Abstract:

Nearly 7 million liters of chemical dispersant were applied as part of the response to the Deepwater Horizon oil spill. While previous work has shown that the dispersant, Corexit 9500, is not toxic to early life stage mahi-mahi in terms of acute (96 h) mortality at environmentally relevant concentrations, sublethal impacts of acute exposures have yet to be examined. To this end, a microplate respirometer was employed to examine mahi-mahi embryos and larvae exposed to two different concentrations of dispersant for 24 h to investigate potential impacts on metabolic rate. Potential increases in metabolic rate would likely induce a more rapid depletion of yolk, reflecting a diversion of energy from growth to detoxification. As the yolk is the sole source of nutrition prior to mouth opening and first feeding by the larvae, such potential effects of dispersant thus could have important downstream implications for survival that would be missed by employing standard 96 h bioassay approaches. This dataset provides the metabolic rate measurements from these experiments.

Suggested Citation:

Mager, E., Pasparakis, C.. 2018. Effect of Corexit on the Oxygen Consumption of Early Life Stage Mahi-Mahi. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-93a3-1a26

Purpose:

To test the effects of different percentages of dispersant (Corexit) exposure on the oxygen consumption of mahi mahi embryos and larvae.

Data Parameters and Units:

DOSS Analysis K1700505.csv and DOSS Analysis K1705411.csv: Client, Project, Service Request, Sample, Lab Code, Sample Type, Date Collected, Date Received, Date Extracted, Date Analyzed, Extraction Method, Method, Matrix, Basis, Units (ug/L, %, ug/kg), Component, Dilution Factor, Reporting Limit, Detection Limit, Result, Result Notes, Spike Concentration, Percent Recovery, Acceptance Limits, Average, RPD, Retention Time, Regulatory Limit. Sample Inventory.csv: Sampling date (DD-MM-YYYY), Sampling time (1145), Tank ID Dilution (%) or Stock Code, Number of organisms per sample, Unique ID (103-108), Sample ID, Storage location, Notes, Recorded by. Tank ID Dilution or Stock Code.csv: Tank ID Dilution or Stock Code (C1-3, T1-6, C1-3, T1-6), Start date (DD-MM-YYYY), Start time, End Date (DD-MM-YYYY), Nominal Treatment Concentration, Treatment Units (%), Replicate (1-3), Notes (Embryo Corexit or Larval Corexit), Recorded by. Test Performance Monitoring.csv: Tank ID (C1-3, T1-16, C1-13, T1-6), Date (DD-MM-YYYY), Time, Number at test start, Number observed treatment mortalities, Number from non-treatment mortality, Number observed alive, Notes (24 hour embryos, 24 hour larvae), Recorded by. WAF Preparation.csv: For WAF prep 1 and 2: prep start date, start time, end date, end time, prep method, oil type, water/diluent volume (L), mass of dispersant added (mg), calculated nominal concentration (mg/L), time of HEWAF transfer to sep. funnel, time when drain sep. funnel, CEWAF stir start time, CEWAF stir end time/settle start time, CEWAF settle end time, filtered before use (y/n), Recorded by. Water Quality Monitoring.csv: Tank ID Dilution or Stock Code, Date (MM/DD/YYYY), Time, Period , Water temp. (Celsius), pH, D.O. (mg/L), Salinity (ppt), Total ammonia (uM), Notes (24 hour embryo or 24 hour larvae), Recorded by. Oxygen consumption files: oxygen consumption data for mahi embryos and larvae exposed to different concentrations of dispersant (Corexit). Files are labeled by life stage tested (embryo and larvae) and date of experiment. Data is separated into Control (no dispersant), 1% or 5% dispersant concentrations. Oxygen consumption data is reported in picomole per individual (either embryo or larvae) per minute. Two different (but identically made) Loligo System microplates were used (labeled 368 or 538) to increase sample size in some experiments. Each plate had 24 separate wells which contained 125 ul of SW in each. The mean and standard error of mean are calculated for each treatment. Microplate number, wells, oxygen consumption (picomole per individual), average, standard deviation, count, standard error.

Methods:

Embryos were exposed to different concentrations of dispersant (Corexit) for approximately 24-hpf and larvae were exposed for approximately 48-hpf. Control and treatment mahi were maintained in a temperature and light-controlled laboratory setting for the duration of these experiments. After the exposure period was completed, control and dispersant exposed mahi were randomly placed in different wells on the same Loligo microplate. The Loligo microplate is a 24-channel optical fluorescence oxygen sensing system for high through-put data. For analysis, oxygen consumption as a function of time was plotted for individual wells. The first 10–20% (pO2 in % air saturation) linear decreases in oxygen were used to calculate oxygen consumption over time. Any portion of the slope that dipped below 70% air saturation was not used for analysis. Last, the data were corrected for background respiration, volume of seawater and number of individuals per well and expressed as picomoles individual−1 min−1.

Instruments:

The microplate respirometer used to measure oxygen consumption in the early life stages of mahi was purchased at Loligo Systems.

Individual Files: