Life Stage, chorion, and hatchery origin differences in the toxicity of 6PPDQ to coho salmon
Data files
Oct 07, 2025 version files 47.51 KB
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Acute_Exposure.csv
3.62 KB
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Concentration_Persistence.csv
3.08 KB
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Dechorionation_Survival.csv
3.49 KB
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Episodic_Exposure_6PPDQ.csv
194 B
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Episodic_Exposure_Light_Test.csv
2.14 KB
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Episodic_Exposure_Morphometric.csv
4.07 KB
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Episodic_Exposure_Survival.csv
24.68 KB
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README.md
6.24 KB
Abstract
Several salmonid species die from acute exposure to 2-((4-methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione (6PPDQ) – a ubiquitous pollutant that enters waterways via roadway runoff. Coho salmon (Oncorhynchus kisutch) is the most sensitive species. Toxicity has been characterized for some coho life stages, but differences in study design and source populations between studies diminish comparability of life stage sensitivity. Coho were exposed to 6PPDQ at five distinct life stages (embryos, alevins, fry, parr, and adults) and as alevins from two different hatcheries; results were characterized by measures of sublethal morphological and behavioral effects, survival analysis, and concentration response analysis. Exposures during embryo development significantly altered morphology and caused post-hatch mortality and differences in phototaxis. Dechorionated embryos were vulnerable to 6PPDQ, with increased mortality relative to intact embryos. Embryos did not die in acute exposures, but 24-h LC50s were 784 ng/L for alevin, 239 ng/L for fry, and 71 ng/L for parr. Adults were as sensitive as parr. Alevins from different hatcheries had similar sensitivity. These findings reshape understanding of 6PPDQ toxicity to early life stage coho and reveal novel sublethal effects.
Dataset DOI: 10.5061/dryad.j6q573nsk
Description of the data and file structure
Files and variables
File: Acute_Exposure.csv
Description: rows describe the conditions and outcomes of each acute exposure aquarium.
Variables
- Measured_6PPDQ_ng_L: the concentration of 6PPDQ, measured by LC-MS/MS, in nanograms per liter from 200 milliliter water samples taken from the replicate at the beginning of the experiment.
- Number_Dead: the number of individual coho salmon in the replicate that were determined to be dead after 24 hours of exposure.
- Number_Total: the total number of individual coho salmon included in the replicate.
- MortalityRate: Number_Dead/Number_Total
- Group: the life stage or creek of origin of the individuals in the replicates.
- Days_Post_Fertilization: the age in days since fertilization of the individuals in the replicates. The age of adults is estimated.
- Days_Post_Hatch: the age in days since hatching of the individuals in the replicates. The age of adults is estimated.
File: Concentration_Persistence.csv
Description: rows include data pertaining to the LC-MS/MS measured 6PPDQ concentrations in water samples in each 6PPDQ exposure replicate from the acute exposures.
Variables
- Group: the life stage or creek of origin of the coho salmon in the replicate sampled
- Nominal_6PPDQ_ng_L: expected 6PPDQ concentration in nanograms per liter.
- Exposure_Hour: the time in hours, since the beginning of the exposure, that the sample was taken.
- Measured_6PPDQ_ng_L: LC-MS/MS measured 6PPDQ concentration in nanograms per liter.
- C_C0: LC-MS/MS measured 6PPDQ concentration from the sample divided by the LC-MS/MS measured 6PPDQ concentration at the beginning of the exposure.
File: Dechorionation_Survival.csv
Description: each row represents an individual coho salmon embryo with information on its treatment and survival in the exposures of dechorionated or intact embryos to 6PPDQ and relevant controls.
Variables
- Treatment: the treatment group the embryo belongs to."6PPDQ_Dechorionated": embryos that were removed from their chorions and exposed to 6PPDQ, "6PPDQ_Intact": embryos that were not removed from their chorions and exposed to 6PPDQ, "Control_Dechorionated": embryos that were removed from their chorions and kept in clean water, "Control_Intact": embryos that were not removed from their chorions and kept in clean water.
- Replicate: replicate number (1, 2, or 3) that the embryo belonged to.
- Days_Post_Exposure: the day of the exposure that the embryo either died or was removed from the exposure as a survivor (e.g., subsampling or exposure termination).
- Days_Post_Fertilization: the age of the embryo on the day when it either died or was removed as a survivor (e.g., subsampling or exposure termination).
