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1.
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
2.
Production of tropical larvaceans in Kingston Harbour, Jamaica: are we ignoring an important secondary producer? 总被引:2,自引:0,他引:2
The larvacean community was observed during an 18 month periodat the mouth of eutrophic Kingston Harbour, Jamaica. Duringthis period, larvaceans averaged 3607 m3 with a biomassof 2.2mg ash-free dry weight m3 (32.6mg AFDW m2in a community dominated by Oiko pleura longicauda There wereno relationships between larvacean biornass and any size fractionof chlorophyll, suggesting that other factors must normallyregulate larvacean communities. The evidence indicates thatthis regulation is by predation. Annual production by larvaceanswas 586 kJ m3 year 1 (29.3 g AFDW m2 year1);production of houses could represent an added 300600kJ m2 year. While copepod biomass was 10 times higherthan that of the larvaceans during the same period, copepodgrowth rates were only one.third those of larvaceans. Thus,larvacean annual production is at least 30% that of the copepods,due to their rapid growth rates, and at least 50% that of thecopepods when house production is considered. The contributionof larvaceans to plankton production has been underappreciatedhistorically when only their biomass is considered.
1Present address :Monterey Bay Aquarium Research Institute 7700Sandholdt Road, Moss Landing, CA 95039-0628, USA 相似文献
3.
Fish-induced changes in zooplankton grazing on phytoplankton and bacterioplankton: a long-term study in shallow hypertrophic Lake Sobygaard 总被引:1,自引:0,他引:1
Jeppesen Erik; Sondergaard Martin; Jensen Jens Peder; Mortensen Erik; Sortkjaer Ole 《Journal of plankton research》1996,18(9):1605-1625
The impact of fish-mediated changes on the structure and grazingof zooplankton on phytoplankton and bacterioplankton was studiedin Lake Søbygaard during the period 198492 bymeans of in vitro grazing experiments (14C-labelled phytoplankton,3H-labelled bacterioplankton) and model predictions. Measuredzooplankton clearance rates ranged from 025 ml l1h1 on phytoplankton to 033 ml l1 h1on bacterioplankton.The highest rates were found during thesummer when Daphnia spp. were dominant. As the phytoplanktonbiomass was substantially greater than that of bacterioplanktonthroughout the study period, ingestion of phytoplankton was26-fold greater than that of bacterioplankton. Multiple regressionanalysis of the experimental data revealed that Daphnia spp.,Bosmina longirostris and Cyclops vicinus, which were the dominantzooplankton, all contributed significantly to the variationin ingestion of phytoplankton, while only Daphnia spp. contributedsignificantly to that of bacterioplankton. Using estimated meanvalues for clearance and ingestion rates for different zooplankters,we calculated zooplankton grazing on phytoplankton and bacterioplanktonon the basis of monitoring data of lake plankton obtained duringa 9 year study period. Summer mean grazing ranged from 2 to4% of phytoplankton production and 2% of bacterioplankton productionto maxima of 53 and 88%, respectively. The grazing percentagedecreased with increasing density of planktivorous fish caughtin August each year using gill nets and shore-line electrofishing.The changes along a gradient of planktivorous fish abundanceseemed highest for bacterioplankton. Accordingly, the percentagecontribution of bacterioplankton to the total ingestion of thetwo carbon sources decreased from a summer mean value of 8%in Daphnia-dominated communities at lower fish density to 0.71.1%at high fish density, when cyclopoid copepods or Bosmina androtifers dominated. Likewise, the percentage of phytoplanktonproduction channelled through the bacteria varied, it beinghighest (58%) at high fish densities. It is argued thatthe negative impact of zooplankton grazing on bacterioplanktonin shallow lakes is highest at intermediate phosphorus levels,under which conditions Daphnia dominate the zooplankton community. 相似文献
4.
5.
