Update on the Copper BLM vs. MLR performance (Biotic Ligand Model vs. Multiple Linear Regression model) Data source: Boise River Water Effect Ratio Study, City of Boise, 2002 • October 28 presentations and discussions: • BLM predicted actual results fairly well • Hardness-predicted copper toxicity produced weak or spurious patterns compared to actuals UC-Davis Ceriodaphnia dubia Fathead Minnow Chris Mebane, December 11, 2015
However, NMFS (2014) BiOp did not unequivocally endorse the 2007 Cu BLM • Areas where 2007 BLM performance was not optimal: • Soft water • May be overly sensitive to DOC • Not fatal flaws • NMFS review tried to look at the totality of the hardness- criteria vs. alternatives • Even with the softwater & DOC concerns, overall performance of 2007 BLM was so much better than hardness-criteria, it was a reasonable alternative, with caveats
Hardness performance with fathead minnow in diverse waters: pretty bad • With enough data, we Measured Cu LC50s for fathead minnows versus hardness see copper toxicity does tend to decrease with Hard (Ryan wt. al. 2004) increasing hardness, but with great uncertainty Soft (Welsh et al. 1993,1996) Soft (Sciera et al. 2004) • Example: At hardness of 10 000 20 mg/L, confidant that Soft (Van Genderen et al. 2005, 48- hr) dangerous copper Variable hardness (Erickson et al concentrations (LC50s) 1996) will occur somewhere 1 000 between 2 and 400 µg/L Measured Cu LC50s 100 (µg/L) 10 1 1 10 100 1 000 Hardness mg/L) (Figure from NMFS 2014 BiOp, PDF p. 456)
BLM performance with fathead minnow in diverse natural waters: a lot better but biased • BLM was strongly correlated with actual 10 000 model results, but … • BLM results were systematically high- 1 000 biased in soft water High bias → copper was • Predicted Cu LC50s (µg/L) actually more toxic in softwater than predicted 100 Hard (Ryan wt. al. 2004) Soft (Welsh et al. 1993,1996) 10 Soft (Sciera et al. 2004) Soft (Van Genderen et al. 2005, 48-hr) 1 1 10 100 1 000 10 000 Measured Cu LC50s (µg/L) (Figure from NMFS 2014 BiOp, PDF p. 455)
MLR performance with fathead minnow in diverse natural waters: pretty good • Statistical model 10000 self-corrects for Copper P. promelas systematic bias Acute EC50s 1000 Predicted Cu EC50, µg/L 100 Diamond et al. 1997 Lind et al. 1978 10 Ryan et al. 2004 Sciera et al. 2004 Welsh et al. 1993 Erickson et al. 1996 1 1 10 100 1000 10000 Observed Cu EC50, µg/L (Figure courtesy of David DeForest and Kevin Brix, 9Dec2015)
MLR & BLM performance contrasted in diverse natural waters 10000 10 000 Copper P. promelas Acute EC50s 1000 1 000 Predicted Cu EC50, µg/L Predicted Cu LC50s (µg/L) 100 100 Hard (Ryan wt. al. 2004) Soft (Welsh et al. 1993,1996) Diamond et al. 1997 10 Lind et al. 1978 10 Soft (Sciera et al. 2004) Ryan et al. 2004 Sciera et al. 2004 Soft (Van Genderen et al. 2005, Welsh et al. 1993 48-hr) Erickson et al. 1996 1 1 1 10 100 1 000 10 000 1 10 100 1000 10000 Measured Cu LC50s (µg/L) Observed Cu EC50, µg/L
The BLM is highly sensitive to DOC Rainbow trout LC50s (BLM) (Other lines – trying alternatives in the BLM to dampen the DOC Rainbow Trout response) Rainbow trout LC50s (actual) • With these data, BLM too sensitive to DOC • Implications of too steep of a response slope: • Low DOC values, model over-predicts toxicity (over protective) • Higher DOC values, model under-predicts toxicity (under protective) (Figure from: Welsh, P.G., J. Lipton, C.A. Mebane, and J.C.A. Marr. 2008. Influence of flow-through and renewal exposures on the toxicity of copper to rainbow trout. Ecotoxicology and Environmental Safety . 69(2): 199-208. http://dx.doi.org/10.1016/j.ecoenv.2007.04.003
The MLR has a shallower DOC-toxicity slope than does the BLM 350 Acute D. magna pH ~7 300 250 Cu EC50, µg/L 200 150 100 Observed 50 BLM - Ryan (2005) LA50 Pooled MLR 0 0 5 10 15 20 DOC, mg/L (Figure courtesy of David DeForest and Kevin Brix, May2015)
The strengths of the MLR go beyond administrative convenience BLM MLR • • Overall, performance generally similar Suggestions to group: • On the whole, the MLR tends to be slightly • Question of which BLM version or MLR more protective surrogate is not ripe for decision today • (More blue in the surface plots above) Revisit at the April 2016 meeting • • BLM may over-respond to DOC In the interim – complete report from Brix and DeForest will be distributed for review • MLR “tones down” the DOC response (Figure courtesy of David DeForest and Kevin Brix, May2015)
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