INVESTIGADORES
O'FARRELL Ines
congresos y reuniones científicas
Título:
Morphological plasticity of cyanobacterial under different light underwater climates in a pristine natural wetland (Natural Otamendi Reserve, Argentina)
Autor/es:
DE TEZANOS PINTO; O'FARRELL
Lugar:
Sapanca, Turquía
Reunión:
Workshop; 14 th Workshop of the International Association Phytoplankton and Ecology; 2004
Resumen:
“MORPHOLOGICAL PLASTICITY OF CYANOBACTERIA UNDER DIFFERENT LIGHT UNDERWATER CLIMATES IN A PRISTINE NATURAL WETLAND (NATURAL OTAMENDI RESERVE, ARGENTINA)” Paula de Tezanos Pinto and Inés O’Farrell Lab. Limnología, Dpto. Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. CONICET A short-term mesocosm-scale experiment was performed at the Otamendi Natural Ecological Reserve (Buenos Aires, Argentina) in late spring 2003 in order to assess the phytoplankton response to light limitation. In the wetland most extreme light environments the following treatments were assayed: T1, dense intact floating macrophyte cover, the same as the natural system; T2, removal of floating vegetation and addition of a dark mesh to simulate T1 light attenuation; T3, removal of the floating macrophyte cover. Light underwater climates within mesocosms ranged from less than <50 µmol photon m-2 s-1 in T1 and T2 to irradiances greater than 800 µmol photon m-2 s-1 in T3. Initial experimental conditions revealed a phytoplankton community dominated (69-77%) by Planktolyngbya limnetica, Planktothrix agardhii and Cylindrospermopsis raciborskii. This assemblage of shade adapted filamentous cyanobacteria was characterized by optically thin (diameter <3 μm) and straight trichomes with high surface to volume ratio and in particular in P. agardhii and C. raciborskii also by the presence of gas vacuoles. In order to assess if light availability affected the species morphology, the following parameters were measured: trichome length (L), trichome volume (V), trichome length/diameter (L/D), surface/volume (S/V) and presence of gas vacuoles for several individuals of each species for each sampling date and each treatment. Initial values of the studied morphological parameters for P. limnetica were: L: 33-38 μm, V: 26-30 μm3, L/D: 33-38 and S/V: 4 μm–1; for P. agardhii L: 49-53 μm, V: 349-372 μm3, L/D: 16,5-17,5 and S/V: 1,4 μm–1; and for C. raciborskii L: 77-91 μm, V: 546-645 μm3, L/D: 26-30 and S/V: 1,35 μm–1. By the end of the experiment, P. agardhii and C. raciborskii specimens were longer in situations of no light attenuation (T3: 101 and 95 μm respectively) than under dim light conditions (T1: 47,5-69 μm respectively and T2: 66-94 μm respectively). The same trend was registered for V and L/D and was inverse for S/V. P. limnetica, morphological parameters remained similar in all treatments throughout the experiment (L(120h): 35, 39 and 31; V(120h): 27, 31 and 25). Trichomes of P. agardhii and C. raciborskii in T1 and T2 presented gas vacuoles throughout the experiment allowing specimens to remain in the upper centimetres were light constraints were probably lessened. Contrarily, in T3 most specimens did not present gas vacuoles by the end of the experiment.