Close but far apart: edaphic communities from mineral and ornithogenic soils from Cierva Point (Antarctic Peninsula)

MATALONI, G.; GONZÁLEZ GARRAZA, G; BÖLTER, M.; CONVEY, P.; FERMANI, P.

Hokkaido University, Sapporo, Hokkaido

Simposio; International Biology Symposium; 2009

Scientific Committee on Antarctic Research

Three mineral soil and four ornithogenic soil sites were sampled along summer 2006 at Cierva Point (ASPA No. 134) in order to study their bacterial, microalgal and faunal communities in relation to physico-chemical features. Humidity, pH, conductivity, organic matter and nutrient concentrations were consistently lower and more homogeneous at mineral soils. Total bacterial number was highly correlated with concentrations of nitrate, organic matter and Chlorophyll-a. Accordingly, ornithogenic soils supported larger and more variable bacterial abundances than mineral ones. Algal communities from mineral soils were more diverse than ornithogenic ones, yet Chlorophyll-a concentrations were significantly higher in ornithogenic soils. This parameter was also correlated with bioavailable N and P, organic matter and pH. Meiofauna from mineral soils was homogeneous, with the nematode Teratocephalus sp. dominating all samples. Its relative abundance was correlated with that of diatoms, the dominating microalgae at this soil type. Fauna from ornithogenic soils varied widely in composition and abundance. The less enriched site O1 hosted a poor community of rotifers and nematodes. Tardigrades and rotifers dominated the meiofauna at eutrophic O2, where they supported a large population of the predator Coomansus gerlachei. At site O3, high bacterial abundances accounted for high densities of the bacterivorous nematodes Plectus spp. Results allowed us to characterise two different soil types on the basis of their edaphic communities. Also, they showed that biotic interactions play an important role in structuring these complex communities. This research was partially funded by the Instituto Antártico Argentino and projects PIP 5356 (CONICET) and UBACYT X864.