Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

Amino acid compound-specific isotope analysis (AA-CSIA) of tissue samples from four distinct trophic groups across the food web in the pelagic eastern tropical Pacific Ocean: macrozooplankton (euphausiid crustaceans), micronekton (myctophid fishes), cephalopods (squids), and micronektonivores (tunas). Samples were collected onboard two NOAA research ships and numerous commercial tuna purse-seine vessels.

Related publication:
Hetherington E.D., Olson R.J., Drazen J.C., Lennert-Cody C.E., Ballance L.T., Kaufmann R.S., and Popp B.N. (2016). Spatial food-web structure in the eastern tropical Pacific Ocean based on compound-specific nitrogen isotope analysis of amino acids. Limnology and Oceanography. doi:10.1002/lno.10443

Sampling Methodology: Zooplankton, small mesopelagic fishes, and squids were collected from July 28 to December 8, 2006 during the National Oceanic and Atmospheric Administration’s (NOAA's) Stenella Abundance Research (STAR) surveys (Gerrodette et al. 2008). We defined our study area to include a subset of sample locations from the STAR surveys based on the presence of both east-west and north-south productivity gradients across the region, with greater surface chlorophyll a concentrations at the eastern end of the study area and along the equator, according to published oceanographic data. Zooplankton samples were collected with a cylindrical-conical bongo net (333 um mesh), fished to 200 m approximately two hours after sunset, and the samples were frozen within one hour of collection. Specimens of euphausiid crustaceans, Euphausia distinguenda (Ed) and E. tenera (Et) were sorted from the thawed zooplankton samples in the laboratory. Specimens of mesopelagic myctophid fishes Myctophum nitidulum (Mn) and Symbolophorus reversus (Sr) were collected by dipnet at night. Specimens of the squids Dosidicus gigas (Dg) and Sthenoteuthis oualaniensis (So) also were collected at night, using handlines and jigs. (See Olson et al. 2010, Philbrick et al. 2001 for detailed methods).

Three species of tuna, yellowfin (Ta.; Thunnus albacares), skipjack (Kp.; Katsuwonus pelamis), and bigeye (To.; Thunnus obesus) tunas, were sampled year-round during 2003-2005 by observers of the Inter-American Tropical Tuna Commission onboard purse-seine fishing vessels. Samples of dorsal white muscle were taken from each fish adjacent to the second dorsal fin. Fish of uniform size were used for analysis: skipjack tuna 450-550 mm, yellowfin tuna 500-700 mm, and bigeye tuna 450-550 mm. All samples were stored frozen until further processing in the laboratory.

Analytical Methodology:  Methods are described in Hetherington et al. (2016). Briefly: Amino acid (AA) compound-specific isotope analysis (AA-CSIA) was conducted on a subset of 48 of the samples used for isotopic analysis of bulk muscle tissue or whole animals. The basis for sample selection was to represent the range of variability in bulk δ15N values and the range of sample locations along the transect. The d15N values of individual AAs were measured using an isotope ratio mass spectrometer (IRMS) (Delta PlusXP, Delta V Plus or MAT 253) interfaced with a gas chromatograph (Trace GC) through a GC-C III combustion furnace (980 degrees C), reduction furnace (650 degrees C), and liquid-N cold trap. All samples were analyzed in triplicate and the measured AA-d15N values were normalized to known d15N values of two coinjected internal reference compounds (norleucine and aminoadipic acid with d15N reference values of 19.06 ‰ and -5.8 ‰, respectively).

Data processing: Stable isotope analysis of carbon and nitrogen isotopes measures the ratio of the heavier, rare isotope to the lighter, more common isotope (13C:12C or δ13C;15N:14N or δ15N) expressed as parts per mil (‰) relative to a standard (air for N, V-PDB for C).

