الفهرس | Only 14 pages are availabe for public view |
Abstract The following study is the first of its kind to El-Farafra Oasis. It includes a detailed monography on species composition and algal assemblages of different air, water and soil habitats during two successive seasons: summer 2011 and winter 2012. The work contains a taxonomic list of 101 different algal taxa related to 56 genera: Cyanophycophyta (64 taxa), Bacillariophycophyta (3 taxa), Xanthophycophyta (7 taxa), Euglenophycophyta (4 taxa), Chlorophycophyta (22 taxa) and charophycophyta (one species). Of these, 10 species were recorded for the first time in the Egyptian air, freshwater and soil algal flora: Westiellopsis prolifica, Cylindrospermum gregarium, C. licheniforme, Symploca dubia, Chlorocloster caudatus, Tetraktis aktinastroides, Penium margaritaceum, Cosmarium blyttii, Zygnemopsis sp. and Nitellopsis obtusa. This study isolated only five airborne algal taxa during the summer collection: Myxosarcina chroococcoides, Westiellopsis prolifica, Oscillatoria acuminata, Lyngbya limnetica and Schizothrix braunii. Therefore, it can be concluded that high temperature and dryness characterizing the summer season in El-Farafra Oasis resulted in flaking up of dried airborne algal propagules from the soil surface and other ecosystems into the air. In addition, Cyanophycophyta tend be the widely-dispersed division as airborne algae. Springs and their counterpart habitats “wells” inhabiting El-Farafra Oasis are considered to be relatively isolated ecosystems from the physico-chemical and phycological standpoints. Ain El-Balad could be classified as the only “slightly hot” spring, whereas Ain El-Hateyya, Ain Bishwa and Ain Goshna commonly follow the ambient-to-thermal gradients. The drilled wells have thermal-to-hot gradients. All springs, except Ain Goshna, and wells could be assorted as typically freshwater habitats with almost circumneutral to slightly alkaline pH. Ca/Na-chloride salts constituted the dominant water salts in El-Farafra Oasis, with some noticeable contributions by Mg/Ca-bicarbonates and sulphates. The studied groundwater habitats (springs and birs) in ElFarafra Oasis are considered suitable, to a large extent, for human drinking and all other domestic purposes in the context of the maximum-permissible water quality guidelines proposed by the Egyptian Higher Committee for Water “EHCW” and the World Health organization “WHO”. However, they still essentially need a special governmental attention to eliminate /or reduce the relatively higher concentrations of trace elements specifically Fe and Mn. Furthermore, groundwater of El-Farafra Oasis is considered an excellent-to-good resource for irrigation based on the conductivity gradients and Cl concentrations. 76 different algal taxa had been identified from all water habitats including the naturally-propagated and culturing materials. For more details, 64 species were recorded from the natural collected materials and belonged to: Cyanophycophyta (38 taxa), Bacillariophycophyta (3 taxa), Xanthophycophyta (2 taxa), Euglenophycophyta (4 taxa), Chlorophycophyta (16 taxa) and charophycophyta (one taxon). For the culturing waters, 27 species had been revealed, and out of them new 12 species appeared using the different culturing techniques Cyanophycophyta (19 taxa), Chlorophycophyta (6 taxa) and Xanthophycophyta (2 taxa). Representatives of family Oscillatoriaceae constituted qualitatively the highest number in all studied sites. In particular, Oscillatoria tenuis, followed by O. subtilissima, O. jasorvensis and O. okenii were the most widespread taxa in natural waters. Most of the identified algal taxa inhabiting the springs and their artificial habitats “wells” perfectly fit with their ecological preferences, e.g.: Gloeothece samoensis var. major, Westiellopsis prolifica, Scytonema ocellatum, Calothrix elenkinii, Oscillatoria acuminata, O. animalis, O. carboniciphila, O. deflexa, O. jasorvensis, O. okenii, O. redekei, O. sancta, O. splendida, O. subtilissima, O. terebriformis, Phormidium corium, Symploca dubia and Zygnemopsis sp. Nevertheless, there are many other algal taxa that showed a strong affinity to the other studied ecosystems (lakes, agricultural drainage and ditch). For instance, Merismopedia tenuissima, Pseudoholopedia convoluta, Microcystis aeruginosa, Coelosphaerium kuetzingianum, Euglena acus, E. oxyuris, E. texta, Lepociclis fusiformis, Penium margaritaceum, Closterium acerosum, Micrasterias truncata, Cosmarium blyttii, C. laeve, C. pachydermum, Spirogyra reinhardii and the charophyte alga Nitellopsis obtusa. Some of the identified algal taxa are considered as excellent bio-indicators for eutrophication in El-Farafra Oasis. Among them, the widely-distributed, non-heterocytous bluegreen algae Oscillatoria limosa, O. princeps and O. tenuis mightily linked to the relatively-high availability of nitrates and orthophosphates. In general, the algal flora of different habitats in El-Farafra Oasis is composed of some oligosaprobous forms, e.g. Vaucheria geminata and V. sessilis, with the presence of some β- mesosaprobic tolerants such as Oscillatoria limosa, O. princeps, Euglena acus and Coelastrum cambricum var. intermedium. Little contributions of α-mesosaprobic taxa, e.g. Oscillatoria tenuis and Euglena oxyuris and the rarely polysaprobic taxon Anabaena constricta were also detected. The Canonical Correspondence Analysis (CCA) pointed out that there is a strong positive relationship between Cyanophycophyta and the water temperature. But this algal group is inversely correlated with NO2 -N, NO3 -N and S.R.P. Euglenoids usually prefer inorganic and organic polluted habitats rich in nitrates and nitrites such as lakes and agricultural drainages. Green algae usually proliferate in alkaline pH environments. The only representative member of Charophytes Nitellopsis obtusa was found in an alkaline agricultural ditch with moderately-hard water during the winter collection. Regarding to the soil algal composition, Cyanophycophyta contributed the dominant division with 33 different species belonging to 18 genera and most of them are related to orders Nostocales and Oscillatoriales. Other identified taxa were belonged to Chlorophycophyta (5 species), Xanthophycophyta (5 species) and diatoms (3 species). The dominance of blue-green algae in the desert soil of El-Farafra Oasis is compatible with its alkaline nature. However, there is no absolute relationship between each algal division and the determined physico-chemical parameters.Finally, this study highly recommends using of the isolated blue-green algal taxa of El-Farafra Oasis, specifically Scytonema ocellatum and Westiellopsis prolifica due to their highest potentials on atmospheric nitrogen fixation, as ecofriendly environmental natural biofertilizers for the sustainable development promised in this desert habitat. |