Tracking down carbon inputs underground from an arid zone Australian calcrete.

Freshwater ecosystems play a key role in shaping the global carbon cycle and maintaining the ecological balance that sustains biodiversity worldwide. Surficial water bodies are often interconnected with groundwater, forming a physical continuum, and their interaction has been reported as a crucial driver for organic matter (OM) inputs in groundwater systems. However, despite the growing concerns related to increasing anthropogenic pressure and effects of global change to groundwater environments, our understanding of the dynamics regulating subterranean carbon flows is still sparse. We traced carbon composition and transformations in an arid zone calcrete aquifer using a novel multidisciplinary approach that combined isotopic analyses of dissolved organic carbon (DOC) and inorganic carbon (DIC) (δ13CDOC, δ13CDIC, 14CDOC and 14CDIC) with fluorescence spectroscopy (Chromophoric Dissolved OM (CDOM) characterisation) and metabarcoding analyses (taxonomic and functional genomics on bacterial 16S rRNA). To compare dynamics linked to potential aquifer recharge processes, water samples were collected from two boreholes under contrasting rainfall: low rainfall ((LR), dry season) and high rainfall ((HR), wet season). Our isotopic results indicate limited changes and dominance of modern terrestrial carbon in the upper part (northeast) of the bore field, but correlation between HR and increased old and 13C-enriched DOC in the lower area (southwest). CDOM results show a shift from terrestrially to microbially derived compounds after rainfall in the same lower field bore, which was also sampled for microbial genetics. Functional genomic results showed increased genes coding for degradative pathways-dominated by those related to aromatic compound metabolisms-during HR. Our results indicate that rainfall leads to different responses in different parts of the bore field, with an increase in old carbon sources and microbial processing in the lower part of the field. We hypothesise that this may be due to increasing salinity, either due to mobilisation of Cl- from the soil, or infiltration from the downstream salt lake during HR. This study is the first to use a multi-technique assessment using stable and radioactive isotopes together with functional genomics to probe the principal organic biogeochemical pathways regulating an arid zone calcrete system. Further investigations involving extensive sampling from diverse groundwater ecosystems will allow better understanding of the microbiological pathways sustaining the ecological functioning of subterranean biota

Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem

Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved organic carbon (DOC) to higher trophic levels of the anchialine food web in the Yucatan Peninsula (Mexico). Methane and DOC production and consumption within the coastal groundwater correspond with a microbial community capable of methanotrophy, heterotrophy, and chemoautotrophy, based on characterization by 16S rRNA gene amplicon sequencing and respiratory quinone composition. Fatty acid and bulk stable carbon isotope values of cave-adapted shrimp suggest that carbon from methanotrophic bacteria comprises 21% of their diet, on average. These findings reveal a heretofore unrecognized subterranean methane sink and contribute to our understanding of the carbon cycle and ecosystem function of karst subterranean estuaries

The DarCo project: A cost-effective plan to incorporate subterranean ecosystems in post-2020 biodiversity and climate change agendas

Subterranean ecosystems host a broad diversity of specialized and endemic organisms that account for a unique fraction of the global taxonomic, phylogenetic, and functional diversity. Furthermore, they deliver crucial ecosystem services—especially the provisioning of potable water to more than half of the world’s population. Yet, these out-of-sight ecosystems are systematically overlooked in post-2020 biodiversity and climate change targets. Only 6.9% of known subterranean ecosystems overlap with the global network of protected areas, with just a few of these areas designed to account for their vertical dimension. Two main impediments are responsible for this lack of protection. First, subterranean biodiversity patterns remain largely unmapped, even in areas with a long speleological tradition such as Europe. Second, we lack a mechanistic understanding of subterranean species' response to human-induced perturbations. The project DarCo (2023–2026; biodiversa+ funding scheme) aims to map subterranean biodiversity patterns across Europe and develop an explicit plan to incorporate subterranean ecosystems in the European Union (EU) Biodiversity Strategy for 2030. To this end, we have established a multidisciplinary team of leading scientists in subterranean biology, macroecology, and conservation science from a broad range of European countries. The project is articulated in three interconnected work packages devoted to direct research (WP2–4), plus a fourth package (WP5) aimed at maximizing the dissemination of results and engagement of stakeholders to implement practical conservation. First, by compiling existing databases and leveraging a capillary network of international collaborators, we will gather distribution data, traits, and phylogenies for all major subterranean animal groups, including crustaceans, mollusks, insects, and vertebrates (WP2). These data will serve to predict species responses to human threats using Hierarchical Modelling of Species Communities (WP3). Models' predictions of biodiversity change will provide the basis for a dynamic mapping of European subterranean life. By intersecting maps of diversity patterns, threats, and protected areas, we will design a plan to protect subterranean biodiversity complementing the current EU network of protected areas (Natura 2000), while taking into account climate-driven shifts in subterranean ecoregions (WP4). Finally, through target activities in WP5, we seek to raise societal awareness about subterranean ecosystems and invite stakeholders to incorporate subterranean biodiversity in multilateral agreements. In compliance with the European Plan S, we will make all data open and re-usable by the development of a centralized and open database on subterranean life—the Subterranean Biodiversity Platform. This will ensure that future generations will be able to build upon knowledge accumulated on subterranean biodiversity and monitor the effectiveness of today’s protection measures in the years ahead

Indicative Distribution Maps for Ecological Functional Groups - Level 3 of IUCN Global Ecosystem Typology

This dataset includes the original version of the indicative distribution maps and profiles for Ecological Functional Groups - Level 3 of IUCN Global Ecosystem Typology (v2.0). Please refer to Keith et al. (2020). The descriptive profiles provide brief summaries of key ecological traits and processes for each functional group of ecosystems to enable any ecosystem type to be assigned to a group. Maps are indicative of global distribution patterns are not intended to represent fine-scale patterns. The maps show areas of the world containing major (value of 1, coloured red) or minor occurrences (value of 2, coloured yellow) of each ecosystem functional group. Minor occurrences are areas where an ecosystem functional group is scattered in patches within matrices of other ecosystem functional groups or where they occur in substantial areas, but only within a segment of a larger region. Most maps were prepared using a coarse-scale template (e.g. ecoregions), but some were compiled from higher resolution spatial data where available (see details in profiles). Higher resolution mapping is planned in future publications. We emphasise that spatial representation of Ecosystem Functional Groups does not follow higher-order groupings described in respective ecoregion classifications. Consequently, when Ecosystem Functional Groups are aggregated into functional biomes (Level 2 of the Global Ecosystem Typology), spatial patterns may differ from those of biogeographic biomes. Differences reflect the distinctions between functional and biogeographic interpretations of the term, biome