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  • 1
    Electronic Resource
    Electronic Resource
    An experimental study of the effects of nutrient supply and Chaoborus predation on zooplankton communities of a shallow tropical reservoir (Lake Brobo, Côte d'Ivoire) (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Based on two mesocosm experiments and 10 in vitro predation experiments, this work aimed to evaluate the impact of nutrient supply and Chaoborus predation on the structure of the zooplankton community in a small reservoir in Côte d'Ivoire.2. During the first mesocosm experiment (M1), P enrichment had no effect on phytoplankton biomass (chlorophyll a) but significantly increased the biomass of some herbivorous zooplankton species (Filinia sp, Ceriodaphnia affinis). During the second experiment (M2), N and P enrichment greatly increased phytoplankton biomass, rotifers and cladocerans (C. affinis, C. cornuta, Moina micrura and Diaphanosoma excisum). In both experiments, nutrient addition had a negative impact on cyclopoid copepods.3. Larger zooplankton, such as cladocerans or copepodites and adults of Thermocyclops sp., were significantly reduced in enclosures with Chaoborus in both mesocosm experiments, whereas there was no significant reduction of rotifers and copepod nauplii. This selective predation by Chaoborus shaped the zooplankton community and modified its size structure. In addition, a significant Chaoborus effect on chlorophyll a was shown in both experiments.4. The preference of Chaoborus for larger prey was confirmed in the predation experiments. Cladocerans D. excisum and M. micrura were the most selected prey. Rotifer abundance was not significantly reduced in any of the 10 experiments performed.5. In conclusion, both bottom-up and top-down factors may exert a structuring control on the zooplankton community. Nutrients favoured more strictly herbivorous taxa and disadvantaged the cyclopoid copepods. Chaoborus predation had a strong direct negative impact on larger crustaceans, favoured small herbivores (rotifer, nauplii) and seemed to cascade down to phytoplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01096.x
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  • 2
    Electronic Resource
    Electronic Resource
    Role of bacteria as food for zooplankton in a eutrophic tropical pond (Ivory Coast) (1994)
    Springer
    Aquatic ecology 28 (1994), S. 167-174 
    Details
    ISSN: 1573-5125
    Keywords: bacteria ; zooplankton ; grazing ; tropical pond ; eutrophic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of the study was to determine whether bacteria could be a substantial source of carbon for zooplankton and whether the grazing pressure of these metazoan filter-feeders could influence the fate of bacterial production. Eight grazing experiments using natural bacteria labelled with3H thymidine were conducted in a tropical pond (Ivory Coast) during various phases of biological colonization (rotifer-dominated and copepod-dominated phases of the colonization). Higher grazing and clearance rates were observed with rotifers (Brachionus plicatilis andHexarthra intermedia), while very low values were obtained when the cyclopoid copepodApocyclops panamensis was dominant. Less than 1% of the bacterial production was harvested when copepods were dominant, whileB. plicatilis consumed up to 36% of this production. However, this consumption of bacteria appeared to contribute only to an insignificant proportion of the daily carbon intake (e.g. 0.9 to 7.1% of body carbon for rotifers). The low contribution of bacteria in the nutrition of zooplankton is discussed in terms of their cell size and their relative abundance in the total amount of seston available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02333987
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  • 3
    Electronic Resource
    Electronic Resource
    Cross frontal variability in hydrological and biological structures observed in a river plume area (Rhône mouth, NW Mediterranean Sea) (1996)
    Springer
    Hydrobiologia 324 (1996), S. 131-140 
    Details
    ISSN: 1573-5117
    Keywords: plume ; variability ; dissolved matter ; particles ; bacteria ; flagellates ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the Rhône River plume area, NH inf4 + , DFAA, seston particles, bacteria, flagellates and mesozooplankton were studied over 24 hours at a fixed station. Variations of both abiotic and biotic variables demonstrated rapid changes in vertical structure, from stratified towards mixed. This evolution was related to hydrodynamical changes caused by wind. Strong variability resulting from hydrological changes was apparent in surface water where the plume edge crossed the station as evident by sharp increase in particle volume (20–25 µm ESD range), NH inf4 + (from 9 to 12 µM) and DFAA (from 1 to 3 µM) concentrations. This frontal ecosystem favored fast growing organisms such as bacteria of which densities reached 19 and production 0.22–0.26 µg C l−1 h−1, and flagellates which showed densities of 1.5 to 2 µg C l−1. Among DFAA, the relative concentration (mole %) of serine increased from 13.3% in the plume water to 44–45% in the front system. The biomass and feeding activity of zooplankton also increased at the plume boundary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018174
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  • 4
    Electronic Resource
    Electronic Resource
    Variation nycthémérale de la répartition verticale et de l'efficacité de collecte du zooplancton en lagune Ebrié (Côte d'Ivoire) (1990)
    Springer
