Chapter 2 Literature Review
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CHAPTER 2 LITERATURE REVIEW 2.1 Diversity of algae Biodiversity is the variety of life forms, it also refers to variation at all levels of biological organization. It can be divided into three groups: genetic diversity, species diversity and ecosystem diversity. Genetic diversity refers to the total number of genetic characteristics in the genetic makeup of a species. Whereas, the species diversity refers to the number and distribution of species in one location. It contains the taxonomic difference from individual to species, genera and higher taxonomic level. Ecosystem diversity compasses the scale of physical conditions different from populations to niches and habitats (Gaston and Spicer, 2004). The diversity is influenced by many environmental factors. The most influenced factors are habitat characteristic and ecological complex. High diversity of organisms reflects to complex ecosystem, while the decreased of diversity will obviously affect ecosystem changing (Baimai, 2003). Algae is a highly diverse group of photoautotrophic organisms with chlorophyll-a and unicellular reproductive structures which play very important role in aquatic habitats. There are approximately 8 upto 19 divisions with 26,900 species of algae have been described in the list of species of living organisms in the world (Wilson, 1988). Algae are ranged in size from microscopic single cell to large visible seaweed. They can be separated by their living habitats into 2 groups: floating algae as phytoplankton and benthic algae which are attached to substrate. Algae are usually found in bodies of water and thus are common in terrestrial as well as aquatic environments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, tropical regions. Sometimes they were also found in extreme environments such as in hot spring, snow or high salinity water (John et al., 2002). 5 2.2 Desmids studies 2.2.1 Classification of desmids Desmids are freshwater algae which composed of unicellular and filamentous green algae. Most desmids arje unicellular algae, few are occurred a simple, unbranched, sometimes very fragile filament. Cells ranged in size from very small (7-10 µm) to more than 1 mm. long. Cell wall may be smooth but often shows a distinct pattern of granules, tubercles or spines. Rich cell wall ornamentation, whether or not in combination with deep semi cellular incisions or long processes (Croasdale and Flint, 1986). The shape of the half-cells (semicells) is varied: ranging from globular to disc- or spindle-like. Desmids exhibit a great diversity in their external morphological and show remarkable complex cell symmetry. Particularly a group which is characterized by their conjugation as a way of a sexual reproduction (Ralfs, 1848). The characteristic of cell wall has been used for identifying the desmids into families (Brook, 1981). The desmids are divided into the Placoderm or true desmids and Saccoderm or false desmids. According to the work of Růžička (1977), Placoderm belongs to the order Desmidiales whereas, Saccoderm belongs to order Zygnematales. Most saccoderm desmids are unicellular, with cylindrical or ellipsoidal cells which do not consist of two semicell and possess a one-piece cell wall similar to that of the filamentous Zygnematales (e.g. Spirogyra). The placoderm desmids, cells are generally solitary, but sometimes form colonies or unbranched filaments with their cell wall of two or more pieces. The wall of each cell consists of two symmetry semicell and unique morphology. Round (1973), Brook (1981) and Gerrath (1993) had primarily characterized desmids based on their cell wall structure into 4 families, 43 genera and 3,000 species which could be described as the following; Division Chlorophyta Class: Conjugatophyceae Order: Zygnematales Family: Zygnemataceae Family: Mesotaeniaceae (Saccoderm desmids) 6 Genus: Ancylonema, Cylindrocystis, Geniculus, Mesotaenium, Netrium, Roya, Spirotania Order: Desmidiales (Placoderm desmids) Family: Peniaceae Genus: Genicularia, Gonatozygon, Penium Family: Closteriaceae Genus: Closterium, Spinoclosterium Family: Desmidiaceae Genus: Actinotaenium, Allorgeia, Amscottia, Bambusina, Bourrellyodesmus, Cosmarium, Cosmocladium,Desmidium, Docidium, Euastrum, Groenbladia, Haplataenium, Hyalotheca, Ichthyocercus, Ichthyodontium, Micrasterias, Oocardium, Phymatodocis, Pleurotaenium, Prescolliella, Sphaerozosma, Spinocosmarium, Spondylosium, Staurastrum, Staurodesmus, Streptonema, Teillingia, Tetmemorus, Triplastrum, Triploceras, Xanthidium 2.2.2 Ecology and distribution Desmids are freshwater algae. Only few species are known to distribute in brackish water. They are commonly found in lakes and ponds which are widespread throughout the world (Lind and