Vol.:(0123456789) 1 3 Limnology (2021) 22:347–355 https://doi.org/10.1007/s10201-021-00662-2 RESEARCH PAPER Nematode fauna associated with freshwater microbialites in Bacalar Lake, Quintana Roo, Mexico Alberto de Jesús‑Navarrete 1  · Alfredo Yanez‑Montalvo 1  · Luisa I. Falcón 2  · Abel Vargas‑Espósitos 1 Received: 10 September 2020 / Accepted: 24 June 2021 / Published online: 12 July 2021 © The Japanese Society of Limnology 2021 Abstract Bacalar Lake is characterized by a high saturation of calcium, bicarbonate, sulfate and silicate in its water and these condi- tions harbor a microbialite community. To explore the nematode fauna, associated with microbialites, 11 sites along the lake were selected. The collected microbialites were carefully dissolved and nematodes extracted manually. Nematodes were represented by 2 classes, 10 orders, 17 families, and 22 genera. Dorylaimidae and Xyalidae were the richest in genera (3 each), while the family Selachinematidae was represented by Choanolaimus, which is frst reported in epicontinental systems. Dichromadora (48), Epitobrilus (31), Dorylaimus (30), Ischiodorylaimus (24), Belondira (13), Aphanolaimus (11) and Monhystera (10) were the most abundant genera. All Nematode’s freshwater feeding types were present, but deposit feeders (DF) were observed with 35%. We concluded that nematodes are an important component of the metazoan fauna in microbialites from Bacalar Lake, with a higher diversity than reported in other lakes and marine environments. Nematodes can take advantage of the micro-spaced texture of microbialites and function as bioturbators, as well as escape predation, taking advantage of available food, which is refected in the structure of nematode feeding types. More research on the inter- action of microbialites-nematodes is necessary to understand their role in this poorly known environment. Keywords Feeding types · Freshwater · Lacustrine · Meiofauna · Sedimentary environments Introduction Stromatolites, the oldest known fossil evidence of life on Earth have been dated at approximately 3.5 billion years (Allwood et al. 2006; Nutman et al. 2016) and were abun- dant during the Archean era. Stromatolites are organic sedimentary structures formed by the interaction between benthic microbial communities and environmental hydro- geochemistry, involving processes capable of trapping, bind- ing, and precipitating minerals (Burne and Moore 1987; Riding 2011). Microorganisms were the frst biological colonizers on Earth and their metabolic diversity enabled them to interact with biogeochemical elements, build an oxygen-rich atmosphere, and create a scenario that infu- enced the evolution of life (Falkowski et al. 2008; Breitbart et al. 2009). Paleontological studies suggest that the frst multicellular organisms coexisted near microbialites, up tak- ing the organic matter, and taking advantage of the oxygen produced by photosynthetic organisms (Gingras et al. 2011; Rishworth et al. 2016). In the Precambrian, stromatolites were still abundant on the surface of the planet yet burrowing and grazing by metazoans caused a decrease in these communities, and today they are found in environments with extreme condi- tions for eukaryotes (Awramik 1971; Tarhan et al. 2013). Modern stromatolites are called microbialites and have been described from environments with extreme physicochemical parameters including salinity, pH, temperature, and nutrients limiting the development of eukaryotic life, both in marine and lacustrine environments (Chagas et al. 2016). Modern microbialites are considered microbial ecosys- tems, where viruses and organisms from the three domains of life (Archaea, Bacteria and Eukarya) coexist through their metabolic capabilities, favoring mineral lithifcation (White * Alberto de Jesús-Navarrete anavarre@ecosur.mx 1 Departamento de Sistemática y Ecología Acuática, El Colegio de La Frontera Sur, Grupo, Estructura y Función del Bentos. Av. Centenario km 5.5, Chetumal Quintana Roo, México 2 UNAM, Instituto de Ecología, Parque Científco Y Tecnológico de Yucatán, Sierra Papacal, 97302 Yucatán, México