Award: OCE-1756859

At latitudes that undergo significant seasonal variation in productivity, some zooplankton species such as copepods undergo a period of hibernation called diapause to get through periods of low productivity. Species often hide in cold water at great depth during diapause both to reduce the risk of predation and further reduce their metabolic rates. Although metabolic rates are low during diapause, copepods must rely on lipids stored in a specialized storage sac to fuel their hibernation. Thus, the amount of lipid stored and the factors that trigger diapause are important aspects of their life history. Lipid storage is doubly important in Neocalnaus copepods because unlike most diapausing species the female does not feed after diapause and she must also fuel her entire reproductive output from the lipids she carries into diapause. In this collaborative proposal between Petra Lenz from the University of Hawaii at Manoa, and Russ Hopcroft at the University of Alaska Fairbanks, we combined molecular profiling approaches with more classic empirical studies to understand the lead-up to diapause and the factors that trigger it. Of the two alternative diapause hypotheses - the lipid accumulation window hypothesis, which holds that individuals enter diapause only after they have accumulated sufficient lipid stores, and the developmental program hypothesis, which holds that once the diapause program is activated, progression occurs independent of lipid accumulation - we found most support for the former. The specific project objectives were to: 1) determine the effect of food levels during Neocalanus flemingeri copepodite stages on progression towards diapause using multiple physiological and developmental markers; 2) characterize the seasonal changes in the physiological profile of Neocalanus flemingeri across environmental gradients and across years; 3) compare physiological profiles across co-occurring calanid species; and 4) estimate the reproductive potential of the overwintering populations of N. flemingeri. Three graduate students and several post-doctoral fellows participated in this project. A total of 8 peer-reviewed articles were published. The broader scientific significance includes the acquisition of new genomic data and molecular resources made publicly available through established data repositories, and the development of new tools for routinely obtaining physiological profiles of copepods. Last Modified: 07/09/2024 Submitted by: RussellRHopcroft