Brook, 1981). Several habitats can be rich in desmids flora such as mire, peat swamp, quark fen and pool (Croasdale, 1994). However, they are being rather rare in lotic environment (Brook, 1981). The acidic (low pH 4-7) and highly colour water also have a large desmids population. Pools in bog or fen are often rich in desmids, which are especially common in aufwuchs around submerged Sphagnum plant. As shown in Lenzenweger’s study, that found high diversity of desmids, 233 species in low pH level of water in several bog of Austria. (Lenzenweger, 2000) 7 Two typical living forms of desmids were revealed that planktonic forms are most recognized in open water. Genus Cosmarium and Staurastrum are commonly found in plankton. Nevertheless, most species of desmids are benthic and live on or between submerged plants around the margin of water body. The attached species can be derived from the submerged plants to open water. Large and diverse desmid populations were on macrophytes with finely leaves sush as Ceratophylum, Myriophylum and especially Utricularia (Coesel, 2001). Desmids are generally common and diverse in oligotrophic lakes (poor in nitrate and phosphate); low productivity, low conductivity, low bicarbonate alkalinity and low pH (Coesel, 1981). However, they are also found in mesotrophic or eutrophic lakes, most of them belong to the genera Closterium, Cosmarium and Staurastrum (Coesel, 1983). Stamenković and Cvijan (2008) expressed that Closterium spp. were found to be dominated in polluted water in Serbia. Palmer (1970) also pointed that Closterium is a high tolerant species for polluted environments. If desmids are not found in large quantities, they seems to be useful as indicator of oligotrophic conditions of those habitats where they occur (Coesel, 1983). It could be indicated that the presence of desmids assemblages might be revealed a conservation value of aquatic environment (Coesel, 2001). Desmids diversity have been extensive interested for over 150 years. Consequently, there are some 8,000 references relating to these organisms throughout the botanical and limnological literatures. The majority of these papers related to their morphology and taxonomy since the publication of the first book on identification of British Desmidiaceae by Ralfs in 1848. A succession of keys has been distributed in Europe, Russia, The United States and Japan (Brook, 1981). Therefore, several publications of desmids diversity have been done in many parts of the world. In Europe, most desmids flora were studies intensively for example, a monograph of the British Desmidiaceae. The whole series focused on diversity of desmids encountered in the United Kingdom, applicable to the greater part of Europe (West and West, 1904, 1905, 1908, 1912). The other importance study is work of Krieger (1933, 1939) on all Mesotaeniaceae genera, as well as the Desmidiaceae genera Penium, Closterium, Docidium, Pleurotaenium, Triploceras, Ichthyocercus, Tetmemorus, Euastrum and Micrasterias. This study not only done with European species but also with a fair number 8 of many tropical desmids. Similarly to the work of Förster (1982) which is focused on planktonic desmids of selected taxa from all over the world. Thus, there are but few really euplanktonic species among the desmids. This selection was composed of some tychoplanktonic species (the great majority in the desmids). Ruzicka flora in 1981 deals with the genera Gonatozygon, Genicularia, Penium, Closterium, Docidium, Pleurotaenium, Triploceras, Triplastrum, Actinotaenium, Tetmemorus, Euastrum and Micrasterias in central European area. Similarly, Lenzenweger’s flora (1996, 1997, 1999, and 2003a) revealed the desmids flora of Austria where approximately 600 species of temperate climatic or alpine regions area were presented. The latest flora represented all desmids taxa known from the Netherlands and lowland areas. Over 28 genera, 500 species and 150 additional varieties are dealt with (Coesel, 2007). The other valuable desmids flora are from North America in which nearly 1,000 species of Placoderm and Saccoderm desmids were descript (Prescott et al., 1972, 1975,1977,1981,1982 and 1983). Moreover, the investigation of 30 genera, 117 taxa of desmids from New Zealand were shown as rich desmids diversity. At least 17% of them occur only in New Zealand (Croasdale et al., 1994). However, the floras mentioned above were all from temperate zone. In other regions, the desmids diversity mostly report in some specific publications. The tropical region is wildly known for its high diversity of organisms. In the same way as the desmids diversity was high. The characteristic of the biogeography of desmids was declared as Indo-Malaysian and North Australian Region following West and West (1902) that recognized this regions