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M. Soledad Fuentes – Post-Doctoral Associate: PhD, Environmental and Evolutionary Biology, University of Louisiana at Lafayette; Biólogo Marino, Universidad Católica del Norte, Chile; Licenciado en Ciencias Marinas, Universidad Católica del Norte, Chile

Project Title: Environmental Copper and Silicate Regulation of Domoic Acid Expression: Relevance to Offshore Mussel Aquaculture
Mentor: Gary Wikfors

Summary: One of the main concerns in shellfish farming is the occurrence of harmful algal blooms, which result in annual economic losses in the range of tens of millions of dollars. In the northeastern USA, harmful blooms of dinoflagellates from the genus Alexandrium that produce Paralytic Shellfish Toxins are studied and monitored. Other harmful microalgal species, however, are also present in the area. Populations of the diatom Pseudo-nitzschia spp., responsible for production of the neurotoxin domoic acid (DA), are endemic in northern New England coastal waters. Pseudo-nitzschia spp. can cause Amnesic Shellfish Poisoning (ASP) in consumers of contaminated shellfish, and recent evidence suggests that local blooms of these species are increasing along the northern New England coast where mussel aquaculture is a growing industry.  It is hypothesized that the physiological role of domoic-acid in Pseudo-nitzschia spp. is as a copper chelator, and that this amino acid is involved indirectly in the acquisition of iron by facilitating copper uptake. Hence, diatoms producing domoic acid would have a copper-based, high-affinity, iron-acquisition system, similar to that in yeast, in which cell-surface bound ferrireductases and multi-copper oxidases facilitate iron uptake. In diatoms, it has been suggested that copper also enters the cell via the silicic-acid transport site.  In open-ocean aquaculture settings, copper is used as an algaecide in gear paint, as a feed supplement, and to treat and prevent fungal and bacterial diseases.  Thus, aquaculture practices may increase copper inputs locally, thereby stimulating domoic-acid production in non-toxic Pseudo-nitzschia populations.  To confirm the physiological mechanisms underlying this risk, it is necessary to understand environmental triggers for up-regulation of domoic-acid production by endemic Pseudo-nitzschia populations.
The current study, funded by the NOAA National Aquaculture Program, is focused on understanding the risk of increased incidence of toxin expression in benign populations of Pseudo-nitzschia spp. in mussel-aquaculture areas. Specifically, the hypothesis that cellular copper, iron, and silicate status determines regulation of enzyme pathways leading to DA synthesis is being tested in laboratory experiments and field sampling employing molecular methods to assess expression of relevant genes.

Future Directions: In the future I would like to continue my research on phytoplankton eco-physiology, including harmful algal blooms, focusing on improving the understanding of phytoplankton physiological ecology and evolution, interactions with nutrients, and how this affects growth and toxin production.