Plasticity in dormancy behaviour of Calanoides acutus in Antarctic coastal waters

• Published in: ICES Journal of Marine Science
• Main Authors: Biggs, Tristan E.G., Brussaard, Corina P.D., Evans, Claire, Venables, Hugh J., Pond, David W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2020
• Subjects: Antarctic; Southern Ocean; Antarctic Peninsula; Antarc*; Copepods
• Online Access: http://nora.nerc.ac.uk/id/eprint/527438/; https://nora.nerc.ac.uk/id/eprint/527438/1/fsaa042.pdf; https://academic.oup.com/icesjms/advance-article/doi/10.1093/icesjms/fsaa042/5815632

Copepods that enter dormancy, such as Calanoides acutus, are key primary consumers in Southern Ocean food webs where they convert a portion of the seasonal phytoplankton biomass into a longer-term energetic and physiological resource as wax ester (WE) reserves. We studied the seasonal abundance and lipid profiles of pre-adult and adult C. acutus in relation to phytoplankton dynamics on the Western Antarctic Peninsula. Initiation of dormancy occurred when WE unsaturation was relatively high, and chlorophyll a (Chl a) concentrations, predominantly attributable to diatoms, were reducing. Declines in WE unsaturation during the winter may act as a dormancy timing mechanism with increased Chl a concentrations likely to promote sedimentation that results in a teleconnection between the surface and deep water inducing ascent. A late summer diatom bloom was linked to early dormancy termination of females and a second spawning event. The frequency and duration of high biomass phytoplankton blooms may have consequences for the lifespan of the iteroparous C. acutus females (either 1 or 2 years) if limited by a total of two main spawning events. Late summer recruits, generated by a second spawning event, likely benefitted from lower predation and high phytoplankton food availability. The flexibility of copepods to modulate their life-cycle strategy in response to bottom-up and top-down conditions enables individuals to optimize their probability of reproductive success in the very variable environment prevalent in the Southern Ocean.