Bomb radiocarbon - Yelloweye Rockfish

Yelloweye rockfish and bomb radiocarbon

Publication year 2004

Radiocarbon in otoliths of yelloweye rockfish (Sebastes ruberrimus): a reference time series for the coastal waters of southeast Alaska.

Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal that has provided a useful tracer and chronological marker in oceanic systems and organisms. The bomb-generated 14C signal retained in fish otoliths can be used as a time specific recorder of the 14C present in ambient sea-water, making it a useful tool in age validation of fishes. The goal of this study was to determine 14C in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a reference time series for the coastal waters of southeast Alaska. Radiocarbon values from the first year’s growth of 43 yelloweye rockfish otoliths plotted against estimated birth year produced a 14C time series (1940-1990) for these waters. The initial rise of 14C occurred in 1958 and 14C levels rose to peak values (60-70‰) between 1966 and 1971, with a subsequent declining trend through the end of the record in 1990 (-3.2‰). In addition, the 14C data confirmed the longevity of the yelloweye rockfish to a minimum of 44 years and strongly support higher age estimates. This 14C time series will be useful for the interpretation of 14C accreted in biological samples from these waters. A New Wave Research micromilling machine (Elemental Scientific Lasers, Bozeman, MT, USA; http://www.nwrlasers.com/milling/micromill/) was used to extract the series of otolith cores used in this study.

Pictured above is the mushroom-shaped cloud (brief Wilson Chamber effect) and water column from the underwater Baker nuclear explosion of July 25, 1946. Photo was taken from a tower on Bikini Island, 3.5mi (5.6km) away. These early tests were on the order of kilotons; hence, the pictured explosion was small relative to the megaton events of the 1950s and 1960s.

Cross section of a sagittal otolith from a yelloweye rockfish with successive zooms to show the fine growth zone structure. These zones were counted out to about 120 years and this age estimate is valid based on lead-radium dating.

Publication:

Kerr et al 2004 Yelloweye bomb.pdf