Abstract
Aim:
We identified and analyzed the developmental phases (exponential and loss) of periphyton on artificial substrates based on biomass accrual rate in dry and rainy seasons in a shallow mesotrophic reservoir (Ninfeias Reservoir, Parque Estadual das Fontes do Ipiranga, São Paulo, Brazil). We evaluated the colonization time required for the developmental phase to change, as well as related limnological variables.
Methods
Samplings were carried out weekly, totaling 98 days of substrates exposure. We analyzed the limnological and periphyton variables (chlorophyll a, ash free dry mass, net and gross accrual rate).
Results
Maximum biomass occurred on the 42nd day in rainy season and on the 98th day in dry season. In the rainy season, the exponential phase of biomass accrual continued until the 28th day of colonization, followed by a fluctuation phase (35th to 77th day) and then a loss phase (84th to 98th days). In the dry season, the exponential phase continued until the 35th day, followed by a loss phase (42th to 63rd day) and then a fluctuation phase (70th and 77th day). In the same season, we observed the beginning of a new exponential phase (84th to 98th day). The biomass peak was recorded on the 42nd colonization day in the rainy season and on the 98th day in the dry season. Biomass and gross and net accrual were higher in the dry season than in the rainy season.
Conclusions
Periphyton biomass and net and gross accrual rates were higher during the dry season, which was characterized by high total nitrogen concentration, water transparency and low rainfall. We concluded that periphyton biomass accrual and the duration of the developmental phases (exponential, loss and fluctuation) changed with variations in limnological conditions in each climatic period in the tropical shallow reservoir studied.
Keywords:
artificial substrates; ash free dry mass; chlorophyll a; gross and net accrual rate
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