This dataset describe the distribution of two hyporheic crustacean taxa (Bogidiellidae, Amphipoda and Anthuridae, Isopoda) in streams of New Caledonia. We sampled the two taxa at 228 sites. At each site, we quantified nine local predictors related to habitat area and stability, sediment metabolism and water origin, and eight catchment predictors related to geology, area, primary productivity, land use and specific discharge.

Presence/absence data

We collected presence/absence data for Bogidiellidae and Anthuridae from 228 freshwater hyporheic sites during a scientific expedition to New Caledonia. Bogidiellidae Hertzog, 1936 is a species-rich family of subterranean amphipods (Koenemann and Holsinger 1999). New Caledonian bogidiellids had previously been reported from a single littoral cave in Lifou Island (Jaume et al. 2007) and two hyporheic sites on the main island (Mary and Marmonier 2000). The anthurids collected during the expedition belonged to the subterranean genus Stygocyathura Botosaneanu & Stock, 1982. This genus had previously been reported from only two coastal, interstitial sites in New Caledonia (Wägele 1982). All bogidiellid and anthurid specimens collected during the expedition were blind and depigmented. Although these specimens undoubtedly belong to several new species, following Qiao et al. (2017) we assumed that these species shared similar ecological traits and modelled their distribution at the family (Bogidiellidae) and genus level (Stygocyathura, thereafter referred to as anthurids).

We carried out sampling in November 2016, November 2017 and July 2018, during low flow periods. We obtained hyporheic samples by hammering a perforated pipe to a depth of 60 cm below the streambed (Boulton et al. 2003). We used a hand piston pump to extract 10 L of hyporheic water and sediments that we elutriated and filtered through a 150-µm-mesh net. We immediately searched for the presence of bogidiellids and anthurids in the filtered sample using a field-dissecting microscope. When one or both taxa were not present in the first replicate sample, we collected up to four replicate samples to ascertain their absence at a site. All filtered samples were preserved in 96% ethanol and were again processed under a laboratory dissecting microscope to check for the presence/absence of bogidiellids and anthurids.

 Local predictors

We used nine local predictors to describe in-stream habitat conditions: river width, specific conductance, dissolved oxygen (DO), redox potential, pH, temperature of hyporheic water, mean annual air temperature, elevation and stream slope. We used one-time measurements of physio-chemical parameters assuming that temporal variations in stream water chemistry and temperature were low at a depth of 60 cm into the streambed sediment of tropical streams. We measured river width as the width of the area occupied by low-flow channels and unvegetated gravel bars (Bertrand and Liébault 2019), and used it as a surrogate of the sedimentary habitat area available for hyporheic organisms. We measured specific conductance, temperature, pH, redox potential and DO of hyporheic water with a multi-parameter probe (Odéon, Aqualabo, France). Specific conductance is a proxy for the origin of water; it increases with increasing residence time of water in the subsurface, either in the hyporheic zone or in lateral aquifers hydrologically connected to it (Cox et al. 2007). DO, redox potential and pH are indicators of hyporheic sediment metabolism: they are expected to be lower in hyporheic sediments that receive higher organic matter supply because microbial respiration would rapidly consume terminal electron acceptors along hyporheic flow paths (Malard et al. 2002, Reeder et al. 2018). In addition to one-time measurement of hyporheic water temperature, we extracted mean annual air temperature from the WorldClim 2 dataset (30 arc-second resolution, Fick and Hijmans 2017) as a surrogate of mean annual stream water temperature. We obtained elevation of the sites from a 10-m resolution digital elevation model (DEM) of New Caledonia. We computed river slope for every 50 m-long stream segment of the digital stream network of New Caledonia.

 Catchment predictors

We used eight predictors to describe catchments: catchment area, areal proportion of peridotite, three land cover predictors, normalized difference vegetation index (NDVI), mean annual precipitation and low flow specific discharge. We produced a digital stream network of New Caledonia using a 10-m-resolution DEM. The network contained 29,405 nodes regularly located at every 0.1-km² increase in catchment area from a minimum catchment area of 5 km². We computed each predictor for the entire upstream contributing catchment area associated with each sampled site. We computed the areal proportion of peridotite rocks from the 1:50 000 geological map of New Caledonia. We derived the three land cover predictors from the 1:12 000 land cover map of New Caledonia using a procedure described in Appendix 1 (Supplementary material Appendix 1, Fig. A1). Values of land cover predictors 1 and 2 increased with increasing proportion of bare soil and decreased with increasing proportion of mature forests and herbaceous vegetation, respectively. Values of land cover predictor 3 increased with increasing proportion of shrubs. We used mean NDVI to assess differences in above-ground biomass among catchments. We computed the index from 12 NDVI raster files available at a resolution of 250 m over the period 2000–2011. From WorldClim 2, we extracted mean annual precipitation averaged over the upstream contributing catchment area associated with each site. We obtained the low flow specific discharge for each catchment, defined as the average daily flow exceeded 355 days per year, from hydrological models by Romieux and Wotling (2016). We performed all geospatial analyses in ArcGIS 10.2.2 (Esri, Redlands, California, USA).

See related article (https://doi.org/10.1111/ecog.06099) for references and related script (https://doi.org/10.5281/zenodo.6104368) for data analysis.

This dataset allows to reproduce the statistical analysis whose results are presented in the article:
"Unique and shared effects of local and catchment predictors over distribution of hyporheic organisms: does the valley rule the stream? ", Mouron et al. 2022, Ecography (https://doi.org/10.1111/ecog.06099)

This analysis can be reproduced using the script submitted to Zenodo at https://doi.org/10.5281/zenodo.6104368

- "Mouron_et_al_2022_Landcover.csv" : Landcover data from GIS analysis to perform correspondence analysis (see script).
Variables : "Bare soil","Herbaceous","Shrubs","Mature forest","Urban","Water" ; i.e. the land cover composition for the 228 catchments (see Supplementary material Appendix 1, Fig. A1).

- "Mouron_et_al_2022_data.csv" : main dataset that contain occurences of Bogidiellids and Anthurids, local predictors and catchment predictors for 228 sites.

The 228 freshwater hyporheic sites are identified by a code ("Site_Code") and coordinates in WGS 84 ("X_long","Y_lat").

Occurences ("Bogi","Anthu") are presence/absence data for subterranean crustaceans Bogidiellidae and Anthuridae sampled in November 2016, November 2017 and July 2018. The nine local predictors describe in-stream habitat conditions : river width ("River_width", m), specific conductance("Sp_conductance", µS/cm), dissolved oxygen ("DO", mg/L), redox potential ("Redox_potential", mV), pH ("pH"), temperature of hyporheic water ("Temperature", °C), mean annual air temperature ("Mean_annual_temp", °C), elevation ("Elevation", m) and stream slope ("Stream_slope", m/m).

The eight catchments predictors describe the entire upstream contributing catchment : catchment area ("Catchment_area", km²), areal proportion of peridotite ("Peridotite", %), three land cover predictors ("Landcover1","Landcover2","Landcover3"), normalized difference vegetation index ("NDVI"), mean annual precipitation ("Precipitation", mm/year) and low flow specific discharge ("Discharge", L/s/km²).