An estimate of global primary production in the ocean from satellite radiometer data 总被引:32,自引:0,他引:32
Longhurst Alan; Sathyendranath Shubha; Platt Trevor; Caverhill Carla 《Journal of plankton research》1995,17(6):1245-1271
An estimate of global net primary production in the ocean hasbeen computed from the monthly mean near-surface chlorophyllfields for 19791986 obtained by the Nimbus 7 CZCS radiometer.Our model required information about the subsurface distributionof chlorophyll, the parameters of the photosynthesis-light relationship,the sun angle and cloudiness. The computations were partitionedamong 57 biogeochemical provinces that were specified from regionaloceanography and by examination of the chlorophyll fields. Makingdifferent assumptions about the overestimation of chlorophyllby the CZCS in turbid coastal areas, the global net primaryproduction from phytoplankton is given as 4550 Gt C year1.This may be compared with current published estimates for landplants of 4568 Gt C year1 and for coastal vegetationof 1.9 Gt C year1. 相似文献
6.
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
7.
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1990,12(1):125-131
The production rate of participate nitrogen (PN) in Lake Biwafrom March to June 1986 was calculated by monthly measurementsof the proteinaceous nitrogen production rates. The newproduction rate was estimated from the decrease in nitrate inthe euphotic zone; during this period (91 days) it was estimatedas 93 mg atoms m2, and accounted for 20% of the totalPN production (460 mg atoms m2). This implies that {smalltilde}80% of the PN produced might be recycled in the euphoticzone. The increase in PN in the euphotic zone during this period(27 mg atoms m2) accounted for 5.9% of the totalPN production. This indicates that the remaining 14% of PN producedin the euphotic zone was vertically transported. Sediment trapexperiments at 30 m depth indicate that 8.1% of the PN producedin the euphotic zone was measured as downward flux at 30 m depthduring the stagnation period. Decompositional loss of PN between12.5 (bottom of the euphotic zone) and 30 m depth was estimatedas 17 mg atoms m2. This was calculated on the basis ofaccumulation of ammonium, which accounted for 3.7% of the totalPN production. The flux from the euphotic zone thus accountedfor 12% of the total PN production, suggestingthe validity of the production model. 相似文献
8.
Mehner Thomas; Huulsmann Stephan; Worischka Susanne; Plewa Matthias; Benndorf Juurgen 《Journal of plankton research》1998,20(9):1797-1811
We analysed the temporal pattern of a Daphnia galeata populationand the development of the age-0 Ash community in a long-termbiomanipulated lake (Bautzen reservoir, Germany) during springand early summer of two successive years. In Bautzen reservoir,the age-0 Rsh-Daphnia interaction is a key process within thefood web due to the low abundance of adult zooplanktivorousfish. Daily consumption of daphnids by age-0 fish, as estimatedby a bioenergetics model, was compared to daily mortality ratesof daphnids. In addition, we estimated life history parametersof Daphnia that may indicate predation impact by fish. A midsummerdecline of daphnids occurred only in July of 1996, whereas in1995 the Daphnia biomass remained >4 mg wet weight 11for the entire summer. The percentage of total Daphnia mortalitydue to fish predation before the onset of the midsummer declinewas 2% day1. Temporal patterns of individual size,clutch size and size at maturity also indicated that the 1996midsummer decline of daphnids was not the exclusive consequenceof age-0 fish predation. Instead, low reproductive capacityof daphnids also contributed significantly to the decline. Consequently,year-to-year variation of the Daphnia dynamics may be determinedby a fine-tuned timing between the period of reducedfecundity and the time of the strongest predation impact byage-0 fish. 相似文献
9.
The International Council for the Exploration of the Sea (ICES)Mackerel Working Group recognises two mackerel stocks in Europeanwaters, the North Sea stock and the Western stock. From Marchto July 1977 an Anglo-French plankton survey was carried outin the shelf waters of the Bay of Biscay, Celtic Sea and westof Ireland to estimate the size of the Western stock. Sampleswere collected with a 76 cm Lowestoft pattern high-speed planktonsampler fished to a maximum depth of 100 m. The number of eggsm2 at each of five development stages were raised todaily production estimates with development rate coefficientsmeasured with live material collected in March. The mean numberof stage I eggs m2 d1 was raised to a total dailyproduction estimate for each month by the area within the minimumcontour level, and a production curve was drawn for the spawningseason. The total egg production was estimated at 1.98 x 1015eggs, + 30%, 20%. With a mean fecundity of 361 000 anda sex ratio of 0.64 males per female this is equivalent to 8995 million fish. 相似文献
10.
