Assessment of the Reactions of Algal Communities t< Influence of Climatic Factors in the North-Western Blacl Sea Ecosystem*

摘要

The paper gives an overview of methodological problems (i.e., methods and indicators) in assessing the reactions of algae communities to climatic factors. We discuss the resistance of algal communities to the fluctuations and anomalous impact of climatic factors (solar energy flow, water temperature, precipitation, and river runoff) with reference to various life forms of Black Sea algae. To assess the reaction of algal communities impacted by climatic factors, a number of methodological approaches are proposed. It is necessary to carry out a comparison of the variability of both climatic factors and plant communities at appropriate levels of organization in natural systems (local, regional, and global). The changeability of climatic factors and algal communities must be measured using unified methods and indicators (variability, anomalies, etc.), and within the same time intervals (monthly, seasonally, and annually). Authors propose to use the ratio of oscillation coefficients (Fr, %) for the structural-functional parameters of algal communities, and climatic factor indices: (^lUgaecommtnities/^R) climatic factors, as a measure of "stability" in different life forms of algae. For a sound conclusion about the significant impact of climatic factorson plant communities, we proposed to use the criterion of a significant (more than 30%) deviation of structural-functional parameters of algae communities from several years on a regional level. Analysis of the original results of both long-term observations (1997-2016) and the model period (2008-2009) made it possible to assess the stability of macrophytobenthos, phytoplankton, and microepiphyton to fluctuations in climatic factors, as well as their anomalous manifestations. High-natural stability ofalgal communities of the northwestern part of the Black Sea (NWBS) ecosystems to variability of climatic factors, as well as the synchronism of anomalous reactions of algae with anomalous climatic conditions is noted. It includes intra- and inter-annualsynchronicity of the oscillation coefficient (KR, %) of climatic factors (water temperature, solar energy flow) and morphofunctional parameters of algae (phytobenthos, phytoplankton, and epiphyton). Cases ofviolation to such synchronism may indicate the effect of a group of third factors not related to climatic conditions, for example, changes in nutrient concentrations, biotope disturbance, etc. For the period of 1978-2016, synchronicity of the dynamics between climatic anomalies and structural-functional parameters of algal communities of the NWBS was recorded. Annual anomalies of climatic factors, exceeding 20% of the regional norm, cause evident restructuring of algal communities. Particularly strong anomalous reactions of plant communities (35-60% from the regional norm) were recorded in 2002-2003 under the long-term anomaly of water temperature and in 2010 under combination of high anomalies of two factors: the Danube runoff (45%) and water temperature (22%).