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1.
The taxonomic composition, abundance and biomass of microzooplanktonwere studied at eight stations in Lake ShinjiOhashi RiverLakeNakaumi brackish-water system, Japan, monthly from April 1998to March 1999. Over the entire area, naked ciliates numericallydominated the microzooplankton community (annual mean 39.6%)followed, in order, by tintinnids (30.3%), copepod nauplii (24.6%)and rotifers (5.5%). The abundance of each taxonomic group ofmicrozooplankton varied geographically due to large salinityvariations (range 1.533.3 p.s.u.). It was notable thatnaked ciliates occurred overwhelmingly in Lake Shinji (54.9%of total microzooplankton) and rotifers were relatively numerousin Lake Shinji (8.8%) and Ohashi River (11.1%), where the salinitywas lower (annual mean 4.1 and 13.6 p.s.u., respectively) thanin Lake Nakaumi and Sakai Strait (26.3 and 29.8 p.s.u., respectively).Owing to large seasonal temperature variation (range 5.429.8°C),the abundance of microzooplankton showed marked seasonal variations,being higher in spring and summer than in the remaining seasons.A total of 49 species of tintinnids were identified, and 15of these species reached concentrations >500 individualsl-l. The occurrence of most tintinnid species was confined tocertain months or locations, closely associated with species-specifictemperature and salinity preference and/or tolerance. In thiseutrophic system, food supply for microzooplankton might besufficient due to extremely high chlorophyll a concentration(annual mean 8.8 µg l-lin Sakai Strait to 22.6 µgl-l in Lake Shinji). However, microzooplankton biomass remainedmoderate (range 0.1918.7 µg C l-l) due probablyto heavy predation by mesozooplankton, which inhabit this brackish-watersystem at extremely high biomass. 相似文献
2.
The geographical distribution, seasonal life cycle, biomassand production of a copepod Calanus sinicus were investigatedin and around Kii Channel of the Inland Sea of Japan. The distributioncenter of the population was located in Kii Channel. The patternof the seasonal variation in abundance of copepodites and adultsdiffered geographically within the study area. In Kii Channel,for example, they were most abundant in June-July and leastabundant in October. Over the study area, the reproduction ofC.sinicus took place throughout the year, indicating the absenceof diapause phase. In adults, females usually outnumbered males.The prosome length of late copepodites and adults was inverselycorrelated with water temperature. The annual mean biomass washighest (4.87 mg C m3 or 231 mg C m2) in Kii Channel.The potential production rate of the population exhibited aseasonal variation more or less similar to that of the biomassand the annual potential production rate was 358 mg C m3year1 (14.1 g C m2 year1) in Kii Channel.Daily production and biomass (P/B) ratios in Kii Channel increasedfrom 0.11 at 11.8°C to 0.26 at 20°C. 相似文献
3.
Annual pattern of micro- and mesozooplankton abundance and biomass in a subtropical estuary 总被引:7,自引:0,他引:7
The pattern of biomass and abundance of microzooplankton andmesozooplankton were studied over an annual cycle in the NuecesEstuary, Texas. Zooplankton samples and associated hydrographicdata were collected at four locations at biweekly intervalsfrom September 1987 through October 1988. This is a broad, shallowbay system with an average depth of 2.4 m. The concentrationof chlorophyll a in the surface waters averaged 7.4 µgl1with 85% passing through a 20 µ mesh. Microzooplankton(20200 µ in length) were extremely abundant throughoutthis study. Abundances of ciliates (including both aloricateciliates and tintinnids) ranged from 5000 to 400 000 l,with a mean of 38 000 l1 of seawater over the entirecourse of the study. Mesozooplankton (2002000 µmin length) abundance averaged 6100 m3 for samples collectedduring the day and 10 100 m3 for samples collected atnight. Mesozooplankton were dominated by Acartia tonsa whichmade up {small tilde}50% of the total. Biomass estimates formicrozooplankton (based on volume estimates) were often higherthan measured biomass of mesozooplankton. Given the shortergeneration times and higher metabolic rate of microzooplanktoncompared to mesozooplankton, microzooplankton should have agreater effect on the trophic dynamics of the Nueces Estuarythan mesozooplankton. 相似文献
4.
