Vertical and temporal distribution of free-living nematodes dwelling in two sandy-bed streams fed by helocrene springs

Traunspurger, Walter; Threis, Ilka; Majdi, Nabil

doi:10.1163/15685411-00002914

Cited by 20 publications

(18 citation statements)

References 41 publications

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“…The temporal shift in the Ems seemed not to have been cyclic, but more likely reflected a change in the packaging of biomass in response to a previously occurring environmental change. Attributing this temporal shift to a specific variable, or set of variables, is speculative but is in agreement with a previously described dramatic shift in the nematode species assemblages dwelling in the upper sediment of the Ems that occurred during the same period (Traunspurger et al ). The latter study reported a shift from dense populations of bacterial‐feeding nematodes in February and April 2010 toward scattered but more functionally balanced assemblages.…”

Section: Discussionsupporting

confidence: 88%

“…Chl a was higher in the waters of the Furlbach than in those of the Ems. The BChl a concentration was also higher in the Furlbach, but did not significantly differ from that in the Ems, due to high fluctuations throughout the year (Traunspurger et al ). The amount of BOM was higher in Furlbach than in Ems sediments (Table ).…”

Section: Resultsmentioning

confidence: 98%

“…: 30 μgC) and are hereafter referred to as temporary meiofauna. Nematode species composition is detailed elsewhere (Traunspurger et al ). Most groups discriminated along Axis 1, scoring toward either the left or the right side of the biplot (Fig.…”

Section: Resultsmentioning

confidence: 99%

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It's the little things that count: Meiofaunal density and production in the sediment of two headwater streams

Majdi

Threis

Traunspurger

2016

Limnology & Oceanography

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The distribution of biomass production and its allocation across populations under environmental constraints draw a picture of community dynamics and energy flows in ecosystems. However, microscopic benthic invertebrates (meiofauna) are often overlooked in stream production budgets. We monitored the meiofauna dwelling in the sediment at two headwater stream sites (Ems and Furlbach, NW Germany) during 1 year. The two streams were similar in their granulometries and temperature regimes, but they differed in their flow velocities and nutrient balances, which allowed investigations of the effects of these factors on the density and production of different taxonomic groups of meiofauna. Meiofaunal production in the top 10‐cm sediment at Ems and Furlbach was 2.58 and 5.46 gC m−2 yr−1, respectively; these values are among the highest reported so far for a streambed. Allocation of density and production across taxonomic groups differed between the two streams. Tardigrades, rotifers, oligochaetes, and gastrotrichs thrived in the phosphate‐rich, slow‐flowing waters of the Ems, whereas nematodes, micro‐turbellarians, and harpacticoid copepods were better adapted to the nitrate‐rich, fast‐flowing waters of the Furlbach. Body‐size distribution varied across site and depth and was mostly multi‐modal, with important contributions of minute individuals weighing between 0.01 and 0.1 μgC. Our study shows that, despite their small size, meiofauna can produce substantial amounts of biomass and should thus be better considered in budgets and models of stream ecosystems.

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Section: Discussionsupporting

confidence: 88%

Section: Resultsmentioning

confidence: 98%

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It's the little things that count: Meiofaunal density and production in the sediment of two headwater streams

Majdi

Threis

Traunspurger

2016

Limnology & Oceanography

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“…This difference in the vertical distribution was not surprising, as previous studies also detected vertical variations in the meiofaunal community at a centimetre (Kotwicki, Troch, Urban‐Malinga, Gheskiere, & Weslawski, ; Vieira & Fonseca, ) and even a millimetre (Joint, Gee, & Warwick, ) scale. However, most studies on the vertical distribution of meiofauna in lentic sediments investigated the sediment layer at the centimetre (Traunspurger et al., ; Wu, Fu, Liang, & Chen, ) to metre (Traunspurger & Drews, ; Traunspurger et al., ) scale; at these large depth intervals, microscale changes are likely to be overlooked. Moreover, changes in the vertical distribution of meiofauna are also of importance at the species level, as the densities of different species may be differentially affected by sediment depth (Traunspurger, ).…”

