The effect of environmental factors on population dynamics of Drepanopus bispinosus (Calanoida: Copepoda) in Burton Lake, Antarctica

The population dynamics of Drepanopus bispinosus (Calanoida: Copepoda) was studied throughout the year from December 1983-January 1985 in Burton Lake, a littoral saline lake in the Vestfold Hills, Antarctica. Also the environmental factors of the lake were observed simultaneously. D. bispinosus is univoltme The population life cycle could be in 20-21 months. Their reproductive activities spread from winter to early summer. The adults (male and female) and naupln mainly constitute the winter population. Adult females and copepodites are absolutely components of the summer population. From late summer through autumn, the population consists mainly of copepodites in stages II-V. The densities of population components have presented considerable variations throughout their life time Most of naupln occurring in winter might not develop and transform into further stages because of restrictive conditions such as low oxygen content and food scarcity. Earlier stage copepodites of new generation appear largely in summer, when the lake is rich m oxygen and phytoplankton. The adult females decrease markedly after their reproductive activities when the strong salinity was diluted in early summer. Such variations of densities of population compositions are closely related to changing of environmental factors m the lake The material obtained from another saline lake m the same hills supported the above

Effect of Environmental Factors on Population Dynamics of Drepanopus Bispinosus in Burton Lake, Antarctica

The population dynamics of Drepanopus bispinosus (Calanoida: Copepoda) was studied throughout the year of December 1983 - January 1985 in Burton Lake, a littoral saline lake on Vestfold Hills, Antarctica, and the environmental factors of the lake were observed simultaneously. D. bispinosus is univoltine. Its population life cycle could be in 20-21 months and reproductive activity stays from winter to early summer. The adults (male and female) and nauplii mainly form the winter population. Adult females are instead of male and, copepodites are instead of nauplii in summer population. Then it consists of copepodites mainly in stages II-V from late summer through autumn. The density of population components considerably varies for their whole life. Most of nauplii appearing in winter may not develop and transform into further stages under the restrictive conditions, such as low oxygen content and scarce food. Earlier stage copepodites of new generation appear largely in summer, when the lake is rich in oxygen content and phytoplankton. The adult females decrease markedly after their reproductive activities, as the sharp salinity diluting in early summer. This density variation of population compositions is mostly related with the change of environmental factors in the lake. The conception is supported by the data obtained from another saline lake on the Vestfold Hills

ナンキョク ベストフォードヒルズ ノ バートンコ (エンコ)ニオケルDrepanopus bispinosus(ドウキャクルイ)ノ コキュウリョウ ノ キセツ ヘンカ ニ オヨボス ショヨウイン

東南極の塩湖に生息するかいあし類の一種Drepanopus bispinosusの雌成体の冬季および夏季の酸素消費量を測定した。測定は種々の水温, 塩分, 溶存酸素量, および餌濃度の実験条件下で行った。呼吸量は水温の上昇とともに増大するが, とくに, 生息水温(0±2℃)から致死水温(13.1℃)範囲で顕著な呼吸量の増大がみられた。8月から12月にかけての呼吸量のQ_値は1.65-1.89の範囲にあったが, 1月には3.11-3.32に増大した。通常の生息塩分濃度(37.2-39.5‰)で呼吸量は最も低く, それより高塩分あるいは低塩分で増大した。溶存酸素量および植物プランクトン濃度もまたある程度呼吸量の変化に影響をあたえているらしいことが推測された。8月から1月にかけてD. bispinosusの雌成体の呼吸量は連続的に減少する傾向を示した。この呼吸量の減少は繁殖期には繁殖活動の結果によるものであり, 繁殖期以降は老衰による生理的機能の低下に起因しているものであることが示唆された。Oxygen consumption of adult females of Drepanopus bispinosus living in a marine derived saline lake in East Antarctica was measured under different conditions of temperature, salinity, dissolved oxygen and food concentration both in winter and summer. Variations in respiration paralleled temperature changes, particularly when the animals were in temperatures higher than in the normal habitat (0±2℃) and below the upper thermal limit (13.1℃). The Q_ values for respiration lay between 1.65 to 1.89 from August to December, but increased to 3.11 and 3.32 in January. Respiration also increased when the animals were subjected to salinities either higher or lower than normal habitat conditions (37.2-39.5‰). Oxygen consumption appeared to be related to the dissolved oxygen content and to some extent to the concentration of phytoplankton cells in the medium. The seasonal variation in respiration of adult females D. bispinosus revealed a tendency to decrease continually from August to January. This might have resulted from their reproductive activities during the period of their reproduction. Food concentration, as well as dissolved oxygen, were possible environmental factors influencing oxygen consumption. After that, it could have been mainly related to decline of their physiological functions resulting from senescence

