Ecological studies of aquatic moss pillars in Antarctic lakes 3. Light response and chilling and heat sensitivity of photosynthesis

The light-photosynthesis relation was measured using a PAM chlorophyll fluorometric method in a moss, Leptobryum sp., which is the primary component of aquatic moss pillars, in cultured Leptobryum sp. on an agar plate, and in both aquatic and terrestrial forms of Bryum pseudotriquetrum. The morphology of the plate-cultured Leptobryum sp. was clearly different from the sample growing on an aquatic moss pillar; the leaves and shoots were considerably thickened and enlarged in the former. In spite of the great difference of morphology, photosynthetic light responses such as light-PS II yield, -non-photochemical quenching and the relative rate of electron transport of both samples were nearly the same. On the other hand, the responses of B. pseudotriquetrum collected from a moss pillar and terrestrial habitat differed greatly. Light-PS II yield and light-ETR relationships of the Leptobryum sp. showed rather shade-plant type response, low effective PS II yield at any light intensity and low maximum ETR with low light saturation point, while B. pseudotriquetrum from a terrestrial habitat showed rather \u27sun-plant\u27 type responses. Aquatic B. pseudotriquetrum showed the lowest values of effective PS II yield and ETR at almost all light intensities among the present samples. Chilling/heating stress was experimentally added to the aquatic Leptobryum sp., and it was found that both maximum and effective yield of PS II showed quite narrow and cryophilic relationships with treatment temperatures. These photosynthetic features observed in the Leptobryum sp., shade-plant type light response and very naive sensitivity to the changes of temperature, suggest that the species can perform photosynthetic growth within the aquatic habitat; however, it cannot survive or prevail in the terrestrial habitat in severe East Antarctica

Xanthophyll-cycle of ice algae on the sea ice bottom in Saroma Ko lagoon, Hokkaido, Japan

Using the ice algal community prevailing on the sea ice bottom in Saroma Ko lagoon, Hokkaido, Japan, the response of a photosynthetic system to exposure to light was investigated, focusing on xanthophylls-cycle features, diel changes of the pool size of xanthophylls-cycle pigments and the effective quantum yield of PS II in early February, 1998. By pigment analysis, β-carotene, chlorophylls a and c, diadinoxanthin, diatoxanthin and fucoxanthin were detected as major pigments, which suggests that diatoms dominated as ice algae during this study. When such ice algae were exposed to irradiance nearly 4 times higher than the daily maximum level at the ice bottom, the interconversion between diadinoxanthin and diatoxanthin continued for ca. 20 min immediately after the onset of irradiation in spite of the sub-zero Celsius ambient temperature. Although the pool size of this xanthophylls-cycle (relative amount of diadinoxanthin plus diatoxanthin per chlorophyll a) was not so large compared to that of mesophilic diatoms, it showed a circadian change increasing during the daytime and decreasing at night. This change correlated well with the effective quantum yield of PS II. These results suggest that ice algae at the sea ice bottom possess a relatively effective xanthophylls-cycle to regulate light energy usage. However, the xanthophylls-cycle in ice algae may be poor compared to that of algae living in intermediate irradiance, which can be interpreted from the point of view of bioenergetic aspects of shade adapted ice algae

Ecological studies of aquatic moss pillars in Antarctic lakes 2. Temperature and light environment at the moss habitat

To understand the environmental conditions, which control the growth of moss pillars in lake bottoms, water temperature and light in the moss pillar habitat in lake Kuwai Ike in Skarvsnes, Soya Coast, East Antarctica, were continuously measured for about one year, February 1999 to Jannuary 2000. Limnological characteristics of surface water of the lake were investigated in summer 2000, and compared with those in four neighboring lakes. Low contents of ions, neutral pH and dissolved oxygen in saturation level in the surface water in Kuwai-Ike lake were comparable to the values of the other oligotrophic freshwater lakes in Soya Coast and Schirmacher Oasis, located in Queen Maud Land, East Antarctica. The temperature at the lake bottom showed uni-modal seasonal change, in the range 0-12°C. Several sudden temperature drops of > 2°C within a few hours were recorded in the ice-free autumn season; they may have been correlated with the wind-induced vertical mixing events which occurred before complete ice cover development on the lake surface. Light reaching the lake bottom showed clear diel and seasonal fluctuations, and the flux density was strongly affected by the attenuations of water, ice and snow: the photosynthetically active radiation (PAR) measured at the lake bottom was s^ was recorded for nearly 2 months in winter; however, daily fluxes over 1 mol m^ day^ were recorded for the other ca. 8 months, with >100μmol m^ s^ of instantaneous peak fluxes around noon

Reproductive phenology of subalpine moss, Polytrichum ohioense Ren. et Card.

