This is the first record of the red alga Polysiphonia carettia Hollenberg (Rhodomeleaceae) in the Gulf of Gabes, Tunisia (Mediterranean Sea). This species was first described growing on the carapace of the loggerhead sea turtle Caretta caretta (L.) from Santa Catalina Island, California, USA. In the Mediterranean, it was reported only from two loggerhead turtles captured by a Spanish longline vessel. The morphology, habitat and geographical distribution of P. carettia were examined.
With 44 figures and 2 tables Abstract: The analysis of samples taken in different aerial microhabitats in Europe (Germany and Luxembourg) revealed the presence of a new and interesting small-celled naviculoid diatom species. Based on detailed light and scanning electron microscopy, one taxon previously misidentified as Sellaphora saugerresii is here described as Mayamaea petersenii sp. nov. The ecological preferences and a detailed analysis of its frustule ultrastructure lead to propose its generic placement in Mayamaea, followed by a discussion concerning key characters of the genera Sellaphora, Eolimna and Chamaepinnularia.
Ecology and Evolution Group, Department of Biology, P.O. Box 60, Middle Tennessee State University, Murfreesboro, TN 37132 USA With 1 figure and 1 table Abstract: The genus Acetabularia represents a group of historically important, macroscopic, single-celled green algae initially used by Joachim Hammerling to demonstrate localization of genetic material within the nucleus of a cell (by grafting one species onto another and allowing it to regenerate its original form). Acetabularia, and the related genus Acicularia, are considered to be “living fossils” within the family Polyphysaceae because of their long and uninterrupted fossil record, and, as such, are important taxa in the evolutionary progression of green algae (and plants). To date, there is just a single published study on the sterols of Acetabularia mediterranea. Sterols, tetracyclic lipids which act to reinforce eukaryotic plasma membranes, are often used as chemotaxonomic indicators to assess relationships between eukaryotes. Examination of sterols within Acetabularia and Acicularia may help further identify an ancestral set of sterols that has since radiated throughout many green algae. Two C28 and three C29 sterols commonly found in green algae, all with Δ5 unsaturations and with the dominant one being 24-ethylcholest-5-en-3β-ol, were observed in four species of Acetabularia and one of Acicularia. The chemotaxonomic and evolutionary aspects of this finding are discussed herein.
Abstract: u2029The feeding behavior of the dinoflagellate Oxyrrhis marina with the prasinophyte Pyramimonas grossii as prey was studied in order i) to determine the ingestion rate for this armed microalga, ii) to survey the impact and fate of ejectisomes discharged within predatory cells, and iii) to check if birefringent bodies occur in both, starved and fed Oxyrrhis cells. Oxyr-rhis which was grown to stationary phase and then added to cultures of Pyramimonas captured and digested more than 95% of the prasinophyte within ten days. The decline of non-digested Pyramimonas cells monitored by regular cell counting using light microscopy, was also measured by fluorescence emission spectroscopy and registered by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Transmission electron microscopy revealed that the ejectisomes of Pyramimonas which were discharged within the food vacuole did not harm Oxyrrhis. Mainly the body scales and the ejectisomes were not digested but excreted. Both, starved and fed Oxyrrhis cells contained birefringent bodies. Besides the longitudinal banding, a faint and rather oblique running striation was registered for them.
For sustainable harvesting of wild stocks of economically important seaweed species, knowledge on the temporal variation of the standing stock biomass of the target species is an important prerequisite before any commercial harvesting concession can be granted. In this regard, a monthly in situ monitoring of the standing stock biomass of Laminaria ochroleuca (Bachelot de la Pylaie, 1824) was conducted during a two-year cycle at Sidi Bouzid located on the Moroccan Atlantic coast in the south of the city of El Jadida. Development of morphological parameters as proxy for growth i.e. blade length (L; cm), stipe length (S; cm) and dry biomass (kg.m-2) were monitored and measured. The shortest blade length was recorded in January 2004 and 2005 respectively (51.1 and 60 cm), the maximum was recorded in June 2004 and 2005 respectively (103.2 and 121.6 cm). Minimum biomasses are recorded in January of the two cycles of growth, it is about 0.60 kg.m-2 in 2004 and 0.98 kg.m-2 in 2005, the highest biomasses are recorded in May–June 2004 (1.9 kg.m-2) and in August for the year 2005 (3.9 kg.m-2). Individuals found in June 2005 have shorter stipe (8.21 cm) while maximum stipe length was recorded on October 2005 (22.8 cm). Mean yearly densities of L. ochroleuca were 34 and 32 plants/m² in 2004 and 2005 respectively. Therefore, the exploitation of this species should be carried out from June with harvest period reduced to a maximum of 2 months to allow the algae to grow in autumn.
