Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic

Abstract

Johnson, C. L., Leising, A. W., Runge, J. A., Head, E. J. H., Pepin, P., Plourde, S., and Durbin, E. G. 2008. Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic. – ICES Journal of Marine Science, 65: 339–350. Demographic time-series from four fixed stations in the Northwest Atlantic Ocean demonstrate variable timing of entry into and emergence from dormancy in subpopulations of the planktonic copepod Calanus finmarchicus. A proxy for timing of entry was established as the date each year when the proportion of the fifth copepodid stage (CV) in the subpopulation rose to half its overall climatological maximum CV proportion at that station. The proxy for timing of emergence at each station was set as the first date when adults were more than 10% of the total abundance of copepodid stages. An alternate emergence proxy date was determined by back-calculating the spawning dates of the first early copepodid stages appearing in spring, using a stage-structured, individual-based model. No single environmental cue (photoperiod, surface temperature, or average surface-layer chlorophyll a concentration) consistently explained entry or emergence dates across all stations. Among hypotheses put forward to explain dormancy in Calanus species, we cannot eliminate the lipid accumulation window hypothesis for onset of dormancy or a lipid-modulated endogenous timer controlling dormancy duration. The fundamental premise of these hypotheses is that individuals can only enter dormancy if their food and temperature history allows them to accumulate sufficient lipid to endure overwintering, moult, and undergo early stages of gonad maturation.

Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

“…The entry of C. finmarchicus diapause has been hypothesized to be controlled by the amount of lipid accumulated prior to diapause (Johnson et al, 2008); while the duration and exit of C. finmarchicus diapause is mainly controlled by bottom temperature-dependent metabolic depletion rate of lipid (Saumweber and Durbin 2006;Pierson et al 2013) (Pierson et al, 2013;Saumweber and Durbin, 2006). Surface temperature at onset of diapause is a better proxy of diapause duration than winter/spring temperature (Johnson et al, 2008). Thus, an earlier spring surface warming may influence phytoplankton phenology more than that of their zooplankton grazers.…”

Composition of wax esters is linked to diapause behavior of Calanus finmarchicus in a sea loch environment

“…It has previously been proposed that potential triggers for the initiation and termination of diapause in C. finmarchicus are the wax ester stores, which must achieve a minimum threshold value before diapause is entered and declines below a certain threshold before diapause is terminated (Irigoien 2004;Johnson et al 2008). In laboratory experiments primarily investigating the energetic cost of gonad maturation in C. finmarchicus, Rey-Rasset et al (2002) calculated that this species requires a minimum of , 70 mg C wax ester before entering diapause.…”

“…A key, yet little understood aspect of the life cycle of C. finmarchicus is its overwintering behavior when it enters into diapause, effectively a state of dormancy when metabolic processes are greatly reduced (Hirche 1996). Mechanisms controlling diapause have remained elusive because the initiation and termination of diapause is highly variable between regions and not linked to the physical environment (Johnson et al 2008).…”

Phenology and fitness of Calanus glacialis, C. finmarchicus (Copepoda), and their hybrids in the St. Lawrence Estuary

“…Differences in hybrid proportion ob served between samples from 2008 (Parent et al 2012) and 2010 (this study) in the St. Lawrence Estuary may also be due to interannual variability in abundance and egg production rate of hybrids. Fluctuation in hybrid abundance could be due to variation in the length of the critical temporal window for hybridization caused by variations in overwintering duration and timing of arousal from diapause (Johnson et al 2008) or to imports from adjacent areas with different proportions of hybrids (Parent et al 2012). Hybrid abundance could also increase if the peak of primary production is earlier in the year, as observed previously (Plourde et al 2001).…”