Buffering Efficiency of Phytoplankton on Acidic Borehole Water for Fish Production in Port Harcourt, Nigeria

Low water pH has been a major problem affecting growth and profitability of aquaculture in Port Harcourt, Rivers State, Nigeria. In recent times, organic agriculture is being advocated for safe and healthy food thus alternative buffer agent is necessary to combat this challenge in order to boost fish production. Based on this, a study was conductedat the Aquaculture Centre of the Department of Fisheries and Aquatic Environment, Rivers State University, Port Harcourt, Nigeria, to determine buffering efficiency of phytoplankton on pH and other water quality parameters. Fifteen (15), 18-litre shaded plastic tanks (3/4- filled, pH 4.48) of three replicates per treatment of 0litre (T0), 1 litre (T1), 2 litres (T2), 3 litres (T3) and 4 litres (T4) of green water containing phytoplankton were used. These tanks were screened with plastic net to keep off mosquitoes and other unwanted objects throughout the study. Dissolved oxygen, pH, temperature, total dissolved solids, electrical conductivity, alkalinity and ammonium of water were measured once daily (morning) for 25 days using standard methods. Phytoplankton were analysed microscopically and its density was calculated following standard method. Data were subjected to analysis of variance and descriptive statistics using Microsoft Excel.Some photosynthetic species in families of Chlorophyceae, Cyanophyceae, Eugleneophyceae, Pyrrophyceae and Xanthophyceaewere observed. These might be responsible for the recorded pH values. pH values ranged between 4.76 (T0) and 6.10 (T4) within five days though not within the acceptable range (6.0-9.0) for fish production except T4. This study therefore recommends the use of at least 4 litres of green water containing phytoplankton as organic source of buffer for treatment of 14 litres of acidic water for minimum of five days for aquaculture.It is free of cost and safe for fish production and human consumption.