Sub Lethal Effects and Mussels as Indicator Organisms

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Sub- Lethal Effects and Mussels as Indicator
Organisms

• DAnn Wilkins
• Wilkins Environmental Consulting Laboratories

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What is WET?

• A biological endpoint test to determine lethal or
  sub-lethal effects.
• Lethal- A significant effect in survival compared
  to control.
• Sublethal- A significant effect in growth and
  reproduction compared to control

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Why do we use indicator organisms?

• To determine the effects of the effluent matrix
  as a whole. (vertebrate and invertebrate)
• What affects the individual constituents in the
  effluent (ie. additive, synergistic etc.)
• Constituents such as Cd, Zn, Ni, Pd, Cu
• (toxicity varies ug/L to mg/L) together very
  toxic! (invertebrate)
• Wastewater treatment products (both species)
• TDS (invertebrate)
• Ammonia (vertebrate)
• You can be meeting numerical limits and still
  fail a WET test!

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What types of tests?

• Acute high flow stream-48 hour
• Chronic low flow stream -7 day
• Acute and chronic in between
• 21 Day life cycle Daphnia magna

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What type of organisms?

• Invertebrates
• Daphnia pulex 48 hour acute
• Daphnia Magna 48 hour acute, 21 day
• Ceriodaphnia dubia 7 day chronic
• Vertebrates
• Pimephales promelas 48 hour acute, 7day

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Lethal and Sublethal Effects

• What does that mean from a compliance
  perspective?
• Lethal effects covered by TRE trigger
• Retesting required
• Sublethal recognized only as a case by case
  basis.
• No retesting requirement in permit
• PMSD is key

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What is PMSD

• Percent Minimum Significant Difference
• Measures the intra-variability within a WET test.
• Laboratories must adhere to acceptability
  criteria for test to be valid.
• Further analysis of statistics required to
  determine true sublethal effect.

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Sublethal

• Can truly be like looking for a needle in a hay
  stack!
• Type of toxicant determines toxic signal
• Biologically active-not persistent (organic)
• Not biologically active-persistent (inorganic)
• Toxic signal varies by concentration.
• Need strong signal to determine toxicant.
• Treatability or source control.

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TRE vs. TIE

• TRE- Toxicity Reduction Evaluation Study
• Sublethal can require TRE, more extensive study
  longer period of time.
• TIE- Toxicity Identification Evaluation
• Study is specific to toxic sample.
• length of study depends on type of toxicant.

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What about mussels?

• Also used as indicator organism.
• Not considered part of WET narrative criteria.
• Not consistent to represent health of in-stream
  mussel community. (bioassessments)
• Good test for presence of chemical constituents.

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Continued.

• Test relatively new to Oklahoma.
• Not required for any facilities.
• May be considered for more facilities.
• Must be definitive and reliable.
• Open to scrutiny.

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Indicator Organisms

• An excellent tool if correct test used.
• Representative of effluent quality
• Test results must be reliable.
• Proper test in place LC/50 vs. NOEC
• LC/50 48 hour test to determine lethal effects
  only.
• NOEC 7 day test to determine lethal and sub
  lethal effects.

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Questions

• DAnn Wilkins
• 832 N.W. 67th St.
• Oklahoma City, OK 73116
• Phone [phone]
• Cell 405-570-9027