity in a warm monomictic,relatively shallow lake: Lake Volvi,Macedonia, Greece 总被引:3,自引:3,他引:0
Maria Moustaka-Gouni 《Hydrobiologia》1993,249(1-3):33-42
In Lake Volvi, phytoplankton dominance was examined in relation to the main phases of the fluctuating physical state of the water column and nutrient levels. Four stages of algal succession were identified. The successional pattern was, in general, similar from year to year. External disturbances such as increased wind mixing and high floods had the effect of setting the succession back to an earlier stage.Nanoplanktic diatoms and flagellates dominated during the first stages of succession. The succession was running from r-selected species in early stages to K-strategists in summer and towards a mixed community in the terminal stage.Diversity was expressed by the indices of Gleason and Shannon (based on physical units and biomass). Interpretation of species diversity took into account the differential variations of its two components, the number of species and the evenness of their distribution. Diversity was more affected by evenness than by number of species.Diversity increased in late stages of succession corresponding to the complexity of the community (high number of species, high evenness). Physical disturbances influenced positively the diversity. The maximal diversity appeared in the transition periods between the compositional changes generated by disturbances and the true successional development. Disturbances may generate a more uniform distribution of diversity throughout the whole water column.The role of physical disturbances in increasing the phytoplankton diversity may be demonstrated from comparisons of diversity — evenness — species number of the same stages under different meteorological conditions. 相似文献
10.
Cladoceran in situ feeding rates on natural bacteria labelledwith [methyl-3H] were studied in parallel with feeding ratedeterminations on 14C-labelled Chlorella in a hypertrophic subtropicalreservoir (Lake Hartbeespoort) through spring and summer (1986/87).Community filtration rates (CFR5) on bacteria and algae weresimilar, but selection for Chlorella (relative to natural bacteria)increased from midsummer in association with declining bacterialdensity and increasing dominance of inedible componentsof the natural phytoplankton. Species-specific filtration rates(SSFRs) were determined for Daphnia pulexllongispina, Ceriodaphniareticulata, Diaphanosoma excisum, Bosmina longirostris and Moinamicrura during their respective seasonal occurrence in the studyperiod. SSFRs on algae and bacteria increased with body length(L, mm) in all species apart from Bosmina. Species-specificdifferences in absolute feeding rate (FR, ml animal1day1), the slope of the FR-L relationship and bacteriaselectivity were evident. The feeding rate of all cladoceranson bacteria is described by the power equation FR 5.231L1.42FR values on bacteria relative to FR values on algae averaged 相似文献
11.
Gonadal changes in two species of Cerastoderma occurring indiscrete populations in South Wales were monitored by stereologicalanalysis during the breeding seasons of 1981 and 1982. Fecundityand spawning efficiencies were determined quantitatively. Therelationship between reproductive activity and changes in meatcondition are discussed. Both species are opportunistic breeders. Their normal patternsof reproduction are similar, consisting of minimum activityin winter and peak activity during spring/early summer. Thetwo species were affected differently by the severe winter of198182C. glau-cum exhibited a single, epidemicspawning and resumed gametogenesis after a 4-month resting period.C. edule adopted a polycyclic pattern withouta resting period. Both of these unusual reproductive strategies,augmented by reduced predation resulted in heavy spatfalls. (Received 20 March 1985; revised 20 March 1985; 相似文献
12.
Characterization of a small eutrophic Antarctic lake (Otero Lake, Cierva Point) on the basis of algal assemblages and water chemistry 总被引:2,自引:0,他引:2
Otero Lake is the main water body of Cierva Point, Danco Coast (SSSI No. 15). During the 1992/1993 and 1994/1995 seasons,
abiotic parameters and the structure and dynamics of the phytoplankton were studied. Algal assemblages from the phytoplankton,
from algal clumps encased in the lake ice and from the benthic algal felt were compared. Low Jaccard similarity indices between
these three assemblages suggest different survival strategies. The higher species richness of phytoplankton when studied during
the whole summer also suggests that external propagule inputs can heavily influence the structure of this community. High
levels of phosphate, nitrate and ammonium throughout the study periods indicate that they do not limit summer growth of the
phytoplankton community. Blooms of Chlamydomonas subcaudata Wille are apparently characteristic. This group of features define Otero Lake as a highly eutrophic water body, in which
outflow seems to be the main cause of phytoplankton loss during summer.
Received: 23 December 1996 / Accepted: 29 August 1997 相似文献
13.
