Abstract
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.
Highlights
The specific aims of the research were to: (1) characterise the biophysical variables of three co-occurring mine pit lakes in Collie, Western Australia, (2) collect macroinvertebrates and microbes (Archaea, Bacteria) from the pit lakes, (3) determine if assemblages were significantly different among lakes, (4) seek biophysical variables that correlated with assemblages, and (5) ascertain if, in relation to macroinvertebrates, microbial assemblages provide alternative or complementary understanding of pit lake ecosystems
Pearson–Kendall correlation analysis (|r| = 0.01, 40 ≥ 0.393) indicated that principal components analyses (PCA) axis 1 was most strongly correlated with bank geomorphology, PCA axis 2 was most strongly correlated with vegetation, and PCA axis 3 was most strongly correlated with leaf litter (|r| > 0.629)
Turbidity was the only significantly correlated water quality variable associated with nonmetric multidimensional scaling (NMDS) axis 1 (|r| = 0.840), separating Lake Stockton from lakes Kepwari and WO5H (n.b., partially driven by a highly turbid data point in Lake Stockton)
Summary
Mountaintop removal, construction of new landforms, and the creation of thousands of open pits occurs across every inhabited continent on earth (Blanchette and Lund 2016). There is growing recognition that successful mine closure is a stakeholder-driven process (Bainton and Holcombe 2018), and communities are increasingly unwilling to tolerate abandoned pit lakes on their doorstep (see Kean 2009; Woodbury 1998)
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