BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

XIV. INSTRUMENTS AND METHODS FOR RESEARCHING AQUATIC VEGETATION

Assessment of the state of aquatic ecosystems based on structural and functional characteristics of macrophytes.

Macrophytes are more conservative indicators of the state of aquatic ecosystems than phyto-, zooplankton, and benthos communities, which consist of small, motile organisms. Except for extreme conditions (salinity, acidic bog waters, heavily polluted or, conversely, clean, oligotrophic waters), upon initial acquaintance with a Water body, their indicative properties are of little information to the researcher. The same species can develop under different environmental conditions due to a wide range of species tolerance, environmental Variability, the leveling effect of leading environmental factors, and compensatory effects.

The aforementioned does not deny the possibility of using macrophytes to assess the state of aquatic ecosystems of various types. This is evidenced, in particular, by

Directive 2000/60/EC [121] (Annex V), which considers macrophytes as an important "quality element for the Classification of ecological status" of natural water bodies and "ecological potential" of heavily modified and artificial water bodies. Under these conditions, for rivers and lakes, higher aquatic plants are recommended to be used as a "biological quality element", while for coastal marine waters with a strong influence of saline waters, marine macroalgae and angiosperms (flowering plants) are recommended. When studying modified and artificial water bodies, it is recommended to use "biological quality elements" based on the characteristics of those types of natural surface water bodies to which the studied water bodies are most similar.

Regarding various types of surface waters in Ukraine, a team of specialists from the Institute of Hydrobiology of the NASU developed a quantitative nine-rank classification of macrophyte development based on three indicators (phytomass, percentage of overgrowth of the water body as a whole, and projective cover within thickets). It can be used as a criteria-based foundation for assessing the degree and nature of macrophyte development.

The indicative properties of aquatic macrophytes should be considered based on the similarity of Structural and functional changes in a group of species (stenobiotic regarding a given factor) during repeated observations. For example, in botanical indication of trophicity in clean water, the indicative properties are demonstrated by the vitality of populations of *Lobelia dortmanna* L., *Isoetes lacustris* L., and *Myriophyllum alterniflorum* DC. The onset of the eutrophication process is indicated by The Development of duckweed. The mass appearance of filamentous Algae also indicates significant eutrophication of the water body, potentially leading to a shift in its productive-functional Organization if anthropogenic pressure persists or increases [103].

Indicators of water current velocity can include *Glyceria fluitans* (L.) R. Br., *Sparganium emersum* Rehm., submerged forms of *Butomus umbellatus*, *Sagittaria sagittifolia*, and certain pondweed species (*Potamogeton perfoliatus*, *P. natans*). Water bodies with mineralized water are characterized by *Zostera marina* L., *Z. noltii* Hornem., *Schoenoplectus litoralis* (Schrad.) Palla, *S. triqueter* (L.) Palla, *S. tabernaemontani* (C.G. Gмеl.) Palla, and others. Eurybionts also well tolerate salinity: *Phragmites australis*, *Najas marina*, *Myriophyllum spicatum*, *Potamogeton pectinatus*, and others. In general, an increase in water mineralization impoverishes the plant species composition. Species with floating leaves are almost never found in mineralized water.

The alternation of sharp decreases and increases in water level triggers the mass appearance, through the completion of a full life cycle, of species such as *Polygonum amphibium* and *Sagittaria sagittifolia*. Indicators of a constant water level and the absence of currents are species of the genus *Utricularia*.

Elevated temperatures are well tolerated by *Myriophyllum spicatum*, *Potamogeton perfoliatus*, *Vallisneria spiralis*, and *Najas marina*.

Ya. Kozina [40] cites data that with a decrease in pH value, reed and bulrush thickets become sparser, and sedges, marsh horsetail, and water mannagrass develop in their place. When the pH drops to 6.8, pondweeds begin to disappear.

Species composition, distribution pattern, Structure of Plant communities, indicators of phytomass, and area of the overgrown water area are markers that visually reveal the ecological state of water bodies. Observations of the dynamics of Qualitative and quantitative indicators of aquatic vegetation development make it possible to determine the direction of aquatic ecosystem succession. Data on vegetation changes can be obtained through observations of the water area of the entire water body or a part of it. Experiments are carried out on stationary plots or transects with clearly fixed boundaries (so that they can be replicated in subsequent years). They are established in areas with Different types of overgrowth at the contact points of phytocenoses. Transects are usually laid out from the shore to the center of the water body. Plots (transects) are mapped regularly (several times a month, season, or annually - depending on the research objectives) with precise plotting of community boundaries and their detailed description; the phenological features of species, their quantitative measurements, and environmental factors are taken into account. Entering (swimming into) the middle of a plot or transect is not recommended so as not to damage the plants. Control samples are collected in adjacent similar areas.

Comparisons are made across all parameters characterizing the community: overgrown areas (total, occupied by a species, ecological group, formation, or vegetation Class); species composition, structure (vertical or horizontal), and production characteristics. Their changes can be seasonal (phenological changes) or multi-annual in nature (fluctuations), caused by changes in climatic conditions, FEATURES OF PLANT biological rhythms, the mass development of animals affecting them, or anthropogenic pressure on the water body and its catchment area. Seasonal changes and fluctuations are chaotic yet reversible. They are regarded as a temporary shift in community structure and contrasted with ecological successions - directional changes caused by external or internal factors that are irreversible in nature. To understand precisely what changes are occurring in communities, long-term observations (at least 5-10 years) are required.

Changes in aquatic vegetation communities are assessed using special mathematical indices: Jaccard and Sørensen indices take into account the number of species in descriptions regardless of their quantitative representation.

Jaccard index: K =

Sørensen index:

where K is the coefficient of community similarity, a and b are the number of species in the compared descriptions, and c is the number of shared species. Species significance (a group of assessments by which species in communities can be compared - projective cover, Abundance, ACM) is accounted for in the coefficient of relative similarity or the Shorygin index:

where p_a is the value of the species expressed in decimal fractions in description A; p_b is the value of the same species in description B [85].