Foraminifera From Atarctic Glaciers: its Distribution Related to Environmental Factors

The present investigation is an attempt to understand which abiotic parameters of the bottom water (depth, salinity, temperature, conductivity and density) might be the controlling factor to describe recent foraminifera fauna associated to glaciers environments from two antarctic islands (King George and Elephant islands). The principal component analyses (PCA) of the environmental data reveals a marked environmental gradient, with 90.1% of the cumulative percentage variation explained by the first two principal components. The coefficients of the linear combinations of environmental variables show temperature and conductivity factors as the largest positive loadings on PC1, and high negative for density, salinity and depth. The PC2 axis is characterized by positive loadings for all variables, showing the strongest positive loading for conductivity on this axis. A plot of PC1 versus PC2 scores reveals 4 distinct groups: Group I includes G5, G6, G7, G8, and G11 stations with negative scores on both principal components, suggest lower temperature and conductivity with high values salinity, density from deeper sites. Group II includes G10 and G12 stations that have negative scores on PC1 and positive scores on PC2, reflecting deeper environments with low temperature and conductivity and intermediate salinity. Group III includes G2 and G9 stations which have positive scores on PC1 and negative scores on PC2 and they have high temperature and conductivity in shallow environments with low salinity and density values. Group IV includes G13, G14 and G15 stations with positive scores on both principal components reflecting environments with intermediate depths and lower salinities. The most ecologically meaningful pattern obtained in the Multi-Dimentional Scaling (MDS) ordination of the data by foraminiferal species reveals three facies (A, B and C). The assemblage associated with MDS A is dominated by Hemisphaerammina bradyi (3.16%, average relative abundance) and Quinqueloculina patagonica (2.67%) from one of the shallowest sites. MDS B is associated to Globocassidulina biora (53.92%), Globocassidulina subglobosa (7.53%), Psammosphaera fusca (5.95%), Buccella peruviana (4.62%), Quinqueloculina seminulum (2.55%) and Miliammina arenacea (2.19%) and is related to sites deeper than 25 meters with lower temperatures and higher salinities. MDS C contains Portatrochammina antarctica (4.86%), Bolivina pseudopunctata (2.31%), Cassidulinoides parkerianus (2.07%) and Hippocrepinella hirudinea (1.82%) characteristic of higher temperature environments. Our data suggest that the main controlling factors of the twelve dominate species are temperature and depth.