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Planktonic ciliate distribution relative to a deep chlorophyll maximum: Catalan Sea, N.W. Mediterranean, June 1993
Dolan, J.R.; Marrasé, C. (1995). Planktonic ciliate distribution relative to a deep chlorophyll maximum: Catalan Sea, N.W. Mediterranean, June 1993. Deep-Sea Res., Part 1, Oceanogr. Res. Pap. 42(11-12): 1965-1987
In: Deep-Sea Research, Part I. Oceanographic Research Papers. Elsevier: Oxford. ISSN 0967-0637, more
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  • Dolan, J.R., more
  • Marrasé, C.

Abstract
    Vertical distributions and relative contributions of distinct trophic guilds of ciliates wereinvestigated in an oligotrophic system with a deep chlorophyll maximum (DCM) in early summer.Ciliates were classified as heterotrophic: micro and nano ciliates, tintinnids and predacious forms orphotosynthetic: large mixotrophic oligotrichs (Laboea sfrobilia. Tontoniu spp.), and the autotrophicMesodinium rubrum. Variability between vertical profiles (O-200 m) was relatively lowwith station to station differences (C.V.s of ~30%) generally larger than temporal (1-4 day)differences (C.V.s of ~15%), for integrated concentrations. Total ciliate biomass, based onvolume estimates integrated from O-SO m, averaged ~ 125 mg C m-2, compared to ~35 mg m-2 forchlorophyll a (chl a), yielding a ciliate to chl ratio of 3.6, well within the range of 1 to 6 reported forthe euphotic zones of most oceanic systems. Heterotrophic ciliate concentrations were correlatedwith chl ti concentration (r = 0.83 and 0.82, biomass and cells I-1, respectively) and averaged~230cells I-1 in near surface samples (chl a = 0.1 fig I-1) to ~850cells I-1 at 50 m depth, coinciding withthe DCM (chl a = I-2pg I-1). Tintinnid ciliates were diverse (36 species in 19 genera) but a minorpart of heterotrophic ciliates. Nanociliates represented -1, were an importantpart of total ciliate biomass, representing 63% at 5 m and 21% integrated over O-80 m. Mesodiniumrubrum was found throughout the water column, usually with a sub-surface peak (~100 cells I-1),Concentrations of neither large mixotrophic oligotrichs, nor the autotrophic M. rubrum, werecorrelated with chl a. Estimates of the contribution of photosynthetic ciliate chl (mixotrophic andautotrophic) to total chl a (based on literature values of chl a cell-1) ranged from ~20% in somesurface samples to <0.5% in the DCM.INTRODUCTIONIn diverse marine systems, subsurface chlorophyll maximum layers are common, and avariety of governing mechanisms such as nutrient supply, differential grazing, and cellsinking have been proposed to account for them (e.g., Bienfang et al., 1983). In theoligotrophic Catalan Sea, a deep chlorophyll maximum (DCM) is present from earlyspring to autumn, between 40 and 60 m depth, coinciding with depth of both nitrate andphosphate nutriclines (Estrada et al., 1993). Production in the DCM ranges from 15 to*CNRS/INSU, Observatoire Oceanologique, URA 716, B.P. 28. F-06230 Villefranche-sur-mer. France.E-mail: dolan@ccrv.obs-vlfr.fr.tlnstitut de Citncies del Mar (CSIC), Passeig Joan de Borbo s/n, E-08039 Barcelona, Spain.E-mail: celia@masagran.icm.csic.es.1965

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