Seasonal patterns of growth, dehydrins and water-soluble carbohydrates in genotypes of Dactylis glomerata varying in summer dormancy 总被引:1,自引:0,他引:1
Background and Aims Summer dormancy in perennial grasseshas been studied inadequately, despite its potential to enhanceplant survival and persistence in Mediterranean areas. The aimof the present work was to characterize summer dormancy anddehydration tolerance in two cultivars of Dactylis glomerata(dormant Kasbah, non-dormant Oasis)and their hybrid using physiological indicators associated withthese traits. Methods Dehydration tolerance was assessed in a glasshouseexperiment, while seasonal metabolic changes which produce putativeprotectants for drought, such as carbohydrates and dehydrinsthat might be associated with summer dormancy, were analysedin the field. Key Results The genotypes differed in their ability tosurvive increasing soil water deficit: lethal soil water potential(s) was 3·4 MPa for Kasbah (althoughnon-dormant), 1·3 MPa for Oasis,and 1·6 MPa for their hybrid. In contrast, lethalwater content of apices was similar for all genotypes (approx.0·45 g H2O g d. wt1), and hence the greater survivalof Kasbah can be ascribed to better drought avoidancerather than dehydration tolerance. In autumn-sown plants, Kasbahhad greatest dormancy, the hybrid was intermediate and Oasishad none. The more dormant the genotype, the lower the metabolicactivity during summer, and the earlier the activity declinedin spring. Decreased monosaccharide content was an early indicatorof dormancy induction. Accumulation of dehydrins did not correlatewith stress tolerance, but dehydrin content was a function ofthe water status of the tissues, irrespective of the soil moisture.A protein of approx. 55 kDa occurred in leaf bases of the mostdormant cultivar even in winter. Conclusions Drought avoidance and summer dormancy arecorrelated but can be independently expressed. These traitsare heritable, allowing selection in breeding programmes. 相似文献
14.
Some effects of artificial mixing on the dynamics of phytoplankton populations in large limnetic enclosures 总被引:14,自引:0,他引:14
Reynolds C.S.; Wiseman S.W.; Godfrey B.M.; Butterwick C. 《Journal of plankton research》1983,5(2):203-234
Effects of a series of artificial mixings of part of the watercolumn of a limnetic enclosure (Lund Tube C, BlelhamTarn, Cumbria) upon the rates of net change in the standingpopulations of selected species of phytoplankton are described.Increase of Sphaerocystis and Anabaena was relatively fasterunder the quiescent, stratified conditions ofunmixed columns whereas mixing generally favoured the net increaseof diatoms (e.g., Fragilaria) or, at times, of Oscillatoria.The sequences corresponded closely to supposed successionalpathways, which are thus suggested to be naturally regulatedby seasonally-changing physical characteristics of the watercolumn. Performance characteristics of the mixing apparatusand a mathematical expression of the net rate of change in naturalFragilaria populations are appended. 相似文献
15.
'Shore avoidance' in zooplankton: a predator-induced behavior or predator-induced mortality? 总被引:1,自引:0,他引:1
The distribution of two Daphnia species dominant in near-surfacewaters of a eutrophic lake, Lake Ros, showed offshore-inshoregradients in density with a dramatic decrease towards nearshorewaters, suggesting a strong shore-avoidance behavior.Much smaller body sizes and much smaller clutches in the nearshorefractions of the two populations, however, showed that the lowerpopulation density of each species in the nearshore areas wasrather a direct effect of high mortality selectively generatedin more conspicuous larger individuals and in individuals withgreater clutches that are more vulnerable to predation by littoralfish, mostly abundant perch juveniles. Hydroacoustic and trawlingdata revealed that young perch move offshore in the eveningto feed on pelagic zooplankton, but their feeding cannot beas efficient later in the dark when they eventually reach themost distant Daphnia patch in the center of the lake. High predationrisk in the littoral neighborhood may be considered an ultimatefactor behind the evolution of shore-avoidance behavior in zooplankton. 相似文献
16.
Summer dynamics of the deep chlorophyll maximum in Lake Tahoe 总被引:3,自引:0,他引:3
Coon Thomas G.; Lopez Matilde M.; Richerson Peter J.; Powell Thomas M.; Goldman Charles R. 《Journal of plankton research》1987,9(2):327-344
Vertical profiles of chlorophyll and phytoplankton biomass weremeasured in Lake Tahoe from July 1976 through April 1977. Adeep chlorophyll maximum (DCM) persisted during summer and earlyautumn (JulyOctober) near 100 m, well below the mixedlayer and at the upper surface of the nitracline. The DCM coincidedwith the phytoplankton biomass maximum as determined from cellcounts. In addition, the composition of the phytoplankton assemblagewas highly differentiated with respect to depth. Cyclotellastelligera was the predominant species in the mixed layer whilethe major species in the DCM layer included C. ocellata andseveral green ultraplanktonic species. In situ cell growth playsa substantial role in maintaining the DCM, but sinking of cellsfrom shallower depths and zooplankton grazing above the DCMmay contribute to the maintenance of the DCM. Calculations supportthe interpretation that the summer DCM persists at the boundarybetween an upper, nutrient-limited phytoplankton assemblageand a deeper, light-limited assemblage. 相似文献
17.
