Award: OCE-1301524

During the one year NCE period (8/2013 - 7/2014) the Hawaii Pacific University team completed and submitted a manuscript entitled "Nitrogen isotope fractionation and amino acid turnover rates in the Pacific white shrimp, Litopenaeus vannamei" to Marine Ecology Progress Series. The authors of this manuscript are CAMEO co-Investigators Brian Popp and Carolyn Holl and Holl's graduate student, Eileen Downs. Eileen Downs is the first author on this manuscript and, as such, led the team in writing and editing the manuscript. The manuscript is a portion of her MasterÆs thesis which was entitled "The use of compound-specific isotope analysis to elucidate dietary nitrogen sources and trophic position in the Hawaiian bobtail squid (Euprymna scolopes) and Pacific white shrimp (Litopenaeus vannamei)." She successfully defended this thesis in the spring of 2013. The reviews from MEPS were very favorable and minor revisions were completed in July 2014. We just got word on September 2, 2014 that this manuscript, a first for Downs, was fully accepted and is in press at MEPS. ABSTRACT: Fluctuations in an animalÆs trophic position (TP) can indicate changes within an ecosystem. Traditionally, bulk tissue or whole animal nitrogen (N) isotope analysis has been used to determine an animalÆs TP but there are limitations to the application of this approach. Amino acid compound-specific isotope analysis (AA-CSIA) can be used to determine TP based on the difference between the δ15N values of certain amino acids, commonly glutamic acid and phenylalanine. The rate at which 15N is incorporated into amino acids is largely unknown and this may affect the accuracy of relative TP estimates especially during periods of ecosystem change or ontogenetic changes in diet. To study amino acid turnover rates, the diet of the Pacific white shrimp, Litopenaeus vannamei, was changed in the laboratory from an unlabeled diet (7.2‰) to a 15N-enriched diet (24‰) and animals were sampled over the course of seven weeks. AA-CSIA revealed that turnover times of amino acids vary considerably with some amino acids having much more rapid turnover than others. The TP of L. vannamei (using δ15N values of glutamic acid and phenylalanine) over the course of the experiment remained constant and shrimp TP averaged 2.14 ± 0.15 (mean ± SD, n=7) relative to its diet, which was as expected. Our results indicate that the δ15N values of glutamic acid and phenylalanine can be used to accurately determine TP even while shrimp are undergoing a change to a diet with a different δ15N value. This CAMEO grant provided an important research opportunity for Eileen Downs who has now successfully gone on to the School of Veterinary Medicine at Michigan State University. Last Modified: 09/03/2014 Submitted by: Carolyn M Holl