The effect of toxic Microcystis aeruginosa on four different populations of Daphnia

Cyanobacteria reduce the fitness of many Daphnia species, and blooms in eutrophic lakes may place strong selective pressure upon these primary consumers. This study examines the ability of daphnids to resist the deleterious effects of toxic Microcystis and determine if this resistance is related to the trophic conditions of their native lakes. Three populations of Daphnia pulex/pulicaria were examined; D. pulicaria from eutrophic Klamath Lake in Oregon, D. pulex from eutrophic Old Durham Reservoir in New Hampshire, and D. pulicaria from oligotrophic Russell Pond in New Hampshire. D. carinata from meso-oligotrophic Lake Rotoaira in New Zealand was used as a known cyanobacteria-sensitive species. Ten-day old 5th-6th instar animals were exposed to a mixture of Microcystis aeruginosa and Chlorella vulgaris (25% and 100% M. aeruginosa). Body length, lipid index, reproductive index and clearance rate were assessed for each population after 120 hours of treatment. A feeding bioassay response quantifying the energetic (feeding rate) cost of post abdominal rejections was also determined for a gradient of M. aeruginosa concentrations from 0% to 100%. The four populations of Daphnia exhibited different rates of decline in overall fitness when exposed to Microcystis. Populations exposed to Microcystis exhibited reduced thoracic beat rate, lower lipid and reproductive indexes, and higher cost of post abdominal rejections in comparison to daphnids in the control Chlorella. Length was not a sensitive indicator of fitness level. D. pulex from eutrophic Klamath Lake had a mean clearance rate in 100% Microcystis that was three to four times higher than D. pulicaria from oligotrophic Russell Pond. In general, daphnids from oligotrophic lakes exhibited a more drastic decline in fitness than daphnids from eutrophic lakes. This suggests that taxonomically related populations of Daphnia have evolved a suite of adaptations to Microcystis depending upon their history of exposure

Are we approaching pit lake closure from the wrong perspective?

Pit lakes are similar to natural lakes formed by faulting, glacial action, volcanic action and asteroid collisions. These natural lakes have, after thousands of years, developed into environmentally significant ecosystems. As artificial constructs, pit lakes can be modified prior to filling to enhance lake attributes, such as modification of catchment size, creation of littoral zones and addition of organic matter. Significant advances could be made in successful closure and relinquishment of pit lakes, by 1) choosing appropriate model lakes, 2) understanding successional processes, 3) designing pit lakes to enhance ecological values, and 4) recognizing that it will take time to develop desired characteristics

Pit lakes are a global legacy of mining: an integrated approach to achieving sustainable ecosystems and value for communities

The impact of large-scale mining on the landscape is a permanent legacy of industrialisation and unique to the Anthropocene. Thousands of lakes created from the flooding of abandoned open-cut mines occur across every inhabited continent and many of these lakes are toxic, posing risks to adjacent communities and ecosystems. Sustainable plans to improve water quality and biodiversity in ‘pit lakes’ do not exist due to: (1) confusion as to the ultimate use of these lakes, (2) involvement of ecologists only after the lake is filled and (3) pit lake ecology struggling to reach the primary literature. An integrated approach to pit lake management engages ecologists in pit lake design, prioritising ecological progress and passive treatment in mine closure planning, ultimately empowering communities with post-mining options

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

Mine pit lakes are formed when open-cut pits flood with water, and these lakes occur by the thousands on every inhabited continent. The remediation and closure of pit lakes is a pressing issue for sustainable development and provision of freshwater ecosystem services. While pit lakes can be spectacular examples of recreation and renewal, pit lakes may be better known for their poor water qualities and risks to communities and the environment. Often the public wants to simply “fill the pits in” to restore a terrestrial landscape, but this is not always possible. Therefore, planning for remediation and future uses is likely to provide the best outcome. Poor water quality is not necessarily a barrier to future use, although it may limit the number of uses. Short-term future uses tend to require commercial viability, active infrastructure investment, and maintenance, and should transition to complementary long-term uses that promote biodiversity. Long-term future uses require relatively less ongoing maintenance beyond the initial investment and adhere to the principles that pit lakes should be safe, sustainable, and non-polluting in perpetuity. Pit lakes will eventually develop “ecosystem values,” and the time to do so depends on the nature of the intervention and the values ascribed by the community. Where possible, closing pit lakes as sustainable ecosystems is the most realistic goal that permits a variety of future uses that is likely to see pit lakes valued by future generations. This article is categorized under: Engineering Water \u3e Planning Water Human Water \u3e Value of Water Human Water \u3e Water as Imagined and Represente

Aquatic ecosystems of the anthropocene: Limnology and microbial ecology of mine pit lakes

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

IMWA insight: Understanding public perceptions of a new pit lake in As Pontes, Spain

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature. The introduction of coal mining in the 1940’s transformed the landscape and economy of As Pontes, Spain. Industrialisation created successive waves of economic and population booms, but when the mining slowed in the 1990s, the region experienced economic depression. Real and perceived social divisions and environmental abuses on the part of the mining company remained entrenched in people’s memories. This paper provides an overview of the factors that likely affected community acceptance of the new pit lake in As Pontes, Spain. Pit lakes are often attractive closure options for companies, and community opinion of pit lakes can influence pit end use. Community perceptions of the pit lake before, during, and after filling were assessed using case studies, interviews, and focus groups, and by tracking news events and analysing internet forums. The results broadly indicated high community acceptance of the pit lake by people residing in the town. However, interviews revealed that acceptance of the pit lake was influenced by previous experiences with the mining company; company employees and local politicians were more likely to be positive about the benefits of the lake, whereas those not directly affiliated with the lake (long-term residents, remote villagers, school teachers) were more likely to have a negative view of it. Thus, technical success is not the only factor that influences community acceptance of pit lakes and company closure plans. Unresolved social issues can also influence the way certain people perceive the new landscape, regardless of ecological and aesthetic impacts

