PREDICTIVE ASSESSMENT OF THE ECOLOGICAL STATUS OF THE UKRAINIAN SECTOR OF THE BLACK SEA BASED ON CHANGES IN MORPHOFUNCTIONAL INDICATORS OF AUTOTROPHIC COMMUNITIES UNDER THE INFLUENCE OF CLIMATIC FACTORS END THE CONSEQUENCES OF MILITARY ACTIONS (PART 2: FO

Abstract

This study is a logical continuation (Part 2: Forecast) of previous studies by the authors’ team, in which statistically significant relationships were determined between morphofunctional indicators of various life forms of aquatic vegetation of the marine ecosystem of the Odessa region of the northwestern part of the Black Sea (NWBS) and the average monthly volumes of river runoff of the Danube and the Dnipro in the spring months of the year (March-June) for the long-term period since the beginning of the 21st century (Minicheva et al. 2025). Methodologically, the work is based on the study of a functionally related system: river runoff – marine autotrophs – ecological state of the sea, which is used as a logical chain of predictive assessment. The main goal of the second part of the work is to obtain forecast assessments of expected changes of the ecological status class (ESC) categories of marine waters of the NWBS, associated with the impact of changing climate conditions on the runoff of the Danube and the Dnipro rivers in the period up to the 70s of the 21st century, under the RCP8.5 climate scenario. This scenario is based on the fact that by the 60s–70s of the 21st century, one should expect in the spring period: a decrease in the Danube River runoff by an average of 14% according to moderate assessments, and up to 30% according to maximum assessments; a decrease in the Dnipro River runoff by an average of 10% according to moderate assessments (up to 16% in May), and up to 30% according to maximum assessments, compared to the reference period before the beginning of the century. Using classification scales for determining ESC categories according to the standards of the European Water Directives (WFD, MSFD) and calculated, using statistically reliable relationships, values of morphofunctional indicators of macrophytes, microepiphyton, phytoplankton, and satellite data of bloom areas by Chl-a concentration, predictive assessments of expected ESC categories were established under scenario A (moderate reduction in runoff) and scenario B (maximum reduction in runoff) by the 60s–70s of the 21st century. In general, based on morphofunctional indicators of all life forms of autotrophs, predictive assessments of the improvement of ESC categories in the zones of influence of the Danube and the Dnipro rivers for the next 40-year period were obtained. The projected improvement in the ecological status of the Ukrainian sector will be accompanied by positive changes in the development of coastal and shelf vegetation. These trends will contribute to the recovery of valuable Black Sea macrophyte species: in the coastal zone – populations of the brown alga Cystoseira s.l., and in the shelf zone – populations of the red alga Phyllophora Greville. Forecast assessments of changes in the ESC of the marine ecosystem of the NBWS based on the Chl-a indicator showed that by the 60s–70s of the 21st century, there will be a reduction in the area of eutrophicated zones. For the “Poor” category, by -8.4% and -18.8%, and for the “Bad” category, by -16.9% and -29.6%, in accordance with Scenarios A and B, respectively. In addition to climate change, the ESC of the marine system can be significantly affected by active military actions that cause environmental disasters, such as the destruction of the Kakhovka Reservoir dam. As a result of the loss of the regulatory function of the Kakhovka Reservoir, according to a preliminary prognostic assessment based on the S/W index of macrophyte communities, the ESC category in the Dnipro influence zone may decrease from “High” to “Moderate”, and according to the C_e index of microphytes – from “Moderate” to “Poor”. Assessments based on phytoplankton indicators also indicate a possible transition from the “High” to “Moderate” category and increased ecosystem instability.