Phytoplankton seasonal variation in a shallow stratified eutrophic reservoir (Garças Pond, Brazil)

• Autor(a) principal: Bicudo, Carlos Eduardo de Mattos
• Data de Publicação: 2007
• Outros Autores: Fonseca, Bárbara
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UCB
• Texto Completo: http://twingo.ucb.br:8080/jspui/handle/10869/713; https://repositorio.ucb.br:9443/jspui/handle/123456789/7892
• topic: Algas de águas continentais; Dinâmica de comunidade; Fitoplâncton; Reservatório; Sinecologia

This study aimed at describing the phytoplankton dynamics and structure in a shallow eutrophic reservoir, the Garc¸as Pond, located in the Parque Estadual das Fontes do Ipiranga (23 38040.600 S, 46 37028.000 W), in the Municipality of Sa˜o Paulo, southeast Brazil. Samples were collected monthly from January to December 1997 in five depths (subsurface, 1 m, 2 m, 3 m, and 20 cm above the bottom) in the pelagic zone (Zmax = 4.7 m). Abiotic variables studied were: water temperature, turbidity, transparency, conductivity, pH, dissolved oxygen, alkalinity, inorganic carbon, and N and P dissolved and total forms. Altogether 236 phytoplankton taxa distributed among 10 classes were identified. Phytoplankton seasonal and vertical variation was related to shifts in the water chemical features as a consequence of a warm-wet season with stratified water column (phase 1, January–March and September– December) alternating with a cool-dry season with mixed water column (phase 2, April–August). There were shifts in cyanobacterial dominance over the entire year. During phase 1, Raphidiopsis/Cylindrospermopsis was one of the most important taxon. During phase 2, Raphidiopsis/Cylindrospermopsis biomass decreased, whereas richness and diversity increased and diatoms were relatively abundant. In September, when the water column was markedly stratified, a cyanobacterial bloom (Sphaerocavum brasiliense) occurred. Changes in water chemical variables caused by the bloom allowed recognition of a phase 3, in which pH and chlorophyll a, TP and CO3 2- concentration reached their highest values. According to Reynolds and collaborators’ functional groups approach, phase 1 was marked by groups S/ W1/W2/H1/Y, phase 2 by groups K/LM/LO/D/P/X1/ F, and phase 3 by group M. This sequence was corroborated by canonical correspondence analysis (CCA) results.