Species composition and abundance of microalgae in an antarctic runnel, Reeve Hill, Casey Station, Antarctica.

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Date
2006-04
Authors
Mohd Sidik Merican, Faradina Merican
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Abstract
The ephemeral runnel of Reeve Hill, (66° 16.855'S, 110° 31.045'E) Casey Station, Antarctica forms an impermanent water body which was dominated by Cyanobacterial mats and diatoms. The filamentous Cyanophyta form cohesive mats on the bed of the upper runnel while diatoms showed total dominance in the lower part of the runnel. A total of 21 species ranging from freshwater to marine were recorded from the upper to the lower runnel area. To date, nine species of freshwater algae have been identified at the upper and middle runnel which includes Oscillatoria fracta, Oscil/atoria sp., Navicula muticopsis, Pinnularia borealis, Nitzschia sp., Prasiola crispa, Chlorococcum sp., Synechococcus aeruginosus and Synechococcus maior. The species diversity was higher in the upper runnel compared to the middle runnel. Species composition however changes along the length of the runnel. Due to intrusion of sea water, samples of the lower runnel were dominated mainly by marine Bacillariophytes. The most abundant species was the Corethron criophilum which was spotted in high numbers in every sample examined. Other species detected- includes Fragilaria kerguelensis, Fragi/aria linearis, Eucampia antarctica, Thalassiosira tumida, Pseudonitzschia lineola, Pseudonitzschia turgiduloides, Achnanthes brevipes and Odontel/a litigiosa. Diversity analysis performed using Shannon's Index indicated highest species diversity in the lower runnel (H=2.485) while the middle runnel showed the lowest value (H=2.079). Similarity analysis performed using both Jaccard and S0renson ,. Index indicated that the algal community of the upper runnel was very similar to the community present in the middle runnel (Jaccard lndex=0.889 and S0renson lndex=0.941). However, there were no mutual resemblance of the algal species between the lower runnel and the other two sites. Diversity gradient has been used as an argument to explain the variation in species richness and diversity observed in the study. An attempt to discuss the distribution of algal species in a wider scale was made by looking into the significant contributions of this very simplified ecosystem towards understanding the global diversity pattern.
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Antarctic runnel, Reeve Hill , Casey Station, Antarctica
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