In this study five species of Spirogyra (Zygnemataceae) from lentic (pools, lagoons, lakes) and lotic (stream) habitats in the south of Buenos Aires province, Argentina, are described and illustrated in detail, with precision about their vegetative morphology, conjugation and zygospore ornamentation. Two of the species, S. ellipsospora and S. hyalina, are newly recorded for Argentina and the other three, i.e. S. quadrilaminata, S. maxima and S. majuscula, were previously mentioned with imprecise references and no illustrations for this country.
Biological soil crust (BSC) communities can be found in almost all environments except for the tropics. These microbial mats are especially predominant in ecosystems, which exhibit harsh conditions, in which they play a key role as primary producers. Studying their metatranscriptomic data enables scientists to shed light on taxa composition, the interactions between those organisms and their ability to cope with abiotic stressors in the extreme environments, e.g.the polar regions. The basis of a successful metatranscriptomic analysis is the isolation of pure RNA of high quality and integrity. Nucleic acid extraction from soil samples is challenging due the diverse chemical and physical properties of soil. Humic substances are often co-extracted and, subsequently, contaminate the sample. In this study, different RNA extraction techniques were tested and evaluated for the isolation of high quality RNA from four BSC samples, three isolated in Germany and one polar BSC: a CTAB based protocol, the Spectrum™ Plant Total RNA Kit and the Precellys Plant RNA Kit. The CTAB based method provides high quality RNA at a low yield and with an average degree of contamination for all tested samples. RNA obtained by using the Spectrum™ Plant Total RNA Kit is of high quality with only little contamination but only half of the samples could be processed successfully. A high throughput approach is the Precellys Plant RNA Kit resulting in a fair RNA quality but with the highest level of contamination. Furthermore, only three out of four samples yielded any results. Further purification is often necessary as DNA and humic substances often cannot be easily removed. Using enzymatic digestion DNA can be specifically cleaved while humic substances can be separated from the RNA fraction by using either gel filtration or RNA affinity binding columns.
Marine macroalgae are key organisms in polar coastal ecosystems. Brown macroalgae dominate rocky shores in both polar hemispheres, where they form huge kelp beds, which are habitat and feeding ground for diverse organisms. To compare physiological response of Arctic vs. Antarctic habitat structuring brown algae to different abiotic factors, Saccharina latissima (Kongsfjorden, Arctic) and Desmarestia anceps (Potter Cove, Antarctic) were exposed for 8h to 12 combinations of photosynthetically active radiation (PAR), UV radiation (UVR) and temperature. The data provide basis information on short abiotic stress in S. latissima and D. anceps. Temperature alone did not cause changes in photosynthetic efficiency, while UVR and high PAR decreased the maximum quantum yield of PS II down to 30% of the initial values. The endemic species D. anceps showed mostly similar responses to the applied stress treatments compared to the generalist S. latissima, indicating a certain tolerance of D. anceps to short periods of UVR and temperature stress. More data are needed to predict biological effects and ecological implications of changing abiotic factors, future studies should include several stress exposure times and gradual changing abiotic factors.