Recent studies indicate that Oithona spp. contribute significantlyto total copepod biomass. Little is known, however, about theirecological significance, particularly in the case of the estuarineOithona nana. A study comprising three sites within SouthamptonWater was conducted to evaluate the late-stage copepodite/adult(stages IVVI) O. nana community, using 120-µm meshnets. Although present throughout the estuary, there was a strikingspatial gradient with O. nana most common in the upper estuary.A clear seasonal pattern was observed with O. nana as the mostabundant copepod species from late summer until early winter.It comprised 61% of all copepods recorded, with a biomass of757.22 mg C m3. Production estimates of O. nana werederived from the instantaneous-growth approach,using appropriate growth equations. The estimated productionof O. nana ranged from 1.50 mg C m3 year1 withinthe lower estuary to 146.77 mg C m3 year1 in theupper estuary. In the upper estuary, this compares with productionrates of 187.47 mg C m3 year1 for all Acartiacongeners (excluding nauplii), the most common calanoid genus.Throughout the estuary, O. nana annual production represented18% of total copepod production clearly indicating that, atleast in the upper estuary, O. nana production may be directlycomparable with calanoid production. 相似文献
11.
Richardson Tammi L.; Cullen John J.; Kelley Dan E.; Lewis Marlon R. 《Journal of plankton research》1998,20(2):219-241
We present a numerical model of nutrient uptake and photosynthesisduring migrations of the marine diatom Rhizosolenia that wasdeveloped to estimate fluxes of carbon and nitrogen due to thesemigrations in the open ocean. The predicted specific rate ofincrease of Rhizosolenia was 0.110.15 day1, whereas thetotal time for one migration cycle ranged between 3 and 5 days.Using published estimates of Rhizosolenia abundance, we estimatethat new primary production due to Rhizosolenia migrations rangesbetween 0.018 and 0.033 mmol N m2 day1. Thesevalues represent up to 17% of new production due to turbulentdiffusive fluxes of nitrate into the euphotic zone and are ofthe same order of magnitude as new production due to nitrogenfixation in tropical oceans. Large-scale contributions of Rhizosoleniato oceanic new production are limited by their relatively lowstanding crop. Variations in the formulation of losses withdepth greatly affected gross and net fluxes of carbon and nitrogen.Better characterization of losses of Rhizosolenia and improvedestimates of its abundance will help determine more accuratelythe contributions of Rhizosolenia to global biogeochemical cycles.
1Present address: Department of Agricultural and EnvironmentalScience, The Queen's University of Belfast New forge Lane, BelfastBT95PX, UK 相似文献
12.
Autotrophic picoplankton in southern Lake Baikal: abundance, growth and grazing mortality during summer 总被引:5,自引:0,他引:5
Nagata Toshi; Takai Kenji; Kawanobe Kyoko; Kim Dong-Sup; Nakazato Ryoji; Guselnikova Nina; Bondarenko Nina; Mologawaya Oliga; Kostrnova Tatyana; Drucker Valentine; Satoh Yasuhiro; Watanabe Yasunori 《Journal of plankton research》1994,16(8):945-959
Autotrophic picoplankton were highly abundant during the thermalstratification period in late July in the pelagic area (waterdepth 5001300 m) of southern Lake Baikal; maximum numberswere 2 x 106 cells ml1 in the euphotic zone ({small tilde}15m). Unicellular cyanobacteria generally dominated the picoplanktoncommunity, although unidentified picoplankton that fluorescedred under blue excitation were also abundant (maximum numbers4 x 105 cells ml1) and contributed up to {small tilde}40%of the total autotrophic picoplankton on occasions. Carbon andnitrogen biomasses of autotrophic picoplankton estimated byconversion from biovolumes were 1484 µg C l1and 3.621 µg N l1. These were comparableto or exceeded the biomass of heterotrophic bacteria. Autotropicpicoplankton and bacteria accounted for as much as 33% of paniculateorganic carbon and 81% of nitrogen in the euphotic zone. Measurementsof the photosynthetic uptake of [l4C]bicarbonate and the growthof picoplankton in diluted or size-fractionated waters revealedthat 80% of total primary production was due to picoplankton,and that much of this production was consumed by grazers inthe <20 µ.m cell-size category. These results suggestthat picoplankton-protozoan trophic coupling is important inthe pelagic food web and biogeochemical cycling of Lake Baikalduring summer. 相似文献
13.