- Outcome: a binary describing embryos that died (1) or were removed alive (0).
File: Episodic_Exposure_6PPDQ.csv
Description: each row describes LC-MS/MS measured 6PPDQ concentrations from each exposure episode during the episodic exposures.
Variables
- Episode_Number: the sequential number of the 6PPDQ exposure.
- Days_Post_Fertilization: the age of the embryos (day of the exposure) at which the 6PPDQ sample was taken.
- Measured_6PPDQ_ng_L: the LC-MS/MS measured 6PPDQ concentration in the sample.
File: Episodic_Exposure_Light_Test.csv
Description: each row represents a minute at which a count of alevin was taken during the light/dark experiments with alevin that had been episodically exposed to 6PPDQ and alevin from the control replicates in that experiment.
Variables
- Treatment: whether the aquaria contained alevin from 6PPDQ exposures or control replicates.
- Replicate: the replicate number in the episodic exposure (1,2,3,4,5, or 6) from which the alevin came from.
- Minutes_Post_Switch: the time in minutes since the alevin finished their 10-minute acclimation to the half light, half dark aquarium.
- N_in_Light: the number (out of 20 total alevin) counted in the light half of the aquarium.
- Days_Post_Fertilization: the age of the alevin, in days since fertilization, at which the count was made.
File: Episodic_Exposure_Morphometric.csv
Description: each row represents an embryo that was removed from an episodic exposure or control replicate, and includes information on its measurements
Variables
- Treatment: the treatment group (6PPDQ or control) from which the embryo was subsampled.
- Replicate: the replicate (1,2,3,4,5, or 6) from which the embryo was subsampled.
- Eye_Area_sq_mm: the eye area in square millimeters measured from microscopic images of the embryo.
- Yolk_Area_sq_mm: the yolk area in square millimeters measured from microscopic images of the embryo.
- Length_mm: the length in millimeters measured from microscopic images of the embryo.
- Developmental_Stage: the developmental stage of the embryo determined at the time of imaging.
- Days_Post_Fertilization: the age of the embryo at the time of imaging, in days since fertilization and the beginning of the episodic exposure experiment.
File: Episodic_Exposure_Survival.csv
Description: each row represents an individual coho salmon embryo with information on its treatment and survival in the episodic exposures and associated controls.
Variables
- Treatment: the treatment group the embryo belongs to."6PPDQ": embryos that were exposed to 6PPDQ on 13 occasions over the course of their development; "Control": embryos that were and kept in clean water for their development.
- Replicate: replicate number (1, 2, 3, 4, 5, or 6) that the embryo belonged to.
- Days_Post_Fertilization: the age of the embryo (synonymous to the day of the exposure) on the day when it either died or was removed as a survivor (e.g., subsampling or exposure termination).
- Outcome: a binary describing embryos that died (1) or were removed alive (0).
Code/software
The data can be brought into RStudio and viewed using the read.csv() function in the R programming language.
Six replicate aquaria containing ~100 coho salmon embryos each were episodically exposed to 6PPDQ on 13, 24-hour intervals over the first 55 days of development, alongside six replicate control aquaria. Mortality rates were recorded daily for all replicates, and on two occasions five individuals from each replicate were subsampled and their yolk sizes, eye sizes, and lengths were measured. After hatching, 20 individuals from each replicate were placed in light/dark decision aquaria and the number of fish observed in the lighted half of each aquarium was recorded each minute in two, 10-minute tests.
In another experiment, the survival of three replicates containing 10, 27-day-post-fertilization coho salmon embryos of each of four treatments was monitored for 17 days. The dechorionated exposure treatment exposed embryos that had been removed from their chorion to 6PPDQ for 24 hours followed by 16 days of clean water. The intact exposure treatment exposed embryos with intact chorions to the same exposure regime as the dechorionated exposure treatment. The dechorionated control was embryos removed from their chorions in clean water, and the intact control was embryos with intact chorions clean water.
In acute exposures, coho salmon were exposed in groups of 4 to 10 individuals per aquarium to a series of 6PPDQ concentrations and their survival was assessed after 24 hours. Acute exposures were conducted with coho salmon alevin 11 days after hatch, fry 31 days after hatch, parr one year after hatch, and adults three years after hatch. All the above were from Voights Creek except for the adults, which came from nearby Clark Creek. Additionally, coho alevin from a different creek of origin, Bingham Creek, were exposed acutely for comparison with the Voights Creek alevin.