Spiniferites cruciformis: a fresh water dinoflagellate cyst?

Palynological studies of cored lacustrine sediments from the late Quaternar y of Lake Kastoria, northern Greece, revealed a Late Glacial interval with abundant dinoflagellate cysts. Cyst assemblages include two identifiable sp ecies, Spiniferites cruciformis and Gonyaulax apiculata. The presence of th e fresh water species G. apiculata is consistent with the lacustrine settin g of these deposits, but that of S. cruciformis is anomalous. Previously, t his species has only been recorded in abundance from presumed brackish mari ne sediments from the Black Sea and Marmara Sea sediments where geochemical data clearly record brackish salinities. Therefore, it has been regarded a s a low salinity cyst type with a wide range of morphological variation tha t some workers have suggested to reflect salinity fluctuations. Specimens f rom Greece display only part of the range of morphological variability prev iously described from these (brackish) marine settings. Encountered morphol ogical variation includes ellipsoidal/pentameral and cruciform endocyst sha pes with rare intermediate shapes, and highly variable septa development. S pecimens characterized by extremely reduced ornamentation known from (brack ish) marine environments have not been recorded. Our records of S. crucifor mis indicate that: (1) it could thrive in fresh water conditions; and (2) t hat apparently most of the strong morphological variations of the cysts are an intrinsic phenomenon for this taxon, and may only partly be linked to s alinity variations as suggested earlier. We suggest that S. cruciformis ess entially is a fresh water taxon, and that its records in (brackish) marine environments, with the exception of specimens with strongly reduced ornamen tation, may be due to transportation, to short-lived fresh water surface co nditions in such environments, or to tolerance of the species to brackish c onditions. (C) 2001 Elsevier Science B.V. All rights reserved.