481
exposure to oil, dispersed oil, and dispersants must (1) follow rigorous protocols
which are well supported in the scientific literature, (2) produce reproducible and
verifiable results, and (3) have well-defined and accepted statistical criteria for
interpreting as well as rejecting results (NRC 2005; Bejarano 2018).
This chapter summarizes the traditional laboratory toxicity tests that have been
conducted on MC252 (and surrogate) oils and/or Corexit 9500, pertinent to the
DWH oil spill for standardtest species and also nontraditional estuarine and marine
species reporting lethal and sublethal (i.e., growth, reproduction) endpoints from
both short-term acute and chronic toxicitytests (either published in peer reviewed
literature or reported on NOAA DIVER).
Keywords NRDA · EPA · Standard toxicity testing · CROSERF · Corext 9500 ·
WAF · CEWAF · LC50 · EC50
28.1 Introduction
In the event of an oil spill, like the Deepwater Horizon (DWH), a Natural Resource
Damage Assessment (NRDA) is mandated to document observable or measurable
adverse changes to a natural resource or predict a future impairment of a natural
resource. The assessment of health and integrity of estuarine and marine aquatic
resources following exposure to contaminants and/or other environmental stressors
relies on using established standard protocols and metrics for evaluating chemical, biological, and toxicological status. One of the key tools available for assessing environmental damage is the use of realistic laboratory- and mesocosm-scale toxicity
experiments to expose organisms to various concentrations of oil and/or chemical dispersant employing an array of biological endpoints. However, widely varying methods
of laboratory testing have been used together with extrapolation procedures that are not
fully reliable for environmental assessments of oil spills (NRC 2005; Coelho et al.
2013; Bejarano et al. 2014; Bejarano 2018). There is often a severe lack of understanding in how to conduct aquatic toxicity tests correctly with respect to the questions being
asked (i.e., toxicological comparisons between different oil mixtures, different species
or life stages, or specific parameters unique to a spill event). There are many examples
of serious errors (i.e., under and overestimations of toxicity) resulting from using inadequate methods for experimental design, chemical analyses of exposure media, and
data analysis/interpretation. Studies that evaluate biological responses and measureable adverse changes from exposure to oil, dispersed oil, and dispersants must (1) follow rigorous protocols which are well supported in the scientific literature, (2) produce
reproducible and verifiable results, and (3) have well-defined and accepted statistical
criteria for interpreting as well as rejecting results (NRC 2005; Bejarano 2018).
It was clear nearly four decades ago that the critical issue in the interpretation
and comparison of laboratory toxicity data for oil, dispersants, and dispersed oil was
the lack of standardization of laboratory toxicity testing protocols (NRC 1989;
Tjeerdema 1990). Therefore, in the mid-1990s, the Chemical Response to Oil Spills:
Ecological Effects Research Forum (CROSERF) was established to provide guide28 A Synthesis of DWH Oil: Chemical Dispersant and Chemically Dispersed Oil…
exposure to oil, dispersed oil, and dispersants must (1) follow rigorous protocols
which are well supported in the scientific literature, (2) produce reproducible and
verifiable results, and (3) have well-defined and accepted statistical criteria for
interpreting as well as rejecting results (NRC 2005; Bejarano 2018).
This chapter summarizes the traditional laboratory toxicity tests that have been
conducted on MC252 (and surrogate) oils and/or Corexit 9500, pertinent to the
DWH oil spill for standardtest species and also nontraditional estuarine and marine
species reporting lethal and sublethal (i.e., growth, reproduction) endpoints from
both short-term acute and chronic toxicitytests (either published in peer reviewed
literature or reported on NOAA DIVER).
Keywords NRDA · EPA · Standard toxicity testing · CROSERF · Corext 9500 ·
WAF · CEWAF · LC50 · EC50
28.1 Introduction
In the event of an oil spill, like the Deepwater Horizon (DWH), a Natural Resource
Damage Assessment (NRDA) is mandated to document observable or measurable
adverse changes to a natural resource or predict a future impairment of a natural
resource. The assessment of health and integrity of estuarine and marine aquatic
resources following exposure to contaminants and/or other environmental stressors
relies on using established standard protocols and metrics for evaluating chemical, biological, and toxicological status. One of the key tools available for assessing environmental damage is the use of realistic laboratory- and mesocosm-scale toxicity
experiments to expose organisms to various concentrations of oil and/or chemical dispersant employing an array of biological endpoints. However, widely varying methods
of laboratory testing have been used together with extrapolation procedures that are not
fully reliable for environmental assessments of oil spills (NRC 2005; Coelho et al.
2013; Bejarano et al. 2014; Bejarano 2018). There is often a severe lack of understanding in how to conduct aquatic toxicity tests correctly with respect to the questions being
asked (i.e., toxicological comparisons between different oil mixtures, different species
or life stages, or specific parameters unique to a spill event). There are many examples
of serious errors (i.e., under and overestimations of toxicity) resulting from using inadequate methods for experimental design, chemical analyses of exposure media, and
data analysis/interpretation. Studies that evaluate biological responses and measureable adverse changes from exposure to oil, dispersed oil, and dispersants must (1) follow rigorous protocols which are well supported in the scientific literature, (2) produce
reproducible and verifiable results, and (3) have well-defined and accepted statistical
criteria for interpreting as well as rejecting results (NRC 2005; Bejarano 2018).
It was clear nearly four decades ago that the critical issue in the interpretation
and comparison of laboratory toxicity data for oil, dispersants, and dispersed oil was
the lack of standardization of laboratory toxicity testing protocols (NRC 1989;
Tjeerdema 1990). Therefore, in the mid-1990s, the Chemical Response to Oil Spills:
Ecological Effects Research Forum (CROSERF) was established to provide guide28 A Synthesis of DWH Oil: Chemical Dispersant and Chemically Dispersed Oil…