Athena Economou-Amilli

Morphology and molecular evaluation of Iphinoe spelaeobios gen. nov., sp. nov. and Loriellopsis cavernicola gen. nov., sp. nov., two stigonematalean cyanobacteria from Greek and Spanish caves

Caves have generally been found to host phototrophic micro-organisms from various taxonomic groups, with cyanobacteria comprising an important group that have adapted to these stable and highly specific environments. A polyphasic study based on aspects of classical morphology and molecular data revealed two new monospecific genera from fresh material of Greek and Spanish caves. Both taxa are characterized by obligatory true branching (T-type, V-type and false branching), the presence of heterocysts, and reproduction by hormocysts and akinetes. They shared some similarities in their morphological characteristics as revealed by light, scanning electron and transmission electron microscopy, but phylogenetic analysis based on 16S rRNA gene sequences showed that the two phylotypes were different (89.8% similarity); this represents an example of shared morphology in genetically different strains of cave-adapted species. Phenotypic and genetic traits strongly support classification of the phylotypes as independent taxa in the order Stigonematales (the most differentiated and complicated group of cyanobacteria), family Loriellaceae Geitl 1925. Hence, the names Iphinoe spelaeobios Lamprinou and Pantazidou gen. nov., sp. nov. and Loriellopsis cavernicola Hernández-Mariné and Canals gen. nov., sp. nov. are proposed.

Abundance and growth response of microalgae at Megalon Embolon solar saltworks in northern Greece: An aquaculture prospect

There is continuous interest in many countries in maintaining and manipulating the rich ecological value of hypersaline ecosystems for aquaculture. The Megalon Embolon solar saltworks (northern Greece) were studied in sites of increasing salinity of 60–144 ppt to evaluate Dunaliellasalina abundance and microalgal composition, in relation to physical and chemical parameters. Cluster and ordination analyses were performed based on the biotic and abiotic data matrices. Using fresh aliquots from 60 and 140 ppt salinity waters, phytoplankton performance was appraised with flask cultures in the laboratory by varying the inorganic PO4-P concentration at 23 °C and 30 °C. At the saltworks, among the most abundant microalgae identified were species of the genera Dunaliella, Chlamydomonas, Amphora, Navicula, and Nitzschia. Dunaliella salina populations were predominant comprising 5–22% of the total microalgal assemblages during spring, but only 0.3–1.0% during the summer, when grazing by Artemia parthenogenetica and Fabrea salina was intense. D. salina cell density in April–July was in the range of 0.4–12.5 × 106 L−1 with typical densities of 1.5–4.5 × 106 L−1. Overall, microalgal densities were high in salinities of ≥100 ppt when inorganic-P concentrations were ≥0.20 mg L−1 within saltworks waters. Multivariate analysis of species abundance showed that algal growth responses were primarily related to variation in salinity and inorganic-P concentrations, but also to NO3-N concentration. In the laboratory, experiments indicated effective fertilization and denser microalgal growth under high inorganic PO4-P applications (4.0 and 8.0 mg L−1) at 60 ppt salinity and 23 °C. The lower PO4-P applications (0.6–2.0 mg L−1) were more effective at 60 ppt salinity and 30 °C. At 140 ppt salinity, microalgal growth response was less obvious at any of the corresponding phosphorus concentrations or temperatures. In both salinity experiments, Dunaliella salina bloomed easily and was predominant among the microalgae. Our observations indicate that Dunaliella salina populations and the overall rich microalgal profile of the saltworks, along with their performance in laboratory mono–and mixed cultures hold promise for mass cultivation within the M. Embolon saltworks basins.

Euendolithic shell-boring cyanobacteria and chlorophytes from the saline lagoon Ahivadolimni on Milos Island, Greece

Samples of typical estuarine mollusc shells (Cerastoderma glauca, Abra ovata and Hydrobia acuta), differing in appearance, size and age, were collected from littoral habitats of a saline water lagoon (Ahivadolimni on Milos Island, Greece). Each shell sample was examined for the distribution, frequency and taxonomy of its shell-boring cyanobacteria and chlorophytes, and the associated attached (epizoic) diatoms. The euendolithic microflora was extracted using Perenys solution and observed by light microscopy (LM). The results of microbial penetration (traces of euendoliths) were examined by scanning electron microscopy (SEM) after a hypochlorite treatment. The three-dimensional patterns of microbial penetration (boring patterns) were investigated under SEM by applying the resin-casting technique for modern euendoliths. Of the five euendolithic cyanobacteria found, one (Cyanosaccus atticus) was established from Greek marine biotopes, three (Hyella caespitosa var. arbuscula, H. inconstans and H. reptans) are second records and new for Europe, whereas one cyanobacterium (Leptolyngbya terebrans = Plectonema terebrans) and the three euendolithic chlorophytes found (Phaeophila dendroides, Ostreobium quekettii and Gomontia polyriza) show a cosmopolitan distribution. A survey of the diatoms found as epizoic on the mollusc shells (30 taxa) shows that most of them are typical representatives of marine to brackish water of coasts and estuarine areas. A systematic account of all euendoliths found in the mollusc shells is given. The morphological variability of the cyanobacterium Hyella inconstans, and of the chlorophytes Ostreobium quekettii and Gomontia polyriza is presented, with extended taxonomic comments for the latter species. The susceptibility of molluscs to infestation, as well as the morphological variability, world distribution and penetration patterns of the euendoliths within the host mollusc shells are also discussed.

Screening for marine nanoplanktic microalgae from Greek coastal lagoons (Ionian Sea) for use in mariculture.

