Relative importance of nanoflagellates and ciliates as consumers of bacteria in a coastal sea area dominated by oligotrichous Strombidium and Strobilidium

Ichinotsuka, Daisuke; Ueno, Hiroyuki; Nakano, Susumu

doi:10.3354/ame042139

Cited by 37 publications

(28 citation statements)

References 42 publications

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“…Bacterial turnover rates were also within the range usually measured in the sea (Ichinotsuka et al 2006). Thus, bacterial losses attributable to total grazing commonly accounted for most BP, indicating that grazing would be the main loss process of bacteria in this system.…”

Section: Discussionmentioning

confidence: 64%

Significant year‐round effect of small mixotrophic flagellates on bacterioplankton in an oligotrophic coastal system

Unrein

Massana

Alonso‐Sáez

et al. 2007

Limnology & Oceanography

213

189

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The seasonal variation in the grazing effect of mixotrophic flagellates on bacterioplankton was assessed during an annual cycle in an oligotrophic coastal station in the northwest Mediterranean Sea. Ingestion rates of fluorescently labeled bacteria were estimated for different size categories of phytoflagellates (PF) and heterotrophic flagellates (HF) in short-term experiments and compared with long-term grazing estimates and published empirical models. The mixotrophic flagellates included haptophyte-like cells, cryptophytes, and dinoflagellates. The group-specific grazing rates (SGR) averaged 1.1 (3-5 mm PF), 1.3 (5-20 mm PF), 4.0 (,5 mm HF), and 15.4 bacteria individual 21 h 21 (5-20 mm HF). Lower SGR but higher abundances of PF resulted in an average mixotroph contribution of 50% to the total flagellate grazing. Remarkably, the effect was relatively high all through the year (35-65%). Regardless of the presence of chloroplasts, flagellates ,5 mm in size accounted, on average, for about 80% of total flagellate bacterivory and ingested a large percentage of their cell carbon per day from bacteria. Soluble reactive phosphorus concentration was negatively correlated with the ingestion rate of both groups of PF, suggesting that mixotrophic flagellates would be using their phagotrophic capability to obtain phosphorus when this nutrient is limiting. HF grazing activity showed a marked seasonality, with grazing being higher during the warmer seasons, and clearance rates were positively correlated with water temperature. Total bacterivory accounted for most of the bacterial production. Short-term and long-term bacterivory measurements were highly correlated, confirming that the smallest flagellates were the main causative agent of bacterial loss. The bacterivory values were also well correlated to a published empirical model that considers HF as the only bacterivorous. However, this model underestimated (up to 50%) total flagellate grazing during periods of high effect of mixotrophic flagellates.

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Section: Discussionmentioning

confidence: 64%

Significant year‐round effect of small mixotrophic flagellates on bacterioplankton in an oligotrophic coastal system

Unrein

Massana

Alonso‐Sáez

et al. 2007

Limnology & Oceanography

213

189

View full text Add to dashboard Cite

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“…In general, HNF have been reported as the main bacterial consumers in most aquatic systems (Boenigk et al, 2002;Gasol et al, 2002;Ichinotsuka et al, 2006). However, in some environments, the ciliates may be the most important consumers of bacterioplankton (Zingel et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Ichinotsuka et al, 2006) and ciliates (e.g. Zingel et al, 2007), which act as a link to higher predators.…”

Section: Introductionmentioning

confidence: 99%

The importance of protozoan bacterivory in a subtropical environment (Lobo-Broa Reservoir, SP, Brazil)

