Pages: 70

This chapter aims to provide an introduction to the many different aspects of the world of algae. The first two sections try to define this heterogeneous assemblage of organisms, which includes both prokaryote and eukaryote species, reporting a tentative scheme of classification whose main purpose is to give a survey of the diversity of algae in a very practical way, especially useful for students. The third section is a summary of the 12 algal phyla, describing the main characteristics of the different taxonomic groups. Morphology and structure, nutrition strategies, and reproduction methods are summarized in separate sections. Occurrence and distribution are then described to highlight the multifaceted strategies algae use to colonize and thrive in an enormous diversity of environmental settings and to establish mutually beneficial interactions with many other organisms. Examples are given of algae involved in these interactions with viruses, bacteria, arthropods, and other animals and also with humans, together with examples of algae thriving in extreme habitats, from snowfields to desert crust to space flights. The last section is dedicated to endosymbiosis and its role in the acquisition of the photosynthetic capacity by the wide variety of photosynthetic eukaryotes nowadays present on earth.

Pages: 29

This chapter focuses on the way algae have shaped the planet we live in today, analyzing the details of their influence on Earth’s biogeochemistry and the roles they played in the past and still play at present in the global biogeochemical cycles. These roles are becoming ever more significant as human impacts on ecosystems result in massive alteration of biogeochemical cycling of chemical elements. Algae are especially important for the biogeochemical cycling of the chemical elements they uptake, assimilate, and produce, such as carbon, oxygen, nitrogen, phosphorus, silicon, iron, and sulfur, which eventually affect the life of all other organisms, man first. In the different sections of this chapter, the biogeochemical cycling processes of these elements are described to understand the interactions between algae, the environment they affect, and other organisms. In addition, we discuss the ecological importance of recycling of the so-called growth-limiting nutrients, that is, those nutrients that can be in short supply, such as nitrate (NO3 -), iron (bioavailable Fe), phosphate (PO4 3-), and dissolved silicon [Si(OH)4], which are most often found in concentrations well below the half-saturation levels required for maximum phytoplankton growth.

Pages: 113

This chapter describes the anatomy of the algal cell from the outside structures to the inside components, giving details only for those structures that are not comparable with analogous structures found in most animals and plants. The description begins with the cell surface, which is not only the border between the external word and the inside of the cell but also a protective barrier preventing free flow of material and allowing interactions with the outside world. The different basic types of cell surface are examined, giving examples of algae possessing them. Flagella and associated structures are then described, with the corresponding internal construction (e.g. axoneme, rods), together with basal bodies and root systems of the different algal groups. Motor apparatus, where present, are correlated to different types of swimming, with examples of peculiar swimming pattern of some algae that have thoroughly investigated in their details by digital microscopy. Since movements are based on exploitation of light information, photoreceptive apparatus are detailed in their universal structural, behavioral, and physiological features, analyzing the photoreception process of Euglena gracilis as example. The anatomical description then proceeds with internal cell components, chloroplasts, nucleus, and organelles that may serve defense purposes or as feeding adjuvants, with detailed examples in the different taxonomic groups.

Pages: 41

This chapter deals with light and the use algae make of it as energy in transduction processes, supported by chloroplasts in photosynthesis. Light characteristics and spectral distribution are essential information to understand how algae convert the energy of radiation into biologically usable energy by means of reduction and oxidation reactions. The photosynthetic process is detailed in its light-dependent and light-independent reactions (e.g. the reaction pathway of the Z scheme and the Calvin Benson Bassham cycle). The different types of pigments are described together with the structure, function, and organization of the two photosystems and of the components of the electron and proton transport chains. The energy relationships along the photosynthetic pathway are clarified in the balance sheet. Absorption spectra in the visible range, from 400 to 700 nm, measured in vivo on photosynthetic compartments (thylakoid membranes, chloroplasts) of single cells belonging to each algal division are presented. The light response curve is discussed to introduce the concepts of light limitation, saturation, acclimation, and inhibition, giving examples of algae thriving in light-limited environments.

Pages: 50

The different culture types are dealt with, analyzing the most important parameters regulating algal growth, that is, nutrient quantity and quality, light, pH, turbulence, salinity and temperature, and their interdependence. The selection of media composition and preparation are discussed, and recipes of most common fresh water and marine media are given, also providing information about culture collections present in the world to refer to in order to have a full range of media not listed in the chapter. The different culture methods used worldwide are presented and described separately for micro- and macroalgae, from lab-scale to commercial-scale cultures, from open to closed systems, from tanks to photobioreactors. A last section is dedicated to the quantitative determination of algal density and growth, analyzing generation time and growth rate.

Pages: 78

Algae have been utilized by man for hundreds of years as food, fodder, remedies, and fertilizers. This chapter explores the many categories of products algae can supply, with examples from the different taxonomic groups. Special attention is given to the so-called functional foods and nutraceuticals, which can reduce the risk of many diseases and promote human health and well-being, such as antioxidant compounds, dietary fibers, polysaccharides, vitamins, and minerals. Harmful algal blooms are then explored because the frequency and extent of these phenomena are globally increasing across the freshwater-to-marine boundaries within estuaries and coastal waters, pointing to a complexity of interplaying causes, such as ongoing eutrophication, new introductions of harmful species, increasing temperature, ecosystem disruption by human-caused nutrient over-enrichment, and global climate changes. Algae can also play an important role as tool for environmental monitoring, since they do reflect the overall water quality, integrating in their metabolism the effects of physical and chemical changes over time. Methodologies used for the analysis of algae present in environmental samples are herein described. Since algae can also act as bio-remediating organisms for heavy metal-contaminated waters and for food industry wastewaters, examples are given of algae applications in this field. The last section of the chapter is dedicated to algae in a bio-based economy; in this panorama, algae have being gaining increasing attention for their huge potential for bio-refinery processing within a circular economy framework, where they are no longer wastes and by-products but co-products, which can also be marketed.

Pages: 36

The characteristics of light as electromagnetic radiation with particle and wave properties are explained, together with the standard units of measure for its characteristic amplitude, wavelength, and frequency. Since during their travel, light waves interact with matter, their behavior differentiates between scattering, which makes the sky blue and the clouds white, and absorption, the process in which light is retained by molecules. Other phenomena related to the two main behaviors are also described, such as interference, reflection, refraction, dispersion diffraction, and fluorescence. Another part of the chapter is dedicated to the description of the most important lab instrument for people working on algae: the microscope. Setup procedures and bright field and fluorescence microscopes are examined, together with the different available light sources and the best criteria to choose them. Digital microscopy, microscopes coupled with digital cameras, special hardware setups and sophisticates image-processing algorithms are detailed for the contributions they can give to the in vivo analysis of metabolic process dynamics of algae under physiological conditions and/or in response to environmental stressors. The last part is dedicated to field instruments, such as PAR detectors, with a lexicon of the terms and conversion units of light measurements necessary to avoid confusing terminology.