Phycology - Kostikov I.Yu. - 2009-2013

Conclusion

Algae are unicellular, colonial, less frequently multicellular, and only occasionally acellular (lacking Cell walls) organisms represented by both prokaryotic and eukaryotic forms. Their sizes range from a few micrometers to tens, and sometimes hundreds, of meters. Prokaryotic algae (cyanoprokaryotes - blue-green algae) lack a true Nucleus (lacking a nuclear membrane), Endoplasmic reticulum, Golgi bodies, microtubules, membrane-bound Organelles such as Mitochondria and Plastids, DNA-histone complexes in Chromosomes, mitosis, and true sexual reproduction.

The Cell Structure of eukaryotic algae is similar to that of higher plants, encompassing all the standard components, yet it exhibits certain deviations from the higher plant structural type, possessing unique features and specific structural traits (such as the diversity in chloroplast types and structures, cell walls, extracellular membranes, and surface coatings).

The presence of various pigments causes A wide variety of colors in algae, resulting in diverse pigmentation (green, blue-green, yellow-green, red, brown, etc.). The Emergence of diverse Photosynthetic Pigments in algae was a major milestone in plant evolution, enabling these organisms to develop and thrive under a wide range of conditions. The primary pigment in algae is chlorophyll "a", although Other forms of chlorophyll ("b", "c") as well as numerous other pigments, such as carotenoids and phycobilins, are found in certain groups. The combination of different pigments enables Photosynthesis (oxygenic photosynthesis) across diverse ecological niches, including varying Water depths and turbidities. Thus, in terms of their mode of Nutrition, algae are predominantly autotrophic; however, they can also exhibit heterotrophic nutrition, utilizing CARBOHYDRATES as a carbon source in the dark. In addition to carbon, some algae are capable of assimilating nitrogen not only from mineral compounds (nitrates) but also from organic sources—amines, Amino Acids—and sometimes even directly from the air (in the case of blue-green algae). Exceptionally, some algae demonstrate holozoic (animal-like), saprophytic, and occasionally parasitic Types of nutrition, though these are secondary traits manifested in the presence of their primary nutritional mode.

To understand these organisms and study their characteristics, the following Methods of phycological research are employed: floristic and systematic (floristic-taxonomic) - the oldest and most time-consuming approach, which involves studying algal diversity, taxonomic affiliation, and systematic hierarchy; morphological - the description of external appearance, shape, coloration, etc.; ontogenetic - The Study of an Organism's developmental history throughout its life cycle; cytological - the investigation of intracellular structures using specialized stains and fixatives via light and Electron Microscopy; ecological - the study of organism-environment interactions, comprising a) descriptive field observations and b) experimental Laboratory studies; physiological - the investigation of physiological processes occurring within living organisms; and molecular-genetic - the study of heredity, Variability, molecular Organization, and structure of living organisms.

Comprehending algae requires grouping and systemizing them based on specific diagnostic features. However, algal Taxonomy is currently in a state of flux. Classification schemes at the higher taxonomic ranks (division, Class) are numerous and often contradictory. Recent insights gained from electron-microscopic, physiological-biochemical, and molecular-biological studies have yielded new data that do not always align with traditional classifications based on classical morphological and physiological traits. Nevertheless, the types of photosynthetic Pigments and Their combinations (complexes), alongside morphological-reproductive, ultrastructural, and certain molecular-Biological features of representative taxa, form The basis of the current classification of algae into divisions. According to the modern System of the organic world and our current understanding of how individual groups are delineated, algae are distributed across 16 divisions.

Algae play a vital role in nature and human life because they: - are primary phototrophic organisms that enriched the atmosphere with oxygen; - are used in wastewater Treatment, as: a) they are photosynthesizers that enrich water with oxygen; b) they are also mixotrophic organisms and thus directly participate in the decomposition of Organic compounds; - serve as bioindicators in: a) biological water analysis (acting alongside other organisms, such as Bacteria and invertebrates, in water self-purification processes; several species are used as indicators of organic water pollution); b) sedimentary rock dating and the Formation of primary humus, which they promote by colonizing rocks; c) forensic practice; - provide raw Materials for industry (marine forms—macrophytes—are used to obtain iodine, bromine, Agar-agar, etc., while filamentous freshwater algae are sources of certain chemical compounds, such as alcohols, ethers, and organic acids, as well as Vitamins (spirulina), Antibiotics, and growth stimulants); - are utilized (both macrophytes and unicellular forms) as a food source for humans on Earth and in closed ecosystems during space travel (simultaneously producing oxygen), as well as livestock feed; - are applied in agriculture: a) through the artificial Introduction of algae into soils (marine algae, certain freshwater green and blue-green filaments, charophytes, and algal biomass responsible for "water bloom"); b) via the targeted cultivation of nitrogen-fixing blue-green algae (cyanoprokaryotes) for soil algalization (in Japan, China, and Uzbekistan), where they fix atmospheric nitrogen, accumulate organic matter in the soil, lock in mineral fertilizers (preventing them from leaching due to rain or irrigation water), and positively impact physical soil properties; - are actively researched to develop agrochemical measures that promote vigorous plant growth; - are used for the industrial extraction of certain rare elements (e.g., gold, silver, etc.) from geological deposits.

Concrete Examples of the Practical significance of algae include the following. Blue-green and red algae, together with corals, have formed and continue to form underwater structures known as reefs. Ancient reefs are closely associated with bauxite ore deposits in the Eastern Sayan Mountains and near the eastern slopes of the Urals (Russia), and particularly with petroleum deposits in Iran, Russia (Bashkortostan), and Ukraine (the Carpathian region).

Well known is the ridge of high (up to 70 m) forest-covered hills stretching from Brody to Kamianets-Podilskyi, known as Medobory. On both sides of this ridge lie the rocky Tovtry hills. These represent an ancient barrier reef built primarily by red Algae in the coastal zone of a warm sea during the latter half of the Tertiary period.

Charophyte algae are crucial for improving the hydrological regime of water bodies, establishing a distinct biocenosis that Supports the abundant growth of epiphytic algae, bacteria, and insect larvae, which in turn serve as an excellent food source for fish. Furthermore, it has been observed that water bodies with dense charophyte growth either lack mosquito larvae entirely or have very low populations. Oospores of charophyte algae serve as food for migratory birds, particularly ducks.

However, algae also exhibit negative impacts, notably: - "water bloom"; - toxicosis and fish mortality or zooplankton die-offs caused by algal metabolites and the consumption of water thus contaminated; - biological corrosion of metals and damage to various materials, particularly in humid tropical climates.