Identifying Marine Phytoplankton (eBook)

Carmelo R. Tomas (Herausgeber)

eBook Download: EPUB

1997 | 1. Auflage
858 Seiten
Elsevier Science (Verlag)
978-0-08-053442-8 (ISBN)

Infos

Identifying Marine Phytoplankton is an accurate and authoritative guide to the identification of marine diatoms and dinoflagellates, meant to be used with tools as simple as a light microscope. The book compiles the latest taxonomic names, an extensive bibliography (referencing historical as well as up-to-date literature), synthesis and criteria in one indispensable source. Techniques for preparing samples and containing are included as well as hundreds of detailed, helpful information. Identifying Marine Phytoplankton is a combined paperback edition made available by popular demand of two influential books published earlier--Marine Phytoplankton and Identifying Marine Diatoms and Dinoflagellates.

Key Features
* Contains hundreds of illustrations showing critical characteristics necessary for proper identification, plus keys and other guides
* Provides up-to-date taxonomic revisions
* Includes species from around the world
* Updates synthesis of modern and historical literature presented by active researchers in the field
* Compiles literature from around the world into one handy source

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Identifying Marine Phytoplankton is an accurate and authoritative guide to the identification of marine diatoms and dinoflagellates, meant to be used with tools as simple as a light microscope. The book compiles the latest taxonomic names, an extensive bibliography (referencing historical as well as up-to-date literature), synthesis and criteria in one indispensable source. Techniques for preparing samples and containing are included as well as hundreds of detailed, helpful information. Identifying Marine Phytoplankton is a combined paperback edition made available by popular demand of two influential books published earlier--Marine Phytoplankton and Identifying Marine Diatoms and Dinoflagellates. - Contains hundreds of illustrations showing critical characteristics necessary for proper identification, plus keys and other guides- Provides up-to-date taxonomic revisions- Includes species from around the world- Updates synthesis of modern and historical literature presented by active researchers in the field- Compiles literature from around the world into one handy source

Textauszug

Chapter 2 Marine Diatoms

Grethe R. Hasle, Erik E. Syvertsen

INTRODUCTION

The study of diatoms began in the 18th century. The name of the class Bacillariophyceae was derived from the genus Bacillaria Gmelin 1791, whereas “Diatom” refers to the genus Diatoma De Candolle 1805. Despite more than a century of devoted morphological and taxonomic investigations, electron microscopy, introduced to diatom research in the middle of the 20th century, revealed additional information. A reevaluation of the established classification systems and the current ideas and information on biogeography was required, and a new era of diatom investigations began.

Simonsen (1979) introduced a diatom system based on results from light and electron microscopy and constructed a key to the diatom families. Other ideas on classification, evolution, and critical evaluations at the higher taxonomic levels followed, based on the increasing amount of information (Cox, 1979; Round & Crawford, 1981, 1984; Fryxell, 1983; Glezer, 1983; Nikolaev, 1984; Williams & Round, 1986, 1987), resulting in two partially diverging diatom systems (Glezer et al., 1988; Round et al., 1990).

Publications summarizing the new information on diatom morphology as well as a revision of the classical identification literature were needed. To meet this requirement several diatom atlases, floras and handbooks were published during the past decade or so, most of them concentrating on a particular geographical region. Ricard (1987) constructed keys to families and genera with genus as the lowest rank, the genera being illustrated with light and electron micrographs of one or a few species of each. The diatom handbooks by Priddle & Fryxell (1985) and Medlin & Priddle (1990) both deal with polar species. The focus of the former is on some planktonic diatoms commonly recorded in the Southern Ocean. The latter, a more comprehensive handbook, includes the two polar regions and has an ecological as well as a taxonomic part with keys to species. The diatom atlas from India and the Indian Ocean region (Desikachary, 1986–1989) contains only light micrographs of the diatoms recorded in the area with no additional text, and the phytoplankton atlas by Delgado & Fortuño (1991) has text as well as line drawings and scanning electron micrographs of diatoms from the Mediterranean.

The publications by Rivera (1981), Makarova (1988) and Rines & Hargraves (1988) have the character of monographs of the marine planktonic genera Thalassiosira (the former two publications) and Chaetoceros (the latter publication), although based on material from specific geographical areas. The investigation of Rhizosolenia, a third important marine planktonic genus, by Sundström (1986) is based on material from almost all oceans, and the Unesco Manual on Harmful Microalgae has a chapter on this category of diatoms (Hasle & Fryxell, 1995).

The monumental diatom volume by Round et al. (1990) differs from all the publications mentioned previously in content as well as size; it consists of sections on the biology of the diatoms, a summary of the introduced classification, and a generic atlas. Linnaeus, a catalogue and expert system for the identification of protistan species (Estep et al., 1992), includes diatoms, and the catalogue by Gaul et al. (1993) lists papers containing electron micrographs of diatoms and is thus useful to those studying the fine structure of the diatom frustule.

Despite these recent publications, teaching experience tells us that there is still a need to fill in respect to the global aspect of the identification of marine planktonic diatoms at the specific level. We hope to fill a part of this need with this chapter.

GENERAL CHARACTERISTICS

Systematics: Class Bacillariophyceae in the division Chromophyta.

