Preservation and incubation time-induced bias in tracer-aided grazing studies on meiofauna

Moens, Tom; Verbeeck, L; Vincx, Magda

doi:10.1007/s002270050444

Cited by 39 publications

(25 citation statements)

References 33 publications

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“…Nematodes contributed negligibly to benthic carbon mineralization in our study, with considerably less than 0.1% of the processed 13 C showing up in nematode biomass at any given time, in agreement with Moodley et al (2002). Even if we take into account that this represents assimilation rather than uptake, and that assimilation is underestimated because of (1) leakage of low-molecular weight material from frozen and thawed specimens (Moens et al 1999), and (2) (unknown) carbon turnover times in nematode tissues, nematodes contributed less than 1% to the recorded benthic carbon mineralization. While several authors have suggested a quantitative importance of meiofauna in benthic carbon and energy flows (a.o.…”

Section: Pulse-chase Experimentssupporting

confidence: 79%

Carbon sources of Antarctic nematodes as revealed by natural carbon isotope ratios and a pulse-chase experiment

et al. 2007

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d13 C of nematode communities in 27 sites was analyzed, spanning a large depth range (from 130 to 2,021 m) in five Antarctic regions, and compared to isotopic signatures of sediment organic matter. Sediment organic matter d 13 C ranged from -24.4 to -21.9& without significant differences between regions, substrate types or depths. Nematode d 13C showed a larger range, from -34.6 to -19.3&, and was more depleted than sediment organic matter typically by 1& and by up to 3& in silty substrata. These, and the isotopically heavy meiofauna at some stations, suggest substantial selectivity of some meiofauna for specific components of the sedimenting plankton. However, 13 C-depletion in lipids and a potential contribution of chemoautotrophic carbon in the diet of the abundant genus Sabatieria may confound this interpretation. Carbon sources for Antarctic nematodes were also explored by means of an experiment in which the fate of a fresh pulse of labile carbon to the benthos was followed. This organic carbon was remineralized at a rate (11-20 mg C m -2 day -1 ) comparable to mineralization rates in continental slope sediments. There was no lag between sedimentation and mineralization; uptake by nematodes, however, did show such a lag. Nematodes contributed negligibly to benthic carbon mineralization.

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Section: Pulse-chase Experimentssupporting

confidence: 79%

Carbon sources of Antarctic nematodes as revealed by natural carbon isotope ratios and a pulse-chase experiment

et al. 2007

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“…Differences between nematode C uptake in the aforementioned studies possibly arise due to differences in the organic substrates added (see Ingels et al 2010). They may also be attributable to differences in sample processing techniques (e.g Moens et al 1999), as well as the structure and functional diversity of nematode communities. It is apparent that the lack of knowledge on the life cycles, energy requirements, and food preferences of deep-sea nematodes has so far hampered the full exploitation of stable isotope labelling techniques in understanding the role of these organisms in deep-sea C cycling.…”

Section: Community Responsementioning

confidence: 99%

Processing of 13C-labelled diatoms by a bathyal community at sub-zero temperatures

Gontikaki¹,

Mayor²,

Thornton³

et al. 2011

Mar. Ecol. Prog. Ser.

