Nanoflagellate predation on auto- and heterotrophic picoplankton in the oligotrophic Mediterranean Sea

Christaki, Urania; Giannakourou, Antonia; Grégori, Gérald

doi:10.1093/plankt/23.11.1297

Cited by 156 publications

(135 citation statements)

References 61 publications

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“…Oligotrophy seems to be mainly due to the very low concentration of inorganic phosphorus, which is assumed to limit primary production (Berland et al, 1980;Thingstad andRassoulzadegan, 1995, 1999;Thingstad et al, 2005). Additional features of the MS are i) the decreasing west-east gradient in chl a concentration, as shown by color remote sensing (D'Ortenzio and Ribera d 'Alcalá, 2009;Barale et al, 2008) as well as by in situ data (Turley et al, 2000;Christaki et al, 2001), ii) a high diversity compared to its surface and volume (Bianchi and Morri, 2000), and iii) a relatively high number of bioprovinces (sensu Longhurst, 2006), with boundary definition mostly based on the distribution of the benthos and the necton (Bianchi, 2007). The MS is also a site of intense anthropic activity dating back to at least 5000 years BP, the impact of which on the marine environment has still to be clearly assessed and quantified.…”

Section: Introductionmentioning

confidence: 99%

Plankton in the open Mediterranean Sea: a review

et al. 2010

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Abstract. We present an overview of the plankton studies conducted during the last 25 years in the epipelagic offshore waters of the Mediterranean Sea. This quasi-enclosed sea is characterized by a rich and complex physical dynamics with distinctive traits, especially in regard to the thermohaline circulation. Recent investigations have basically confirmed the long-recognised oligotrophic nature of this sea, which increases along both the west-east and the north-south directions. Nutrient availability is low, especially for phosphorous (N:P up to 60), though this limitation may be buffered by inputs from highly populated coasts and from the atmosphere. Phytoplankton biomass, as chl a, generally displays low values (less than 0.2 µg chl a l −1 ) over large areas, with a modest late winter increase. A large bloom (up to 3 µg l −1 ) is observed throughout the late winter and spring exclusively in the NW area. Relatively high biomass values are recorded in fronts and cyclonic gyres. A deep chlorophyll maximum is a permanent feature for the whole basin, except during the late winter mixing. It is found at increasingly greater depths ranging from 30 m in the Alboran Sea to 120 m in the easternmost Levantine basin. Primary production reveals a west-east decreasing trend and ranges between 59 and 150 g C m −2 y −1 (in situ measurements). Overall, the basin is largely dominated by small autotrophs, microheterotrophs and egg-carrying copepod species. The microorganisms (phytoplankton, viruses, bacteria, flagellates and ciliates) and zooplankton components reveal a considerable diversity and

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Section: Introductionmentioning

confidence: 99%

Plankton in the open Mediterranean Sea: a review

et al. 2010

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“…Following viral infection and lysis, picoplankton cellular products are released into surrounding waters and are rapidly assimilated by bacteria in an essentially semi-closed system (Middelboe et al, 2003); as much as one quarter of photosynthetically fixed organic carbon may short circuit back through the microbial food web (Wilhelm and Suttle, 1999). Alternatively, other mechanisms such as particle scavenging (as discussed above) and grazing of picoplankton by nanoplankton (Christaki et al, 2001) may act similarly to shape the distributions of the picoplankton community.…”

mentioning

confidence: 99%

Biophysical characteristics of a morphologically-complex macrotidal tropical coastal system during a dry season

Jones

Patten

Krikke

et al. 2014

Estuarine, Coastal and Shelf Science

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“…It has long been assumed that HNF feed on pico-sized phytoplankton (Fenchel 1982, Azam et al 1983), yet recent studies on the grazing potential of HNF focus on quantifying bacterivory and neglect the additional portion of carbon taken up via picophytoplankton (Tanaka et al 1997, Iriarte et al 2008. They are, how ever, major grazers of picophytoplankton (Christaki et al 2001, Sherr & Sherr 2002, Brę k-Laitinen & Ojala 2011, and it remains for future studies to resolve the importance of HNF grazing. We here would suggest splitting the group into large and small HNF to test whether the size groups have different prey-size preferences as speculated by Sherr & Sherr (2002) and Vaqué et al (2008).…”

Section: Heterotrophic Protist: Top-down Control On Picophytoplankton?mentioning

confidence: 99%

Winter-spring transition in the subarctic Atlantic: microbial response to deep mixing and pre-bloom production

Paulsen¹,

Riisgaard²,

Thingstad³

et al. 2015

Aquat. Microb. Ecol.

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In temperate, subpolar and polar marine systems, the classical perception is that diatoms initiate the spring bloom and thereby mark the beginning of the productive season. Contrary to this view, we document an active microbial food web dominated by pico-and nanoplankton prior to the diatom bloom, a period with excess nutrients and deep convection of the water column. During repeated visits to stations in the deep Iceland and Norwegian basins and the shallow Shetland Shelf (26 March to 29 April 2012), we investigated the succession and dynamics of photosynthetic and heterotrophic microorganisms. We observed that the early phytoplankton production was followed by a decrease in the carbon:nitrogen ratio of the dissolved organic matter in the deep mixed stations, an increase in heterotrophic prokaryote (bacteria) abundance and activity (indicated by the high nucleic acid:low nucleic acid bacteria ratio), and an increase in abundance and size of heterotrophic protists. The major chl a contribution in the early winter−spring transition was found in the fraction <10 µm, i.e. dominated by pico-and small nanophytoplankton. The relative abundance of picophytoplankton decreased towards the end of the cruise at all stations despite nutrient-replete conditions and increasing day length. This decrease is hypothesised to be the result of top-down control by the fast-growing population of heterotrophic protists. As a result, the subsequent succession and nutrient depletion can be left to larger phytoplankton resistant to small grazers. Further, we observed that large phytoplankton (chl a > 50 µm) were stimulated by deep mixing later in the period, while picophytoplankton were unaffected by mixing; both physical and biological reasons for this development are discussed herein.

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Nanoflagellate predation on auto- and heterotrophic picoplankton in the oligotrophic Mediterranean Sea

Cited by 156 publications

References 61 publications

Plankton in the open Mediterranean Sea: a review

Plankton in the open Mediterranean Sea: a review

Biophysical characteristics of a morphologically-complex macrotidal tropical coastal system during a dry season

Winter-spring transition in the subarctic Atlantic: microbial response to deep mixing and pre-bloom production

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