A review of ecogeochemistry approaches to estimating movements of marine animals

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 58 (2013): 697-714, doi:10.4319/lo.2013.58.2.0697.Ecogeochemistry—the application of geochemical techniques to fundamental questions in population and community ecology—has been used in animal migration studies in terrestrial environments for several decades; however, the approach has received far less attention in marine systems. This review includes comprehensive meta-analyses of organic zooplankton δ13C and δ15N values at the base of the food web, dissolved inorganic carbon δ13C values, and seawater δ18O values to create, for the first time, robust isoscapes for the Atlantic Ocean. These isoscapes present far greater geographic variability in multiple geochemical tracers than was previously thought, thus forming the foundation for reconstructions of habitat use and migration patterns of marine organisms. We review several additional tracers, including trace-element-to-calcium ratios and heavy element stable isotopes, to examine anadromous migrations. We highlight the value of the ecogeochemistry approach by examining case studies on three components of connectivity: dispersal and natal homing, functional connectivity, and migratory connectivity. We also discuss recent advances in compound-specific stable carbon and nitrogen isotope analyses for tracking animal movement. A better understanding of isotopic routing and fractionation factors, particularly of individual compound classes, is necessary to realize the full potential of ecogeochemistry.We were supported by funding from the National Science Foundation (Division of Ocean Sciences–0825148 to S.R.T.), Award USA 00002 and KSA 00011 from the King Abdullah University of Science and Technology (to S.R.T.), and a National Science Foundation Graduate Research Fellowship (to L.H.)

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

This paper is not subject to U.S. copyright. The definitive version was published in Environmental Biology of Fishes 97 (2014): 881-896, doi:10.1007/s10641-013-0189-4.Age and growth estimates for the dusky shark, Carcharhinus obscurus, were derived from vertebral centra collected in the northwestern Atlantic Ocean. Sample collection spanned the years prior to and following the implementation of management measures (1963–2010). Growth was compared pre- and post- population depletion and pre- and post- management to investigate the possibility of density-mediated shifts in age and growth parameters over time. There was no evidence of difference between periods for either sex. Additionally, bomb radiocarbon dating was used to determine the periodicity of band pair formation. Results support the traditional interpretation of annual band pairs up to approximately 11 years of age. After this time, vertebral counts considerably underestimate true age. Maximum validated ages were estimated to be between 38 and 42 years of age (an increase of 15 to 19 years over the band count estimates), confirming longevity to at least 42 years of age. Growth curves estimated using only validated data were compared to those generated using band pair counts. Logistic growth parameters derived from validated vertebral length-at-age data were L ∞  = 261.5 cm FL, L o  = 85.5 cm, t o  = 4.89 year and g = 0.15 year−1 for the sexes combined. Revised estimates of age at maturity were 17.4 years for males and 17.6 years for females

Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks

Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ14C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of 14C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Age, movements, and feeding ecology of northwest Atlantic white sharks estimated from ecogeochemical profiles in vertebrae

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 113-127).White sharks (Carcharodon carcharias) are highly migratory, ecologically important, vulnerable, and understudied marine predators. Ecogeochemistry, which takes advantage of natural variations in chemical signatures recorded in body tissues, can help determine lifetime movement, age, and ontogenetic diet history in difficult to study species. Shark vertebrae are constructed of distinct layers of tissue laid down sequentially over an individual's lifetime and may preserve a chemical record of environmental exposure. In this thesis, I investigate the ecology of the understudied northwest Atlantic (NWA) white shark population by applying several ecogeochemistry techniques to their vertebrae. I generate the first radiocarbon ([delta]¹⁴C) age estimates for adult white sharks, dramatically extending the maximum age and longevity compared to earlier age studies. [delta]¹⁴C results also verify a lack of reworking of vertebral material and hint at possible sexual dimorphism in growth rates. Using amino acid and bulk stable isotope analyses, I show that individual sharks have marked variation in feeding and movement, and that pinnipeds do not constitute a large portion of their diet. Finally, I explore the utility of elemental chemistry to retrospectively infer movement. This work provides an important informational baseline for future NWA white shark ecological studies and conservation and management efforts.by Li Ling Hamady.Ph. D

Photomicrographs of sectioned vertebrae.

<p>A) Upper section of vertebra taken from WS105. B) WS 100 vertebra; first dot is the birth band. Visible band pairs are marked by dots on the corpus calcareum. The lines indicate the vertebral radius (16.6 mm). Vertebral radius is measured at the angle of the vertebra where the intermedialia meets the corpus calcareum.</p

Bivariate plot of δ¹³C versus Δ¹⁴C for individual sharks.

<p>Bivariate plot of δ¹³C versus Δ¹⁴C for individual sharks.</p

Collection and sampling information for individual sharks.^a

<p>^a Discrepancies between band pair counts and bomb Δ¹⁴C age indicate instances where a shift was necessary to align sample Δ¹⁴C values to reference curves.</p><p>^b FL, fork length.</p><p>^c M: mature, I: immature, N/A: information not available.</p><p>^d Estimates based on band pair counts, and ages estimated from Δ¹⁴C values when shark trajectories required adjusting.</p

White shark Δ¹⁴C results compared to three Δ¹⁴C reference chronologies [11], [31], [32].

<p>Results from male (A, B) and female (C, D) white shark vertebrae. Dotted line is porbeagle data smoothed with a Loess curve. For panels B and D, the arrows indicates the vertebral Δ¹⁴C curves that had to be shifted to line up with the reference chronologies (white open symbols are initial data, black symbols are data shifted to align with the references).</p