(From NSF Award Abstract)

Evidence increasingly demonstrates that selective removal of marine life can induce restructuring of marine food webs. Trophic structure is the central component of mass balance models, widely used tools to evaluate fisheries in an ecosystem context. Food web structure is commonly determined by stomach contents or by bulk tissue stable isotope analyses, both of which are limited in terms of resolution and versatility. The investigators will refine a tool, Amino Acid Compound-Specific Isotopic Analyses (AA-CSIA), which can be broadly applicable for quantifying the time-integrated trophic position (TP) of consumers. Differences in source and trophic nitrogen isotopic composition for specific amino acids will provide an unambiguous and integrated measure of fractional trophic TP across multiple phyla, regardless of an animal's physiological condition or of the biogeochemical cycling at the base of the food web. AA-CSIA will allow testing of the efficacy of trophic position estimates derived from ecosystem-based models and promote the evolution of these models into decision-support tools.

This project has three goals: 1. To validate the application of AA-CSIA across multiple marine phyla under differing physiological conditions. 2. To compare the application of AA-CSIA across systems with contrasting biogeochemical cycling regimes. 3. To develop the use of AA-CSIA TP estimates for validating trophic models of exploited ecosystems. The investigators will test and refine the approach using a combination of laboratory feeding experiments and field studies across regions with differing biogeochemical cycling regimes. They will determine the applicability of the AA-CSIA approach in a variety of marine organisms assessed in controlled studies. Subsequently, ecosystem components will be sampled from the eastern tropical Pacific, coastal California and the subtropical Pacific gyre. They will also test the effects of sample preservation on the isotopic composition of individual AA to determine whether the approach can be used on archived samples. This tool will allow testing of the efficacy of ecosystem-based models currently used to gain insight into the ecological effects of fisheries removals and improve the reliability of future models required to manage marine resources. In addition to the goal of developing AA-CSIA for use as a TP indicator, the information obtained through this project will provide important species-specific biological data on the feeding behavior of marine organisms that could have implications for their resilience to anthropogenic pressures and climate change.

CAMEO Science Plan (2012).

The Comparative Analysis of Marine Ecosystem Organization (CAMEO) program was implemented as a partnership between the NOAA National Marine Fisheries Service and National Science Foundation Division of Ocean Sciences. The purpose of CAMEO was to strengthen the scientific basis for an ecosystem approach to the stewardship of our ocean and coastal living marine resources. The program supported fundamental research to understand complex dynamics controlling ecosystem structure, productivity, behavior, resilience, and population connectivity, as well as effects of climate variability and anthropogenic pressures on living marine resources and critical habitats. CAMEO encouraged the development of multiple approaches, such as ecosystem models and comparative analyses of managed and unmanaged areas (e.g., marine protected areas) that can ultimately form a basis for forecasting and decision support. Central to the program was the emphasis on collaborations between academic and private researchers and federal agency scientists with mission responsibilities to inform ecosystem management activities. (adapted from CAMEO website)

This funding opportunity implemented CAMEO research by supporting the development of research tools and strategic approaches through the following types of proposals:

1. Development of strategies and methodologies for comparative analyses that can be applied consistently across spatial and temporal scales and ecosystems, and that facilitate the design of decision support tools for marine populations, ecosystems and habitats.

2. Development of models that address key scientific questions by comparing ecosystems and ecosystem processes. Models that are geographically and temporally portable, and that incorporate assessment of modeling skill, are particularly encouraged.

3. Retrospective studies that analyze, re-analyze or synthesize existing information (historic, time-series, ongoing program, etc.) using a comparative approach.

4. Studies that integrate the human dimension within ecosystem dynamics. The CAMEO program seeks to promote interdisciplinary research using comparative approaches to link marine ecosystem research with the social and behavioral sciences in new and vital ways.

To guide program priorities, a Science Steering Committee was formed through Dr. Linda Deegan and the initial Scientific Planning Office at the Marine Biological Laboratory in Woods Hole, MA. This Committee was designed to provide scientific advice and broad direction to NOAA and NSF regarding the CAMEO program.