Liu Zhensheng Wang Chunsheng Zhang Zhinan Cai Yuming Zhang Dongsheng 《Frontiers of Biology in China》2006,1(4):434-442
The species composition, biomass, abundance, and species diversity of zooplankton were determined for samples collected from
August 2002 to May 2003 from 14 stations in Yueqing Bay, China. Phytoplankton growth rate and microzooplankton grazing rate
were obtained by using the dilution method developed by Landry and Hassett. The spatial and temporal variations of zooplankton
and its relationship with environmental factors were also analyzed. The results showed that the zooplankton in the Yueqing
Bay could be divided into four ecotypes, namely coastal low saline species, estuary brackish water species, offshore warm
water species, and eurytopic species. A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic
larva were identified in the Yueqing Bay. The coastal low saline species was the dominant ecotype in the study area, and the
dominant species were Labidocera euchaeta, Acartia pacifica, Acrocalanus gibber, Pseudeuphausia sinica, and Sagitta bedoti among others.
There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas. The peak biomass appeared
in August, descending in November and in May, and the lowest biomass appeared in February. Similarly, the highest abundance
of zooplankton was observed in August, with the abundance descending in the following months: May, November, and February.
There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton. They both increased
from the upper to the lower bay in February and May, but decreased from the upper to the lower bay in August. Biomass and
abundance were evenly distributed in the Yueqing Bay in November. Moreover, there was marked seasonal variation in the species
diversity of zooplankton, which conformed to the abundance of zooplankton. Results of the dilution experiments indicated that
there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of
microzooplankton grazing on phytoplankton varied seasonally. Phytoplanktons were growing at 0.26–2.07/d and grazed by microzooplankton
at a rate of 0.15–0.48/d in different seasons.
__________
Translated from Acta Ecologica Sinica, 2005, 25(8): 1853–1862 [译自: 生态学报, 2005, 25(8): 1853–1862] 相似文献
5.
Martin Günther Joachim L?der Alexandra Claudia Kraberg Nicole Aberle Silvia Peters Karen Helen Wiltshire 《Helgoland Marine Research》2012,66(1):11-23
A monitoring programme for microzooplankton was started at the long-term sampling station “Kabeltonne” at Helgoland Roads
(54°11.3′N; 7°54.0′E) in January 2007 in order to provide more detailed knowledge on microzooplankton occurrence, composition
and seasonality patterns at this site and to complement the existing plankton data series. Ciliate and dinoflagellate cell
concentration and carbon biomass were recorded on a weekly basis. Heterotrophic dinoflagellates were considerably more important
in terms of biomass than ciliates, especially during the summer months. However, in early spring, ciliates were the major
group of microzooplankton grazers as they responded more quickly to phytoplankton food availability. Mixotrophic dinoflagellates
played a secondary role in terms of biomass when compared to heterotrophic species; nevertheless, they made up an intense
late summer bloom in 2007. The photosynthetic ciliate Myrionecta rubra bloomed at the end of the sampling period. Due to its high biomass when compared to crustacean plankton especially during
the spring bloom, microzooplankton should be regarded as the more important phytoplankton grazer group at Helgoland Roads.
Based on these results, analyses of biotic and abiotic factors driving microzooplankton composition and abundance are necessary
for a full understanding of this important component of the plankton. 相似文献
6.
The vertical distribution patterns of paralarvae from severalabundant cephalopod taxa were examined from depth-stratifiedtows in the northeast Pacific (4456°N, 145165°W)during three summer surveys in 19992001. A total of 309cephalopods representing 10 taxa in three families were collected.Gonatid squids composed 97% of the total catch, and the mostnumerous taxa were Berryteuthis anonychus (59% of the totalcatch), Gonatus spp. (21%) and Gonatopsis borealis (17%). B.anonychus and Gonatus spp. were both most abundant in the upper20 m; catches of both taxa varied significantly with depth andwere significantly higher above the thermocline than in andbelow the thermocline. Gonatopsis borealis was collected mostlybetween 20 and 50 m, and catches were significantly higher inthe thermocline than above and below the thermocline. Paralarvaeof the three major taxa showed no evidence of diel verticalmigration. Mantle lengths of Gonatus spp. and G. borealis eachvaried significantly with depth, and Gonatus spp. showed a strongpositive correlation between mantle length and depth. 相似文献
7.
