Distribution of dinoflagellate cysts and other aquatic palynomorphs in surface sediments from the Beagle Channel, Southern Argentina

Abstract

Palynological analyses of 22 surface sediment samples from the Beagle Channel, Tierra del Fuego, Argentina, were performed in order to investigate the distribution of dinocyst assemblages and other aquatic palynomorphs and to explore their relationships with sea-surface conditions, which are regionally characterized by cold and low salinity conditions (4-9. °C and 27-33.5, respectively). Results show relatively low dinocyst concentrations (253 to 5568. cysts/g) and species diversity (19 taxa identified). The assemblages are mostly composed of Protoperidiniaceae and appear typical of a marginal marine environment with surface waters characterized by low to moderate salinity and high nutrient content due to river inputs. The assemblages are thus compatible with the occurrence of freshwater to brackish water taxa Botryococcus braunii, Botryococcus sp., Polyasterias sp., Halodinium sp., and Radiosperma corbiferum. The dinocyst assemblages are dominated by Brigantedinium spp., Echinidinium spp. and Selenopemphix quanta accompanied by cysts of Pentapharsodinium dalei, Islandinium minutum, Votadinium spinosum, Polykrikos kofoidii and Polykrikos schwartzii. The assemblages from the Beagle Channel show similarities with those of high latitude regions of the Northern Hemisphere. However, some taxa, which were exclusively reported from relatively warm environments in the Northern Hemisphere, occur in relatively high percentages in the Beagle Channel (e.g. Echinidinium delicatum and Votadinium spinosum). The absence of Selenopemphix antarctica in the Beagle Channel is consistent with its known ecological affinities, since it characterizes environments marked by seasonal sea-ice cover.