Aquatic Ecosystems of the Anthropocene: Limnology and Microbial Ecology of Mine Pit Lakes

Abstract

Mine pit lakes (‘pit lakes’) are new aquatic ecosystems of the Anthropocene. Potentially hundreds of meters deep, these lakes are prominent in the landscape and in the public consciousness. However, the ecology of pit lakes is underrepresented in the literature. The broad goal of this research was to determine the environmental drivers of pelagic microbe assemblages in Australian coal pit lakes. The overall experimental design was four lakes sampled three times, top and bottom, in 2019. Instrument chains were installed in lakes and measurements of in situ water quality and water samples for metals, metalloids, nutrients and microbe assemblage were collected. Lakes were monomictic and the timing of mixing was influenced by high rainfall events. Water quality and microbial assemblages varied significantly across space and time, and most taxa were rare. Lakes were moderately saline and circumneutral; Archeans were not prevalent. Richness also varied by catchment. Microbial assemblages correlated to environmental variables, and no one variable was consistently significant, spatially or temporally. Study lakes were dominated by ‘core’ taxa exhibiting temporal turnover likely driven by geography, water quality and interspecific competition, and the presence of water chemistry associated with an artificial aquifer likely influenced microbial community composition. Pit lakes are deceptively complex aquatic ecosystems that host equally complex pelagic microbial communities. This research established links between microbial assemblages and environmental variables in pit lakes and determined core communities; the first steps towards developing a monitoring program using microbes.

Non-charismatic waterbodies and ecosystem disservices: Mine pit lakes are underrepresented in the literature

“…In contrast to acidic pit lakes, non-acidic (pH > 6.5) moderately saline pit lakes are often considered benign environments with low rehabilitation priority. Thus, like natural saline lakes ( Williams, 1996 ), saline pit lakes are under-researched ( Williams, 1996 ; Mori et al, 2019 ; Blanchette and Lund, 2021 ). Similar to acid pit lakes, saline pit lake rehabilitation strategies would focus on water quality improvement or minimization of pit outflows ( Mehanna et al, 2010 ; Mouhamad et al, 2017 ; Nielsen, 2020 ).…”

“…Although research on microbial taxonomic diversity in pit lakes has been limited, pit lakes host a diverse microbial community within their waters and sediments ( Blanchette et al, 2020 ; Grettenberger et al, 2020 ; Blanchette and Lund, 2021 ; Xin et al, 2021 ). From our knowledge of other aquatic ecosystems, microbes will play a key role in pit lake ecosystem function through nutrient cycling, the fate and transport of metals and metalloids, mineral formation, biogeochemical processes, decomposition of organic matter, and interactions with other organisms ( Oren, 2004 ; Pace et al, 2016 ; Gupta et al, 2017 ; Flemming and Wuertz, 2019 ; Morris et al, 2020 ).…”

Closing pit lakes as aquatic ecosystems: Risk, reality, and future uses

“…Toxicity to aquatic and terrestrial animals, groundwater and surface water contamination, salinization, groundwater drawdown, outflow groundwater mixing, drowning risks, and disease reservoirs were initially identified as the main risks of pit lakes (McCullough & Lund, 2006). More recent studies have identified risks such as radioactivity (Manjón et al, 2013; Manjón et al, 2019; Mantero et al, 2020), watercourse “flow‐throughs” (Lund et al, 2018), build‐up of gasses (Boehrer et al, 2016; Sánchez‐España, Yusta, & Boehrer, 2020), and cyanobacterial blooms (Blanchette & Lund, 2021; Goździejewska et al, 2021). Each pit lake is unique, and depending on future use, requires a tailored approach for delivering ecosystem services and community benefits.…”

“…Pit lakes can increase the diversity of post‐mining landscapes by adding aquatic ecosystems where formerly there were only terrestrial ecosystems (McCullough & van Etten, 2011; Figure 5). Development as aquatic ecosystems is an inevitability for most pit lakes, although the timeframe for this to occur could be great and the ecosystem endpoint is often undefined (Blanchette et al, 2019; Blanchette & Lund, 2021). Small and shallow pit lakes have been successfully closed and rehabilitated or have naturally evolved (Campbell & Lind, 1969; King et al, 1974; Opitz et al, 2020; Stephenson & Castendyk, 2019).…”

Chapter 4. Bacterial and archaeal DNA from lake sediments

“…Since these effects are influenced by microbial community composition, it is necessary to study the link between lacustrine environmental conditions (Lewis, 2009), species distributions and mechanisms of selection (Bryanskaya et al, 2016). Thus, sedDNA surveys are necessary in order to understand microbial community assembly in emergent ecological niches (Mandakovic et al, 2018) and assess environmental resilience as pristine ecosystems transit to human-dominated ecosystems of the Anthropocene (Sun et al, 2017;Blanchette and Lund 2021;Fiskal et al, 2021).…”