This study documents the monsoonal and lunar effects on species composition and abundance of microzooplankton in a tropical estuary. We investigated microzooplankton abundance in relation to the various environmental and biotic parameters, sampled in the Matang mangrove (Malaysia) from April 2013 to February 2014. A total of 39 microzooplankton taxa comprising four major groups, i.e. loricate ciliates (37.72%), aloricate ciliates (29.46%), dinoflagellates (24.33%) and meroplanktonic nauplii (8.49%) were identified. The loricate ciliates were the most diverse group with 31 taxa recorded. Four major species of loricate ciliates were identified, i.e. Tintinnopsis beroidea, Tintinnopsis rotundata, Stenosemella avellana and Tintinnidium primitivum, while Strombidiidae and Strobilidiidae dominated the aloricate ciliates. Although small loricate ciliates were ubiquitous, redundancy analysis shows marked shifts in microzooplankton community structure, from one that was dominated by loricate ciliates during the drier SW monsoon, to aloricate ciliates at the onset of the wet NE monsoon, and then to dinoflagellates towards the end of the drier NE monsoon period. These shifts were associated with rainfall, dissolved inorganic nutrients, salinity, temperature and microbial food abundance. There was no clear lunar effect on abundance of microzooplankton except for Favella ehrenbergii and copepod nauplii, which were more abundant during neap than spring tides. 相似文献
8.
Mesozooplankton distribution was investigated under the sea ice in the Kara Sea at five stations in February of 2002 by Juday
net hauls. Copepods dominated the mesozooplankton community, accounting for 46–88% of the total abundance and 68–99% of the
biomass. Oithona similis was the most abundant species in Yenisei Bay, being present with all age stages (including egg-carrying females). For the
first time, Oithona atlantica (CIII–CV copepodites, females and males) were found in the southeastern Kara Sea. In the southern part, Copepoda nauplii
prevailed in terms of total abundance while the mesozooplankton in the northwestern part was entirely dominated by older stages
of Pseudocalanus minutus. The mesozooplankton structure appears to be determined by available food resources and increased water temperature due to
a strong influence of warm Atlantic waters. 相似文献
9.
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
10.
Regional variations in mesozooplankton composition, abundance and biomass were studied during a cruise in August 2006 near
Novaya Zemlya Archipelago (eastern Barents Sea) using Juday net hauls from the bottom (or 100 m depth) to the surface. A comparison
with multiannual literature values revealed that the mean temperature and salinity in the south and centre of the study area
were similar to typical values, while temperature in the north was significantly higher. A total of 36 species and higher
taxa were identified. Mesozooplankton abundance and biomass varied from 47 to 851 ind m−3 and from 5 to 74 mg dry weight m−3, respectively. Copepods dominated the mesozooplankton community, reaching 73–98% and 61–97% of the total abundance and biomass.
Calanus finmarchicus and Oithona similis were the most abundant species at all stations. The biodiversities (Shannon indices) of the mesozooplankton community varied
between stations from 1.10 to 2.46 (estimated from species abundances) and from 0.19 to 1.92 (estimated from species biomasses),
averaging 1.93 ± 0.127 and 1.34 ± 0.151, respectively. Three groups at the 48% level of dissimilarity of species abundance
were delineated by cluster analyses. The clusters differed significantly with respect to temperature and salinity. The total
mesozooplankton abundance and biomass as well as quantitative parameters of most common taxa scaled negatively with temperature. 相似文献
11.
Aboulghasem Roohi Ahmet E. Kideys Ameneh Sajjadi Abdolla Hashemian Reza Pourgholam Hasan Fazli Ali Ganjian Khanari Elif Eker-Develi 《Biological invasions》2010,12(7):2343-2361
Monitoring for 6 years (2001–2006) showed that the population explosion of the alien ctenophore Mnemiopsis leidyi in the southern Caspian Sea coincided with a decline in the abundance and species number of mesozooplankton. While this decline
appeared to have reduced the nourishment of sprat (also known as kilka), it seemed to have affected phytoplankton favorably
mainly due to the decrease in grazing pressure. During 2001–2002, when M. leidyi abundance and biomass were at their highest levels, abundance of dinoflagellates and cyanophytes exceeded that of diatoms.
