Vernal abundance, structure and development of epipelagic copepod populations of the eastern Weddell Sea (Antarctica)

Abstract

Summary. Pelagic copepod populations under the pack ice of the Antarctic Weddell Sea were sampled with a 50 gm net between October 2 and December 7, 1986, to study their abundance and developmental stage composition before and at the onset of the vernal phytoplankton bloom. Subadult stages and adult females were incubated to estimate rates of development and egg production. Copepod densities in the upper 200 m were highest for the small-sized species Oithona similis, Oncaea curvata and Ctenocalanus citer. About 95% of the copedite stages belonged to these species, dominated by Oithona. The copepodids were outnumbered by the nauplii in all species, except in Oncaea. The stage distribution in the small-sized species was bimodal with peaks in N3 and C4. The larger species Calanuspropinquus and Metridia gerlachei showed peaks in nauplii only. Eggs were relatively abundant in all small and large species. Animals smaller than 1 mm not only were more abundant than the larger ones, but also had a higher total potential respiration. Eggs were produced by incubated females in sea water virtually without food at 0 °C. Eggs hatched, and Oithona nauplii developed at a rate of about 7 days per stage. Copepodite stages did not develop significantly. Reproduction in the most abundant species commonly occurred before the algal spring increase when food levels were very low. Maintenance of a stable stage distribution at the expense of a high juvenile mortality seemed to be characteristic for the overwintering strategy of Antarctic copepods.

Seasonal lipid dynamics of the copepods Pseudocalanus minutus (Calanoida) and Oithona similis (Cyclopoida) in the Arctic Kongsfjorden (Svalbard)

“…Generally, high wax ester levels are indicated by clearly visible large lipid droplets, especially in the November specimens (personal observation). Similarly, Fransz (1988) observed large oil globules in epipelagic copepods from the Weddell Sea (Antarctica) including O. similis. A continuous decrease in the amounts of fatty alcohols of all stages during the overwintering period, with signiWcantly lower values in spring than in summer, suggests that O. similis survived the winter at least partly using internal lipids as energy reserves.…”

“…Hence, the origin of these long-chain alcohols remains a matter of conjecture. At times, fatty alcohols and thus wax esters seemed to play an important role in all stages of O. similis, although it is not a diapausing species and therefore does not depend on primary production, but stays active and reproduces the whole year (Fransz 1988). Kattner et al (2003) also found high-wax ester levels in the adult males of O. similis from Antarctic waters (70%).…”

Mesoscale distribution and population dynamics of Rhincalanus gigas and Calanus simillimus in the Antarctic Polar Open Ocean and Polar Frontal Zone during summer

“…However, work has indicated that In some diapausing species overwintering costs may not be great and that a proportion of the lipid is invested in reproduction (Sargent & FalkPeterson 1988). Spawning in a number of polar species seems to precede the spring bloom (Fransz 1988, S m~t h 1990, Hirche & Kattner 1993. Ward & Shreeve 1995 and a picture is emerging that during certain phases of a female's reproductive life, lipid can be used to fuel egg production.…”

Regional differences in the life cycle of Calanoides acutus (Copepoda:Calanoida) within the Atlantic sector of the Southern Ocean

“…It follows, therefore, that to allow time for egg hatching and naupliar development at these temperatures, egg laying must start before chlorophyll a concentrations increase. This was suggested for the Weddell Sea from the timing of appearance of nauplii (Fransz 1988) and from gonad maturity and lipid levels (Schnack-Schiel , Hagen & Schnack-Schiel 1996.…”