Mediterranean mariculture uses imported strains of marine phytoplankton, raising questions of ecological risk and ability to adapt to local conditions for mass culture outdoors. In this context, we report here on the mass-culture potential and chemical composition of six strains of Prasinophyceae (five strains of Tetraselmis sp. and one Pyramimonas sp.) isolated from a Greek coastal lagoon. Proximate composition had a pattern of 10–20% ash, 35–65% protein, 6–10% lipids, and 25–45% other organics including carbohydrates. The amino acid profiles were typical for the marine representatives of the class. All strains had a high PUFA content with dominant the ω3 fraction in four of them. The fatty acid profiles indicated a Tetraselmis strain with high EPA (14%) and a Pyramimonas strain with high DHA (6%). These strains might be a good alternative for the common commercial strains used in Mediterranean aquaculture.

A polyphasic taxonomic approach in isolated strains of Cyanobacteria from thermal springs of Greece.

Strains of Cyanobacteria isolated from mats of 9 thermal springs of Greece have been studied for their taxonomic evaluation. A polyphasic taxonomic approach was employed which included: morphological observations by light microscopy and scanning electron microscopy, maximum parsimony, maximum likelihood and Bayesian analysis of 16S rDNA sequences, secondary structural comparisons of 16S-23S rRNA Internal Transcribed Spacer sequences, and finally environmental data. The 17 cyanobacterial isolates formed a diverse group that contained filamentous, coccoid and heterocytous strains. These included representatives of the polyphyletic genera of Synechococcus and Phormidium, and the orders Oscillatoriales, Spirulinales, Chroococcales and Nostocales. After analysis, at least 6 new taxa at the genus level provide new evidence in the taxonomy of Cyanobacteria and highlight the abundant diversity of thermal spring environments with many potential endemic species or ecotypes.

Distribution survey of Cyanobacteria in three Greek caves of Peloponnese

Caves and hypogean environments host various phototrophic microorganisms, with Cyanobacteria constituting the major group. The spatial and temporal distribution of Cyanobacteria (156 taxa in total) from three Greek caves, located in the limestone arc of Peloponnese and differing in morphology, was studied. The community patterns in different ecological niches were analyzed in relation to environmental parameters (Photosynthetically Active Radiation, Temperature, and Relative Humidity). Cyanobacterial communities were found to thrive in patchy biofilms and showed known protective strategies against desiccation and irradiation. The nMDS analysis of the cumulative seasonal samples per sampling site showed no general pattern of distribution, with a clear differentiation of cyanobacterial communities among the three caves. Only in the typical cave ‘Kastria’, cyanobacterial taxa showed growth habits in accordance with the gradient of light from entrance inwards.

The show cave of Diros vs. wild caves of Peloponnese, Greece - distribution patterns of Cyanobacteria

*aamilli@biol.uoa.gr 2011). Under such conditions the oligotrophic nature of cave environments is expected to change through organic inputs that alter both the food web, and the abundance and distribution of cave organisms (Hoyos et al., 1998; Fernández-Cortés et al., 2006; Saiz-Jimenez et al., 2011; Saiz-Jimenez, 2012). Additionally, the artificial lighting system in the show caves affects the photosynthetic microflora in areas around the installed illumination equipment. The photosynthetic community thriving in proximity to artificial lighting is known as ‘Lampenflora’– a term introduced by Dobàt (1963) – and it was first studied in Austrian caves (Kyrle, 1923; Morton and Gams, 1925). Further research has shown that the growth and distribution of these floristic aggregations depend on abiotic factors such as light quality and intensity, temperature, relative humidity, as well as type and coherence of the underlying substratum (Roldán et INTRODUCTION

CYCLOTELLA ELYMAEA, A NEW FOSSIL SPECIES FROM THE NEOGENE BASIN OF KOZANI-AEANI-SERVIA, NORTHERN GREECE

A new fossil species of Cyclotella, C. elymaea, has been studied by LM and SEM. It was dominant in Neogene deposits of the Kozani-Aeani-Servia basin, northern Greece, accompanied by numerous hemispherical valves which are assumed to be or derive from initial cells. Analysis of morphometric parameters revealed significant variation in valve structure, mostly related to the degree of silicification of the frustules and the decrease in valve diameter resulting from cell division. This comprised variation in the pattern of ornamentation in the central zone, in the density of the marginal fultoportulae and in the structure of the striae. However, since the general characteristics of the valve are constant throughout C. elymaea and transitional forms can be recognized between the variants, it is suggested that the morphotypes are all part of the same life cycle. In the informal subdivision of Cyclotella that has been proposed, C. elymaea would fall within the “andancensis” group.

Freshwater algae from lakes in the lower Niger Delta system (Nigeria)

Samples from two flood plain lakes (Umuorodog-wum I and II) and one permanent natural lake (Oguta) of the lower Niger Delta system (Imo State, Nigeria), representing the outcome of a single sampling campaign in January 1993, are analysed taxonomically. Emphasis is given on the diatom flora but also on some other accompanying algae; a list of 172 algal taxa is currently presented for the area. The relative species abundance patterns and autecology data confirm the frequent occurrence of taxa capable of tolerating the wide environmental fluctuations determined by local conditions of climate and water chemistry. Comparisons are made between the studied lakes including one disturbed site. The results on the water chemistry and biology corroborate findings from similar ecosystems in West Africa.

MORPHOLOGY AND ULTRASTRUCTURE OF THE CENTRIC DIATOM CYCLOTELLA DISTINGUENDA

Cyclotella distinguenda Hust. was studied in material from Lake Kournas in the Island of Crete, Greece. It is characterised by a highly variable central area without any processes, a striate zone of varying width with simple alveoli, a single marginal rimoportula. and several marginal fultoportulae. Analyses of the populations reveal two clusters of morphotypes, distinguished by size range and the relative size of the central area, which appears to represent life cycle variation. The affinity of C. distinguenda with other species of Cyclotella is discussed.