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Sub- Lethal Effects and Mussels as Indicator Organisms

Sub- Lethal Effects and Mussels as Indicator Organisms. D’Ann Wilkins Wilkins Environmental Consulting & Laboratories. What is WET?. A biological endpoint test to determine lethal or sub-lethal effects. Lethal- A significant effect in survival compared to control.

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Sub- Lethal Effects and Mussels as Indicator Organisms

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  1. Sub- Lethal Effects and Mussels as Indicator Organisms D’Ann Wilkins Wilkins Environmental Consulting & Laboratories

  2. 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

  3. 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!

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Questions • D’Ann Wilkins 832 N.W. 67th St. Oklahoma City, OK 73116 Phone: 405-286-0468 Cell: 405-570-9027

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