Dynamics of the phytoplankton community and physical and chemical variables in experimental tanks with different organic manure

Abstract

The influence of different types of organic manure in the phytoplankton community is provided. Experiment was undertaken during 40 days in 1000L asbestos tanks. Tanks were fertilized with poultry (PO), pig (PI), cattle (CA) and rabbit (RA) manure, in a randomized design, with four treatments and five replications. First fertilization consisted of 50 g of manure, with 25 g fertilizations at seven-day intervals. Plankton was collected every three days by filtering 250 mL of water in a 20 µm net and fixed in 10 mL formaldehyde 2%. Qualitative and quantitative analysis was undertaken by optic microscope. At the same time, physical and chemical variables were monitored. Highest mean density of phytoplankton was detected with PO on the 40^th day (26,842 org./L), followed by PI (17,164 org./L) on the 22^nd day, RA (8,880 org./L) on the 28^th day and CA (5,564 org./L) on the 22^nd day. Genera Scenedesmus, Cyclotella and Acanthosphaera were predominant. pH values and electrical conductivity oscillated according to changes in phytoplankton densities. PO had the best values of parameters in most collections. Different treatments influenced density of phytoplankton groups. Highest density of algae was obtained by poultry manure, and successively by pig, rabbit and cattle manure