    Hydrobiologia 194 (1990), S. 247-265 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vertical distribution and night and day collecting efficiencies of both nets and a Schindler trap, were studied in two shallow (4 m) unstratified bays of the Ebrié Lagoon. Some of the organisms migrate (Mysidacae, copepodite and adult stages of Acartia clausi and Pseudodiaptomus hessei) and others do not (all the nauplii, copepodite and adult stages of Oithona brevicornis, rotifers, mollusca larvae). The first are found more or less near the bottom at noon and are evenly distributed throughout the water at the beginning of the night. Mysidaceae and P. hessei strongly exhibit this pattern, none (Mysidacea) or very few specimens being collected in the water during the day. For A. clausi, depth concentration increases from C1 to adult. Net and trap estimated night densities are higher than the day ones for migrating organisms, except for C1 or A. clausi. The Night/Day ratios are equal to 28 (net) and 25 (trap) for P. hessei, 5 and 13 for the adults of A. clausi and lies between 2 and 5 for the different copepodite stages of this last species. The possible causes and consequences of the vertical distribution are discussed, the interference of turbulence on vertical distribution being outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007124
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  • 5
    Electronic Resource
    Electronic Resource
    Zooplankton feeding on seston in the Rhone River plume area (NW Mediterranean Sea) in May 1988 (1990)
    Springer
    Hydrobiologia 207 (1990), S. 241-249 
    Details
    ISSN: 1573-5117
    Keywords: River plume ; zooplankton ; particle spectrum ; grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the Rhone delta area the seston concentration was maximum in the plume waters where small-sized particles dominated, while marine waters were characterized by large particles. The food conditions were optimal for grazers in the interface layer, where the high chlorophyll concentration contrasted with the low values found under the plume. The mesozooplankton specific composition did not show marked difference in and outside the plume. No special pattern for particle size selection by grazers appeared in the plume, contrary to marine waters, where largest particles were the most intensively grazed. The calculations of specific ingestion and filtration rates show that the plume waters (particularly at the salinity interface) were more favourable to zooplankton feeding than the marine ones (outside and under the plume). Nevertheless, taking into account the high level of seston biomass in the whole area studied, the daily grazing pressure of mesozooplankton was very low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041462
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  • 6
    Electronic Resource
    Electronic Resource
    Premiéres données sur la nutrition d'Acartia clausi en Lagune Ebrié (Côte d'Ivoire) obtenues par des mesures de la fluorescence de broyats d'animaux (1985)
    Springer
    Hydrobiologia 121 (1985), S. 83-95 
    Details
    ISSN: 1573-5117
    Keywords: nutrition ; Acartia clausi ; Ebrie lagoon ; Ivory Coast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Circadian variations in gut repletion were observed in adults of Acartia clausi, based on fluorescent pigments measurements. Maximum values lies between 2.00 and 8.00 p.m. and minimum values between 2.00 and 8.00 a.m. This variation which is associated with a less important variation of the concentration of organic particles in water, is assumed to result from a circadian variation in filtration rate. This assumption is discussed on the basis of a rough simulation of the variation of gut repletion. Daily ration estimated according to the observed gut repletion values lies between 35 and 86% of the body organic dry weight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035233
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  • 7
    Electronic Resource
    Electronic Resource
    Comparaison de deux techniques de prélèvement du zooplancton, le filet et la trappe de Schindler, en lagune Ebrié (Côte d'Ivoire) (1989)
    Springer
    Hydrobiologia 173 (1989), S. 167-172 
    Details
    ISSN: 1573-5117
    Keywords: Ivory Coast ; tropical lagoon ; zooplancton ; comparison trap vs net
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The analysis of net (bottom to surface vertical hauls) and trap samples taken at night shows that net hauls underestimate abundance of all planktonic organisms from nauplii and mollusc larvae to adult calanids. There is no obvious explanation for this. The underestimation probably results from low net filtering efficiency. The mean ratio between trap and net observed densities is 1.46 (1.2 to 1.9) and does not change significantly according to the organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008964
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  • 8
    Electronic Resource
    Electronic Resource
    Répartition verticale du phytoplancton, des bactéries et du zooplancton dans un milieu stratifié en Baie de Biétri (Lagune Ebrié, Cote d'Ivoire). Relations trophiques (1983)
    Springer
    Hydrobiologia 106 (1983), S. 135-148 
    Details
    ISSN: 1573-5117
