Morphometric, taxonomic, and functional trait data of deep-sea nematodes from a colonisation experiment simulating organic matter deposition at HAUSGARTEN (Fram Strait)
Description
This dataset contains individual-based morphometric, taxonomic, and functional trait data of deep-sea nematodes collected during a colonisation experiment conducted at the long-term observatory HAUSGARTEN in the Fram Strait (Arctic Ocean). The experiment aimed to investigate the colonisation dynamics and trait-based responses of nematode communities to different qualities of organic matter input in artificially prepared deep-sea sediments. During the RV Polarstern expedition PS85 (June 2014), a bottom lander was deployed at 1265 m water depth near HAUSGARTEN station HG-I (79°8.69'N, 6°8.23'E). The lander carried twelve colonisation cores filled with azoic, artificial sediments and exposed for three months on the seafloor. Three treatments were applied, each with four replicate cores: (1) enrichment with fresh Phaeocystis (FP), (2) enrichment with decayed Phaeocystis (DP), and (3) unenriched control cores. This design simulated the effect of phytodetritus deposition in different degradation states on early colonisers within benthic communities. As a natural reference, sediment samples were taken from undisturbed seafloor using a multiple corer (MUC) at 1244 m depth at the same station (79°8.01'N, 6°6.39'E). For both the artificial colonisation cores and natural MUC samples, subsampling was conducted using 2.2 cm diameter cut-off syringes. From each core, the upper 3 cm of sediment were collected, sliced into 1 cm layers, and fixed in 4% borax-buffered formalin prepared with filtered seawater. Individual nematodes were identified to genus level. Body length and width were measured, and biomass (µg dry weight) was calculated. Each genus was assigned a feeding type based on Wieser (1953) and a coloniser–persister (c–p) value following Bongers (1990) and Bongers et al. (1995), providing insight into their trophic role and life-history strategy. This dataset enables comparative analysis of nematode traits under controlled experimental enrichment versus natural background conditions, and contributes to a better understanding of benthic ecosystem responses to variable organic matter input in Arctic deep-sea environments.
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Steps to reproduce
For nematode analysis, one subsample was taken from each of the four replicate cores per experimental treatment (fresh Phaeocystis [FP], decayed Phaeocystis [DP], and control) and from three replicate multiple corer (MUC) cores representing natural sediments at HAUSGARTEN station HG-I. Sediment was collected using cut-off syringes (2.2 cm inner diameter). The upper 3 cm of each core were sliced into 1 cm layers (0–1, 1–2, 2–3 cm) and fixed in 4% borax-buffered formalin prepared with filtered seawater. Samples were rinsed with freshwater over a 32 µm sieve to remove excess fixative. Nematodes were then separated from sediment using density-gradient centrifugation with LUDOX® TM-50 colloidal silica (specific gravity 1.18 g/cm³; Sigma-Aldrich), following Heip et al. (1985). Each sample was centrifuged twice at 900 rpm for 15 minutes. The supernatant from each spin was sieved again through 32 µm mesh to remove LUDOX® and stained with Rose Bengal to support visual sorting. All nematodes present in each sample were extracted, identified, and analysed. Identification to genus level was conducted using light microscopy with Nomarski differential interference contrast (DIC), based on morphological keys provided by Platt & Warwick (1983, 1988), Warwick et al. (1998), and Schmidt-Rhaesa (2014). Nematodes were hand-picked under an Olympus SZX16 stereomicroscope, transferred to anhydrous glycerol (De Grisse, 1969), and permanently mounted on glass slides. Each individual was measured for body length (excluding filiform tails) and maximum width using digital images captured with an Olympus® microscope and analysed using cellP software. Wet weight (WW, µg) was calculated based on the formula by Andrassy (1956): WW = (L × W²) / 1.6 × 10⁶, where L is body length and W is width (both in µm). Dry weight (DW) was assumed to be 25% of WW. To assess functional composition, each nematode genus was classified according to feeding type (Wieser, 1953) and coloniser–persister (c–p) value (Bongers, 1990; Bongers et al., 1995). Additionally, each genus was matched with its corresponding AphiaID from the World Register of Marine Species (WoRMS) to ensure taxonomic standardisation. Note: In the dataset table, some nematode specimens lack length and width measurements because their position on the slide made accurate measurement impossible.
Institutions
- Alfred-Wegener-Institut Helmholtz-Zentrum fur Polar- und Meeresforschung