The reproductive phenology of Polytrichum ohioense was investigated in a sub-alpine forest at the foot of Mt. Tyausu, in the Yatsugatake Mountains, Central Honshu, Japan. Shoots were collected every 2 weeks from May to October from the study site. Developmental stages of gametangia and sporophytes formed in the current and previous year were registered. The temperature above the turf occasionally dropped below 0℃ before June, while the temperature in the turf did not drop below 0℃. Juvenile antheridia formed about one month earlier than archegonia. Mature antheridia and archegonia are observed from late May to early August and from late June to mid-July, respectively. Fertilization seems to occur from late June to mid-July. Longer persistence of mature antheridia is supposed to contribute to higher efficiency of fertilization to supply its sperm for a relatively long period. And delayed formation of archegonia in the warm season may contribute to the adaptation to the temperature decrease at the beginning of the growing season. Sporophytes were found first at the end of June, then gradually grew and reached the ECI stage by October. The sporophytes seemed to spend the period of snow cover in the ECI stage, and started to grow again in the next growing season in May. Spore dispersal was observed from mid-July to mid-August. Sporophytes took 13 months to mature including a 6 month resting period. The phenological parameters observed in the present study provide a way to adapt to the the short growing season in the sub-alpine zone in Central Honshu, Japan

Diatoms composing benthic microbial mats in freshwater lakes of Skarvsnes ice-free area, East Antarctica

Diatoms composing benthic microbial mats in Skarvsnes lakes, East Antarctica, were studied in terms of their taxonomy and relationship to environmental factors. Samples were collected from 13 freshwater lakes in the area. Amphora sp. (cf. veneta) was dominant in 11 of the 13 samples, while Craticula sp. (cf. molesta) and Diadesmis sp. (cf. perpusilla) were respectively dominant in the remaining 2 samples. Navicula ectoris Van de Vijver was also reported here for the first time in continental Antarctica. Mosses in the microbial mats did not have a significant effect on the diatom species composition. Redundancy analysis revealed that the main environmental gradient for diatoms was electric conductivity, despite its relatively narrow range (18-390 mS m^(-1)). Our results suggest that Diadesmis sp. and Psammothidium metakryophilum are halophobes, whereas Amphora sp. is a halophile

The lichens around the South Pole Syowa Station

The Tenth Symposium on Polar Science/Ordinary sessions : [OB] Polar Biology, Wed. 4 Dec. / Entrance Hall (1st floor) , National Institute of Polar Researc

ショウワキチ シュウヘン ノ ナンキョク コショウ ニオケル センスイ チョウサ ホウコク

第45次観測隊の陸上生物グループでは,南極湖沼生態系の観測計画であるREGALプロジェクトの一環として南極湖沼でのSCUBAダイビングによる潜水観測を実施した.潜水者および支援隊員は国内において周到な準備を行った後,2004年1月23日にスカルブスネスのB-4池,26日に同じくなまず池において湖底の生物調査を行った.B-4池(仮称)では,コケ坊主の林立する詳細な植生構造の高画質の映像が撮影され,試料が採取されたほか,現場での光合成活性データが取得された.なまず池(仮称)においても同様の調査が行われ,水深3mから20mの最深部までの全域にコケ植物の分布が確認され,10m以深ではトサカ状の特異な植生構造が発達していることが観察された.Biological surveys of lake bottom vegetation, sediments structure, and photosynthesis activity by SCUBA diving were performed in January 2004, in two lakes in the Skarvsnes area, about 50km south of Syowa Station. Two biologists of the 45th Japanese Antarctic Research Expedition (JARE) participated in the surveys. B-4 Ike (tentative name) is a freshwater lake with only 3m depth maximum. Structures of moss pillars and algal mats were investigated in detail, and photosynthesis activity was measured on-site. Namazu Ike (tentative name) is a freshwater lake with 20m depth maximum. Mosses were found from 3m to the deepest bottom of the lake. A crest-like vegetation structure was found at the bottom deeper than 10m

Ecological studies of aquatic moss pillars in Antarctic lakes 1. Macro structure and carbon, nitrogen and Chlorophyll a contents

Structures of a typical \u27moss pillar\u27 submerged in Antarctic lakes were investigated to analyze the sizes, age distribution, and composition such as shoot density, dry weight, carbon, nitrogen and chlorophyll a using a sample collected from lake B-4 Ike in the Skarvsnes region, East Antarctica. The moss pillar was mainly composed of shoots of a moss species, Leptobryum sp. Most of the green shoots of the species were located at the top surface of the pillar, and brownish old shoots with prominent vegetative diaspores, so-called rhizoidal tubers, formed the internal body of the pillar. The internal core of the pillar was nearly empty, and seemed to be decomposed considerably. Dry weight, carbon, nitrogen and chlorophyll distributions in the pillar took heterogeneous patterns, that is, they were largely centered at apical parts. It is suggested that growth of the moss pillar occurred extensively at the apical part. The age was estimated ca. 250 years at ca. 20 cm below the apical top by the AMS method. The presence of the moss pillar in lake B-4 Ike indicates that a tremendous amount of biomass has been produced under the oligotrophic freshwater Antarctic lake environment over more than a quarter millennium

Remarkable morphological characteristics of Milnesium sp. from Inhovde, East Antarctica

第6回極域科学シンポジウム[OB] 極域生物圏11月16日（月）　国立極地研究所１階交流アトリウ