The interaction between toxic diatoms and their zooplankton grazers, as well as the food web transport of these toxins through food chain, are poorly known. Increasingly, attention is being focused on the trophic fate of the toxin produced by various species of Pseudo-nitzschia, which often bloom in Monterey Bay, California. In the food web of Monterey Bay, euphausiid crustaceans (krill) are important grazers of diatoms and are major prey for various organisms. To determine how heavily krill are feeding on local Pseudo-nitzschia species, we initially compared krill gut contents to diatom populations in samples collected from Monterey Bay, CA in July 1998. Examination of samples by scanning electron microscopy indicated that krill heavily consume Pseudo-nitzschia. Secondly, we conducted experiments to determine krill grazing rates on toxic diatoms in laboratory conditions. Krill were collected from Monterey Bay in May 1999 and fed clones of locally isolated Pseudo-nitzschia multiseries. Interestingly, each krill specimen consumed about cells 5x10e4 in 6 hours. We still need to better understand the extent of krill exposure to toxic species and whether krill can transfer the toxin to higher trophic levels. Based on grazing experiments and field data, we estimate that each krill is capable of transferring 75 ng domoic acid (DA)/ krill/ hour to higher trophic levels. These results provide a perspective that will ultimately help us to understand toxin transfer from toxic blooms, which appear to be a rising threat to the health of coastal environments.