The biogeochemical response of the north-western Black Sea to the Kakhovka Dam breach

Abstract The Kakhovka Dam explosion is an example of the far-reaching environmental consequences of warfare. The resulting dam collapse released some 14.4 billion cubic meters of water, flooding downstream environments and flushing unknown quantities of debris, pollutants and sediments into the north-western Black Sea. With a combined satellite and hydrological modelling approach, supported with in situ data, we assessed the short-term impact on the north-western Black Sea. The dam breach impacted more than 50% of the area of the north-western Black Sea, experiencing over 50 times the ambient Chlorophyll- a and suspended sediment concentrations. Significant increases of nitrate and phosphate were also observed in the Odesa coastal environment. This environmental shock triggered severe algal blooms within one week, that persisted for a further 20 days. This event may have impacted the biodiversity of the north-western Black Sea and its ecosystem response. Continued monitoring is required to assess the longer-term impacts.