Aspects of the study of the life cycles of Antarctic copepods

• Published in: Hydrobiologia 2001-06, Vol.453-454 (1), p.9-24
• Main Author: Schnack-schiel, Sigrid B
• Format: Article
• Language: English
• Subjects: Autumn; Calanoides acutus; Calanus propinquus; Calanus simillimus; Copepoda; Ctenocalanus citer; Developmental stages; Distribution patterns; Egg production; Esters; Euchirella rostromagna; Gonads; Life cycles; Lipids; Marine; Metridia gerlachei; Microcalanus pygmaeus; Migratory species; Mortality; Overwintering; Paralabidocera antarctica; Physiology; Phytoplankton; Seasonal variations; Seasons; Spawning; Stephos longipes; Summer; Vertical distribution; Winter
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1013195329066

Different approaches to the study of life cycle strategies of Antarctic copepods are described in an attempt to shed new light on our present knowledge. To date, most studies were carried out on abundance, horizontal and vertical distribution and stage composition during different seasons and in various regions. Hence, the seasonal pictures had to be compiled from different years and sampling regions. The physiological method includes measurements on e.g. egg production, feeding, respiration and excretion rates, C:N and O:N ratios, lipid and protein contents. However, both physiological and biochemical data are still rare. Results of field observations are given in this paper for investigations conducted within the last 15 years in the eastern Weddell Sea, while data of physiological parameters are based on a broader geographical region. In the eastern Weddell Sea, eight copepod species account for about 95% of copepod abundance and for more than 80% of copepod biomass. Within the calanoids, the small species Microcalanus pygmaeus dominates by numbers with 66%, while the large species Calanoides acutus and Calanus propinquus comprise together 52% of the biomass. Species abundance is lowest in winter and highest in summer/autumn, however, seasonal changes in the abundance of M. pygmaeus are small and this species occurs in similar quantities throughout the year. All copepod species show a distinct seasonal vertical distribution pattern and they occur in upper water layers in summer, in contrast to the other seasons. However, the depth layers of maximum concentration differ between species. The ontogenetic vertical migration is most pronounced in C. acutus and relatively weak in C. propinquus. The age structure also shows seasonal differences with the youngest population observed in summer for C. acutus, C. propinquus, Ctenocalanus citer or autumn for Metridia gerlachei, whereas the M. pygmaeus population is oldest during summer. The youngest copepodite stage and the males are not always present in C. acutus and C. propinquus. In contrast, all developmental stages and both sexes occur throughout the year in M. gerlachei, M. pygmaeus and C. citer. Gonad maturation in the dominant calanoid species proceeds well before the onset of phytoplankton production in the eastern Weddell Sea. However, the highest portion of females with ripe gonads and hence highest egg production rates coincide with the productive period in spring and summer. In autumn, ovaries of the