Delhon Patricia; Gojon Alain; Tillard Pascal; Passama Lucien 《Journal of experimental botany》1996,47(7):885-892
According to the Dijkshoorn-Ben Zioni model, NO3 uptakein the roots is stimulated by NO3 assimilation in theshoots, through downward phloem transport of malate synthesizedin response to reduction of NO2 to NH3. In this paper,one hypothesis resulting from this model was tested, i.e. thatthe diurnal changes in NO3 uptake are due to the lightdependence of NO3 reduction in the leaves. This dependencewas studied in detached leaves transferred to deionized wateror supplied via the transpiration stream with similar amountsof 15NO3 in light or darkness. In the dark, the reductionof previously stored NO3 or xylem-borne 15NO3was generally about 4050% of that measured in the light.Glucose supply to the detached leaves stimulated NO3reduction in the dark, but not enough to increase it up to thesame rate as in the light. Nitrite reduction in detached leaveswas much less affected by darkness, and could be maintainedat a high level by exogenous supply of substrate. Advantagewas taken from this last observation to sustain NO2reductionin attached darkened shoots at the same rate as in the light,by ensuring an appropriate delivery of NO2 from the xylem.Although this was assumed to restore the light level of theassociated synthesis of malate, it led to a marked inhibitionof NO3 uptake. In addition, the direct supply of malateto the shoots or to the roots failed to prevent the decreaseof NO3 uptake in darkness. Thus, our conclusion is thatthe mechanisms evoked in the Dijkshoorn-Ben Zioni model do notplay an important role in the diurnal variations of NO3uptake in soybean plants. Key words: Glycine max, light/dark cycle, malate synthesis, NO3 reduction, NO3 uptake 相似文献
14.
Light-shade adaptation and assimilation numbers 总被引:14,自引:0,他引:14
The photobiological and ecological derivations of the assimilationnumber concept are explored. Based on theoretical calculations,a maximum assimilation number of about 25 µg C ·hr1 is calculated. This number is estimated from photosyntheticturnover times and the number of photosynthetic units. The variationsin this number are primarily due to the effects of nutrients,temperature, cell size and light history. The interactions ofthese variables is discussed with emphasis on light historyand the physiological adaptability of marine phytoplankton.An equation is presented to estimate light-utilization indicesfor photosynthesis in the euphotic zone. This index is estimatedas 0.43 g C · g chlorophyll1 · ein1· m2 in New York Bight. 相似文献
15.
SYNOPSIS. This paper develops a model based on egg-laying ratesand female oviposition temperature preferences in two speciesof cicada, Cacama valvata and Tibicen bifidus, from a centralNew Mexico desert grassland habitat. Output from the model indicatesthat C. valvata achieves maximal daily egg production (eggsfemale1 day1) on days when maximum shade ambienttemperatures reach 41°C; the corresponding value for T.bifidus is 33°C. These differences correlate with the thermalregime experienced by each species in its respective typicalhabitat. Simulations of the effects of variation in mean habitatambient temperature on egg production demonstrated that knowndistributional limits for T. bifidus correspond to thermal conditionsthat reduce daily egg production by only about 510% relativeto long-term means at the study site. The same is true for C.valvata only in lower-ambient temperature habitats. In higher-temperaturehabitats, C. valvata exhibits an unusual plasticity in the timingof adult activity and reproduction that allows it to occupya much wider geographic range than T. bifidus. Contrary to expectations,frequency distributions of predicted daily egg production rateswere negatively skewed in each species' respective typicalhabitat, and Gaussian only in thermally marginal habitats.The findings are discussed in the context of attempts to modelpopulation- and community-level effects of climatic change. 相似文献
16.
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
17.
