Grantee Research Project Results
2005 Progress Report: Domoic Acid Kinetics and Trophic Transfer in Shellfish: An Integrated Laboratory and Estuarine Mesocosm Study
EPA Grant Number: R831703Title: Domoic Acid Kinetics and Trophic Transfer in Shellfish: An Integrated Laboratory and Estuarine Mesocosm Study
Investigators: Schultz, Irvin R. , Skillman, Ann D. , Woodruff, Dana
Institution: Pacific Northwest National Laboratory
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2005 through December 31, 2007 (Extended to December 31, 2008)
Project Period Covered by this Report: January 1, 2005 through December 31,2005
Project Amount: $449,735
RFA: Ecology and Oceanography of Harmful Algal Blooms (2004) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water
Objective:
The objective of the research project is to determine whether physiologically based pharmacokinetic models mathematically analogous to the type developed in vertebrates can be adapted for marine invertebrates based on the known physiology of decapod crustaceans and bivalve mollusks. These models will be used to predict the uptake and disposition of the marine algal toxin domoic acid in Dungeness crabs, Pacific razor clams, and blue mussels. Validation of individual kinetic model predictions and trophic transfer of domoic acid will be achieved through a combination of focused laboratory experiments and the use of large-scale estuarine mesocosms containing razor clams and Dungeness crabs. Laboratory studies will determine the toxicokinetics of domoic acid in shellfish after intravascular injection and repetitive hemolymph removal. This technique will be used in conjunction with controlled laboratory feeding studies to develop a detailed data set on the uptake, tissue distribution, and elimination of domoic acid in shellfish. In mesocosm studies, razor clams verified to contain domoic acid will be collected from contaminated Washington State coastal sites. The clams will be added to the mesocosm along with adult Dungeness crabs (previously unexposed to domoic acid), which will feed on the clams. Individual clams and crabs will be repetitively monitored for hemolymph concentrations during the study.
Progress Summary:
During Year 1 of the project, we completed experiments with crabs that measured domoic acid elimination after intravascular injection of a 1 mg/kg dose. A graphical summary of these results is presented in Figure 1. The results from these experiments indicated that domoic acid concentrations in the hemolymph compartment slowly changed during the initial 48 hours after dosing. After this time period, hemolymph levels declined in a log-linear manner with an elimination half-life of 139 hours. These results suggest zero-order elimination was occurring during the initial 48-hour time period when hemolymph concentrations of domoic acid were above 4000 ng/mL. To investigate this further, a follow-on study was initiated using a dose of 0.1 mg/kg domoic acid. The results from this experiment are not available at present and will be included in the next project report.
A second large experiment using Dungeness crabs was completed that orally dosed crabs with domoic acid (1 mg/kg) mixed with razor clam homogenate. At selected times up to 540 hours, groups of three to four crabs were terminated and tissues (hepatopancreas, kidney, muscle, gonads, gills, skin, stomach, upper and lower intestines) removed and analyzed for domoic acid. Figure 2 summarizes the results for domoic acid concentration in the hepatopancreas. Domoic acid levels steadily increased until peak levels, which occurred at 16 hours after dosing. Afterwards, domoic acid levels decreased rapidly until 148 hours and then remained relatively constant until 540 hours. Analysis of stomach contents after dosing indicated that all of the oral dose was removed from the stomach within 1-2 hours after dosing. Very little of the dose (<1-2%) was measured in the upper and lower intestines. These results indicate rapid and near-complete absorption of domoic acid from the stomach of Dungeness crabs.
Other ongoing experiments include intravascular dosing of mussels and razor clams with domoic acid and pilot feeding experiments with crabs to determine the amount of razor clams crabs will eat during a 2-week time period. The latter experiments are being used to accurately determine the number of crabs and clams that can be placed in the mesocosm study.
Figure 1. Domoic Acid Elimination From Crab Hemolymph After Direct Intravascular Injection of a 1 mg/kg Dose. Mean ± SD, n=6.
Figure 2. Domoic Acid Concentration in Crab Hepatopancreas After Oral Dosing With a 1 mg/kg Dose Dissolved in Razor Clam Homogenate. Mean ± SD, n=3-5.
Future Activities:
We will complete controlled laboratory dosing studies involving bivalves and crabs. We also will evaluate and refine existing toxicokinetic models for domoic acid in shellfish against data collected in this study. Finally, we will complete the mesocosm study of domoic acid accumulation in crabs feeding on razor clams.
Journal Articles:
No journal articles submitted with this report: View all 6 publications for this projectSupplemental Keywords:
oral gavage, toxicokinetics, computer modeling,, RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Water, ECOSYSTEMS, algal blooms, Ecological Risk Assessment, Aquatic Ecosystems, Ecology and Ecosystems, Environmental Monitoring, mesocosm experiments, estuaries, algal toxins, pharmacokinetic models, trophic transfer of phycotoxins, domoic acid producing diatoms, benthic algae, trophic interactionsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.