Screening for Potential Toxicity Risk of Freshwater Ecosystems in Rapu Rapu Island, Albay, Bicol using Modified Allium Test

Abstract

A modified Allium test was used to screen the potential toxicity risk of water samples obtained from three freshwater ecosystems: Binosawan River, Pagcolbon Pond and Mistika Creek in Rapu Rapu Island, Albay, Bicol. There were five experimental groups and two control groups. Experimental setups include Binosawan water sample without pH adjustment (BI); Binosawan water sample with pH adjustment (BIPH); Pagcolbon water sample without pH adjustment (PA); Pagcolbon water sample with pH adjustment (PAPH); and Mistika Creek water sample without pH adjustment (MI). Varying concentrations of all water samples with and without pH adjustments were prepared: 1%, 2%, 10%, 50% and 100%. Allium cepa L. bulbs were grown directly in varying concentration of water samples with and without pH adjustments. The mean root lengths of Allium cepa L. bulbs grown in varying concentrations with adjusted pH (BIPH and PAPH) were compared to the mean root lengths grown in water samples without pH adjustments (BI and PA). Using One-way ANOVA and its application to CRD, no significant difference was obtained from 1%, 2%, 10%, 50% and 100%. Only those grown in water samples from Pagcolbon River at 100% concentration showed significant difference using t-test (P=0.05). The mean root lengths of Allium cepa L. bulbs grown in water samples from BI, BIPH, PA, PAPH and MI at varying concentrations were also compared. Using One-way ANOVA and its application to RCBD, no significant difference was obtained from 1%, 2%, 10%, 50% and 100%. Expression of mean root lengths as a percentage of control at 100% concentration showed that PA had the lowest value (2.62%). All Allium cepa L. bulbs exhibited straight and white roots which indicate normal appearance. Only PA water samples showed effective concentration at 38.2% that caused 50% root growth restriction in the Allium population (EC5o)- However using the same water sample with a pH adjusted to 7, an EC5o value of 74.35% was obtained. Relative to the growth inhibition and statistical analyses, only the water samples from Pagcolbon Pond indicate potential toxicity risk.