Consistent declines in aquatic biodiversity across diverse domains of life in rivers impacted by surface coal mining

Abstract

The rivers of Appalachia (United States) are among the most biologically diverse freshwater ecosystems in the temperate zone and are home to numerous endemic aquatic organisms. Throughout the Central Appalachian ecoregion, extensive surface coal mines generate alkaline mine drainage that raises the pH, salinity, and trace element concentrations in downstream waters. Previous regional assessments have found significant declines in stream macroinvertebrate and fish communities after draining these mined areas. Here, we expand these assessments with a more comprehensive evaluation across a broad range of organisms (bacteria, algae, macroinvertebrates, all eukaryotes, and fish) using high-throughput amplicon sequencing of environmental DNA (eDNA). We collected water samples from 93 streams in Central Appalachia (West Virginia, United States) spanning a gradient of mountaintop coal mining intensity and legacy to assess how this land use alters downstream water chemistry and affects aquatic biodiversity. For each group of organisms, we identified the sensitive and tolerant taxa along the gradient and calculated stream specific conductivity thresholds in which large synchronous declines in diversity were observed. Streams below mining operations had steep declines in diversity (À18 to À41%) and substantial shifts in community composition that were consistent across multiple taxonomic groups. Overall, large synchronous declines in bacterial, algal, and macroinvertebrate communities occurred even at low levels of mining impact at stream specific conductivity thresholds of 150-200 µS/cm that are substantially below the current U.S. Environmental Protection Agency aquatic life benchmark of 300 µS/cm for Central Appalachian streams. We show that extensive coal surface mining activities led to the extirpation of 40% of biodiversity from impacted rivers throughout the region and that current water quality criteria are likely not protective for many groups of aquatic organisms.

Fishing for fish environmental DNA: Ecological applications, methodological considerations, surveying designs, and ways forward

“…However, a holistic view of ecosystems is urgently needed to comprehend the whole myriad of impacts and potential consequences incurred on ecosystem processes and functions. By examining eDNA from streams impacted by mountaintop coal mining in Central Appalachia, USA, Simonin et al (2021) found, even at low mining levels, synchronous declines in aquatic biodiversity across domains of life, thus suggesting that current regulations provide insufficient environmental protection. Such pan‐ecosystem eDNA biomonitoring would enable comprehensive assessments of anthropogenic environmental impacts and facilitate ecosystem‐scale management for effective mitigation.…”

Anthropogenic Chemicals As Underestimated Drivers of Biodiversity Loss: Scientific and Societal Implications

“…Consequently, biodiversity surveys commonly do not include chemical analytics but tend to rely on other indicators of environmental quality instead, even in cases where biodiversity changes are likely to be directly influenced by chemical pollutants. For example, in a recent study that documented an up to 40% biodiversity loss in streams affected by mining activity, the observed biodiversity patterns were correlated to water conductivity . While a useful initial indicator of water quality, this parameter does not inform on the accompanying risk factors, such as exposure to heavy metals or other contaminants leaching from mining sites.…”

Fighting symptom or root cause? - The need for shifting the focus in climate politics from greenhouse gases to environmental protection

“…The environmental risks of coal mine drainage on aquatic biodiversity have been documented in numerous cases (e.g. (Simonin et al, 2021). Land use change related to mining activities such as mountain top removal may be devastating for the affected ecosystems.…”