et al. 2014

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This study evaluated the importance of heterotrophic nanoflagellates (HNF) and ciliates bacterivory in a mesotrophic subtropical environment (Lobo-Broa Reservoir, Brazil) by the quantification of their ingestion rates. The in situ experiments using fluorescently labelled bacteria (FLB) were carried out bimonthly over one year (three surveys in the dry season and three in the rainy one) at the sub-surface of two sampling points that have different trophic degrees. The ingestion rates for both ciliates and HNF were higher in the meso-eutrophic region (point 2) due to the higher water temperatures, which accelerate the metabolism of protozoans and the higher bacteria densities. Concerning total protozoan bacterivory, the HNF had the greatest grazing impact on bacterial community, especially the HNF <5µm. The data showed that HNF grazing, in addition to regulating the bacteria abundance, also induced changes to the bacterial community structure, such as increasing size and numbers of bacterial filaments. The ciliates were also important to the system bacterivory, especially in point 2, where there were high densities and ingestion rates. The protozoan bottom-up control was more important in the dry season and the top-down control was more important in the rainy season, so, these two forces are equally important to the bacterial abundance regulation in this reservoir in an annual basis.Keywords: grazing, bacteria, nanoflagellates, ciliates, mesotrophic.A importância da bacterivoria por protozoários em um ambiente subtropical (Reservatório do Lobo-Broa, SP, Brasil) ResumoEste estudo avaliou a importância da bacterivoria por nanoflagelados heterotróficos (NFH) e ciliados em um ambiente subtropical mesotrófico (Reservatório do Lobo-Broa, Brasil) pela quantificação de suas taxas de ingestão. Os experimentos in situ utilizando bactérias marcadas por fluorescência (FLB) foram realizados bimestralmente durante um ano (três estudos no período seco e três no período chuvoso) na superfície de dois pontos de coleta que apresentam graus de trofia diferentes. As taxas de ingestão, tanto para os ciliados quanto para os NHF, foram maiores no ponto 2 (P2) devido provavelmente as maiores temperaturas da água, que aceleram o metabolismo dos protozoários, e as maiores densidades de bactérias. Em relação à bacterivoria total por protozoários, as populações de NFH causaram maior impacto de predação sobre a comunidade bacteriana do reservatório, principalmente os NFH menores que 5µm. Os dados indicaram que a predação por NFH, além de regular a abundância de bactérias, provavelmente também induziu modificações na estrutura da comunidade bacteriana, como o aumento do tamanho e da quantidade de filamentos bacterianos. Os ciliados também contribuíram significativamente para a bacterivoria no sistema, principalmente no P2, onde apresentaram altas densidades e taxas de ingestão. O controle bottom-up teve maior importância no período seco e o controle top-down maior importância no período chuvoso, assim, estas duas forças são igualmente...

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“…The fixed samples were treated the same as for the enumeration of HNF. At least 300 HNF cells were inspected for each sample using epifluorescence microscopy under UV excitation, and the FLBeads in the HNF food vacuoles were counted under blue light excitation (Sanders et al 1989, Ichinotsuka et al 2006.…”

Section: Hnf Bacterivorymentioning

confidence: 99%

“…Heterotrophic nanoflagellates (HNF) and ciliates are significant consumers of bacterioplankton in oxic waters (Sanders et al 1989, Vaqué & Pace 1992, Nakano et al 1998a, Ichinotsuka et al 2006). In contrast, little is known about the ecology of HNF and ciliates in the microbial loop of anoxic waters.…”

Section: Introductionmentioning

confidence: 99%

Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

Okamura¹,

Mori²,

Nakano³

et al. 2012

Aquat. Microb. Ecol.

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The abundance and bacterivory of heterotrophic nanoflagellates (HNF) were seasonally followed in the oxic and anoxic layers of the meromictic Lake Suigetsu between May 2008 and November 2010. The HNF abundance in the anoxic layer was always lower than in the oxic layer during the study period. Ingestion of fluorescently labeled 0.5 µm diameter beads by the anaerobic HNF in the anoxic layer indicated bacterivory by HNF. The specific ingestion rates in the anoxic layers were generally similar to those taken from the oxic layer, with some exceptions. Our data thus suggested that anaerobic HNF were bacterial consumers with high potential bacterivory comparable to that of aerobic HNF in Lake Suigetsu. Bacterial turnover rates by HNF grazing in the oxic layer were estimated to be as high as ~10% d −1 of the bacterial standing stock. In contrast, the rates in the anoxic layer were <1% d −1 due to the low density of HNF in the anoxic layer. Our data thus provide a valuable contribution to understanding the structure and function of microbial food webs in anoxic aquatic environments.

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Relative importance of nanoflagellates and ciliates as consumers of bacteria in a coastal sea area dominated by oligotrichous Strombidium and Strobilidium

Cited by 37 publications

References 42 publications

Significant year‐round effect of small mixotrophic flagellates on bacterioplankton in an oligotrophic coastal system

Significant year‐round effect of small mixotrophic flagellates on bacterioplankton in an oligotrophic coastal system

The importance of protozoan bacterivory in a subtropical environment (Lobo-Broa Reservoir, SP, Brazil)

Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

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