Kateřina Kopalová

Humidophila gen. nov., a new genus for a group of diatoms (Bacillariophyta) formerly within the genus Diadesmis: species from Hawai'i, including one new species

While conducting surveys of freshwater algae from the Hawaii Islands, we encountered several diatom species and populations belonging to the genus Diadesmis, subgenus Paradiadesmis. Upon closer examination of valve morphology with scanning electron microscopy, the species and populations assigned to Paradiadesmis differed considerably in structure and microhabitat fidelity from Diadesmis confervacea Kützing, the type species of the genus Diadesmis. The Hawaii species have each stria composed of a single elongate areola, external distal raphe ends that are straight to curved, and fine hymenate occlusions on the interior of the areolae. These structures are not found in D. confervacea. Therefore, we propose a new genus, Humidophila, to accommodate these taxa formerly belonging to the subgenus Paradiadesmis. One new species from the Hawaii Islands is described and 47 former Diadesmis species are transferred to Humidophila.

Diversity, ecology and biogeography of the freshwater diatom communities from Ulu Peninsula (James Ross Island, NE Antarctic Peninsula)

The diversity, ecology and biogeography of diatoms in lakes, seepage areas and streams on the Ulu Peninsula, a large ice-free area in the northern part of James Ross Island (Weddell Sea), were studied. A diverse diatom flora of 123 taxa was observed, dominated by several Nitzschia taxa, Psammothidium papilio, Eolimna jamesrossensis, Fragilaria capucina and Fistulifera saprophila. The results from the similarity and diversity analysis suggest James Ross Island to be biogeographically positioned within the Maritime Antarctic region, yet with some affinities with the flora of Continental Antarctica, as shown by the presence of Luticola gaussii and Achnanthes taylorensis. Based on our data, James Ross Island can thus be located close to the boundary of the two main Antarctic biogeographical regions. Diatom communities present in streams and seepage areas could be clearly distinguished from those in lakes, the latter being much more species rich. Based on the multivariate analysis, conductivity and nutrients were selected as the two main environmental factors determining the diatom composition in the Ulu Peninsula lakes. The revised taxonomy of the Antarctic diatom flora induced the construction of a transfer function for water conductivity in the studied lakes that can be applied in further palaeoecological studies.

THREE NEW TERRESTRIAL DIATOM SPECIES FROM SEEPAGE AREAS ON JAMES ROSS ISLAND (ANTARCTIC PENINSULA REGION)

A recent survey of the non-marine diatoms from seepage areas on James Ross Island (Antarctic Peninsula Region) resulted in the discovery of three new diatom species belonging to the genera Diadesmis, Eolimna and Luticola. Based on both light and scanning electron microscopical observations, these species were described as new to science: Diadesmis inconspicua sp. nov., Eolimna jamesrossensis sp. nov. and Luticola truncata sp. nov. The morphology of each species was compared to similar species worldwide with a special focus on those present in the Antarctic Region. Notes on the ecology of the species were added.

Structure and ecology of freshwater benthic diatom communities from Byers Peninsula, Livingston Island, South Shetland Islands

Abstract Diatom and water chemistry samples were collected from 49 lakes, pools and rivers on Byers Peninsula (Livingston Island, South Shetland Islands) during the summer of 2009. A diverse diatom flora of 143 taxa was found. Fragilaria capucina s.l., Psammothidium papilio, Navicula dobrinatemniskovae and several Nitzschia taxa dominated the flora. The biogeographical analysis showed that more than 55% of all observed taxa presented a restricted Antarctic biogeographic distribution and only 30% had a cosmopolitan distribution, contrary to previously published data. Cluster analysis and Principal Components Analysis were used to classify the samples based on their chemical characteristics, revealing that nutrients and specific conductance were the main factors dividing the samples into four groups: young lakes, coastal lakes, larger lakes on the central plateau and smaller, temporary pools. Diatom communities corresponded well to this division and were strongly influenced by salinity and nutrients.

Hydrological systems from the Antarctic Peninsula under climate change: James Ross archipelago as study case

Hydrological systems of the ice-free areas of the James Ross archipelago (NE Antarctic Peninsula) provide a unique opportunity for studying recent environmental changes associated with the current Global Warming. Geochemical, hydrological, sedimentological, and magnetic studies were carried out on different lake systems and ephemeral ponds from post-Holocene periglacial environments to characterize their natural variability. Significant differences between the lakes were observed based on physicochemical analyses, and can be attributed to several characteristics and processes taking place (geochemical, diagenetic, biological, etc.) in individual lake catchments. Seymour-Marambio Island’s lakes exhibit high total dissolved solids (~3.300xa0mgxa0L−1) due to the high rate of evaporation in the region, whereas trace elements show differences in the lithological source. Lakes from Vega and James Ross islands are comparatively diluted, with the highest pH values up to 10.2. Within Vega Island, trace elements discriminate lakes into sectors which show statistical differences due to variations in lithological sources. Dissolved sources can be divided according to their kinetics into: high-rate processes which occur during summer months (evaporation, salt precipitation, atmospheric precipitation, melting processes) and low-rate processes (mineral weathering, giving a long-term signature). The present multidisciplinary study contributes to a better understanding of Antarctic lake systems, and can be used as a baseline dataset for further studies investigating the impact of recent climate changes on the biological and geochemical characteristics of these pristine ecosystems in the future.

Morphological observations on Pseudoeunotia linearis Carter (Bacillariophyta) and its transfer to the genus Eunotia

Abstract During a survey of the moss-inhabiting diatom flora of Gough Island (Tristan da Cunha archipelago, southern Atlantic Ocean), a large population of Pseudoeunotia linearis Carter has been observed. A detailed morphological analysis has been made using light and scanning electron microscopy to reveal its ultrastructure. The results show a eunotioid structure with short raphe branches, uniseriate striae with irregularly placed rimmed areolae, and marginal linking spines surrounding the valve face. Based on these features, the position of P. linearis within the genus Pseudoeunotia cannot be confirmed and a transfer to the genus Eunotia is therefore suggested.