Amanda R. Chiaramonte, André V.F. Faria, Estela M. Plastino
Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, 05508-090, São Paulo, Brasil
The increase in global temperature has been proving to have an impact on aquatic environments. The thermal limits of a species are determined by its genetics, that is, by its adaptability and acclimation capacity. Genotypic variations related to adaptation can result in populations with quite diverse genetic pools. Gracilaria caudata is an agarophyte that occurs on almost the entire Brazilian coast, and therefore subject to great climatic diversity. Thus, questions are raised related to the thermal tolerance of the species and the putative occurrence of ecotypes. We evaluated the effect of different temperatures (15-35°C) on growth rates (GRs), thalli length, and photosynthesis of female gametophytes from four populations distributed along 6,024km of the Brazilian coast: Ceará State (CE, 3.23°S), Bahia State (BA, 12.44°S), Espírito Santo State (ES, 20.48°S) and Santa Catarina State (SC, 27.11°S). The temperature of 35ºC was lethal for all of them. BA population showed the highest temperature range survival (15-33°C) when compared to the others (CE, 18-33°C; ES, 15-30°C; SC, 18-30°C). The temperatures that promoted the highest GRs varied among almost all populations (CE and BA, 23-30°C; ES, 25-28°C; SC, 23-28°C). CE population showed the highest GRs (10.85-11.83%), followed by ES (9.80-10.63%), SC (8.28-9.15%) and BA (7.23-9.15%). CE showed higher maximum quantum yield when compared to SC population in almost all of conditions; the farther also showed higher thalli length, and BA and ES showed intermediate values. Our results allow us to affirm that these are ecotypic populations and they may react differently to the global changes.