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

Pit lakes are one of the greatest legacies of open-cut mining. Despite the potential hazards of these lakes, they represent newly formed ecosystems with great scientific and ecological potential. Although thousands of pit lakes occur on every inhabited continent, with more being created, the microbial ecology of pit lakes is relatively under-researched. We evaluated the current state of microbial research in pit lakes by performing a Web of Science search and creating a literature database. Study lakes were categorized according to location and water quality (pH and conductivity) which is a key community and environmental concern. Research technology employed in the study was also categorized. We compared research effort in lakes, rivers, and streams which are the more “charismatic” inland aquatic ecosystems. Pit lake publications on microbes from 1987 to 2022 (n = 128) were underrepresented in the literature relative to rivers and streams (n = 321) and natural lakes (n = 948). Of the 128 pit lake publications, 28 were within the field of geochemistry using indirect measures of microbial activity. Most pit lake microbial research was conducted in a few acidic lakes in Germany due to social pressure for remediation and government initiative. Relatively few studies have capitalized on emerging technology. Pit lake microbial research likely lags other more charismatic ecosystems given that they are viewed as performing “ecosystem disservices,” but this is socially complex and requires further research. Improving understanding of microbial dynamics in pit lakes will allow scientists to deliver safer pit lakes to communities

Bio-physical closure criteria without reference sites: Realistic targets in modified rivers

The use of reference sites for establishing closure criteria in areas disturbed by mining activities is common practice. ‘Reference’ sites are those considered to be largely unimpacted by anthropogenic activity (retaining desirable natural characteristics), and occurring near disturbed sites. Sites are considered rehabilitated when their biophysical condition approximates that of the reference site. However, this approach often creates impossible or unrealistic targets for miners seeking to close rehabilitated lands. For example, reference sites are often limited in availability (or non-existent) due to impacts by other land uses. Further, any available reference sites might not be realistic matches for the rehabilitated sites – in many rivers (for example) it is questionable whether sites which superficially appear similar are actually ecologically similar. We propose a more achievable approach to mine closure by comparing the bio-physical characteristics of rehabilitated sites to overall ecosystem variability, rather than specific target reference sites. Using multivariate ordination - a classic data clustering technique in ecology - as an applied management tool allows managers to measure how different their rehabilitated sites are from co-occurring sites, and how the rehabilitated sites are tracking over time. Our approach also identifies the key biological, physical, and chemical parameters that potentially differentiate a rehabilitated site and, therefore, the necessary actions to bring a rehabilitation site within range of normal river variability. Further, this conceptual paper introduces two unique case studies used to develop the model, involving microbes as indicators of rehabilitation progress and mine water impact in Australian rivers. The challenges and benefits associated with implementation of this approach from the practitioners’ perspectives are discussed. The outcome of this new approach to closure will allow miners to create realistic and definable targets for relinquishing rehabilitation land in already modified landscapes, potentially simplifying closure and project approvals

Macroinvertebrates and microbes (Archaea, Bacteria) offer complementary insights into mine-pit lake ecology

The broad objective of this research was to determine the environmental drivers of macroinvertebrate and microbial assemblages in acidic pit lakes. This is important because pit lake ecosystem development is influenced by prevailing environmental characteristics. Three lakes (Stockton, Kepwari, WO5H) within a larger pit-lake district in Collie, Western Australia were surveyed for spatial variability of benthic macroinvertebrate and microbe (Archaea, Bacteria) assemblage composition as well as potential environmental drivers (riparian condition, aquatic habitat, sediments, and aquatic chemistry) of assemblages. With the exception of sediment chemistry, biophysical variables were significantly different across lakes and reflected riparian condition and groundwater chemistry. Microbial assemblages in pit lakes were significantly different across lakes and correlated with water chemistry, particularly metals in Lake WO5H. However, the most abundant microbes were not readily identified beyond class, making it difficult to speculate on their ecological function. Macroinvertebrate assemblage composition and species richness were also significantly different across all lakes, and in Lake WO5H (a lake with low pH and high metal concentrations), taxa were correlated with benthic organic matter as well as water chemistry. Results indicated that despite poor water quality, input of nutrients from terrestrial leaf litter can support or augment pit lake ecosystems. This is a demonstration of the concept that connection of pit lakes to catchments can positively affect aquatic ecosystems, which can inform management actions for remediation

Regulation of artisanal small scale gold mining (ASGM) in Ghana and Indonesia as currently implemented fails to adequately protect aquatic ecosystems

Artisanal small scale gold mining (ASGM) operations are largely unregulated, informal and transient. Rudimentary mining and processing techniques used in ASGM often result in degraded environmental, safety, health and social conditions. ASGM requires permanent sources of water, placing most operations close to natural water bodies. Until recently, the impact on these environments has been largely overlooked, with most studies focussing primarily on mercury contamination and health concerns. Based on Ghanaian and Indonesian experiences, regulation of ASGM is a good step toward improvement, but here we argue that regulation alone is insufficient to improve environmental performance, particularly when the impacts of ASGM on aquatic ecosystems are largely unknown