Seasonal variability of periphyton nutrient status and biomass on artificial and natural substrates in a tropical mesotrophic reservoir

Abstract

AIM: Study aimed at evaluating the periphytic community seasonal variation, nutrient status and biomass on artificial and natural (Nymphaea spp., Utricularia foliosa Linnaeus) substrates at a shallow mesotrophic reservoir (Ninfeias Reservoir) located in the Parque Estadual das Fontes do Ipiranga, Sao Paulo, southeast Brazil; METHODS: Samplings for physical, chemical and biological characteristics was performed in winter (August-2006), spring (October-2006), summer (January-2007) and autumn (April-2007). Periphyton was collected growing on artificial (microscope glass slides, 28 days colonization) and natural substrate (Nymphaea spp. and Utricularia foliosa). Periphyton attributes studied were: chlorophyll a, dry mass, ash free dry mass, and N and P content; RESULTS: During the study period was recorded the highest values of water transparency and DO in the winter, PO4-P and free CO2 in the spring, temperature and phytoplankton biomass in summer and autumn of DIN. The highest biomass values were recorded in winter and autumn. Periphyton P and N content varied seasonally on the substrates. Nymphaea spp. had the highest periphyton P content in summer, while U. foliosa and artificial substrate presented in the spring. Higher periphyton N content in Nymphaea spp., U foliosa and artificial substrate was recorded in the spring, winter and autumn, respectively. Periphyton and water ratio N: P molar indicated P-limitation, except the water in the spring (N-limitation). CONCLUSION: Periphyton N and P content and biomass variation was controlled by the seasonal scale. However, the microhabitat type seems to influence the periphyton nutrient status, especially in low nutrient availability in the environment.