Factors influencing seasonal changes in the respiration of Drepanopus bispinosus (Copepoda:Calanoida) in Burton Lake, a marine derived saline lake in the Vestfold Hills, Antarctica

Oxygen consumption of adult females of Drepanopus bispinosus living in a marine derived saline lake in East Antarctica was measured under different conditions of temperature, salinity, dissolved oxygen and food concentration both in winter and summer. Variations in respiration paralleled temperature changes, particularly when the animals were in temperatures higher than in the normal habitat (0±2℃) and below the upper thermal limit (13.1℃). The Q_ values for respiration lay between 1.65 to 1.89 from August to December, but increased to 3.11 and 3.32 in January. Respiration also increased when the animals were subjected to salinities either higher or lower than normal habitat conditions (37.2-39.5‰). Oxygen consumption appeared to be related to the dissolved oxygen content and to some extent to the concentration of phytoplankton cells in the medium. The seasonal variation in respiration of adult females D. bispinosus revealed a tendency to decrease continually from August to January. This might have resulted from their reproductive activities during the period of their reproduction. Food concentration, as well as dissolved oxygen, were possible environmental factors influencing oxygen consumption. After that, it could have been mainly related to decline of their physiological functions resulting from senescence

Ecology features of coastal saline lakes related to environmental evolution in the area of Antarctic continental ice edge

An investigation has been made on the ecology of some saline lakes in the Vestfold Hills (60°38'S, 78°06'E), East Antarctica. The results indicate that changes of natural environment and physico-chemical factors, as well as the variation and evolution of biological species do occur in some lakes. This can be attributed to seasonal and local climate changes and geographic differences in this region. These findings are believed to be indicative to the effects from the processes of global climate change, ice sheet retreat, and isostatic uplift, are presently occurring, and a study of the chemistry and biology of these Antarctic lakes may be a significant means of monitoring effects of global climate change in the Antarctic

Study on ecological structures of coastal lakes in Antarctic continent

Coastal region on the Antarctic continent, where it is under the influences both of ocean and ice sheet, as well as frequent human activities, could be considered as a fragile zone in Antarctic ecological environment. There are many lakes in coastal region, showing much differences from each other in physical-chemical features because of individual evolutionary history in their geographical environments, and suffering from different outside factors, such as climate changes and precipitation. Thus, it results in respective biological distribution and ecological structure in lakes. The present paper reports the results from the studies of chemical components, species distributions and community structures, which mainly consisted of planktons in lakes in the Vestfold Hills (68°38'S, 78°06'E), and the Larsemann Hills (69°30'S, 76°20'E), East Antarctica. It also treats the biological diversities and nutrient relationships of these different types of lakes. So as to provide more scientific basis for monitoring of climate changes and environmental protection in Antarctica

Ecological differences of south polar skua populations from Fildes Peninsula of King George Island and eastern Larsemann Hills, Antarctica

A study has been done on the comparison of nesting and feeding behavior, population variances as well as breeding success between two populations of south polar skua (Catharacta maccomicki) from near Great Wall station on Fildes Peninsula and near Zhongshan station in Eastern Larsemann Hills, Antarctica. There are evident differences in their population ecology. The foraging habit is much related to regional ecosystem and food resources near their territorial area. Dependence on human food waste influences skua's diet, which considerably affects their behavior even population variation in both area. The skuas in Zhongshan Station, could shorten and/or regulate the timing for their egg laying and hatching and take precedence of one chick brooding for keeping their breeding success and subsequent species continuation