This book is divided into three thematic areas. The first covers a revision of the taxonomy of algae, based on the algae portal, as well as the general aspects of biology and the methodologies used in this branch of marine biology. The second subject area focuses on the use of algae in environmental assessment, with an intensive implementation in Western economies and some emerging economies. The third topic is the potential use of algae in various industries including food, pharmaceuticals, cosmetics, agricultural fertilizers, and the emerging biofuels industries. Marine algae: General aspects, taxonomy, biology, field and lab techniques. Marine macro algae communities under natural conditions: Problems and possible approaches for the establishment of reference conditions. The multi-facets of opportunistic macroalgae: A brief review. Marine macroalgae and assessment of ecological conditions. Exotic and invasive species: Case studies. Marine algae as carbon sinks and allies to combat global warming. Marine micro algae (toxic algae). Review of marine algae as a source of bioactive metabolites. Analysis by vibrational spectroscopy of seaweed with potential use in food, pharmaceutical, and cosmetic industries. Marine algae culture: techniques, uses, perspectives. Cultivation problems and the impacts of a commercial extract of the brown seaweed Ascophyllum nodosum. Marine algae and the global food industry. Marine algae and human health. Applications of macro algae in animal feeds. Marine algae vs biofuels. Economically successful histories of macro algae uses. Internet information resources for marine algae.