Namib Desert Spring Nematodes
Description
We investigated nematode communities in microbial mats and sediments from seven hypersaline springs in the Namib Desert of Namibia. We hypothesized that salinity is the primary driver of nematode distribution and abundance in this extreme environment. Five taxa were common in these springs: Monhystrella, Rhabdolaimus, Paracyatholaimus, Ethmolaimus, and Oncholaimus. Their abundance was higher in mats than in sediments but showed no correlation with salinity [measured as electrical conductivity (EC)], while nematode diversity was negatively correlated with EC. The least diverse communities, consisting only of Monhystrella, were found at Welwitschia Wash, a semi-permanent spring in the driest region of the Namib. This nematode was widespread and abundant across all sites, suggesting a potential specialization for hypersaline conditions. Notably, live Monhystrella and Rhabdolaimus were found in sediments under water with EC > 500 mS cm⁻¹, which is the highest salinity nematodes have ever been documented to survive. The densest communities were found in a microbial mat in water at 112 mS cm⁻¹. Hypersalinity does not appear to limit nematode presence or abundance in Namib Desert springs. Our findings expand our understanding of the survival limits for nematodes and the ecology of an understudied animal in springs. Several spring characteristics and water parameters were measured (depth, width, EC, DO, pH, electrical conductivity) and are included in the dataset, as well as abundances of the nematode taxa found.
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Steps to reproduce
DO was measured with an Extech DO600, Extech, Nashua, NH). DO subsequently was salinity corrected (Benson & Krause, 1984), and this value was used to estimate oxygen saturation (%, Mortimer, 1956). Electrical conductivity and pH were measured using a calibrated YSI Pro 1030 (YSI, Inc., Yellow Springs, OH). Nematodes were extracted from sediment (60 - 120 g) and mat samples (20 - 60 g fresh weight material) over 72 h using a Baermann funnel technique (Hodda & Abebe, 2006). Sample volume was reduced to approximately 500 µl, and nematodes were fixed in 5% hot and cold formalin solutions. Nematodes were counted and identified to the lowest taxonomic level possible using a Zeiss inverted microscope at up to 1000X (Carl Zeiss, Inc., White Plains, NY) Please see associated manuscript (in prep) for more details.
Institutions
- University of Richmond