Spring mortality of the cyclopoid copepod Oithona similis in polar waters

Hirst, A.G.; Ward, Peter. 2008 Spring mortality of the cyclopoid copepod Oithona similis in polar waters. Marine Ecology Progress Series, 372. 169-180.

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The cyclopoid copepod Oithona similis is highly abundant and ubiquitous in the marine epipelagic environment, yet rates of mortality in this species have rarely been quantified; indeed we are lacking such measurements for Copepoda in general in cold waters. In the present study we examined O. similis stage structure, egg production and mortality rates across the Scotia Sea, Southern Ocean, sampling from the ice edge to the Polar Front in the austral spring of 2006, The population stage structure near the retreating ice edge was indicative of a recruitment pulse moving through the younger stages; therefore, the assumptions of the vertical life table (VLT) approach were not met and mortality was not estimated for those stations. At all other stations the assumptions of VLT were largely met, and mortality rates were determined as across-station averages, The highest rates of mortality occurred across the egg to NIT stages at around 0.04 d(-1), falling to < 0.03 d(-1) in subsequent stages, and then increasing again to 0.11. d(-1) across copepod stage V to adult males. The ratio of adult males to females suggested that males have a mortality rate similar to 12 times greater than females (i.e. the adult male to female abundance ratio is 0.08). It is unlikely that these differences can be attributed simply to the males' shorter physiological longevity (longevity when free of predators); the primary cause is likely elevated predation mortality due to the risks associated with mate locating behaviour.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > Global Science in the Antarctic Context (2005-2009) > DISCOVERY 2010 - Integrating Southern Ocean Ecosystems into the Earth System
ISSN: 0171-8630
Additional Information. Not used in RCUK Gateway to Research.: Free access
Additional Keywords: Oithona similis; Mortality; Stage structure; Egg production; Vertical life table; Scotia Sea
NORA Subject Terms: Marine Sciences
Biology and Microbiology
Ecology and Environment
Date made live: 14 Jan 2011 17:39 +0 (UTC)

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