Section: Discussionmentioning

confidence: 99%

Wide variation in a tiny space: The microdistribution of meiobenthos in an artificial pond

et al. 2018

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Meiofauna play an important ecological role in benthic ecosystems. However, little is known about their small‐scale (<1 m2) distribution. Yet, this knowledge has both theoretical implications, by improving our understanding of how processes generate patterns; and practical outcomes by improving sampling designs. The goal of this study was to obtain insights into the small‐scale distribution of meiofaunal invertebrates dwelling in the sediment of a lentic ecosystem (in this study, an artificial pond). We addressed this aim at coarse and fine taxonomical levels using meiofaunal groups and nematode species assemblages, respectively. For this purpose, 225 sediment samples were collected over a surface of 729 cm2 using a straw corer. Spatial patterns (dispersion index) and the typical patch sizes of the dominant meiofaunal groups were estimated using spatial autocorrelation analysis (Moran's I). We hypothesized that (1) we would find a patchy distribution of organisms with patch radii of a few centimetres, (2) the distribution of microbivorous meiofauna would follow that of OM, and (3) distribution would be patchier at the species level. The densities of the dominant meiobenthic groups (nematodes, gastrotrichs and rotifers) decreased with sediment depth. In all sediment layers, nematodes contributed 61%–82% to total invertebrate densities. Eleven nematode species were identified, with Eumonhystera filiformis (Bastian 1865) and Monhystera cf. paludicola de Man 1881 dominating the assemblage. All meiofaunal groups showed an aggregated distribution pattern (dispersion index >1). Spatial autocorrelation analysis revealed aggregations of nematodes in a patch radius of 3–8 cm according to the different sediment layers. Rotifers were also patchy distributed but with smaller patch radius (3 cm), whereas the respective distributions of gastrotrichs were less patchy. Therefore, our results mainly confirmed hypothesis (1). Our results provide the first insights into rotifer patch sizes. Also, these findings highlight the need for sampling designs better able to capture small‐scale heterogeneities during larger‐scale investigations. We ruled out the organic matter (OM) supply as an important driver of meiofaunal community structure as OM content did not correlate with the density of either meiofaunal groups or nematode species, and therefore arguing against hypothesis (2). Instead, the different distributions suggested responses to qualitative differences in resource availability, oxygen availability, biotic interactions and specific population‐level processes, such as behaviour, dispersal and locomotion. Patchiness did not increase from coarse to fine taxonomic levels, thus contradicting hypothesis (3). Our results instead suggest that the patchiness of the spatial distribution was more closely linked to functional traits.

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“…Samples were collected at the extensively studied Furlbach stream (51.895392°N, 8.715517°E; Traunspurger, Threis, & Majdi, ) in May 2017. Sediment samples (~4 m 2 ) were decanted directly in the field by skimming the upper 10 cm of sediment, transferring it into a bucket and stirring it for 30 s. After the suspension was left to stand for 15 s, the supernatant was poured over a 10‐µm sieve and the contents of the sieve were transferred to a sampling bottle.…”

Section: Methodsmentioning

confidence: 99%

Comparison of morphological, DNA barcoding, and metabarcoding characterizations of freshwater nematode communities

Schenk

Kleinbölting

Traunspurger

2020

Ecology and Evolution

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Biomonitoring approaches and investigations of many ecological questions require assessments of the biodiversity of a given habitat. Small organisms, ranging from protozoans to metazoans, are of great ecological importance and comprise a major share of the planet's biodiversity but they are extremely difficult to identify, due to their minute body sizes and indistinct structures. Thus, most biodiversity studies that include small organisms draw on several methods for species delimitation, ranging from traditional microscopy to molecular techniques. In this study, we compared the efficiency of these methods by analyzing a community of nematodes. Specifically, we evaluated the performances of traditional morphological identification, single‐specimen barcoding (Sanger sequencing), and metabarcoding in the identification of 1500 nematodes from sediment samples. The molecular approaches were based on the analysis of the 28S ribosomal large and 18S small subunits (LSU and SSU). The morphological analysis resulted in the determination of 22 nematode species. Barcoding identified a comparable number of operational taxonomic units (OTUs) based on 28S rDNA (n = 20) and fewer OTUs based on 18S rDNA (n = 12). Metabarcoding identified a higher OTU number but fewer amplicon sequence variants (AVSs) (n = 48 OTUs, n = 17 ASVs for 28S rDNA, and n = 31 OTUs, n = 6 ASVs for 18S rDNA). Between the three approaches (morphology, barcoding, and metabarcoding), only three species (13.6%) were shared. This lack of taxonomic resolution hinders reliable community identifications to the species level. Further database curation will ensure the effective use of molecular species identification.

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Vertical and temporal distribution of free-living nematodes dwelling in two sandy-bed streams fed by helocrene springs

Cited by 20 publications

References 41 publications

It's the little things that count: Meiofaunal density and production in the sediment of two headwater streams

It's the little things that count: Meiofaunal density and production in the sediment of two headwater streams

Wide variation in a tiny space: The microdistribution of meiobenthos in an artificial pond

Comparison of morphological, DNA barcoding, and metabarcoding characterizations of freshwater nematode communities

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