Existing data on feeding, growth rate, fecundity, absorptionefficiency, respiration and excretion rates in the South Africanabalone Haliotis midae Linnaeus are converted to energy equivalentsand utilised to compile individual energy budgets. About 63%of the energy content of the food consumed (C) is lost as faeces(F) and a further 32% expended on respiration (R). Energy lossesin the form of ammonia excretion are negligible, accountingfor less than 1% of consumption. Some 5% of energy intake, or13% of absorbed ration (Ab) is thus available for growth andreproductive output (Pg & Pr). In juveniles (<100mm)this is all allocated towards somatic growth, while in adultsan increasing proportion of production is expended on reproductiveoutput. Although feeding, respiration and excretion rates allincrease with temperature the proportions of energy allocatedto the various components of the energy budget appear to beconsistent. Population energy budgets are calculated from densityand size distribution surveys at two study sites. At MarcusIsland, on the Cape west coast, the population has a standingstock of 82 g (wet flesh weight) m2,.consumes about 3260KJm2y1 algae and has a P/B ratio of 0.46, whereasat Cape Hangklip, on the Cape south coast, the population biomassis_133gm2, consumes 8613KJm2y1 and hasa P/B ratio of 0.70. These figures indicate that a high proportionof kelp bed primary production is directly consumed by grazingabalone in areas where populations have not been reduced byhuman exploitation (Received 16 March 1987; 相似文献
18.
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
19.
Organic carbon release by phytoplankton: its composition and utilization by bacterioplankton 总被引:7,自引:0,他引:7
The present study characterized the rate of production of extracellularlyreleased organic carbon (ROC) by phytoplankton, its molecularweight distribution, subsequent utilization and transformationby bacterioplankton in situ. Primary production rate of phytoplanktonwas high during the study due to continuous blooms of smalldinoflagellates and ranged from 59.8 to 298.7µg CI1h1. The rate of organic carbon release varied from 1.3to 123.7 µg CI1 h1 and constituted from4.0 to 68.9% of the total carbon fixed in photosynthesis. TheROC was fractionated on molecular weight (MW) basis. A low MWfraction less than 500 daltons (18.5% of ROC), a fraction ofMW 10 00030 000 daltons (30% of ROC), and high MW fractionof > 300 000 daltons (15.4% of ROC), were the most dominantin ROC. Bacterioplankton utilized a significant portion of ROC,ranging from 18 to 77%. Part of the utilized ROC incorporatedby the bacterioplankton (31 56%), and the remainderwas respired (mineralized). ROC not utilized by bacteria wascomposed of high MW compounds. The dynamics of the in situ utilizationof ROC and its role as a link between autotrophic and heterotrophicprocesses in the estuary are described.
1Present address: Department of Environmental Microbiology,Institute of Microbiology, Warsaw University, Warsaw, Poland 相似文献
20.
Dynamics of Copepod Faecal Pellets in Relation to a Phaeocystis Dominated Phytoplankton Bloom: Characteristics, Production and Flux 总被引:2,自引:0,他引:2
Frangoulis Constantin; Belkhiria Sami; Goffart Anne; Hecq Jean-Henri 《Journal of plankton research》2001,23(1):75-88
Copepod faecal pellet characteristics and production were measuredin spring 1995, 1996 and 1997 in the North Sea Southern Bightin order to define changes due to the development of the phytoplanktonbloom. Changes were related to the succession from diatomsto a Phaeocystis sp. bloom. Mean monthly pellet productiondecreased during the Phaeocystis bloom development to 0.27 pelletsind. 1 h 1, approximately 80% lower than beforeand after the bloom. Although phytoplanktonic pigments showedsignificant differences between inshore and offshore stations,there was no such significant difference for faecal pellet production.Faecal pellet sinking-rate decreased from 100 to 70 m day 1during the transition from a diatom- to a Phaeocystis-dominatedbloom. This was due to a decrease in pellet density and/or adecrease of the pellet volume. These results supported the ideaof lower feeding of copepods under Phaeocystis bloom conditions.As mean seasonal density of copepod faecal pellets was higher(1.37 g cm 3) than in other seas, accidental ingestionof sedimentary material as the cause of this high density isdiscussed. 相似文献