Ecological productivity of Lake Tinishu Abaya in relation to photosynthetic productivity and biomass of phytoplankton, Rift Valley, Ethiopia

Abstract

The present study was undertaken to investigate the photosynthetic productivity and biomass of phytoplankton with respect to changes in various physicochemical factors for Lake Tinishu Abaya (Ethiopia) to observe the potentiality of the lake water for fish production and other multiple designated water uses. The study was carried out for a year from January to December 2016. For the analysis of various physicochemical parameters, water samples collection was taken from two pre defined sampling stations (open-water and near shore). Biomass of phytoplankton was measured as concentration of chlorophyll a. Primary productivity of phytoplankton was measured at the open station in the euphotic depth using light-dark bottle technique with measuring O 2 concentration and its value was converted to carbon contents. It was observed from the results that the light-saturated rate of photosynthesis (A max), ranged from 0.62 g C m-3 h-1 to 2.02 g C m-3 h-1 and Biomassspecific rate of photosynthetic productivity at light saturation (P max) ranged from 0.02 g C (mg Chl a)-1 h-1) to 0.106 g C (mg Chl a)-1 h-1). The hourly integral photosynthetic production (∑A), varied between 0.247 g C m-2 h-1 and 1.022 g C m-2 h-1 , whereas the calculated pattern of variation for the daily integral rates of photosynthesis (ΣΣA) values was ranged from a minimum of 5.43 g C m-2 d-1 to a maximum of 9.194 g C m-2 d-1. The concentration of phytoplankton biomass (chlorophyll-a) was varied from a minimum of 18.97mg/L to a maximum of 65.05 mg/L. The various physicochemical factors responsible for the observed temporal variations in the physical, chemical and biological features of the lake are discussed and generalized that the lake water was well oxygenated, slightly warm, alkaline, contained more TSS, and EC, very turbid and low transparency. The lake water was fresh based on TDS value. Most of the inorganic nutrients were relatively higher and supports most aquatic lives. Based on the results of the study on various physicochemical factors, photosynthetic productivity and biomass of phytoplankton, it was concluded that the water of Lake Tinishu Abaya was a productive which supports the life of most aquatic lives, production of fish, and other related multidimensional uses.

Pengaruh Parameter Lingkungan Terhadap Kandungan Senyawa Organik Danau Maninjau Sumatera Barat

“…Hal ini menunjukkan bahwa konsentrasi BOD5 dan COD memiliki korelasi yang kuat dan berbanding terbalik dengan DO. Penurunan konsentrasi DO terhadap kedalaman disebabkan oleh kebutuhan oksigen yang lebih besar untuk oksidasi-dekomposisi bahan organik oleh mikroorganisme heterotrof (Enawgaw & Lemma, 2018). Oleh karena itu penurunan nilai DO akan diikuti dengan kenaikan konsentrasi BOD5 dan COD, yaitu kebutuhan oksigen untuk mendekomposisi senyawa organik secara biologi atau kimia.…”