Applied Ecosystem Services, LLC

The Environmental Issues Doctor

Photo of Metals and Aquatic Life


Estimated reading time: 2 minutes

Dissolved metals such as copper, cadmium, and zinc can be toxic to aquatic life, particularly fish. The current tool used to estimate site-specific water quality criteria for a metal is the biotic ligand model (BLM). The BLM intends to quantify how water chemistry affects chemical speciation and biological availability of metals in aquatic ecosystems. This is important because bioavailability and bioreactivity of metals control their potential for acute or chronic harm. A BLM incorporates aquatic chemistry, fish physiology, and ecotoxicology but not ecology.

The biotic ligand model includes numeric submodels that also require assumptions or estimates of missing values, rate constants, and coefficients that have not been measured in natural aquatic ecosystems or are so variable that an estimate is used in the model. This makes model outcomes subjective and not objective.

The toxicological values used in a BLM come from static (sometimes flow-through) survival bioassays in a laboratory. The limitation of laboratory bioassays is that contaminant exposures and resultant ecological impacts in natural environments are significantly more complicated. Natural ecosystems involve mixtures of exacerbating and mitigating chemical influences and complex physical, chemical and biological community structures. Extrapolation of laboratory-derived results to an actual water body is a significant source of uncertainty in predicting ecological effects of metal contamination.

There are alternative analyses of toxic metals and aquatic life that produce objective results that are technically sound and legally defensible. Make use of them to avoid (and resolve) environmental issues.

This work was originally published on the Applied Ecosystem Services, LLC web site at

It is offered under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license. In short, you may copy and redistribute the material in any medium or format as long as you credit Dr. Richard Shepard as the author. You may not use the material for commercial purposes, and you may not distribute modified versions.

Keep reading

  1. Photo of Instream Water Rights and Ecological Flows

    Instream Water Rights and Ecological Flows


    Estimated reading time: 2 minutes

    Instream water rights are (or should be) based on ecological flows. Several western states (including Oregon, Alaska, California, Colorado, and Montana) have statutory requirements for these flows, and the US Geological Survey’s Fort Collins Science Center hosts an ecological flows research center. Incorporating effects of changes in climate, human population size and distribution patterns, and other variables makes it difficult for policy makers to allocate a scarce and varying resource among competing vested interests.
  2. Photo of Natural vs. Man-made Water Bodies

    Natural vs. Man-made Water Bodies


    Estimated reading time: 2 minutes

    Project objectors may claim that mining and energy projects cannot create “real” treams and lakes during reclamation. Regulators ask operators to respond, and too often responses are inconclusive. Delays, litigation, or expensive eforts that inadequately address those concerns follow. Non-ecologists might accept claims of adverse environmental impacts by man-made streams and lakes. However, when complete ecosystems are correctly characterized and classified the dynamics of natural and man-made water bodies are indistinguishable.

Contact me to avoid environmental issues.