| Title | Why bacteria are smaller in the epilimnion than in the hypolimnion? A hypothesis comparing temperate and tropical lakes |
| Abstract | Bacterial size and morphology are controlled by several factors including predation, viral lysis, UV radiation, and inorganic nutrients. We observed that bacterial biovolume from the hypolimnion of two oligotrophic lakes is larger than that of bacteria living in the layer from surface to 20 m, roughly corresponding to the euphotic/epilimnetic zone. One lake is located in the temperate region at low altitude (Lake Maggiore, Northern Italy) and the other in the tropical region at high altitude (Lake Alchichica, Mexico). The two lakes differ in oxygen, phosphorus and nitrogen concentrations and in the temperature of water column. If we consider the two lakes separately, we risk reducing the explanation of bacterial size variation in the water column to merely regional factors. Comparing the two lakes, can we gather a more general explanation for bacterial biovolume variation. The results showed that small bacteria dominate in the oxygenated, P-limited epilimnetic waters of both lakes, whereas larger cells are more typical of hypolimnetic waters where phosphorus and nitrogen are not limiting. Indeed, temperature per se cannot be invoked as an important factor explaining the different bacterial size in the two zones. Without excluding the top-down control mechanism of bacterial size, our data suggest that the average lower size of bacterial cells in the epilimnion of oligotrophic lakes is controlled by outcompetition over the larger cells at limiting nutrients. |
| Source | Journal of limnology (Online) 71 (1), pp. 104–111 |
| Journal | Journal of limnology (Online) |
| Editor | Istituto per lo Studio degli Ecosistemi, Pavia, Italia |
| Year | 2012 |
| Type | Articolo in rivista |
| DOI | 10.4081/jlimnol.2012.e10 |
| Authors | Hernandez Aviles, Salvador J.; Bertoni, Roberto; Macek, Miroslav; Callieri, Cristiana |
| Text | 220004 2012 10.4081/jlimnol.2012.e10 Why bacteria are smaller in the epilimnion than in the hypolimnion A hypothesis comparing temperate and tropical lakes Hernandez Aviles, Salvador J.; Bertoni, Roberto; Macek, Miroslav; Callieri, Cristiana UNAM, FES Zaragoza, Dpt. of Limnology, Av. Guelatao 66, 09230 Iztapalapa, D.F. Mexico ;CNR ISE, Pallanza Verbania ;UNAM, FES Iztacala, Dpt. of Tropical Limnology, Av. De los Barrios 1, 54090 Tlalnepantla, Edo. Mexico, Mexico ;CNR ISE, Pallanza Verbania Bacterial size and morphology are controlled by several factors including predation, viral lysis, UV radiation, and inorganic nutrients. We observed that bacterial biovolume from the hypolimnion of two oligotrophic lakes is larger than that of bacteria living in the layer from surface to 20 m, roughly corresponding to the euphotic/epilimnetic zone. One lake is located in the temperate region at low altitude Lake Maggiore, Northern Italy and the other in the tropical region at high altitude Lake Alchichica, Mexico . The two lakes differ in oxygen, phosphorus and nitrogen concentrations and in the temperature of water column. If we consider the two lakes separately, we risk reducing the explanation of bacterial size variation in the water column to merely regional factors. Comparing the two lakes, can we gather a more general explanation for bacterial biovolume variation. The results showed that small bacteria dominate in the oxygenated, P limited epilimnetic waters of both lakes, whereas larger cells are more typical of hypolimnetic waters where phosphorus and nitrogen are not limiting. Indeed, temperature per se cannot be invoked as an important factor explaining the different bacterial size in the two zones. Without excluding the top down control mechanism of bacterial size, our data suggest that the average lower size of bacterial cells in the epilimnion of oligotrophic lakes is controlled by outcompetition over the larger cells at limiting nutrients. 71 Why bacteria are smaller in the epilimnion than in the hypolimnion A hypothesis comparing temperate and tropical lakes 2012_A0_007.pdf Articolo in rivista Istituto per lo Studio degli Ecosistemi 1723 8633 Journal of limnology Online Journal of limnology Online J. limnol. Online Journal of limnology. Online roberto.bertoni BERTONI ROBERTO cristiana.callieri CALLIERI CRISTIANA |