    Keywords: bacterial vertical distribution ; stratified lagoon ; phototrophic bacteria ; zooplankton feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the period of September–November 1981, a stratified condition was observed in Biétri Bay, a part of Ebrié Lagoon (Ivory Coast, Africa). The epilimnion was oxidised and in the hypolimnion, high concentrations of hydrogen sulfide were noted (200–400 mg · l−1). At the surface of the hypolimnion, a large population of phototrophic bacteria developed, constituting a brown layer composed of the purple and green bacteria Rhodopseudomonas sp., Chromatium gracile, Chlorobium vibrioforme, C. phaeobacteroides and Pelodictyon sp. These bacteria can be considered as particulate organic matter producers. Their production is estimated at about 1 530 mg C · m−2 · day−1. In the epilimnion, the algal production is 2 200 mg C · m−2 · day−1. Therefore, phototrophic bacterial production represented 41% of the total photosynthetic production. In the epilimnion, the zooplankton community (composed of copepods, rotifers and some cyclopids) was particularly concentrated near the chemocline where only low concentration of dissolved oxygen was available. Analysis of gut contents of the copepod Acartia clausi, which is the dominant species of the zooplankton, shows the importance of phototrophic bacteria and especially Rhodospirillaceae and Chromatium in its diet. This copepod seems to prefer phototrophic bacteria to both heterotrophic bacteria and phytoplancton. The vertical migration of the zooplankton community is partly conditioned by the search for nutrients i.e. phototrophic bacteria. Thus, bacteria contribute to the first trophic level of the food chain in this lagoon. Since they derive part of their energy from organic matter formed by primary producers, they cannot be considered as pure primary producers. However, in respect to the food chain they form food material for secondary producers (zooplankton).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006746
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  • 9
    Electronic Resource
    Electronic Resource
    Ecological organization and succession during natural recolonization of a tropical pond (1994)
    Springer
    Hydrobiologia 294 (1994), S. 229-242 
    Details
    ISSN: 1573-5117
    Keywords: bacteria ; phytoplankton ; protozoa ; rotifera ; cyclopoids ; succession ; recolonization ; tropical pond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structure of a planktonic community was studied in April 1990 for 24 days (D1 to D24) during the natural recolonization of a tropical pond (Côte d'Ivoire) made azoic by emptying and liming (D0). Abundances of bacterioplankton, phytoplankton, protozoans and zooplankton were studied twice daily, whereas hydrological descriptors (temperature, conductivity, oxygen, pH, dissolved nutrients, sestonic weights) were recorded several times daily. After the pond treatment, the natural refilling from groundwater began immediately. The microheterotrophic (bacteria, flagellates, ciliates), phytoplanktonic (Coelastrum microsporum) and zooplanktonic (the rotifers Brachionus plicatilis and Hexarthra intermedia) communities were first based on opportunist species favored by the initially large nutritive availability. This close link with the trophic resources induced their rapid elimination, as soon as the food source was depleted by overconsumption. Due to liming effects, great amounts of degradable organic compounds allowed bacterial communities to develop before phytoplankton. This biological succession was first based on a catastrophic-type system, successively controlled by bottom-up factors (proliferation) and top-down factors (species collapse). Then, the colonization was completed with the development of secondary consumers (last stages of Apocyclops panamensis and chironomids). The progressive complexity of the system ensured the attenuation of the disturbing events. Finally, due to volume variations of the pond along the recolonization steps, the effects of the dilution process on bacteria and chlorophyll biomass were studied. In a context of non-limiting nutrient substrata, the microbial community was able to colonize the new volume within a few hours. Phytoplankton showed a more complex adaptation to the volume increase, with mixed effects of grazing, sedimentation and diurnal productions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021296
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  • 10
    Electronic Resource
    Electronic Resource
    Zooplankton food limitation and grazing impact in a eutrophic brackish-water tropical pond (Côte d'Ivoire, West Africa) (1998)
    Springer
    Hydrobiologia 390 (1998), S. 83-98 
    Details
    ISSN: 1573-5117
    Keywords: seston ; size-structure ; Coulter counter ; selectivity ; gut fluorescence ; rotifers ; cyclopids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gut fluorescence, feeding and egg production rates of zooplankton assemblages were measured in a shallow, eutrophic brackish-water pond for 24 days. Brachionus plicatilis, Hexarthra intermedia and Apocyclops panamensis successively developed and exhibited differences in food selectivity. Rotifers selected small particles but also had a preference for larger particles (15–21 μm, Equivalent Spherical Diameter, ESD). B. plicatilis appeared less selective than H. intermedia, which fed mostly on particles 〈6 μm. A. panamensis adults showed a selectivity for 6–21 μm ESD particles. Laboratory experiments suggested that A. panamensis adults were able to shift from seston to carnivorous feeding, depending on the availability of these food resources. Measurements of gut fluorescence and grazing gave comparable ingestion rates. Rotifers displayed the highest ingestion rates (up to 486% body C d-1). Despite high total phytoplankton and seston biomasses, the high ingestion rates and selective grazing of rotifers induced auto food-limitation phenomena and caused major changes in seston abundance and size structure. Grazing impact was less important when A. panamensis dominated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003561821745
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