Grantee Research Project Results
Effects of Protozoan Epibionts on Harpacticoid Copepods in a Louisiana Salt MarshEPA Grant Number: U915391
Title: Effects of Protozoan Epibionts on Harpacticoid Copepods in a Louisiana Salt Marsh
Investigators: Puckett, Gwyn L.
Institution: Louisiana State University - Baton Rouge
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1998 through January 1, 2000
Project Amount: $53,684
RFA: STAR Graduate Fellowships (1998)
Research Category: Fellowship - Zoology , Biology/Life Sciences , Academic Fellowships
The objective of this research project is to determine the impact of ciliate epibionts on harpacticoid copepod grazing, energy reserves, and sensitivity to environmental contaminants.Approach:
This project focuses on the effects of ciliate epibionts found on Coullana sp., an estuarine harpacticoid copepod. Coullana sp. are abundant in the salt marshes along the Louisiana coast, have high incidences of protozoan epibionts, reserve energy as neutral lipids, and have been shown to be susceptible to polycyclic aromatic hydrocarbon (PAH) contaminants. The effects of ciliate epibionts on copepod grazing will be investigated using 14C-radiotracer methods. Uptake of 14C-labeled natural and prelabeled microalgae will determine the grazing rates, and will differentiate between planktonic and benthic feeding. A comparison between the grazing rates of copepods with or without epibionts will allow a determination ofthe effects of epicuticular microorganisms on harpacticoid grazing. The effect of epibionts on energy reserves will be examined in a second experiment. Harpacticoids use stored neutral lipids as energy reserves; reserves that are available for reproduction, development, and routine metabolism during periods of food limitation. Previous studies have shown that decreased lipid energy reserves in harpacticoids are associated with increased epibiont burden. Nile red, a hydrophobic fluorophore that specifically binds to neutral lipids, will be used to examine copepod lipid levels under stress conditions. Copepods are susceptible to anthropogenic contaminants, including PAHs, which are abundant in refined petroleum products such as diesel fuel. Decreased grazing rates on microalgae and increased mortality have been observed among harpacticoid copepods exposed to diesel-contaminated sediment. Copepods are relatively sensitive to contaminants, but responses of individual populations can be highly variable. A third experiment will analyze epibiont effects on Coullana susceptibility to hydrocarbon contaminants, and determine if variation in epibiont burden is partially responsible for variation in copepod sensitivity. This bioassay will measure epibiont influence on copepod survivorship when exposed to diesel-spiked sediments.
The results of this research project will increase our understanding of the role of epibionts in meiofaunal ecology.Supplemental Keywords:
fellowship, harpacticoid, copepod, ciliate, epibiont, grazing rates, neutral lipids.