Before the invasion (1996) and in some years after the invasion (2003, 2004 and 2006) diatom abundance was higher than the
abundance of other groups. In September 2005, an unprecedented bloom of the toxic cyanophyte Nodularia sp. was observed in the southern Caspian Sea. Disappearance of edible zooplankton such as Eurytemora spp. was among the first changes observed after the expansion of M. leidyi in the area. Some changes in the macrobenthic fauna were also conspicuous after the increase of this ctenophore. While the
biomass of some deposit feeders, such as the polychaete Nereis diversicolor and oligochaete species increased, benthic crustaceans decreased sharply in abundance during 2001–2003 and completely disappeared
during 2004–2006. Iranian catches of kilka, the most abundant and widespread zooplanktivorous fish, decreased significantly
in the southern Caspian Sea after 1999. Iranian landings of kilka dropped ~70% from 69,070 ± 20,270 t during 1995–2000 to
23,430 ± 12,240 t during 2001–2006, resulting in a loss of at least 125 million US dollars to the economy. There were also
changes in the total catches of large predators such as the kutum and mullet, which mainly feed on kilka, between 1991 and
2006. 相似文献
12.
Beldade Ricardo; Borges Rita; Goncalves Emanuel J. 《Journal of plankton research》2006,28(11):1003-1013
In this study, we compare the composition, abundance and structureof a temperate fish larval assemblage at different depth intervals(04, 48 and 812 m) in the extreme nearshoreenvironment. We used a plankton net attached to an underwaterscooter to sample in close proximity to the rocky substrate(<50 cm). A total of 868 larvae from 27 taxa in 13 familieswere caught. The majority of larvae belonged to benthic reef-associatedspecies (Blenniidae, Gobiidae, Gobiesocidae and Tripterygiidae),the four most abundant comprising 76% of the total larvae caught.A non-metric multidimensional scaling analysis (MDS) showedthat there was a single multispecific larval patch near thesubstrate in the extreme nearshore up to 12 m depth. Nonetheless,distinct larval abundances were found in this relatively smalldepth range, with the majority of species being more abundantat the deepest interval, particularly Pomatoschistus pictusand Gobius xanthocephalus. Tripterygion delaisi was an exceptionbeing more abundant at the shallowest depth as young larvae.The density of pre-flexion larvae was not significantly differentacross depth intervals, but post-flexion larval density increasedwith depth. The full size range (from hatching to settlement)of P. pictus was present at the extreme nearshore. The innovativesampling technique used here revealed high densities of larvaeclose to the bottom, and depth was found to be an importantfactor influencing the distribution of several taxa and ontogeneticstages. The nearshore component of coastal fish larval assemblagesnear rocky substrates has been poorly studied, and our resultssuggest that the high densities of larvae found to aggregatein these environments must be taken into account when studyingdistribution and functional aspects of these assemblages. 相似文献
13.
P. Ward A. Atkinson A. W. A. Murray A. G. Wood R. Williams S. A. Poulet 《Polar Biology》1995,15(3):195-208
Zooplankton abundance and biomass were determined during January 1990 at two stations to the north-west of South Georgia using a Longhurst Hardy Plankton Recorder (LHPR). At both shelf and oceanic station sites, zooplankton biomass, (excluding Euphausia superba), was found to be ca. 13 g dry mass m–2. Copepods and small euphausiids dominated the catches. These estimates are over 4 times higher than values generally reported for the Southern Ocean and may reflect firstly, the high productivity of the study area, secondly, the time of year, summer, when biomass for many species is maximal, and thirdly, the high sampling efficiency of the LHPR. Principal components analysis disclosed similarities and differences between adjacent depth strata in terms of abundance, biomass and species composition. At both stations most variability occurred in the mixed layer (0–60 m) and thermocline (60–120 m) with depth horizons below this being more homogeneous. Diel migrations were observed for most taxa with abundance increasing in the mixed layer at night. At the oceanic station, species and higher taxa belonging to the mesopelagic community were generally well spread throughout this domain and, with the exception of Pleuromamma robusta and Metridia curticauda, showed little evidence of migration. The grazing impact of the epipelagic community (copepods and small euphausiids) was estimated to remove 3–4% of the microbial standing stock day–1 and a conservative 25% and 56% of daily primary production at the oceanic and shelf stations respectively. 相似文献
14.