The Mesopotamian marshlands are one of the most internationally important wetlands in the Middle East as it constitutes a nursing ground for many species of birds migrating from North Europe as well as for its rich biodiversity. These marshlands have undergone significant environmental changes during the last three decades owing to decreasing freshwater discharge which has led to water quality deterioration and a changing hydrological regime. This has had a considerable effect on the fauna and flora of the marshes, diminishing their ecological value and significance. The work presented here is the first attempt to investigate the marshes environmental condition during the past two centuries using paleolimnology, specifically diatoms as bioindicators in a sediment core. 80 species of diatom belonging to 35 genera were identified. The taxa encountered in the core are a mixture of fresh and brackish water forms. These are epiphytic and benthic taxa, no planktonic species were found. The fossil diatom community shows that the marshes have been exposed to different periods of salinization as well as eutrophication. The dominance of pollution tolerant species in the core indicates poor water quality for the past 160 years. Paleolimnology is important to understand past environmental conditions and forms a milestone for successful future restoration process. Further work is required to extend the time scale to identify natural ecological states and thresholds to guide international aid restoration projects.
In the McMurdo Dry Valleys, located in Southern Victoria Land, Antarctica, endolithic communities are important photoautotrophic primary producers. Being poikilohydric organisms their active time and carbon fixation rates rely on local water availability. In Antarctica the parallel variation in the severity of the thermal and hydric environment makes simple transect and gradient based modelling complicated. Here we interpret samples collected over several seasons in terms of rock type (sandstone, marble and granite) and location (distance from sea, altitude) on the colonization, species composition, chlorophyll content, biomass as well as stable carbon isotopic composition and 14 C age of the endolithic communities. Distance from coast was highly correlated with altitude of the sampling locations and this complicated disentangling of climatic drivers. Nevertheless, stable carbon isotopic composition allowed insight into hydration regime and 14C radiocarbon age into productivity. Endolithic communities in sandstone at high altitude sites have higher biomass but are less often active than communities in lowland granite.
Planktothrix agardhii (P. agardhii), a filamentous cyanobacterium commonly found in freshwater environments, has also been reported in brackish areas. In order to test the hypothesis of an acclimation of P. agardhii to its environmental salinity, we monitored growth and morphometry of P. agardhii brackish and freshwater strains under various salinities (0 to 15 psu). Despite differences in their response under increasing salinities (0–15 psu), the brackish strains show: (i) growth less gradually inhibited by increasing salinities than the freshwater strains; (ii) growth nearly optimal in the salinity of their natural environment (iii) a salt tolerance range wider (0 to [12.5–15 psu]) than that of freshwater P. agardhii (0 to [7.5–10 psu]). Our findings suggest that this tolerance may be due to an acclimation of the strains to their environment by effective salt extrusion and compatible solutes accumulation. This salt acclimation, just as the population response to various salinities, is well reflected by the filaments morphometry. This study highlights the ability of potentially harmful cyanobacteria to acclimate to salinity in a salinization context.
In this report, we describe the investigation of water samples from Majidun Creek, a riparian system emptying into Lagos Lagoon, over a period of twelve months (February 2010– January 2011). Samples were obtained using a 55 μm plankton net towed at low speed for 10mins. Various physico-chemical parameters were monitored; surface water temperature, PO4-P, transparency, NO3-N, SO4 2- and silicate concentrations. All measured chemical parameters were lower in the rainy season while surface water pH ranged from acidic to alkaline (6.2–8.4), chlorophyll ‘a’ showed its highest value in the dry season. There was a remarkable change in seasonal salinity values while conductivity values ranged between 0.01 and 13.15 (mS/cm) in raining and dry seasons, respectively. Fifteen different orders of diatoms were recorded. The Naviculales dominated the diatom spectrum followed by Cymbellales, Fragillariales, Thalassiophysales, Nitzschiales and Eunotiales. Changes in diatom communities appear to be driven by two factors. The first, and dominant factor, is seasonality based on differences between the rainy and dry seasons which is correlating with peak biodiversity and peak biomass in diatom community structures. Anthropogenic impacts appear to be the second force influencing diatom community structure with areas of high population density, showing alterations in community composition when compared to regions with less human activity. Since most of the monographs used by Nigerian algologists are not indigenous, this paper may assist in solving a part of the diatom identification problems.
