Plasticity in dormancy behaviour of Calanoides acutus in Antarctic coastal waters

Citation

Biggs TEG, Brussaard CPD, Evans C, Venables HJ & Pond DW (2020) Plasticity in dormancy behaviour of Calanoides acutus in Antarctic coastal waters. Ices Journal of Marine Science, 77 (5), pp. 1738-1751. https://doi.org/10.1093/icesjms/fsaa042

Abstract
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.

Keywords
copepod; dormancy; life cycle; lipids; phytoplankton; wax ester unsaturation

Journal
Ices Journal of Marine Science: Volume 77, Issue 5