Significance of planktonic ciliated protozoa in the Lower St. Lawrence Estuary: comparison with bacterial, phytoplankton, and particulate organic carbon

Sime-Ngando, Télesphore; Gosselin, Michel; Roy, Suzanne; Chanut, Jean-Pierre

doi:10.3354/ame009243

Cited by 80 publications

(59 citation statements)

References 45 publications

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“…The genus and species of ciliates and autotrophic and heterotrophic flagellates, as well as those of large phytoplankton, were identified by consulting several taxonomic guides and references (Kofoid and Campbell 1939;Grassé 1952;Bick 1972;Cardinal et al 1977;Kudo 1977;Corliss 1979;Maeda and Carey 1985;Sournia 1986;Ricard 1987;Chré-tiennot-Dinet 1990;Sime-Ngando et al 1995;Tomas 1997).…”

Section: Methodsmentioning

confidence: 99%

Experimental test of the effect of ultraviolet‐B radiation in a planktonic community

Mostajir

Demers

Mora

et al. 1999

Limnology & Oceanography

114

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Ultraviolet-B (UVB, 280-320 nm) radiation is a natural component of sunlight that harms organisms and disturbs natural communities in surface waters. A natural planktonic assemblage of organisms (Ͻ240 m) was studied in a mesocosm experiment for 7 d under varying conditions of UVB radiation: UVB excluded, natural radiation, and UVB enhanced at two different levels. The dynamics of several populations at different trophic levels comprising heterotrophic bacteria (Ͻ1 m), heterotrophic flagellates (2-10 m), small phytoplankton (Ͻ5 m), large phytoplankton (5-20 m), and ciliates (15-35 m) were monitored during the experiment. Enhanced UVB provoked a significant decrease in the number of ciliates (66%) and large phytoplankton (63%) relative to natural UVB conditions. The severe effects of UVB radiation on ciliates and large phytoplankton communities shown here would strongly limit upward transfer of mass and energy. The decline of predator abundance (ciliates) under UVB stress relative to natural conditions resulted in a positive feedback between enhanced UVB radiation and prey abundances, shown by increased abundances of bacteria (49%), heterotrophic flagellates (up to 300%), and small phytoplankton (41%). Similarly, with respect to carbon partitioning, the decrease in ciliate and diatom carbon biomass (64 and 56%, respectively) under enhanced UVB exposure was balanced by an increase in the carbon biomass of heterotrophic bacteria (48%), heterotrophic flagellates (126%), and autotrophic flagellates (162%). As a manifestation of enhanced UVB at the community level, the ecosystem develops toward a microbial food web in preference to an herbivorous food web. Thus, enhanced UVB radiation can change the structure and dynamics of the pelagic food web.The pelagic planktonic community functions through a web of energy and nutrient exchanges mediated by a diverse array of producers and consumers, which ultimately depend on the energy supplied by sunlight. Following the discovery of stratospheric ozone depletion (Farman et al. 1985) and the resulting increase in intensity of biologically harmful UVB radiation (280-320 nm) reaching Antarctic waters, the majority of UVB studies have focused on phytoplankton be- AcknowledgmentsWe thank F. Rassoulzadegan, F. Azam, and T. Sime-Ngando for comments; C. Lovejoy and L. Bérard for help with the identification of some planktonic species; and D. Bourget and N. Lafontaine for nutrient analyses.This work was supported by NSERC of Canada, Fonds FCAR of Québec, and FODAR (University of Québec). International collaboration was made possible by NATO collaborative research grant (CRG 95139) to S.D. and P.M. This investigation is a contribution to the research programs of the Groupe de Recherche en Environnement Côtier.

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Section: Methodsmentioning

confidence: 99%

Experimental test of the effect of ultraviolet‐B radiation in a planktonic community

Mostajir

Demers

Mora

et al. 1999

Limnology & Oceanography

114

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“…Moreover, since the coastal ponds are periodically closed systems in which the plankton community undergoes rapid fluctuations, it remains difficult to establish valid criteria for comparisons with open coastal systems. Nevertheless, in terms of potential carbon resources available to the oysters, the amounts calculated for ciliates (63.5 pg C I-') were at the high level found for protozoa in coastal waters (St. Lawrence Estuary: 0.23 to 51.6 pg C I-', Sime-Ngando et al 1995).…”

Section: 126038mentioning

confidence: 99%

Retention of ciliates and flagellates by the oyster Crassostrea gigas in French Atlantic coastal ponds:protists as a trophic link between bacterioplankton and benthic suspension-feeders

Dupuy¹,

Gall²,

Hartmann³

et al. 1999

Mar. Ecol. Prog. Ser.

