Influence of different levels of pond water alkalinity on the growth of Prochilodus lineatus larvae

Abstract

The relations between alkalinity and other chemical variables play an important role in the global productivity of aquatic ecosystems, due to their influence on vital chemical and physiological processes. Liming procedures, that alter water alkalinity, promote a biological reorganization, frequently resulting in favorable response of the biota in a short period of time. Thus, the growth of curimbatá (Prochilodus lineatus Valenciennes, 1836, Characiformes, Prochilodontidae) larvae and limnological variables were studied in ponds with different levels of water alkalinity. The experiment was carried out over a period of 60 days and consisted of three treatments: A - without any correction of natural alkalinity; B í  with weekly alkalinity correction to 30 mg CaCO₃/L; C í  with weekly alkalinity correction to 60 mg CaCO₃/L, each one with two repetitions. The following variables were monitored: maximum and minimum air and water temperature, alkalinity, hardness, calcium, pH, conductivity, dissolved oxygen, suspended solids, transparency, ammonia, nitrite, nitrate, total phosphorus, dissolved phosphate, chlorophyll a and organic fraction weight of zooplankton. The growth in total length and dry weight was determined, as well as the relation between dry weight and total length of the larvae in the different treatments. The results indicate that the maintenance of curimbatá larvae under mean alkalinity value of 34.67 ± 3.75 mg CaCO₃/L (treatment B), which provides mean calcium value of 4.68 ± 0.97 mg Ca⁺²/L, is recommended for promoting better larvae performance in growth and more appropriate limnological conditions.