Young ISDR

Melina Feitl writes about links between diatom valve size and climate  variability Why  Pantocsekiella ocellata ? Diatoms are widely used proxies for reconstructing past climatic and environmental change because of their ecological sensitivity to physical and chemical lake characteristics [1]. These fossil reconstructions are often based on the known ecological ranges of modern taxa.  The Arctic, although particularly interesting climatically, has relatively sparse studies on diatom taxonomy, ecology, and biogeography because of logistical issues involving its remote location.  One of the most important members of the Arctic (and sub-arctic) diatom flora is the planktic species  Pantocsekiella ocellata  (Pantocsek) K.T. Kiss & E. Ács, formerly reported as  Cyclotella ocellata  Pantocsek.   P. ocellata  was first described by Pantocsek in 1902; valves were circular with a marginal ring of striae and a...

by Johannes W. Goessling* The centric diatom Coscinodiscus granii lives in coastal and pelagic marine habitats as a cosmopolitan phytoplanktonic species (algaebase.org) . The genus name is derived from the greek words kóskino (sieve) and dískos (disc) and refers to the disc-shaped structure of the two valves that compose the silicate envelope ( frustule ) surrrounding diatoms. The valves of C. granii are perforated with pores and chambers in an outer layer with small pores (~10 nm), a central layer with hexagonal chambers (~1,200 nm), and an inner layer with large pores (~580 nm) (Fig. 1). So the size of these structures is only 1/100,000 th to 1/1000 th of a mm (!) and can therefore interact with the photons of sunlight. We were interested in the physical interaction of frustules with light, and how it can affect diatom photosynthesis – the conversion of sunlight into chemical energy. We found that the C. granii frustule redistributes sunlight to optimize the exposure...

by Sarah Roberts* Lake Baikal (Siberia, Russia) contains 1/5 th of the world’s freshwater and is thus the largest freshwater lake by volume. This ancient lake is over 25 million years old, it harbours many endemic species, and its ecosystem and water quality are increasingly threatened by rising anthropogenic activity. Recent studies have found shoreline pollution at Lake Baikal, with blooms of algae indicative of eutrophic conditions; t his littoral water deterioration is a result of nutrient enrichment from outdated sewage treatment plants from shoreline settlements (Timoshkin et al., 2016). However, we do not know the extent of the pollution and whether the pelagic regions are now eutrophic . Sedimentary diatom assemblages at Lake Baikal have been extensively studied in the past, with palaeolimnological studies investigating the impacts of pollution and climate change on diatom community composition (Mackay et al., 1998) and predicting future diatom assemblage change wi...

by Xavier Benito-Granell * The South American continent was crucial to inspire Charles Darwin´s Origin of Species . During his travel, Darwin recognized the importance of two factors while developing his famous theory on how nature works: biogeography and history. In Darwin’s words: “ When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the inhabitants in South America, and in the geological relations of the present to the past inhabitants of that continent ”. Professor Christian Ehrenberg was the first to analyze diatoms from South America, in the Tierra del Fuego . Darwin was fascinated by Ehrenberg´s microscopic observations of diatoms in diatom-rich geological deposits ( diatomite ). Due to the old age of such deposits and known diatom forms identified, Darwin thought that diatom distributions should also be old, and probably having wide geographical distributions due to their presence in that extreme region of Earth....