The annual cycle of heterotrophic freshwater nanoflagellates: role of bottom-up versus top-down control 总被引:6,自引:0,他引:6
The population dynamics of heterotrophic nanoflagellates (HNF)were analyzed in pre-alpine Lake Constance over three consecutiveyears. A recurrent seasonal pattern led to the identificationof five seasonal phases: winter, spring, clear-water, summerand autumn. HNF biomass was lowest in winter and highest m latespring several weeks after the phytoplankton spring bloom. Theaverage biomass of HNF was 512% of bacterial biomassand 1334% of ciliate biomass respectively. The largestHNF cells were recorded during the spring phase, whereas theaverage cell size was reduced to one-third during the subsequentclear-water phase. The pronounced differences in the mean cellsize were attributed mainly to varying grazing impact on HNFThroughout most of the year, HNF production was balanced bygrazing of microzooplankton, namely ciliates, within the microbialloop. During the dear-water phase, however, the grazing impactwas mainly due to rotifers and daphnids. Changing grazing impactwas primarily responsible for the observed 2-fold interannualdifference m the mean biomass of HNF Overall, top-down controlby grazing was more important in governing the population dynamicsof HNF than bottom-up control by bacterial food supply. 相似文献
15.
Copepod grazing impact on the trophic structure of the microbial assemblage of the San Pedro Channel, California 总被引:3,自引:0,他引:3
In August 2002 and March 2003 the trophic structure of the microbialassemblage from the San Pedro Channel, California was studiedfollowing the experimental alteration of the number of copepods.Changes in the abundance/biomass of microorganisms <80 µmduring 3-day incubations were monitored in (i) the absence ofmetazoa >80 µm, (ii) the presence of natural abundancesof metazoa and (iii) the presence of an elevated number of copepods.Prokaryotes and small-sized eukaryotes (<4 µm) dominatedplankton biomass during both experimental months. Diatoms numericallydominated the 1080 µm plankton in August 2002,but ciliate and heterotrophic dinoflagellate biomass generallyexceeded diatom biomass on both dates. Ingestion of protozooplankton(predominantly ciliates) contributed substantially to copepoddaily carbon rations. The adult copepod assemblage removed 4.6and 36% per day of the microzooplankton standing stocks (1080µm size fraction) in August and March, respectively. Elevatedcopepod grazing pressure on protozooplankton resulted in increasedbiomass of nanoplankton (<5 µm) presumably via a trophiccascade. Accordingly, the copepodprotozoan trophic linkappears to be a key factor structuring the planktonic microbialassemblage in the San Pedro Channel.
This paper is one of six on the subject of the role of zooplanktonpredatorprey interactions in structuring plankton communities. 相似文献
16.
Abstract Changes in the abundance and biomass of aquatic and terrestrial aerial insects with distance (mid‐stream, 0, 10–15 and 160 m) from lowland streams were examined across the dry season landscape in Kakadu National Park, northern Australia. Malaise traps and sticky intercept traps were used to sample the insects at four streams, spaced over an area of 1650 km2. Malaise and intercept catches were dominated by Diptera (flies and midges), both numerically and by biomass. Chironomid midges were the most abundant taxon, making up 43.4 and 51.0% of the malaise and intercept trap catches, respectively. However, most chironomids were small (less than 3 mm body length), contributing 34.9% to intercept trap biomass, but only 5.2% in malaise traps. Ceratopogonid midges and caddisflies (Trichoptera) accounted for most of the remaining adult aquatic insects. Major terrestrial components were Diptera and Hymenoptera in malaise traps and Coleoptera and Diptera in intercept traps. The total abundance and biomass of insects were much greater over streams and along the water's edge than in riparian (10–15 m) and savanna (160 m) habitats primarily because of the presence of large numbers of adult aquatic insects. The abundance and biomass of terrestrial insects in malaise traps showed no relationship with distance, but intercept trap catches suggested slightly greater abundances over the water and at the water's edge. The great abundance of aquatic insects relative to terrestrial insects close to streams suggests that they have the potential to be an important component of the diets of riparian insectivores, and predation may be an important pathway by which aquatic nutrients and energy are moved into terrestrial food webs. 相似文献
17.
