N-remineralization of phyto- and bacterioplankton by the marine ciliate Euplotes vannus

Gast, V.; Horstmann, Ulrich

doi:10.3354/meps013055

Cited by 22 publications

(9 citation statements)

References 9 publications

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“…The hypotrich ciliate Euplotes vannus has been demonstrated to rapidly excrete ammonium following either an algal or bacterial meal (Gast & Horstmann 1983). Verity (1985) has calculated for Narragansett Bay that ammonium excretion by tintinnid ciliates could supply about 18 % of phytoplankton demands over the annual cycle with a maximum of 29 % during the late summer.…”

Section: 2-mentioning

confidence: 99%

Ammonium regeneration by microplankton in an upwelling environment

Probyn¹

1987

Mar. Ecol. Prog. Ser.

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Size-frachonated measurements of ammonium flux In the southern Benguela upwelllng system provided evldence that regenerahon by microplankton (<200um) was concentrated In the upper water column and generally supported the majonty of phytoplankton demands Based on the present study and literature data lt was demonstrated that ammonium reminerahzabon was dependent on the concentrahon of particulate nitrogen present when viewed on a broad scale The < 15 pm size class, including bactena and nanoflagellates proved to be the predominant mineralizers accounting for 95 % of total microplankton regeneration on average Although ammomf~cahon by heterotrophic p~coplankton (presumably mainly bactenal) was Important in some instances bacte~nvorous nanoflagellates (1 to 15 urn) appeared to supply the bulk of mlcroplankton excretion, i e a mean of 87 % in surface waters and 55 % near the base of the euphot~c zone Bactena were relatively more active at depth than at the surface although in the majonty of cases absolute rates were fastest In surface watersThe posslbdlty e x s t s that bactenal reminerallzation was underesbmated in the < 1 um fracbon due to the absence of nanoflagellates dunng the ~ncubahon Nevertheless, nanoflagellate feeding compnses a n essenhal component of the reminerahzat~on process Ammonlum uptake by the dlfferent size classes was dlrectly proportional to chlorophyll a concentrations Results of thls study are cons~stent wlth the proposed cruclal role for small protozoans as intermediaries between bacterla and hlgher trophic levels and as m~nerallzers of nutrients for pnmary producers

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Section: 2-mentioning

confidence: 99%

Ammonium regeneration by microplankton in an upwelling environment

Probyn¹

1987

Mar. Ecol. Prog. Ser.

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“…From recent studies, however, it is now abundantly clear that both cdiates and phagotrophic rnicroflagellates regenerate NH: in large quantities while grazing (Gast & Horstmann 1983, Sherr et al 1983, Anders-son et al 1985, Van Wambeke & Bianchi 1985. In fact, reported weight-specific rates of NH: regeneration from the few studies on marine microflagellates are considerably higher than those for most macrozooplankton .…”

Section: Introductionmentioning

confidence: 99%

Nutrient cycling in a microflagellate food chain: III. Phosphorus dynamics

Andersen¹,

Goldman²,

Caron³

et al. 1986

Mar. Ecol. Prog. Ser.

100

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As part of a series of grazing experiments in batch cultures, we found that the phagotrophlc microflagellate Paraphysomonas imperforata, while grazing on the diatom Phaeodactylum tn'cornutum or bacteria, was responsible for the bulk of phosphorus regeneration. Regeneration of soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) was negligible in control cultures of the diatom alone, bacteria alone, or the 2 microbes together. When the m~croflagellate grazed on prey organisms that had been precultured with excess nutrients or under nitrogen limitation there was considerable regeneration of total dissolved phosphorus (TDP = SRP + DOP). Rates of TDP regeneration were greatest during exponential growth of the microflagellate and then decreased through the transition and stationary phases. Overall, up to 70 % of the phosphorus initially incorporated into prey biomass was regenerated through the stationary phase. Total excretion of DOP was about 15 to 20% of TDP, although DOP excretion made up a larger fraction of total phosphorus excretion for short periods during the exponential phase of growth. When the prey were phosphoruslimited virtually no TDP was excreted throughout the entire growth cycle of the microflagellate. Our results indicate that Protozoa have higher weight-specific rates of phosphorus excretion than do Metazoa. Although metabolic activity is not the sole indicator of the role Protozoa play in the nutrient regeneration process, our results, together with those from size-fractionation studies on nutrient regeneration, point toward a major role for Protozoa in pelagic waters where they constitute a large fraction of the zooplankton biomass.

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“…It has been shown in recent studies that protozoa are abundant in planktonic ecosystems (Sorokin, 1981;Fenchel, 1982;Davis et al, 1985;Sherr et al, 1984Sherr et al, , 1986, are voracious consumers of bacteria (Sieburth, 1984;Fenchel, 1986), and typically regenerate a substantial fraction of the nutrients in their food (Gast & Horstmann, 1983;Sherr et al, 1983;Gude, 1985;Wambeke & Bianchi, 1985;Andersen et al, 1986). Therefore, in situations where the bacteria are consumers rather than producers of inorganic nutrients, the bacterivorous protozoa may be instrumental in the regeneration of nutrients limiting the growth of the primary producers.…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of the roles of bacteria and bacterivorous protozoa in plankton nutrient cycles

1988

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We have used a model food chain composed of a natural bacterial assemblage, a pennate diatom and a bacterivorous microflagellate to investigate the factors controlling the relative importance of bacteria and protozoa as sources for regenerated nitrogen in plankton communities. In bacterized diatom cultures in which diatom growth was nitrogen-limited, the carbon:nitrogen (C:N) ratio of the bacterial substrate greatly affected which population was responsible for the uptake of nitrogen. When nitrogen was added as NH4+ and the cultures were supplemented with glucose, the bacteria competed successfully with the algae for NH and prevented the growth of algae by rapidly assimilating all NH4 in the cultures. Bacterivorous protozoa inoculated into these cultures grazed the bacterial population and remineralized NH-, thus relieving the nitrogen limitation of algal growth and allowing an increase in algal biomass. In contrast, bacteria in cultures supplemented with the amino acid glycine (C:N = 2) were major remineralizers of nitrogen, and the influence of protozoan grazing was minimal. We conclude that the relative importance of bacteria and protozoa as nutrient regenerators in the detrital food loop is dependent largely on the overall carbon:nutrient ratio of the bacterial substrate. The role of bacterivorous protozoa as remineralizers of a growth-limiting nutrient is maximal in situations where the carbon:nutrient ratio of the bacterial substrate is high.

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N-remineralization of phyto- and bacterioplankton by the marine ciliate Euplotes vannus

Cited by 22 publications

References 9 publications

Ammonium regeneration by microplankton in an upwelling environment

Ammonium regeneration by microplankton in an upwelling environment

Nutrient cycling in a microflagellate food chain: III. Phosphorus dynamics

Experimental demonstration of the roles of bacteria and bacterivorous protozoa in plankton nutrient cycles

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