Late Quaternary dinoflagellate cysts from the Black, Marmara and Aegean seas: variations in assemblages, morphology and paleosalinity

The link between sea surface salinity (SSS) and dinoflagellate cyst morphol ogy was studied quantitatively in cores of Late Quaternary mud from the Bla ck, Marmara and Aegean seas, where oxygen isotopic and planktonic foraminif eral data show salinities of about 5-19, 15-22 and 36-39 ppt, respectively. In the Black Sea, late glacial muds contain low-diversity assemblages of t he cruciform species Spiniferites cruciformis and Pyxidinopsis psilata, wit h most S. cruciformis cysts having expanded septal membranes (form 1: circu lar outline, form 2: irregular). The assemblage is associated with surface salinities of <7 ppt. Overlying sapropelic muds have salinity estimates of similar to 14-18 ppt and contain Lingulodinium machaerophorum-Spiniferites- Cymatiosphaera assemblages, with many L. machaerophorum cysts having short processes and S. cruciformis with reduced septa (forms 3, 4 and 5). The lat e Holocene coccolith-rich sediments, with salinity of similar to 18-20 ppt, have diverse assemblages of Brigantedinium, Peridinium ponticum and other protoperidinioids, together with normal cysts of L machaerophorum and Operc ulodinium centrocarpum (sensu Wall and Dale (1966), Nature 211, 1025-1026) that bear long processes. In the northeast Aegean core, stenohaline species and morphotypes are rare, occurring only as low percentages of S. crucifor mis forms 3 and 4, and O. centrocarpum var. 'truncatum' in a mid-Holocene s apropel that was deposited during a period of high runoff and Black Sea wat er outflow. Marmara Sea cores record surface salinities of 14-18 ppt during late glacial sapropel deposition and 20-22 ppt for the overlying marine se diments. The sapropel is dominated by S. cruciformis forms I and 2 and by P . psilata, with common L. machaerophorum (clavate and normal forms). In sur face sediments, L. machaerophorum is co-dominant with O. centrocarpum (norm al and truncate forms), Brigantedinium and Spiniferites spp. Percentages of S. cruciformis (five forms) and L. machaerophorum (two forms) plotted agai nst proxy-salinity data, however, show no clear correlation, indicating tha t morphological variation is not a simple function of salinity. (C) 2001 El sevier Science B.V. All rights reserved.