Closing the microbial loop: dissolved carbon pathway to heterotrophic bacteria from incomplete ingestion, digestion and absorption in animals

Jumars, Peter A.; Penry, Deborah L.; Baross, John A.; Perry, Mary Jane; Frost, Bruce W.

doi:10.1016/0198-0149(89)90001-0

Cited by 439 publications

(310 citation statements)

References 43 publications

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“…As a consequence, DO 14 C entering the water during incubations could be from two sources: release in a dissolved form of organic 14 C from digestive tracts or faeces, and actual secretion of metabolised organic C-rich compounds from labelled body tissues. As gut passage time of D. magna is about 10 min, and knowing the extremely rapid diffusion of dissolved compounds from zooplankton faeces (90% in <1 s for this kind of faeces; Jumars et al 1989), we used the accumulation of DO 14 C only during the 20-min to 2-h interval as the basis for our model, assuming that this was primarily accounted for by metabolised DOC. Accumulation of DO 14 C in water over time was matched by a saturation curve with a positive non-zero intercept on the y-axis.…”

Section: Doc Excretion Modellingmentioning

confidence: 99%

How Daphnia copes with excess carbon in its food

2003

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Animals that maintain near homeostatic elemental ratios may get rid of excess ingested elements from their food in different ways. C regulation was studied in juveniles of Daphnia magna feeding on two Selenastrum capricornutum cultures contrasting in P content (400 and 80 C:P atomic ratios). Both cultures were labelled with 14 C in order to measure Daphnia ingestion and assimilation rates. No significant difference in ingestion rates was observed between P-low and P-rich food, whereas the net assimilation of 14 C was higher in the treatment with P-rich algae. Some Daphnia were also homogeneously labelled over 5 days on radioactive algae to estimate respiration rates and excretion rates of dissolved organic C (DOC). The respiration rate for Daphnia fed with high C:P algae (38.7% of body C day -1 ) was significantly higher than for those feeding on low C:P algae (25.3% of body C day -1 ). The DOC excretion rate was also higher when animals were fed on P-low algae (13.4% of body C day -1 ) than on P-rich algae (5.7% of body C day -1 ) . When corrected for respiratory losses, total assimilation of C did not differ significantly between treatments (around 60% of body C day -1 ). Judging from these experiments, D. magna can maintain its stoichiometric balance when feeding on unbalanced diets (high C:P) primarily by disposing of excess dietary C via respiration and excretion of DOC.

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Section: Doc Excretion Modellingmentioning

confidence: 99%

How Daphnia copes with excess carbon in its food

2003

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“…Azam et al 1983;Azam and Ammerman 1984;Jumars et al 1989). Bacteria are thought to be supplied directly with organic substrate from phytoplankton via exudation or through lysis of cells (Pomeroy 1974;Azam et al 1983).…”

mentioning

confidence: 99%

“…In the light of relatively high demands of dissolved organic C (DOC) for heterotrophic bacterial production (often 20-40% of C fixation; see Jumars et al 1989 and references therein) and a lack of convincing data that documents direct leakage rates in excess of 10% of primary production in healthy natural phytoplankton populations (Jumars et al 1989), one can ask whether macrozooplankton plays a prominent role in the transfer of organic matter to bacteria. Several recent studies have shown that the ecosystem structure is different between eutrophic and oligotrophic environments.…”

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confidence: 99%

Zooplankton activity fueling the microbial loop: Differential growth response of bacteria from oligotrophic and eutrophic waters

Peduzzi

Herndl

1992

Limnol. Oceanogr.

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The impact of copepods on the pool of organic nutrients (monomeric carbohydrates and dissolved free amino acids) and on bacterial growth during phytoplankton bloom conditions was assessed in laboratory incubation experiments. Different batch cultures were performed with water and bacterial assemblages from oligotrophic and eutrophic sampling sites amended with either phytoplankton, zooplankton, or both. A significant increase in monomeric carbohydrate concentrations could be observed only in incubations supplemented with both types of plankton organisms. The increase in bacterial numbers was also most pronounced in that treatment. Compared to eutrophic bacterioplankton, the bacterial assemblage from oligotrophic waters exhibited elevated growth responses to the presence of eucaryotic plankton with lower generation times in all treatments. Zooplankton activity may play a key role in providing organic substrate for bacterial growth.

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“…However, the similarity of the clearance estimates when either copepod concentration or incubation time were varied (Type 1 and 2 experiments, respectively) suggests that this is a minor source of error, and that microbial degradation played a minor role in visibly removing the fecal pellets. Fecal pellets leak DOC rapidly after egestion, which is utilized primarily by non-attached bacteria (Jumars 1989, Urban-Rich 1999, Thor et al 2003. Leakage of DOM, however, does not change the appearance of the pellets beyond recognition and they may still be counted as intact pellets or fragments.…”

Section: Estimation Of Clearance On Own Fecal Pelletsmentioning

confidence: 99%

Coprophagy and coprorhexy in the copepods Acartia tonsa and Temora longicornis: clearance rates and feeding behaviour

Poulsen¹,

Kiørboe²

2005

Mar. Ecol. Prog. Ser.

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Decades of sediment trap studies have revealed that zooplankton fecal pellets constitute a much smaller fraction of the sedimentary flux than expected from the abundance of copepods and their anticipated production rates of fecal pellets. The explanation for this is thought to be coprophagy (ingestion) of fecal pellets by copepods. We examined fecal pellet clearance rate of Acartia tonsa and Temora longicornis and feeding behaviour of A. tonsa. Pellet clearance rates in A. tonsa and T. longicornis females were similar but low on their own pellets (11 to 22 ml female -1 d -1 ). Our own data together with observations compiled from the literature revealed that copepod fecal pellet clearance rates decrease with increasing relative pellet size and that all species can be described by a common relationship. In A. tonsa, the presence of alternative phytoplankton food increased pellet clearance rate. Direct observations revealed that this was accomplished through the modulating effect of phytoplankton on the feeding behaviour. In the absence of phytoplankton, A. tonsa is nonmotile but perceives sinking fecal pellets at distance. However, only a small fraction of the pellets that came within detection distance elicited an attack. In the presence of phytoplankton food, A. tonsa switched to suspension feeding, and all fecal pellets entrained in the feeding current were encountered. Independent of the feeding mode, fecal pellets were mainly degraded by fragmentation during rejection and only a small fraction was actually ingested (5%). The main impact of A. tonsa on the vertical flux of fecal pellets is therefore through coprorhexy (fragmentation) turning fecal pellets into smaller, slower-sinking particles.

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Closing the microbial loop: dissolved carbon pathway to heterotrophic bacteria from incomplete ingestion, digestion and absorption in animals

Cited by 439 publications

References 43 publications

How Daphnia copes with excess carbon in its food

How Daphnia copes with excess carbon in its food

Zooplankton activity fueling the microbial loop: Differential growth response of bacteria from oligotrophic and eutrophic waters

Coprophagy and coprorhexy in the copepods Acartia tonsa and Temora longicornis: clearance rates and feeding behaviour

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