Size‐fractionated NH4+ regeneration in the pelagic environments of two mesotrophic lakes

Haga, Hiroki; Nagata, Toshi; Sakamoto, Mitsuru

doi:10.4319/lo.1995.40.6.1091

Cited by 37 publications

(16 citation statements)

References 27 publications

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“…Abundant populations of planktonic protozoa and other microorganisms have been found in tropical lakes (Hecky and Kling 1981;Lewis 1985;Beaver and Crisman 1982;Finlay et al 1987). The central role of the microbial food web in N recycling has been reported for different temperate pelagic environments (Caron and Goldman 1990;Haga et al 1995;Miller et al 1995;Selmer et al 1993;Suzuki et al 1996) and was suggested from size-fractionation studies in Lake Calado ). This conclusion agrees with the high correlation that we observed between N cycling rates and the HNAN : bacterial biomass ratio, a variable that potentially characterizes the relative proportion of bacterial biomass transferred to the next trophic level for growth and metabolism.…”

Section: Discussionmentioning

confidence: 84%

Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela

Gardner¹,

Cavaletto²,

Bootsma³

et al. 1998

Limnology & Oceanography

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Isotope dilution experiments with IsN& were conducted in Lake Maracaibo, Venezuela, to examine potential N turnover rates and light effects and to examine the hypothesis that nutrient dynamics are biologically driven in this tropical, hypcreutrophic lake. Ammonium and nitrate concentrations were both Cl PM as compared to particulate N concentrations of 9-29 PM N. Chlorophyll (Chl) levels ranged from 2.5 to 22 pg liter-'. Numbers and biomass of bacteria ranged from 1.0 to 9.1 X lo6 cells ml-' and 45 to 138 pg C liter-' and those of heterotrophic nanoflagellates (HNAN) ranged from 0.5 to 3.5 X 10" cells ml-' and 2.3 to 17.5 pg C liter-l, respectively. Highest Chl concentration and microbial abundance occurred in a region affected by sewage discharge from the city of Maracaibo. Potential ammonium uptake rates in near-surface waters ranged from about 1 PM h-l to 8 PM h--l. Chlspecific uptake rates were highest in central regions that were dominated by chroococcoid cyanobacteria. Ammonium regeneration rates ranged from near detection to 2 PM h-I and correlated significantly with the ratio of HNAN to bacterial biomass, likely reflecting the degree of bacterivory. The high ratio of potential turnover rates to ambient ammonium concentrations suggests that internal recycling is a major nutrient supply process in the lake. Incubation bottle characteristics (e.g., light intensity, spectral quality, or possibly headspace differences) apparently affected potential uptake rates, which were relatively low in polystyrene bottles and in quartz tubes. Uptake rates were lower in screened polystyrene bottles than in screened polypropylene syringes, with different spectral characteristics, even though total-light attenuation was similar (45% vs. 53%).

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Section: Discussionmentioning

confidence: 84%

Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela

Gardner¹,

Cavaletto²,

Bootsma³

et al. 1998

Limnology & Oceanography

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“…≤ 6.5 µM d -1 ; Glibert 1982, Wheeler & Kirchman 1986, Probyn 1987, Metzler et al 2000, Varela et al 2003, and in mesotrophic lake environments (e.g. 0.26 to 6.2 µM d -1 ; Haga et al 1995).…”

Section: Discussionmentioning

confidence: 99%

Ammonium cycling under a strong oxygen gradient associated with the Oxygen Minimum Zone off northern Chile (~23°S)

Molina

Farı́as²,

Eissler³

et al. 2005

Mar. Ecol. Prog. Ser.

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“…Previous studies have reported the gross primary production (910 to 1,460 mg C m Ϫ2 day Ϫ1 ) (33), bacterial production (ca. 30% of the primary production) (29), and microbial trophic interactions (16,30,31) The water samples were filtered through 0.8-m-pore-size Nuclepore filters (Whatman) with gentle pressure (Ͻ20 mm Hg) in order to eliminate protozoan grazers. The filtrates were dispensed into acid-washed polycarbonate bottles (250 ml; Nalgene) and incubated at the in situ temperature in the dark.…”

Section: Methodsmentioning

confidence: 99%

Vertical and Seasonal Variations of Bacterioplankton Subgroups with Different Nucleic Acid Contents: Possible Regulation by Phosphorus

Nishimura

Kim

Nagata

2005

Appl Environ Microbiol

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We used flow cytometry to examine seasonal variations in basin-scale distributions of bacterioplankton in Lake Biwa, Japan, a large mesotrophic freshwater lake with an oxygenated hypolimnion. The bacterial communities were divided into three subgroups: bacteria with very high nucleic acid contents (VHNA bacteria), bacteria with high nucleic acid contents (HNA bacteria), and bacteria with low nucleic acid contents (LNA bacteria). During the thermal stratification period, the relative abundance of VHNA bacteria (%VHNA) increased with depth, while the reverse trend was evident for LNA bacteria. Seasonally, the %VHNA was strongly positively correlated (r ‫؍‬ 0.87; P < 0.001) with the concentration of dissolved inorganic phosphorus, but not with the concentration of chlorophyll a. The growth of VHNA bacteria was significantly enhanced by addition of phosphate or phosphate plus glucose but not by addition of glucose alone. Although the growth of VHNA and HNA bacteria generally exceeded that of LNA bacteria, our data also revealed that LNA bacteria grew faster than and were grazed as fast as VHNA bacteria in late August, when nutrient limitation was presumably severe. Based on these results, we hypothesize that in severely P-limited environments such as Lake Biwa, P limitation exerts more severe constraints on the growth of bacterial groups with higher nucleic acid contents, which allows LNA bacteria to be competitive and become an important component of the microbial loop.In pelagic ecosystems, heterotrophic bacteria comprise the most important trophic level for processing dissolved organic matter (DOM) and consume a substantial fraction (40 to 60%) of the primary production (1, 6, 7, 31). Generally, previous studies have treated bulk bacterial communities as a homogeneous pool (1, 6, 7, 31), even though they consist of diverse subgroups that differ in metabolic state (14), DOM use (9), growth rate (10, 46), susceptibility to grazing (17), and phylogenetic affiliations (15). One of the contemporary challenges for aquatic microbial ecology is to clarify variations and regulation of different bacterial subgroups in order to facilitate establishing ecologically useful functional units with which the internal dynamics of the bacterioplankton "black box" can be better understood.Flow cytometry has become a powerful tool for discriminating bacterial subgroups based on cellular nucleic acid content (13,26,37). Recent studies using flow sorting have revealed that bacteria with high nucleic acid contents (HNA bacteria) and bacteria with low nucleic acid contents (LNA bacteria) differ in phylogenetic composition (49), although Servais et al. (36) found that common phylotypes are present in both subgroups. Some investigators have suggested that HNA and LNA bacteria represent active and less active components, respectively (14, 22), leading to the proposition that the percentage of HNA bacteria relative to the total bacterial abundance (%HNA) can be an indicator of the fraction of active cells in bacterial communities (14,19). ...

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Size‐fractionated NH4+ regeneration in the pelagic environments of two mesotrophic lakes

Cited by 37 publications

References 27 publications

Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela

Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela

Ammonium cycling under a strong oxygen gradient associated with the Oxygen Minimum Zone off northern Chile (~23°S)

Vertical and Seasonal Variations of Bacterioplankton Subgroups with Different Nucleic Acid Contents: Possible Regulation by Phosphorus

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