Greg Lewbart


Hot Topic Article: Variability of marine climate on the North Icelandic Shelf in a 1357-year proxy archive based on growth increments in the bivalve Arctica islandica.

November 16, 2013

Tags: Paul G. Butler, Alan D. Wanamaker Jr., James D. Scoursea, Christopher A. Richardson. 2013. Palaeogeography, Palaeoclimatology, Palaeoecology Volume 373, 1 March 2013, Pages 141151.

This interesting paper by an international team of scientists utilizes accurate aging of the bivalve Arctic islandica to track and age changes in the North Icelandic benthic environment over the last 1300-plus years. As part of the research the scientists have worked with a number of incredibly long-lived animals, some over 300 years of age, and one pin-pointed to 507 years, making it the longest lived single animal ever documented. Quite sadly, the animal died during the aging process.


A multicentennial and absolutely-dated shell-based chronology for the marine environment of the North Icelandic Shelf has been constructed using annual growth increments in the shell of the long-lived bivalve clam Arctica islandica. The region from which the shells were collected is close to the North Atlantic Polar Front and is highly sensitive to the varying influences of Atlantic and Arctic water masses. A strong common environmental signal is apparent in the increment widths, and although the correlations between the growth increment indices and regional sea surface temperatures are significant at the 95% confidence level, they are low (r ~ 0.2), indicating that a more complex combination of environmental forcings is driving growth. Remarkable longevities of individual animals are apparent in the increment-width series used in the chronology, with several animals having lifetimes in excess of 300 years and one, at 507 years, being the longest-lived non-colonial animal so far reported whose age at death can be accurately determined. The sample depth is at least three shells after AD 1175, and the time series has been extended back to AD 649 with a sample depth of one or two by the addition of two further series, thus providing a 1357-year archive of dated shell material. The statistical and spectral characteristics of the chronology are investigated by using two different methods of removing the age-related trend in shell growth. Comparison with other proxy archives from the same region reveals several similarities in variability on multidecadal timescales, particularly during the period surrounding the transition from the Medieval Climate Anomaly to the Little Ice Age.

Selected Works

Science Writing
The Second Edition of Invertebrate Medicine was released in December, 2011. It has been substantially expanded from the first edition to reflect the tremendous growth of the pertinent literature and work that is being accomplished in the fields of invertebrate animal medicine, disease investigation, conservation, husbandry, and animal welfare. In 2012 it is being recognized with a Text and Academic Authors Association TEXTY award for excellence in the Life Sciences Category and first place in the Health Care Professionals (nonphysicians) category of the 2012 American Medical Writers Association Book Awards.
This book, edited by Karen L. Rosenthal, Neil A. Forbes, Frederic L. Frye, and Gregory A. Lewbart, utilizes approximately 400 clinical cases to describe and address many of the major medical and surgical conditions of exotic animal pets.
Invertebrate Medicine is the single most comprehensive resource available today on invertebrate animal medicine.
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Creative Non-Fiction
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....a darn good yarn.
--Ken Moore, Naples Daily News
...well-told and environmentally informative story about buried treasure and smuggling of exotic animals...
--Rod Cockshutt, The News & Observer