TY - JOUR A1 - Pailles, Christine A1 - Sylvestre, Florence A1 - Escobar, Jaime A1 - Tonetto, Alain A1 - Rustig, Sybille A1 - Mazur, Jean-Charles T1 - Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Peten-Itza, Guatemala, Central America JF - Phytotaxa : a rapid international journal for accelerating the publication of botanical taxonomy N2 - While analyzing the fossil diatom flora in one of the longest paleolimnological records (core PI-6) from Lake Peten-Itza, lowland Guatemala, we encountered Aulacoseira Thwaites, Cyclotella (Kutzing) and Discostella (Cleve & Grunow) Houk & Klee species appearing successively in the record. Among them, two new species that are assigned to the genus Cyclotella are described herein. Cyclotella petenensis sp. nov. is characterised by a coarse striation marked by a shadow line and a tangentially undulate central area with an arc of central fultoportulae. Cyclotella cassandrae sp. nov. has an elliptically shaped valve, coarse striae and a scattered ring of central fultoportulae in the central area. Classification and differences to similar taxa in the genus Cyclotella are discussed. KW - Diatom KW - Cyclotella KW - Pleistocene KW - Lake Peten-Itza KW - Guatemala Y1 - 2018 U6 - https://doi.org/10.11646/phytotaxa.351.4.1 SN - 1179-3155 SN - 1179-3163 VL - 351 IS - 4 SP - 247 EP - 263 PB - Magnolia Press CY - Auckland ER - TY - JOUR A1 - Piepho, Maike A1 - Martin-Creuzburg, Dominik A1 - Wacker, Alexander T1 - Phytoplankton sterol contents vary with temperature, phosphorus and silicate supply a study on three freshwater species JF - European journal of phycology N2 - The understanding of environmentally induced changes in the biochemical composition of phytoplankton species is of great importance in both physiological studies and ecological food web research. In extensive laboratory experiments we tested the influence of two different temperatures (10 degrees C and 25 degrees C) and a phosphorus supply gradient on the sterol concentrations of the three freshwater phytoplankton species Scenedesmus quadricauda, Cryptomonas ovata and Cyclotella meneghiniana. The diatom C. meneghiniana was additionally exposed to a silicate gradient. In two separate experiments we analysed (1) possible interactive effects of temperature and phosphorus supply and (2) the effect of four phosphorus levels and three silicate levels on algal sterol concentrations. We observed that sterol concentrations were higher at 25 degrees C than at 10 degrees C in S. quadricauda and C. meneghiniana, but were not affected by temperature in C. ovata. Interactive effects of temperature and phosphorus supply on sterol concentrations were found in C. meneghiniana. This presumably was due to the bioconversion of one sterol (24-methylenecholesterol) into another (22-dihydrobrassicasterol). Increasing phosphorus supply resulted in species-specific effects on sterol concentrations, viz. an optimum curve response in S. quadricauda, a saturation curve response in C. meneghiniana and no change in sterol concentration in C. ovata. Effects of silicate supply on the sterols of C. meneghiniana equalled the effects of phosphorus supply. Albeit we did not observe a general trend in the three phytoplankton species tested, we conclude that sterol concentrations of phytoplankton are strongly affected by temperature and nutrient supply. Interactive effects point out the importance of taking into account more than just one environmental factor when assessing the effects of environmentally induced changes on phytoplankton sterol concentrations. KW - algae KW - Chlorophyta KW - Cryptomonas KW - Cryptophyta KW - Cyclotella KW - diatoms KW - phosphorus KW - Scenedesmus KW - silicate KW - sterols KW - temperature Y1 - 2012 U6 - https://doi.org/10.1080/09670262.2012.665484 SN - 0967-0262 VL - 47 IS - 2 SP - 138 EP - 145 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Piepho, Maike A1 - Arts, Michael T. A1 - Wacker, Alexander T1 - Species-specific variation in fatty acid concentrations of four phytoplankton species does phosphorus supply influence the effect of light intensity of temperature? JF - Journal of phycology N2 - We tested, in the laboratory, the influence of light intensity, temperature, and phosphorus (P) supply on fatty acid (FA) concentrations of four freshwater algae: the green algae Scenedesmus quadricauda (Turpin) Breb. and Chlamydomonas globosa J. Snow, the cryptophyte Cryptomonas ovata Ehrenb., and the diatom Cyclotella meneghiniana Kutz. We investigated the main and interactive effects of two variables on algal FA concentrations (i.e., light intensity and P supply or temperature and P supply). Interactive effects of light intensity and P supply were most pronounced in C. meneghiniana, but were also found in S. quadricauda and C. ovata. Changes in several saturated and unsaturated FA concentrations with light were more distinct in the low-P treatments than in the high-P treatments. Interactive effects of temperature and P supply on various FA concentrations were observed in all four species, but there was no consistent pattern. In lake ecosystems, P limitation often coincides with high light intensities and temperatures in summer. Therefore, it is important to examine how combinations of these environmental conditions affect FA concentrations of primary producers that are important sources of FAs for higher trophic levels. KW - Chlamydomonas KW - Cryptomonas KW - Cyclotella KW - fatty acids KW - light KW - lipids KW - phosphate KW - PUFA KW - Scenedesmus KW - temperature Y1 - 2012 U6 - https://doi.org/10.1111/j.1529-8817.2011.01103.x SN - 0022-3646 VL - 48 IS - 1 SP - 64 EP - 73 PB - Wiley-Blackwell CY - Malden ER -