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Retention of ciliates and flagellates by the oyster. In order to evaluate the importance of the 'protozoan trophic link' for energy transfer from the 'microbial food web' to large benthic suspension feeders, we offered a coastal pond comn~unity of ciliates and flagellates as potential prey to the oyster Crassostrea gigas. Clearance rate, filtered particles and relative retention efficiency were evaluated. In the grazing experiment, 94 % of ciliates and 86% of flagellates (size between 4 and 72 pm), were retained by the oyster. Whatever their size, protists were similarly retained by the oyster gills. In terms of carbon, oysters retain on average 126 pg C h-' g-' dry weight, a value over 4 times h~g h e r than reported for phytoplankton. These results indicate that a field community of protists can contribute in coastal oyster rearing ponds to the energy requirements of the oyster C. gigas. We report here the first experimental ev~dence of a significant retention of a protist community by oysters, supporting the role of protists as a trophic link between picoplankton and benthic filter-feeding bivalves. The importance of phytoplankton in the nutrition of oysters is well documented , Pastoureaud et al. 1996. However, in oyster rearing environments, such as the particularly light-limited turbid estuary of Marennes-Oleron, or in coastal ponds of the Charente where nutrients are quickly exhausted, phytoplankton cannot entirely account for the energy requirements of oysters .In the oceans, more than 50% of the primary production is due to unicellular organisms less than 3 pm in size (Li et al. 1983, Glover et al. 1986), which constitutes a nutrient source of particulate and dissolved organic matter for heterotrophic organisms. Dissolved organic matter (DOM) present in coastal waters (Pomeroy & Wiebe 1993) provides a potential for high bacterial production. Thus, in the 0 Inter-Research 1999Resale of full artrcle not perrnltted

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“…Phytoplankton in the Lower Estuary is dominated by small-sized diatoms (< 25 µm; Levasseur et al 1984) and zooplankton collected in this study were generally >160 µm. Planktonic ciliated protozoa (25 to 75 µm), intermediate in size between phytoplankton and the sampled mesozooplankton, are regarded as an important trophic link between these 2 groups in the Lower Estuary (Sime-Ngando et al 1995). Similarly, the dominant copepod in the Gulf, Calanus finmarchicus, may rely mainly on heterotrophic microzooplankton for egg production and net lipid synthesis (Ohman & Runge 1994).…”

Section: Patterns Of 15 N Signatures and Trophic Relationshipsmentioning

confidence: 99%

Marine mammals and the community structure of the Estuary and Gulf of St Lawrence, Canada: evidence from stable isotope analysis

Lesage¹,

Hammill²,

Kovacs³

2001

Mar. Ecol. Prog. Ser.

162

131

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The trophic relationships of both the benthic and pelagic communities in the Estuary and Gulf of St Lawrence regions were examined, with a special focus on the trophic position (TP) and relationship(s) among harbour, grey, hooded and harp seals and beluga whales. A multiple stable isotope and multiple tissue approach, used in conjunction with conventional dietary information, suggested that marine mammals occupied the highest trophic positions in the food webs of both communities and that they overlapped with one another to some extent trophically. Harbour seals Phoca vitulina and hooded seals Cystophora cristata occupied the highest TP, grey seals Halichoerus grypus, Gulf harp seals Phoca groenlandica, and male beluga whales Delphinapterus leucas were intermediate, and Estuary harp seals and female beluga whales were at the lowest TP. A general pattern of increasing enrichment of 13 C or 15 N with age was observed in marine mammals (as well as fishes), although yearlings showed a decreased enrichment compared to both younger and older age classes. Sex also influenced δ 15 N values. Males were more 15 N-enriched than females, with the difference between the sexes increasing with age, and being most pronounced in species that are sexually dimorphic with respect to body size. Geographical location also influenced isotope abundance. Estuary organisms were generally 13 C-enriched relative to Gulf animals. δ 13 C values were on average lower in short-term diet integrators (blood serum) than in longer-term diet integrators (red blood cells) of harbour seals captured in April to June in the Estuary, which suggests that they probably did not move outside the Lower Estuary during the winter. Grey seals captured in the Lower Estuary did, however, show evidence of having been in the Gulf region some weeks or months before capture.

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Significance of planktonic ciliated protozoa in the Lower St. Lawrence Estuary: comparison with bacterial, phytoplankton, and particulate organic carbon

Cited by 80 publications

References 45 publications

Experimental test of the effect of ultraviolet‐B radiation in a planktonic community

Experimental test of the effect of ultraviolet‐B radiation in a planktonic community

Retention of ciliates and flagellates by the oyster Crassostrea gigas in French Atlantic coastal ponds:protists as a trophic link between bacterioplankton and benthic suspension-feeders

Marine mammals and the community structure of the Estuary and Gulf of St Lawrence, Canada: evidence from stable isotope analysis

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