Closest relatives: Chrysophyceae and Xanthophyceae. (See Round et al., 1990, p. 122.)

Number of species: 10,000–12,000, approx 50,000 (Round & Crawford, 1984, p. 169), or in excess of 100,000 (Round & Crawford, 1989, p. 574); or in marine plankton approx 1400-1800 (Sournia et al., 1991, p. 1085).

Size: ca. 2 μm-ca. 2 mm.

Level of organization: Unicellular, often in colonies.

Cell covering: Siliceous wall and organic layer.

Flagella: Male gametes with one flagellum with stiff hairs.

Chloroplasts: Lamellae with three thylakoids, girdle lamella, and four membranes around the chloroplast.

Pigments: Chlorophylls a and c, betacarotene, fucoxanthin, diatoxanthin, and diadinoxanthin.

Mitochondria: Tubular type.

Storage products: Chrysolaminarin and oil.

Motility: Present in pennate diatoms with a raphe.

Biotopes: Marine and freshwater, plankton, benthos, epiphytic, epizoic (e.g., on whales and crustaceans), endozoic (e.g., in foraminifera), endophytic (e.g., in seaweed), on and in sea ice, and “air diatoms.”

Geological age: Centrics: Jurassic (a few species) and Early Cretaceous (Gersonde & Harwood, 1990). Araphid pennates: Late Cretaceous (Medlin et al., 1993, with references). Raphid pennates: Middle Eocene (Medlin et al., 1993, with references).

LIFE CYCLES

Reproduction (Figs, 1a and 1b)

Diatoms reproduce vegetatively by binary fission, and two new individuals are formed within the parent cell frustule. Each daughter cell receives one parent cell theca as epitheca, and the cell division is terminated by the formation of a new hypotheca for each of the daughter cells. This type of division, with formation of new siliceous components inside the parent cell, leads to size reduction of the offspring. The possible size range of the diatom cells seems to be species dependent, and the specific variation may be as large as 8 to 10 times the length of the apical axis or the diameter.

FIGURE 1 (a) Sexual reproduction of a centric diatom (oogamy) and (b) of a pennate diatom (morphological isogamy, physiological anisogamy). , Zygote; , nucleus; , pycnotic nucleus.

The considerable size variation is often accompanied by a pronounced size dependent change in cell proportions, normally in the form of an increase in the ratio between the length of the pervalvar axis and the apical axis or diameter. In addition, size variation often causes changes in valve ornamentation, like a reduction in the number of central clustered processes in Thalassiosira spp. (E. Syvertsen, personal observations), a loss of special structures like the pili of certain species of the Cymatosiraceae (Hasle et al., 1983), and an alteration of the valve outline of morphologically bipolar species from elongate toward almost circular, e.g., Fragilaria spp. (Hustedt, 1959) and Cymatosiraceae.

The decrease in the average cell size of a diatom population during vegetative growth implies a need for a means of restoring the cell size. This is made possible by auxospore formation, in which a cell sheds its siliceous theca, thereafter forming a large sphere surrounded by an organic membrane. Within this sphere, a new diatom frustule of maximal size is formed, and the cycle starts anew. The first cell formed inside the auxospore, the initial cell, may have a morphology deviating in girdle structure, valve outline, and process pattern from that of a “normal” vegetative cell (vide, Thalassiosira decipiens, Hasle, 1979, Fig. 41; Cymatosira lorenziana, Hasle et al., 1983, Fig. 19).

Auxospore formation is size dependent and normally takes place when the cell has reached about one-third of its maximal size (Drebes, 1977). Below this limit the diatoms seem unable to rejuvenate themselves, and they continue to divide until they reach a stage at which cell division is no longer possible. There are reports in the literature of taxa which do divide without a simultaneous size reduction (Drebes, 1977), and some species seem to be able to multiply at their lower size limit without further size reduction for an extended length of time (E. Syvertsen, personal observations). For most species, however, auxospore formation is a necessary and normal occurrence in their life cycle. It may take place as a vegetative event or as the result of sexual reproduction.

All diatoms are diplonts with a meiosis at the end of the gametogenesis. The zygote develops into an auxospore. In the centric diatoms, sexual reproduction is by oogamy with flagellated male gametes, while most pennate diatoms are morphologically isogamous lacking a flagellated stage. A few araphid species have been shown to be anisogamous (Drebes, 1977) and are considered to represent a transitional stage between centric...

Produkt-Details

• Erscheint lt. Verlag: 12.8.1997
• Sprache: englisch
• Themenwelt: Schulbuch / Wörterbuch ► Lexikon / Chroniken
• Themenwelt: Naturwissenschaften ► Biologie ► Botanik
• Themenwelt: Naturwissenschaften ► Biologie ► Limnologie / Meeresbiologie
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Hydrologie / Ozeanografie
• Themenwelt: Technik ► Umwelttechnik / Biotechnologie
• Themenwelt: Weitere Fachgebiete ► Land- / Forstwirtschaft / Fischerei
• ISBN-10: 0-08-053442-2 / 0080534422
• ISBN-13: 978-0-08-053442-8 / 9780080534428