Assessment of epiphytic algae community as bioindicator of organic pollution: A case study of Orokubu Creek, Bille, Rivers State, Nigeria

Abstract

Orokubu Creek, Bille, is a tidal estuary and tributary of the Centre of the New Calabar River, Niger Delta receiving organic anthropogenic effluents. The study investigated epiphyton assemblage from July to December 2019. Samples were collected from three stations (Frey-Boko, Oruama-Boko and Okpologio) and preserved. Epiphyton samples were identified microscopically. Phosphate (PO₄), Sulphate (SO₄) and nitrate (NO₃), were analyzed in the laboratory. PO₄ recorded (3.39±0.25 mg/L), SO₄ (457.34±20.47 mg/L), NO3 (4.33±0.19 mg/L) and total organic carbon (2.46±0.16 mg/L). Phosphate and Sulphate were higher than 0.1 mg/L, and 100 mg/L recommended international standard. A total of 5 families, 28 genera and 70 species of periphyton assemblage were observed [Bacillariophyceae (16.83%), Chlorophyceae (26.85%), Cyanophyceae (22.81%), Pyrrophyceae (27.43%) and Chrysophyceae (6.08%)] at p<0.05. Bioindicator species found were Raphidiopsis Mediterranea, Phormidiaspp, Microcystis aeruginosa, Nitzschia sigma N. lanceolate N. acicularis, Navicularostellata, Cyclotella comta (Bacillariophyceae), Anabaena spiroides, A. planctonica, Lyngbyahieronymusii, (Cyanophyceae) and Gonyaulaxpolyhedra, Gymnodinium catenatum, G. breve, Prorocentrummican, P. reiculatum (Pyrrophyceae). Bacillariophyceae correlated positively with nitrate. High levels of phosphate and nitrate showed the study area is organically polluted. The polluted wastewater contains detergents used in washing clothes, badges, bunker hose, faecal deposit, gas flaring, illegal local refinery ovens waste and decayed organic log woods. The study, therefore, suggests regular monitoring of the surface water and epiphyton community of Orokubu Creek because of the various industries and houses around this creek.