Geographical distribution,morphology and water quality of caldera lakes: a review

The geographical distribution, morphometry and water quality of lakes within large calderas (> 2 km in diameter) were evaluated through a review of the literature and maps. Eighty-eight lakes in 75 calderas were located in 31 volcanic subregions. As a group, the lakes varied greatly in elevation, surface area, maximum depth, and shoreline development. The average surface area was 16.9 km², surface elevation 873 m, depth 151.1 m, and shoreline development 1.35. Water quality ranged from ultraoligotrophic to highly eutrophic. None of the lakes had an inlet that originated outside the calderas. Most lakes did not have a surface outlet, were circular or subcircular in shape, and covered only parts of the caldera basins. Water clarity in some lakes was among the highest recorded for freshwater systems, but there are indications of possible declining clarity in some cases. Secondary volcanic activity, such as primary (hydrothermal) water and eruptions, has been associated with deteriorated water quality conditions in some lakes.     

Interactions between larvae of the hoverfly <Emphasis Type="Italic">Eristalinus sepulchralis</Emphasis> and microorganisms in the hydrothermal springs of the Uzon caldera,Kamchatka

The physicochemical and microbial characteristics of some medium-temperature hydrotherms of Kamchatka Peninsula (Uzon caldera), habitats of the hoverfly Eristalinus sepulchralis larvae, were studied. In these hydrothermal vents, the larvae were found to use various prokaryotic and eukaryotic microorganisms as a nutrient substrate. The rates of chemo-and photosynthetic activity of the suspended microbial communities inhabiting the hydrotherms and supporting the existence of larvae were measured. By light and electron microscopy, exo-and endosymbiotic prokaryotic microorganisms were revealed in the digestive and respiratory systems of larvae.     

Shifts in morphology and diet of non-native sticklebacks introduced into Japanese crater lakes

An increasing number of exotic animals are causing ecological problems. Therefore, for better ecosystem management, it is important to understand how exotic species colonize and adapt to novel environments. The threespine sticklebacks (Gasterosteus aculeatus) can be a good vertebrate model system to explore the ecological and genetic mechanisms of adaptation not only in natural populations, but also in non-native populations. Although morphological changes have been documented in several introduced populations of stickleback, little is known about the dietary changes during colonization into novel environments. Here, we investigated the morphological and dietary changes of exotic threespine stickleback populations introduced into three Japanese crater lakes (Lake Towada, Lake Kussharo, and Lake Shikotsu). Sticklebacks were introduced into the crater lakes likely along with salmonids transplanted for aquaculture. The stickleback population in Lake Kussharo had multiple mitochondrial haplotypes and had larger phenotypic variances than other crater lake stickleback populations that had only one mitochondrial haplotype. Compilation of historical data on the morphology and stomach contents of the Lake Towada stickleback population showed that substantial shifts in body size and stomach contents occurred after colonization. Some of these changes may be related to an outbreak of the Schistocephalus parasite. These results suggest that sticklebacks can change their morphology and trophic ecology when they colonize novel environments. Therefore, extreme care should be taken when salmonids are transported between watersheds for aquaculture and that long-term monitoring of exotic species is essential for ecosystem management. In addition, further genetic studies on phenotypic changes in crater lake sticklebacks would help elucidate the genetic mechanisms underlying the adaptation of exotic fishes to novel environments.     

Rainforest conifers of Eocene Patagonia: Attached cones and foliage of the extant Southeast Asian and Australasian genus Dacrycarpus (Podocarpaceae)

? Premise of the study: Eocene caldera-lake beds at Laguna del Hunco (LH, ca. 52.2 Ma) and Río Pichileufú (RP, ca. 47.7 Ma) in Argentine Patagonia provide copious information about the biological history of Gondwana. Several plant genera from these sites are known as fossils from southern Australia and New Zealand and survive only in Australasian rainforests. The potential presence of Dacrycarpus (Podocarpaceae) holds considerable interest due to its extensive foliage-fossil record in Gondwana, its remarkably broad modern distribution in Southeast Asian and Australasian rainforests, its high physiological moisture requirements, and its bird-dispersed seeds. However, the unique seed cones that firmly diagnose Dacrycarpus were not previously known from the fossil record. ? Methods: I describe and interpret fertile (LH) and vegetative (LH and RP) material of Dacrycarpus and present a nomenclatural revision for fossil Dacrycarpus from South America. ? Key results: Dacrycarpus puertae sp. nov. is the first fossil occurrence of the unusual seed cones that typify living Dacrycarpus, attached to characteristic foliage, and of attached Dacrycarpus pollen cones and foliage. Dacrycarpus puertae is indistinguishable from living D. imbricatus (montane, Burma to Fiji). Dacrycarpus chilensis (Engelhardt) comb. nov. is proposed for Eocene vegetative material from Chile. ? Conclusions: Modern-aspect Dacrycarpus was present in Eocene Patagonia, demonstrating an astonishingly wide-ranging paleogeographic history and implying a long evolutionary association with bird dispersers. Dacrycarpus puertae provides the first significant Asian link for Eocene Patagonian floras, strengthens the biogeographic connections from Patagonia to Australasia across Antarctica during the warm Eocene, and indicates high-rainfall paleoenvironments.     

Limnology of the Crater Lake Cuicocha,Ecuador, a Cold Water Tropical Lake

Cuicocha (3380 m a.s.l.) is a young, a few hundred years old volcanic lake in the western cordilleras of the Ecuadorian Andes with some post‐volcanic activities, such as emission of volcanic gases and input of hydrothermal water. Water chemistry is influenced by the emission of CO₂ and weathering of the young andesitic rocks in the water shed. A calcium cycle exists in the lake with intensive biological Ca precipitation at the flanks and formation of travertine crusts, while in the hypolimnion dissolution of Ca carbonate occurs. The crater lake is oligotrophic, biodiversity is low; the littoral flora and fauna is more important than the pelagic species. In the littoral zone, a small Totora zone occurs, followed by submerged macrophytes down to 35 m water depth. Phyto‐ and zooplankton occur down into the hypolimnion. Phytoplankton is strongly influenced by down‐welling of water (atelomixis) and by coprecipitation with detritial flocs (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comparison of Recent Siliceous and Carbonate Mat Development on the Shore of Hyper-Alkaline Lake Van and Mt. Nemrut Soğuk Lake,NE Anatolia,Turkey

This article focuses on the molecular geochemistry of previously unreported carbonate- and siliceous-mat assemblages at two adjacent lake-shore environments. The first study area, on the Lake Van shore, is an intersection of hyper-alkaline lake water and seep water discharge, both of which represent an acid-base geochemical barrier. Comparing alkaline lake water with seep water samples collected from a biomineralization site reveals that seep water has an acidic character and is rich in Ca and Si cations. The second study area, Mt. Nemrut, is the largest volcanic caldera located west of Lake Van in eastern Anatolia, and is the only volcano that has erupted in historical time. While the main lithified-mat components of Lake Van's shore environments are Ca-carbonate and diatoms, Na-carbonate and diatom assemblages represent recent biomineralization in the Mt. Nemrut So?uk Lake shores. In particular, the normal habitat for the development of these unique microbial mat assemblages can be changed in a short time by the decreasing seep water discharge into the Lake Van shore environment. A detailed study on these lake shore microbialites, before they are lost, would provide a great opportunity to understand the biogeochemical interactions that produce unique sediment fabrics.