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) of the total processed C, with meiofauna contributing only ~1% to the total metazoan uptake. The bacterial response was characterised by varying bacterial growth efficiency (BGE). During the first half of the experiment, low respiration and high bacterial uptake of the 13 C-labelled substrate resulted in particularly high BGE, while the opposite was observed in the second half of the incubation. We postulate that the high BGE at the start of the experiment represents the absorption and metabolism of the readily available labile components of the added organic matter (OM). The decrease in BGE possibly corresponds to the initiation of the energetically costly hydrolytic processes necessary for the consumption of more recalcitrant OM.KEY WORDS: Stable isotope labelling · Benthos · Bacterial growth efficiency · Bathyal sediments · Faroe-Shetland Channel · δ 13 C · PLFA Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 421: [39][40][41][42][43][44][45][46][47][48][49][50] 2011 nutrients in 2 ways: by producing new biomass (bacterial secondary production, BP) and by remineralizing OC and nutrients (bacterial respiration, BR) (del Giorgio & Cole 1998). The relative magnitudes of BR and BP are expressed by the bacterial growth efficiency (BGE), which represents the amount of new bacterial biomass produced per unit of substrate assimilated and hence the efficiency with which C is made available to higher trophic levels (del Giorgio & Cole 1998). The factors that influence BGE are currently not well understood, and as a result the real magnitude of OC flow through bacteria in the world's oceans remains largely unknown (del Giorgio & Cole 2000). The bacterial response to naturally occurring, seasonal inputs of POC has been documented in various studies (Lochte 1992, Pfannkuche 1993, Pfannkuche et al. 1999. It is first detectable as an intensification of metabolic activity, reflected in adenosine triphosphate concentration (Graf 1989) and extracellular enzyme production (Boetius & Lochte 1994). The extracellular hydrolysis of OM is a prerequisite for bacterial cells to gain access to macromolecules, since only low molecular weight compounds can be transported across bacterial membranes (Benz 1985). Bacterial growth may follow enzyme production provided that the exploitable energy of the substrate is sufficiently high (Boetius & Lochte 1994. Other small-sized organisms, such as protozoa and foraminifera, are also highly responsive to food pulses and may undergo changes in density (Gooday & Rathburn 1999) and species composition (Lambshead & Gooday 1990) or show episodic recruitment of opportunistic species (Ohga & Kitazato 1997). The response of benthic metazoans in terms of population dynamics has been more difficult to establish, perhaps because of their slower turnover rates (Gooday 2002). On the timescale of several months, however, metazoan communities show shifts in their structure in relation to upper-ocean conditions and food supply (Ruhl & Smith 2004, Sellanes et ...

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“…Finally, one should be aware that freezing of samples may result in leakage of label after thawing as was illustrated for cladocerans (Mourelatos et al 1992) and nematodes (Moens et al 1999). As suggested in both studies, sorting of organisms was done within 2 h of thawing in the present study to minimise possible leakage.…”

Section: Discussionmentioning

confidence: 99%

“…Diatom uptake expressed as (A) δ 13 C, (B) total uptake per individual relative to individual biomass and (C) total uptake per unit carbon of copepod. High density corresponds to 4 times the low density it might give inaccurate estimates of overall grazing rates in the field (Moens et al 1999). A combination of natural-abundance isotope surveys and isotopeaddition experiments appears to be a powerful approach for investigating both average patterns and interspecific variability in resource exploitation (Carman & Fry 2002).…”

Section: Discussionmentioning

confidence: 99%

Grazing on diatoms by harpacticoid copepods: species-specific density-dependent uptake and microbial gardening

Troch¹,

Steinarsdóttir²,

Chepurnov³

et al. 2005

Aquat. Microb. Ecol.

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Four common intertidal harpacticoid species (Paramphiascella fulvofasciata, Tigriopus brevicornis, Nitocra spinipes and Harpacticus obscurus) were offered pelagic diatoms (Phaeodactylum tricornutum) as food in laboratory experiments. To ensure generality we used copepod species originating from diverse habitats with different ecological characteristics. The diatoms were enriched in the stable carbon 13 C isotope to facilitate tracing in the harpacticoids. Uptake of diatoms was clearly species-specific and in general P. fulvofasciata was more efficient than the other species. We found significant uptake by 24 h of incubation for T. brevicornis. From 24 h onwards we found an increase for all 3 species. Species had similar δ 13 C values before and after starvation, indicating that labeled material was efficiently assimilated in their tissues. We tested whether diatom assimilation is density-dependent and this was true for 2 species (N. spinipes and P. fulvofasciata) but not for the semi-pelagic T. brevicornis. Finally, a positive effect of faecal pellets on food uptake for the less mobile species was shown, indicating that microbial gardening occurs within benthic harpacticoids as it does for several other crustacean species.

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Preservation and incubation time-induced bias in tracer-aided grazing studies on meiofauna

Cited by 39 publications

References 33 publications

Carbon sources of Antarctic nematodes as revealed by natural carbon isotope ratios and a pulse-chase experiment

Carbon sources of Antarctic nematodes as revealed by natural carbon isotope ratios and a pulse-chase experiment

Processing of 13C-labelled diatoms by a bathyal community at sub-zero temperatures

Grazing on diatoms by harpacticoid copepods: species-specific density-dependent uptake and microbial gardening

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