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23Micropalaeontological studies of the Black Sea, including ostracod records, have 24 suggested that early Holocene salinity values were between ~5-10 psu, contrasting 25 with present values of 18-22 psu. However, more precise palaeoenvironmental 26 reconstructions based on ostracod assemblages require additional information 27 related to their modern ecological affinities. This study uses modern species 28 information collected from samples with living fauna to interpret the fossil Holocene 29 assemblages of two sediment cores, Ak-2575 and Ak-521 collected from the north-30 eastern outer shelf of the Black Sea. A total of 37 ostracod species are recorded in 31 the fossil assemblages, with two related to freshwater/oligohaline environments, 23 32 from Caspian-type environments, and 12 from environments similar to the 33 Mediterranean. Three distinct assemblage zones are identified from Caspian-type 34 dominating in the early Holocene up to 7.4 cal ka BP, a mixed assemblage of 35 Caspian-type and Mediterranean type from 7.4 to 6.8 cal ka BP and a progressive 36 dominance of Mediterranean species from 6.8 cal ka BP. It is very likely that the 37 dominant control of ostracod species occurrence during the period up to ~6.8 cal ka 38 BP is salinity. A range of factors including temperature, biotope and sedimentation 39 rates influenced the species distribution over the last 6.8 cal ka BP.40 41

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