THE IMPACT OF HERBICIDES ON FRESHWATER FUNGI ISOLATED FROM SUBMERGED WOOD

The impact of two herbicides, glyphosate and atrazine, on biomass production of freshwater fungi isolated from submerged wood in a stream located at Rumahuolu in Rivers State, Nigeria was evaluated. Fungal isolation was performed via spread plate method. The predominant isolates were exposed to varying concentrations of glyphosate (0, 10, 50, 100, 500 and 1000 mg/l) and atrazine (0, 10, 50, 100, 500 and 1000 mg/l) in a defined medium for 14 days at 28oC. The biomass production was measured as mycelial dry weight and percent inhibition or increment determined. Eight fungal genera Sporoschisma, Nigrospora, Ochroconis, Fusarium, Cladosporium, Penicillium, Trichophyton and Candida were isolated at dissimilar frequencies with Sporoschisma, Nigrospora and Ochroconis predominating. Generally, fungal growth enhanced at 10 mg/l of herbicides but repressed with increase in herbicides concentrations. The degree of increment and inhibition varied among the fungal isolates. Positive correlations were observed between herbicide concentrations and inhibition values. Fungi isolation from the decaying wood implies that they may be implicated in lignin mineralization and processing in freshwater ecosystem. The decrease in biomass production of wood-inhabiting fungal species exposed to atrazine or glyphosate concentrations greater than 10 mg/l may have negative impact on their functions in the ecosystem. Therefore, the inhibitive effect of herbicides on the fungal species may lead to accumulation of organic substrates in the ecosystem.