PHYTOPLANKTON DIVERSITY AND PHYSICAL-CHEMICAL ASPECTS OF WATER QUALITY OF LAKE JIQUI, RIO GRANDE DO NORTE, BRAZIL

• Autor(a) principal: Lima, Patrícia Luiza da Silva Carmo de
• Data de Publicação: 2013
• Outros Autores: Pessoa, Emilly Kataline Rodrigues, Chellappa, Sathyabama, Chellappa, Naithirithi T.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Biota Amazônia
• Texto Completo: https://periodicos.unifap.br/index.php/biota/article/view/820

The aim of this study was to evaluate the phytoplankton diversity and water quality of Lake Jiqui on spatial and temporal scales. This freshwater ecosystem is an important source of water supply for the city of Natal and the adjacent municipality Parnamirim, Rio Grande do Norte. The water samples were collected from September, 2008 to August, 2009 at four different sites: lake margin, water catchment area, middle of the lake and a site dominated by rooted and floating macrophytes. The samples were collected from surface and bottom waters during the wet and dry season of an annual cycle. Limnological factors such as temperature, pH, transparency and electrical conductivity were measured in situ. Nutrient variables such as nitrate-nitrogen, ammonium-nitrogen and orthophosphate were analyzed in the laboratory. Chlorophyll a concentrations from the fresh samples were analyzed with 90% acetone extraction in the dark at 4°C in the laboratory. Ecological indices such as diversity, equitability (similarity), and species richness for phytoplankton were calculated. Biochemical Oxygen Demand (BOD)data were obtained from CAERN (Water and Sewage Company of Rio Grande do Norte). Significant results were obtained for limnological parameters on temporal scales (dry and wet season) but not on spatial scales. Phytoplankton diversity was moderate to low on both spatial and temporal scales, with the selected dominance of the species Euglena gracilis, Trachelomonas (Euglenophyceae) and Gomphonema, Navicula cuspidata var. cuspidata, Navicula spp, Rhopalodia gibba and Cyclotella sp (Bacillariophyceae). Chlorophyll a concentrations were low throughout the study period, with a mean of 1.07 µgL-1. Chlorophyll concentration and BOD values remained within allowable water quality limits for human consumption. The Lake Jiqui is considered to be an oligotrophic ecosystem because of low chlorophyll concentrations, high transparency, few species of cyanobacteria and low nutrient content.Keywords:  Phytoplankton; chlorophyll a; water quality; oligotrophic status.