In this study, researchers at the University of Hawaii at Manoa will examine the biological magnification of two neurotoxins in the flora and fauna of Hawaiian coral reefs. The toxins, beta-N-methylamino-L-alanine (BMAA), a low molecular weight (ca. 120amu) amino acid, and ciguatoxin (CTX), a large molecular weight (ca. 1,200 amu) polyether, were selected for study because of their different chemical natures and hence potentially very different biological magnification patterns. The work will take advantage of recent advances in the study and interpretation of nitrogen fractionation within specific amino acids to identify an organism's position in the food web relative to the first trophic level. Source amino acids (glycine, lysine, phenylalanine, serine, threonine and tyrosine) record the d15N value of the source of nitrogen at the base of the food web, and trophic amino acids (alanine, aspartic acid, glutamic acid, isoleucine, leucine, proline and valine) reflect the trophic level of the consumer. The relationship between the difference between the d15N values of trophic and source amino acids and toxin concentrations in the tissues of fish and shellfish will be analyzed within the framework of (1) a simple linear food chain and (2) an unstructured food web to determine which theoretical construct is most consistent with experimental results. Additional studies will focus on the degree of environmental control of CTX and BMAA production and the extent to which differences in the concentrations of these toxins in fish and shellfish reflect differences in the feeding/physiology of consumer organisms or variability between species at the producer level.
The proposed work reflects the integration of experimental observations and theoretical understanding to gain insight into the processes that regulate the movement of toxins through marine food webs. Experimentally the use of compound-specific 15N analyses of source and trophic amino acids to determine an organism?s position in a food web is an important recent advancement, and application of unstructured food web theory or variations thereof will likely prove necessary to explain the patterns of biological magnification in the complex food webs that characterize coral reef biological communities. Since the complexity of these food webs is by no means anomalous, insights gained from this study may have broad applicability to marine systems where food webs depart from strict linearity.
The broader impacts of the proposed work include (1) funding for the participation of University of Hawaii (UH) Global Environmental Science majors working on their senior research projects, (2) the inclusion of NSF REU students (C-MORE Research Experiences in Microbial Oceanography - proposal pending), (3) a $200,000 commitment by the UH vice chancellor for research to purchase a quadrupole mass spectrometer with the appropriate APCI/ESI probe hardware to facilitate the determination of the structures of ciguatoxins and related toxins in extracts from coral reef flora and fauna, and (4) the publication of educational materials that target both undergraduate and graduate students, and the inclusion of these material into courses offered by the Department of Oceanography at the University of Hawaii.
