Grantee Research Project Results
2006 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, 2006 through December 31, 2007
Project Amount: $449,735
RFA: Ecology and Oceanography of Harmful Algal Blooms (2004) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water
Objective:
We hypothesize that 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:
Work Progress / Preliminary Data: During this project period, 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 presented in figure 1. The results from these experiments indicated 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 hrs. These results suggest zero-order elimination was occurring during the initial 48hr 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 hrs, groups of 3-4 crabs were terminated and tissues (hepatopancreas, kidney, muscle, gonads, gills, skin, stomach, upper & 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 hrs after dosing. Afterwards, domoic acid levels decreased rapidly until 148 hrs and then remained relatively constant until 540 hrs. Analysis of stomach contents after dosing indicated all of the oral dose was removed from the stomach within 1-2 hrs 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 two week time period. The latter experiments are being used to accurately determined the number of crabs and clams that can be placed in the mesocosm study.
Parameters for DCA human metabolism, poorly estimated the DCA plasma profiles of these initial data sets. Preliminary modeling indicated this was largely due to underestimation of the DCA absorption rate, which appears to be occurring unexpectedly faster at the dose used in this project.
Future Activities:
Planned activity for Project Year 2: Complete controlled laboratory dosing studies involving bivalves and crabs. Evaluate and refine existing toxicokinetic models for domoic acid in shellfish against data collected in this study. Complete 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:
RFA, Scientific Discipline, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems, algal blooms, Environmental Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, estuaries, pharmacokinetic models, trophic transfer of phycotoxins, algal bloom detection, algal toxins, trophic interactions, benthic algae, domoic acid producing diatomsProgress 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.