Recent Observation of a Proliferation of Ranunculus trichophyllus Chaix. in High-altitude Lakes of the Mount Everest Region: Comment

Information on the biodiversity of high altitude lakes in the Stelvio National Park was scarce and fragmentary, in most cases limited to a few studies on a single biological issue. To fill this gap, a multidisciplinary research program was established in 2011 to investigate macroinvertebrates, diatoms, and water chemistry in 8 high altitude lakes within the boundaries of the Park (Rhaetian Alps, Eastern Alps). The results of this study were compared with data on biological assemblages and chemical parameters of Alpine lakes in the Pennine-Lepontine Alps (Western Alps), to evaluate the role of local drivers with respect to regional ones. This comparison was possible thanks to the adoption of standardized sampling methodologies developed since the ’90s by the National Research Council-Water Research Institute (Verbania), in collaboration with several European Research centers. Despite located in a restricted geographical area, the lakes of the Stelvio National Park showed a high variability of chemical composition, and of sensitivity to acidification, lower than that of the Pennine-Lepontine Alpine lakes. Macroinvertebrate and diatom taxa were ubiquitous and frequent along the Alps, and mainly represented by cold-stenothermal species. Richness, Shannon, Simpson, and Pielou indices applied to phyto- and zoobenthos highlighted significantly lower values in Stelvio National Park lakes than in those of Pennine-Lepontine for macroinvertebrates, while no significant differences were found for diatoms. Two groups of lakes were identified by Cluster Analysis, mainly on the basis of major ion concentrations. Canonical Correspondence Analysis showed that the macroinvertebrate assemblage of the lakes studied is driven mainly by altitude and lake surface, and, to a lesser extent, by nutrient content. On the contrary, pH and acid-related variables played a secondary role for diatoms, while nutrients and, more in general, ionic content had significant effects on their species composition. Overall, the results of this first investigation showed that the high elevation of these lakes affects their macroinvertebrate assemblages, while their diatom communities are comparable throughout the Alps.

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Linear and Fractal Heart Rate Dynamics during Sleep at High Altitude

Methods of Information in Medicine ◽

10.3414/me09-02-0053 ◽

2010 ◽

Vol 49 (05) ◽

pp. 521-525 ◽

Cited By ~ 10

Author(s):

P. Castiglioni ◽

F. Rizzo ◽

A. Faini ◽

P. Mazzoleni ◽

C. Lombardi ◽

...

Keyword(s):

Heart Rate ◽

High Altitude ◽

Cardiac Response ◽

Fluctuation Analysis ◽

Similarity Coefficients ◽

Mount Everest ◽

Heart Rate Dynamics ◽

Biological Interpretation ◽

Additional Support ◽

Cardiac Variability

Summary Objectives: To investigate the effects of hypoxia during sleep on linear and self-similar components of heart rate variability (HRV) in eight healthy subjects at high altitude on Mount Everest. Methods: ECG was monitored by using an innovative textile-based device, the MagIC system. For each subject three night recordings were performed at sea level (SL), at 3500 m and 5400 m above SL. RR Interval (RRI) was derived on a beat-by-beat basis from the ECG and the VLF, LF and HF spectral components and the LF/HF ratio were estimated. Short-(α1) and long-term (α2) scale exponents as well as the recently proposed spectrum of self-similarity coefficients, α(n) were estimated by detrended fluctuation analysis (DFA). Results: With respect to SL, all HRV parameters but one (α2) were significantly modified at 3500 m. However, at 5400 m they tended to return to the SL values and this was in contrast with the increase in the hypobaric hypoxia and in the number of central sleep apneas occurring at higher altitude. The only HRV index that displayed changes at 5400 m was the DFA α(n) spectrum, with α(n) values significantly lower than at SL for 20 < n < 50 and higher for 200 < n < 400, being n the box size.. Conclusions: While the biological interpretation of these results is still in progress, our data indicates that the cardiac response to high altitude hypoxia during sleep can hardly be fully explored by traditional HRV estimators only, and requires the additional support of more sophisticated indexes exploring also nonlinear and fractal features of cardiac variability.

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