The importance of crustacean zooplankton in structuring rotifer and phytoplankton communities; an enclosure study 总被引:3,自引:0,他引:3
During the spring clear-water phase of 1993, an enclosure experimentwas performed in the mesotrophic Schöhsee (Plön, FRG)in order to assess the impact of crustacean zooplankton on therotifer and phytoplankton community. Among the crustacean plankton,calanoid and cyclopoid cope-pods were abundant, but Daphnialongispina reached the highest densities in thisexperiment. The colonial rotifer Conochilus unicomis was notaffected by crustacean plankton. The two most abundant species,Synchaeta peclinata and Keratella cochlearis, increased exponentiallywhen macrozooplankton had been excluded from the enclosures,but did not increase when crustaceans were present. Birth anddeath rates of K.cochlearis could be reliably determined inthis field experiment, suggesting that this rotifer specieswas mainly controlled by exploitative competition rather thanby mechanical interference or predation. Daphnia longispinagenerally grazed selectively on the smaller ciliates and algae,thus depriving the rotifers of their phytoplankton resources.The dominant alga, the chrysophycean Dinobryon, increased, whethercrustaceans were present or not, but appeared to be grazed uponto a certain extent despite its considerable cell size and colonialorganization. 相似文献
18.
Seasonal variations in copepod size: effects of temperature, food abundance, and vertebrate predation 总被引:1,自引:0,他引:1
Warren Glenn J.; Evans Marlene S.; Jude David J.; Ayers John C. 《Journal of plankton research》1986,8(5):841-853
Seasonal dry weights of female and male Cyclops bicuspidatusthomasi, Diaptomus ashlandi and Diaptomus minutus were studiedin southeastern Lake Michigan during 19751981. Smallestanimals occurred during summer and early fall, and largest animalsin winter and spring, a pattern reported for other copepods.The range of weights for the species and sexes decreased fromwinter to summer, and converged in summer to a value of approximately2 µg/animal. Surface water temperature and abundancesof young-of-the-year (YOY) fish were inversely correlated withweights of males and females of the three copepod species. Standingstocks of important phytoplankton groups, especially pennatediatoms and flagellates, were positively correlated with copepodweight. Seasonal change of copepod body size appears to be morethan simply a function of temperature; seasonal predation byYOY fish may be a factor influencing sizes of adult copepods. 相似文献
19.
《Journal of Molluscan Studies》1953,29(6):258
Part 1, under the frontispiece portrait of Dr. N. B. Eales,the words President 19481951 should havebeen added. Page 103, line 49, for Newton Collection readNorman Collection (Canon Norman). 185, line 37, for capillaris read capillacca. 188, Table 1, for bemoralis. read nemoralis. 188, Table 2, for Cochlicella acuta (Müll)? ventrosa(Fér.) read Cochlicella ventrosa (Fér.). 191, line 24, for araheo- read archeo-. 相似文献
20.
Modelling of autumn plankton bloom dynamics 总被引:3,自引:0,他引:3
Findlay Helen S.; Yool Andrew; Nodale Marianna; Pitchford Jonathan W. 《Journal of plankton research》2006,28(2):209-220
A simple system of parametrically forced ordinary differentialequations is used to model autumn phytoplankton blooms in temperateoceans by a mechanism involving deepening of the upper mixedlayer. Blooms are triggered provided the increase in nutrientsin the mixed layer is rapid within the first few days of deepeningand provided light-limited phytoplankton growth rate is relativelyhigh. Blooms exist as transient trajectories between quasi-equilibriumstates, rather than as bifurcations of steady states; thereforevery gradual deepening cannot trigger blooms. Very rapid deepeningalso prevents blooms due to the deleterious effect on phytoplanktongrowth rate. The mechanisms identified by this simple modelare vindicated by considering alternative grazing and deepeningregimes and by comparison with a more ecologically complex model(Fasham, 1993, in The Global Carbon Cycle, Springer-Verlag).Modelled estimates of primary productivity from both the simplemodel and the complex model parameterized for Ocean WeatherStation India are around 0.5 g C m2 day1during the autumn bloom, therefore comprising a significantcomponent of annual production in temperate areas. 相似文献