Substrate Effects on Heavy Metal Accumulation and the First Record of Tardigrades in Serpentine Habitats

Serpentine habitats present various harsh conditions and are therefore considered “extreme habitats.” This study investigates the effects of substrate types on heavy metal (HM) dynamics in these stressful environments and the presence of tardigrades, an extremophile group. Accordingly, HM concentrations in Tortula subulata Hedw. from serpentine soil (SSM), serpentine rock (SRM), and tree substrates (STM), and in soil samples, were measured by ICP-OES, and bioconcentration factors (BCF) were calculated. Results showed that substrate types influenced HM accumulation, following the order SSM > SRM > STM for all elements except Cu. SSM most closely reflected the geochemical signature of the serpentine parent material, while high Fe levels and BCF > 1 for Cu in T. subulata point to a potential biomonitoring role, pending further validation. This study also reports the first records of tardigrades in serpentine ecosystems, identifying three species: Echiniscus canadensis, E. blumi, and Cornechiniscus lobatus. Species diversity and abundance varied among substrates, with tardigrade distribution paralleling HM accumulation. Principal Component Analysis (PCA) linked tardigrade species to specific substrates. Overall, substrate type could be a critical determinant of HM accumulation in serpentine habitats. Furthermore, the presence of tardigrades suggests that investigating extremophiles in these habitats may advance adaptation‑tolerance research.