Spatial and Temporal Variations in Physico-Chemical Parameters and Abundance of Mollusc Species in Shiroro Lake, Minna, Niger State

Abstract

species the freshwater have Abstract Physico-chemical parameters, mollusc distribution and diversity in Shiroro Lake, Minna, Niger State was investigated between the months of March and August, 2017 spanning through the wet and dry seasons. Water samples for physico-chemical parameters and snails samples were collected and identified on monthly basis following standard methods. From the results; the temperature ranged from 26.5-32°C. The pH was all basic throughout the period of the study which ranged from 8.5-9.2 across all the stations. Dissolved Oxygen concentration ranged from 2.6-5.2 mg/L, while the BOD ranged from 2.2-4.9 mg/L. Nitrate level (0.43-0.83 mg/L) was high, while phosphate concentration (0.24-0.42 mg/L) was relatively low in all the sampling stations. A total number of 7 snail species were encountered. Station 3 had the highest number (403), station 2 with 363 species and station 1 had the lowest with 345 species. The family Viviparidae and Bithyniidae has 2 species each. The Bellamya phthinotropis has the highest number of species followed by Bellamya capillata; and the lowest was recorded among the species of Gebtella barthi. In general, the abundance of snails was higher during the rainy season than during the dry season. Taxa richness determined as Margalef index showed significant difference among the sampling stations. Similarly, diversity indices (Shannon Wiener, Simpson, dominance) also showed significant difference among the sampling stations. Lower values of diversity and Eveness indices were recorded at station 1. Station 2 had the highest record of diversity and eveness indices. Shiroro Lake is moderately organically polluted and adequate measures should be taken to check-mate this.