Humic Substances Increase Survival of Freshwater Shrimp Caridina sp. D to Acid Mine Drainage

Abstract

Humic substances (HS) are known to decrease the toxicity of heavy metals to aquatic organisms, and it has been suggested that they can provide buffering protection in low pH conditions. Despite this, little is known about the ability for HS to increase survival to acid mine drainage (AMD). In this study, the ability of HS to increase survival of the freshwater shrimp (Caridina sp. D sensu Page et al. in Biol Lett 1:139-142, 2005) to acid mine drainage was investigated using test waters collected from the Mount Morgan open pit in Central Queensland with the addition of Aldrich humic acid (AHA). The AMD water from the Mount Morgan open pit is highly acidic (pH 2.67) as well as contaminated with heavy metals (1780 mg/L aluminum, 101 mg/L copper [Cu], 173 mg/L manganese, 51.8 mg/L zinc [Zn], and 51.8 mg/L iron). Freshwater shrimp were exposed to dilutions in the range of 0.5 % to 5 % AMD water with and without the addition of 10 or 20 mg/L AHA. In the absence of HS, all shrimp died in the 2.5 % AMD treatment. In contrast, addition of HS increased survival in the 2.5 % AMD treatment by ≤66 % as well as significantly decreased the concentration of dissolved Cu, cobalt, cadmium, and Zn. The decreased toxicity of AMD in the presence of HS is likely to be due to complexation and precipitation of heavy metals with the HS; it is also possible that HS caused changes to the physiological condition of the shrimp, thus increasing their survival. These results are valuable in contributing to an improved understanding of potential role of HS in ameliorating the toxicity of AMD environments.

Humic acid decreases acute toxicity and ventilation frequency in eastern rainbowfish (Melanotaenia splendida splendida) exposed to acid mine drainage

“…This is the first study to show that HA significantly decreases ventilation frequency and acute toxicity in fish exposed to AMD. HA have been shown previously to increase survival of shrimp and mayflies to AMD (Holland et al, 2013(Holland et al, , 2014b. This study and results provided in Holland et al (2013Holland et al ( , 2014a, suggest that the presence of HA has a positive effect on aquatic organisms and may aid their survival to multiple stressors such as low pH and heavy metal mixtures associated with AMD.…”

“…This decreased the amount of pH drift during the trial period. The use of MOPS as a buffer was deemed appropriate as previous studies have shown MOPS to be nontoxic to freshwater species (De Schamphelaere et al, 2004;Rendal et al, 2012;Holland et al, 2013), and pilot trials also showed MOPS to also be non-toxic to the eastern rainbowfish used in this study. The use of MOPS buffer was also deemed appropriate as it has been previously used in a number of studies involving the ecotoxicology of metals in freshwater (De Schamphelaere et al, 2004;Rendal et al, 2012) and has been previously shown to not bind to or influence metal speciation (Kandegedara and Rorabacher, 1999).…”

“…Treatment waters consisted of zero per cent (control), two per cent, three per cent and four per cent AMD, with and without the presence of 10 mg/L and 20 mg/L (nominal concentrations) Sigma Aldrich humic acid (AHA) (AHA chemical features: residue on ignition 29.9 per cent, carbon content 40.15 per cent, hydrogen content 3.60 per cent and nitrogen content 0.92 per cent).The use of ten and 20 mg/L was employed to replicate the concentrations previously used in Holland et al (2013); these were originally chosen to represent HS levels commonly found in freshwaters, with 10 mg/L shown to be an average value and 20 mg/L HS to represent the higher limit (20 mg/L). HS levels can often exceed the 20 mg/L level as shown in Thomas and Eaton (1996).…”

“…Each treatment in each trial was replicated five times. Test waters (treatments and controls) were prepared using the method outlined in Holland et al (2013). The AMD was diluted with filtered Dee river water (0.7 mm Whatman GF/F) containing 0.75 g/L three-N morpholinopropanesulfonic acid (MOPS) buffer to limit pH drift.…”

“…D), and mayflies (Atalophlebia spp.) after 96 h (Chapman and Simpson, 2005;Holland et al, 2013Holland et al, , 2014b.…”