Collaborative Research SGER: Domoic acid toxins in the oceanic north Pacific in iron enrichment studies

Louisiana State University, Baton Rouge LA

Investigators

Abstract

The project addresses an emerging issue related to global warming: the necessity to reduce levels of greenhouse gases in the atmosphere. A solution proposed several decades ago is to fertilize the extensive, iron-limited, high nutrient, low chlorophyll (HNLC) regions of the sea, drawing down carbon dioxide that would otherwise exchange with the atmosphere. This solution is highly attractive due to its relatively low cost and evidence that iron fertilization does indeed promote phytoplankton blooms in such regions. Some researchers, however, have expressed alarm about the iron remedy that could result from unanticipated negative effects on the composition and functioning of ecosystems. In this project, the investigators hypothesize that iron fertilization of HNLC regions results in biomass increases of Pseudo-nitzschia that produce domoic acid (DA), a neurotoxin. The consequences of increased DA in HNLC areas could be like those observed in coastal regions, namely contamination and sometimes deaths of predators in those ecosystems. A Small Grant for Exploratory Research (SGER) is provided based on the investigators recent discovery of DA in Pseudo-nitzschia turdigula, which often blooms in iron enrichment experiments in waters of HNLC regions. The investigators developed a new toxin assay to measure DA in samples of P. turdigula collected from HNLC waters of the subarctic NW Pacific. This SGER enables the investigators to participate in an August 2007 NSF-funded research cruise measuring iron in waters of the Gulf of Alaska (GoA) along transects in HNLC (iron poor) regions and naturally enriched eddies containing terrestrially-derived iron. The investigators will measure the associated abundance and DA levels of P. turdigula along the GoA transect and in the grow-out experiments, and to determine the Pseudo-nitzschia species associated with DA production. All samples for Pseudo-nitzschia will have associated nutrient and oceanographic data to provide context for the cellular DA quotas in an oceanographic and physiological context. Results of the research are important in determining ecosystem effects iron enrichment.