The Gulf of Varna is located on the western coast of the Black Sea and includes the Port and city of Varna. With a population of 340 thousand, the city is the third-largest city in Bulgaria, and it has been a significant economic, social and cultural center for almost three millennia. Evidence shows that the Ancient Greeks settled this site because of the nearshore freshwater resources. Nevertheless, the sources and magnitude of submarine groundwater discharge (SGD) at this and similar sites along the coastline of the Black Sea were hardly investigated. Using radon (²²²Rn) as a tracer during the research done in the fall of 2019 (wet season), hotspots of SGD were identified on the southern shore of the gulf. Results indicate that these are primarily saline seepages. We also found that SGD hot spots were associated with high dissolved P and N, which were found in the eastern part of Varna Lake and Varna Beach (next to the city’s historic center). Correlations were observed between groundwater discharge and the Monstrilla sp. and Lamellibranchia veliger populations. The preliminary data indicate that the magnitude of SGD is affected by hydraulic gradients, and the effect of tidal pumping is negligible. Further, we hypothesize that the local gulf circulation might regulate SGD. Observed high nutrient concentration might be related to leakages from artificial channels connecting the gulf with the Lake of Varna. Several toxic wastewater leaks have been reported, affecting water quality in the gulf.

Primary Presenter: Stanislaw Kurowski, University of Alabama (smkurowski@crimson.ua.edu)

Authors:

Stanislaw Kurowski,   ()

Natasha Dimova,   ()

Valentina Doncheva,   ()