Factors affecting the horizontal patchiness of coastal Antarctic seawater bacteria

Previous Antarctic studies have pointed out the ecological importance of ornithogenic soils. However, few data exist to determine the impact of the bird's manuring on surrounding seawater microbial populations. In order to evaluate the influence of birds manuring, the relationships between the spatial distributions of seawater bacterial microflora and some related biological (chlorophyll pigments) and physicochemical (seston, NH4 + & NO3 −) parameters were studied during the Antarctic summer 1988 in the Terre Adelie land area. The clearly decreasing gradient from the shore towards the open sea previously reported for bacterial microflora (from 104 to 1 CFU ml−1 for heterotrophic bacteria and from 105 to 5.0103 cells ml−1 for total bacteria) was also observed for organic and mineral nutrients (from 1.09 mg Cl−1 to 0.1 mg Cl−1 for POC and from 196 to 17 μmole l−1 for NH 4 + ) but not for chlorophyll pigments. The absence of any observable phytoplankton enrichment in the coastal area suggests a direct interaction between the birds manuring and the bacterial seawater microflora.