Showing items related by title, author, creator and subject.

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  Measurements of I-129 in the Pacific Ocean at Scripps Pier and Pacific Northwest sites: A search for effects from the 2011 Fukushima Daiichi Nuclear Power Plant accident and Hanford

  Chang, Ching-Chih; Burr, George S; Jull, A J Timothy; Russell, Joellen; Priyadarshi, Antra; Lin, Mang; Thiemens, Mark; Biddulph, Dana; Univ Arizona, AMS Lab; Univ Arizona, Dept Geosci (ELSEVIER, 2019-11-01)

  Radionuclides from the Fukushima Daiichi Nuclear Power Plant were released directly into the ocean as a result of the Great East Japan Earthquake on March 11, 2011. This material became entrained in surface ocean currents and subsequently transported for great distances. In June 2011, a few months after the disaster, we began a surface ocean 129I monitoring program, with samples from Scripps Pier, La Jolla, California, USA, with the expectation that surface currents originating off the east coast of Japan would eventually carry radionuclides to the La Jolla site. After 7 years of ocean transport, a distinct signal has not yet arrived at Scripps Pier. We have however, recorded an interesting systematic seasonal 129I time series record that stems from surface circulation variations along the California coast. To provide a more comprehensive picture of the 129I budget in coastal surface waters off the west coast of the U.S., we also include 129I data from the Columbia River, and offshore sites along the coast of Washington State. Anthropogenic nuclides are carried by the Columbia River into the Pacific Ocean from the vicinity of the decommissioned Hanford nuclear facility. We find highly elevated 129I/127I values in the Columbia River, downstream from the Hanford site, but this anthropogenic 129I becomes significantly diluted once it reaches the Pacific Ocean. Nonetheless, its imprint persists in surface seawater off the west coast of the U.S. that has significantly higher 129I/127I levels than other surface sites in the Pacific Ocean.
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  Reconstructing Northeastern Pacific Climate Variability from the Annual Growth Increments of Pacific Geoduck

  Black, Bryan A.; Edge, David; Meko, David M.; Thompson, Diane M.; Trouet, Valerie M. (The University of Arizona., 2022)

  The long-term character and range of Northeast (NE) Pacific climate variability is largely unknown due to the short period of instrumental record and poor agreement among existing reconstructions. To address this issue, a multi-centennial record of NE Pacific climate is developed from a new archive, the Pacific geoduck, a long-lived marine bivalve known to form annual growth increments within its shell. The widths of these increments strongly covary with ambient water temperature, and calcium carbonate within these shells contains radiocarbon, precipitated from ambient seawater, and serves as an indicator of ocean circulation. This study describes the development of a multicentennial geoduck chronology, with some chronology segments extending 3000 years before present. The first portion of the study outlines the development of this chronology and the accompanying sea surface temperature (SST) reconstruction from growth-increment widths. The chronology is the first to include dead-collected material from the ocean floor and represents the longest chronology and associated annually resolved SST reconstruction yet developed from any marine organism in the region. In the second portion of the study, radiocarbon is sampled from the geoduck chronology at decadal resolution to quantify water mass variability and assess relationships with SST. This new decadal radiocarbon record is the only record of its kind in the NE Pacific and describes a relatively stable state that can be interrupted by regimes of cold, radiocarbon-old water. In the final portion of this study, the uncertainty of paleoclimate reconstructions, including the geoduck SST reconstruction, are analyzed to determine the most skillful and robust method of defining uncertainties from crossdated paleoclimate proxies. The results lend support to the Maximum Entropy Bootstrap approach recently introduced to dendroclimatology but not yet widely adopted. Thus, this body of work demonstrates that Pacific geoduck can be utilized as both an SST and a water mass proxy over multiple centuries and that synthetic chronology experiments can serve to test novel methods across the growing diversity of crossdated paleoclimate proxies.
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  Drivers for genetic structure at different geographic scales for Pacific red snapper (Lutjanus peru) and yellow snapper (Lutjanus argentiventris) in the tropical eastern Pacific

  Reguera‐Rouzaud, Nicole; Díaz‐Viloria, Noé; Pérez‐Enríquez, Ricardo; Espino‐Barr, Elaine; Rivera‐Lucero, Mailin Isabel; Munguía‐Vega, Adrián; Conservation Genetics Laboratory & Desert Laboratory on Tumamoc Hill, University of Arizona (Blackwell Publishing Ltd, 2020-12-22)

  The tropical eastern Pacific (TEP) is a highly dynamic region and a model system to study how habitat discontinuities affect the distribution of shorefishes, particularly for species that display ontogenetic habitat shifts, including snappers (Lutjanidae). To evaluate the genetic structure of the Pacific red snapper (Lutjanus peru) and the yellow snapper (Lutjanus argentiventris) throughout their distribution range along the TEP, 13 and 11 microsatellite loci were analysed, respectively. The genetic diversity of L. peru (N = 446) and L. argentiventris (N = 170) was evaluated in 10 and 5 localities, respectively, showing slightly higher but non-significant values in the Gulf of California for both species. The genetic structure analysis identified the presence of significant genetic structure in both species, but the locations of the identified barriers for the gene flow differed between species. The principal driver for the genetic structure at large scales >2500 km was isolation by distance. At smaller scales (<250 km), the habitat discontinuity for juveniles and adults and the environmental differences throughout the distribution range represented potential barriers to gene flow between populations for both species. © 2020 Fisheries Society of the British Isles