ASSESSMENT OF BEST DATA SET FOR STATISTICAL ANALYSIS OF COCCOLITHOPHORE DISTRIBUTION IN THE ARGENTINA CONTINENTAL MARGIN

Abstract

Coccolithophore thanatocoenosis from 33 surface sediment samples in the Argentina Continental Margin were analyzed. Emiliania huxleyi, the most ubiquitous species in today´s ocean, occurs at relative abundances higher than 60% and tends to obscure the variations in abundance of less represented species. This study aims to compare two intensively used counting methods in coccolithophore studies: including and excluding E. huxleyi from the data set and compare which of both methodologies better reflects the known oceanographic conditions in the area. In the two data sets, species abundances were converted to percentages and Clusters Analysis were performed. The result including E. huxleyi reveals two groups (A and B) separated of compositional Euclidean distance of 12.8. Group A is restricted to the southeastern area (near Malvinas Islands) and is dominated by Gephyrocapsa muellerae (> 56%). Group B is dominated by E. huxleyi (> 93%) and is distributed into two areas: in the southwest (near Tierra del Fuego) and in the north (between 40°S – 47°S). The result excluding E. huxleyi also shows two groups (A’ and B’) distant to a compositional Euclidean distance of 15.8. Group A’ has both a southern and northern distribution, whereas Group B’ is present only at the northern area. These two groups cannot be explained by the relation between the coccolithophore taxa dominance and the surface oceanographic conditions. Our results indicate that the inclusion of E. huxleyi is the most appropriate approach since it seems to better correlate with the known oceanographic regime in the Argentina Continental Margin.

Keywords

• Calcareous nannoplankton
• Counting methodology
• Data analysis
• Surface sediment
• Southwest Atlantic Ocean