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Toxicity to aquatic algae and cyanobacteria

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All available studies data were used in a weight of evidence approach to cover this endpoint. Literary studies investigating the effects of aluminum in the aquatic environment have extensively used test solutions with aluminum concentrations above that of its solubility limit. Results of these studies therefore  have limited value for the investigation of intrinsic toxicity.

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The algae data from the 2009 and 2010 CIMM datasets demonstrate that elevated pH and elevated DOC are protective against aluminium toxicity, whereas hardness appeared to have a minimal effect.  The evidence of both pH and DOC effects are consistent with the Al BLM. Multiple linear regression models (MLRM) based on nominal DOC, and pH were developed to predict nominal EC10 and EC50 values for the algae dataset. The EC50 and EC10 MLRMs performed reasonably well for the dataset. The EC50 MLRM produced an adjusted R2of 0.747, and the EC10 MLRM produce an adjusted R2of 0.987 (see Figures 7.1.1.3-2, and 7.1.1.3-3, respectively).

Literature Review: Six chronic toxicity studies to a freshwater microalga (Pseudokirchneriella subcapitata)were identified in the literature as Klimisch 1 or 2 studies ( Table # "Overview of effects on algae and aquatic plants". Additional algal studies with Pseudokirchnerella subcapitata were performed at CIMM to evaluate acute and chronic toxicity to algae and for evaluation of water chemistry effects for modelling purposes. All endpoints from CIMM (2009; 2010a) were reported on the basis of nominal Al concentrations because total Al was not measured in these studies. However, CIMM (2010b) compared nominal to measured total Al concentrations in an identical set of algal test solutions prepared to match all water quality conditions and nominal Al exposure concentrations as used in the previous studies (2009; 2010a). In these new test solutions, average total Al concentrations were within 10% of nominal Al concentrations. A linear regression between total and nominal Al concentrations demonstrated a strong relationship with an r2value of 0.99 (Figure 7.1.1.3 -1). Therefore, nominal Al concentrations can be considered a reliable estimator of total Al concentrations in these studies. ECr10s were calculated using raw data provided from each study using the statistical program Toxicity Relationship Analysis Program (TRAP) version 1.10 from the US EPA National Health an Environmental Effects Research Laboratory (NHEERL). All other endpoints were as reported in each study. ECr10s and ECr50s ranged from 0.051 to 3.15 mg Al/L and 0.024 to 4.93 mg Al/L, respectively. Water quality data for these studies suggest a direct relationship between toxicity and pH, hardness, and DOC. Studies that experimentally manipulated water quality werre reported by CIMM 2009 and 2010a. One toxicity study to a higher plant (Lemna minor) was included (Table 8). No toxicity was observed in this study, so both NOEC and EC10 values were > 45.7 mg Al/L.