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Distribution and abundance of pteropods in the western Barents Sea

Kacprzak P., Panasiuk A., Wawrzynek J., Weydmann A.

Oceanological and Hydrobiological Studies

2017

Vol. 46, No. 4

393--404

The abundance and horizontal distribution of three pteropod species, Limacina helicina, Limacina retroversa and Clione limacina were examined in the western entrance of the Barents Sea (Polar Front region) in August 2011. Sixteen samples were collected from 8 sampling sites located along a latitudinal transect. The southern part of the study area (south of 73°N) was dominated by L. retroversa, while L. helicina was mostly observed north of 73°N. Surface water temperature differences between the coldest and the warmest station were around 8°C. The highest density of L. retroversa was found in the south, near the Norwegian coast (nearly 52 000 ind. 1000 m−3), while the highest density of L. helicina was observed in the region of the Arctic water masses (nearly 13 000 ind. 1000 m−3). The sampled population of pteropods comprised mainly juvenile stages. Redundancy analysis (RDA) of the relationships between environmental factors (mean and surface salinity, mean temperature, sampling depth, chlorophyll concentration) and the population structure showed that mean temperature was the most important factor in the study area, explaining 70.5% of the pteropod community variation.

Early Pliocene heteropods and pteropods (Mollusca, Gastropoda) from Santa Maria Island (Azores, Portugal) : systematics and biostratigraphic implications

Janssen A., Kroh A., Avila S.

Acta Geologica Polonica

2008

Vol. 58, no. 3

355-369

A holoplanktonic mollusc assemblage from Neogene sediments of the Azorean island Santa Maria is described and analysed to determine the age of the sediments. Sixteen taxa are documented (three heteropods, thirteen pteropods), fourteen of which are new records for the fossil fauna of Santa Maria Island. The composition of the heteropod and pteropod assemblage indicates a Zanclean age, which contrasts with earlier age assignments to the Early, Middle or Late Miocene based on benthic molluscs, but is in good agreement with more recent data based on foraminiferal and geochemical evidence. The pteropod Cavolinia marginata (BRONN, 1862) is re-described based on abundant topotypic material and a neotype is designated. The species Cavolinia vendryesiana (GUPPY, 1873) is considered to be a junior subjective synonym of C. marginata. The temporal range of the pteropod Limacina trochiformis (D.ORBIGNY, 1836) is extended to the Zanclean.