Macroinvertebrate composition, abundance and biomass were investigated at four intertidal sites throughout the Robbins Passage
wetlands, Tasmania, over a 12-month period, in order to identify differences among and within sites, and to determine whether
environmental variables could explain these differences. As this region is the most important shorebird area in Tasmania,
we wanted to quantify the potential food source for shorebirds within the wetlands. Thirty-five taxa from 28,928 individuals
were identified, with a mean abundance of 6026.6 ind m−2 and biomass of 27.1 gDW m−2. Bivalves and gastropods dominated the assemblage in terms of abundance and biomass (79% and 60%, respectively). There was
a significant interaction among tidal level, site and season for invertebrate abundance and diversity, while biomass differed
significantly among sites. In general, the mid-intertidal stratum had the greatest invertebrate density and diversity, while
the low intertidal stratum had the greatest biomass. Community composition varied among the four sites, with the bivalve Paphies
elongata dominating at two of the sites, while gastropods and polychaetes were more abundant at the other sites. Differences in invertebrate
composition and abundance could partly be explained by seagrass biomass, i.e., dry mass of seagrass leaves and roots. Areas
with seagrass had increased invertebrate abundance and diversity, but mean sediment particle size, % organic carbon and %
seagrass cover had no significant effect. These results will assist in the investigation of habitat use by shorebirds and
the identification of important shorebird feeding areas within the wetlands.
Handling editor: P. Viaroli 相似文献
18.
Planktonic ciliated protozoa: their distribution and relationship to environmental variables in a marine coastal ecosystem 总被引:4,自引:1,他引:3
The spatial distribution of planktonic ciliated protozoa, physicalvariables and potential food items were measured at northernand southern sites off the west coast of the South Island, NewZealand, to examine which variables were important in structuringthe ciliate community. Ciliates contributed 30% of total zooplanktonbiomass. Ciliate abundance was greatest within 55 km of thecoast on the northern transect, but on the southern transectthe greatest abundance was close inshore and at the stationsoffshore of the continental shelf. The ciliate community wasdominated by small oligotrichs and abundance (1141139l1 was comparable with other oligotrophic marine environments.The depth of the pycnocline had a major influence on the verticaldistribution of ciliates, which were closely correlated withprofiles of phytoplankton biomass and picophytoplankton abundance,but not primary production. The results of this study suggestthat physical factors were more important than biotic factorsin influencing the distribution of protozoan ciliates. The deepmixed layer prevented the formation of deep chlorophyll a orciliate maxima. Few studies of microzooplankton have incorporatedpicophytoplankton distribution, but the importance of smallciliates and picophytoplankton suggests that these groups mayplay a pivotal role in mediating the transfer of organic matterto higher trophic levels in this marine coastal ecosystem. 相似文献
19.
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
20.
How important is bacterial carbon to planktonic grazers in a turbid, subtropical lake? 总被引:2,自引:0,他引:2
Work Kirsten; Havens Karl; Sharfstein Bruce; East Therese 《Journal of plankton research》2005,27(4):357-372
This study examined the relative contributions of bacterialand phytoplankton production to the pelagic carbon flow of LakeOkeechobee, a large and shallow subtropical lake. Due to thepredominance of cyanobacteria in this lake, we hypothesizedthat bacterial carbon flow would be larger than phytoplanktoncarbon flow to grazers. Using epifluorescent and light microscopyand radiotracer techniques, we measured the carbon biomass ofplanktonic functional groups and carbon flow between these groups.The functional groups that we used in this study included: picophytoplankton,autotrophic nanoflagellates (ANAN), microphytoplankton, bacteria,heterotrophic nanoflagellates (HNAN), ciliates, microzooplankton(rotifers and copepod nauplii) and macrozooplankton (cladocerans,copepodites and adult copepods). Microphytoplankton dominatedthe carbon biomass of all plankton, whereas the calanoid copepod,Diaptomus, dominated the carbon biomass of the grazers. Phytoplanktoncarbon flow often was higher than bacterial carbon flow to grazers;however, bacterial carbon constituted a large percentage ofthe total carbon flow to grazers (33.7 ± 22.4%). Bacterialcarbon provided roughly one quarter of the carbon flow to macrozooplankton(27.1 ± 25.4%), whereas it provided half of the carbonflow to microzooplankton (57.4 ± 20.3%) and to protozoans(47.2 ± 25.8%). These results suggest that microbialpathways play an important role in the energetics of subtropicallake plankton communities. Although microbial loop pathwaysare important in many systems, direct bacterial carbon flowto macrozooplankton also may be important in copepod- and cyanobacteria-dominatedlakes. 相似文献