Influence of physicochemical parameters on the biodiversity indices of fresh water snails in selected rivers of Osun State, Nigeria

Abstract

Studies have investigated the influence of environmental factors on distribution of vectors of parasites of public health importance but little is known on the role of these factors on the biodiversity indices of the vectors. This study is therefore set to assess the role of physicochemical parameters on biodiversity indices of fresh water snails. The study was carried out in three randomly selected communities across the three senatorial regions of Osun state namely Ere Ijesha, Ede and Erin-Osun. Through reports from community members, a mostly visited river from each community was selected. Three contact points with evident human water contact were identified for snail and water sampling. Morphological identification of snails was done. Physicochemical parameters of water were measured while snail biodiversity indices were determined using Shannon index, snail richness and abundance. Relationship between continuous variables was determined using Spearman’s correlation. There is a significant difference between pH values of Ere Ijesa and Erin Osun while Ede and Erin Osun also show a significant difference in their chloride concentration. A significant positive correlation was observed between pH and diversity (correlation coefficient (rho)= 0.64, P<0.05), pH and Bulinus abundance (rho= 0.68, P< 0.05), chloride and snail richness (rho= -0.65, P< 0.05), chloride and diversity (rho= -0.88, P< 0.01), BOD and snail richness (rho= -0.78, P < 0.05), BOD and diversity (rho= -0.64, P<0.05) COD and snail richness (rho= -0.61, P< 0.05). Ede had highest diversity index while Ere Ijesa had highest Bulinus abundance. Erin Osun was the least in terms of snail richness, diversity and Bulinus abundance. Snail diversity, snail richness and Bulinus abundance significantly differ across the sampling locations (P< 0.01). Physicochemical parameters such as pH, chloride content, BOD and COD have significant role to play in fresh water snail richness, snail diversity and Bulinus abundance.