Viggiano Beltroco, María V.
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Publication Benthic algae biological indicators of trophic status in tropical streams(2014) Viggiano Beltroco, María V.; Santos Flores, Carlos J.; College of Agricultural Sciences; Pérez Alegría, Luis R.; Martínez Rodríguez, Gustavo A.; Sotomayor Ramírez, David; Róman Paoli, Elvin; Department of Crops and Agro-Environmental Sciences; Ríos Hernández, Luis A.This study describes the stressor-response relationships between water quality parameters and periphyton biomass on artificial and natural substrates of three tropical streams with contrasting trophic status. At the nutrient enriched study site, Río Piedras, a 2-day antecedent discharged volume exceeding 3.0x105 m3 negatively impacted the periphyton biomass growth on natural substrates due to physical scouring. No significant negative effects of antecedent cumulative hydrologic discharge were observed at the two other sites, Río Mameyes and Río Guanajibo. To minimize the effect of physical scouring, concrete blocks were used as artificial growth media for periphyton biomass. A seven-day accrual time resulted in positive correlations between periphyton biomass with total phosphorus (TP) (R2 =0.74, p<0.01) and total nitrogen (TN) (R2 =0.58, p<0.01) suggesting that artificial substrates for periphyton growth could be a potential tool for setting the degree of biological impairments as related to nutrient concentrations in stream waters. The benthic chlorophyll-a limit of 70 mg/m2 in natural substrates suggested by Dodds et al. (1998) was used to predict a 7-day periphyton biomass value indicative of impairment of 19.2 mg/m2 in artificial substrates. The nutrient concentrations associated with said threshold (19.2 mg/m2 ) were 0.169 mg TP/L and 1.64 mg TN/L. Numeric nutrient criteria suggested by Sotomayor-Ramírez et al. (2011) for Puerto Rico based on a frequency distribution approach are 0.160 mg TP/L and 1.70 mg TN/L which are similar to the predicted values obtained in this study. The periphyton community structure on the moderately nutrient enriched site experienced a shift from diatoms to cyanobacteria during ten days of incubation. Further studies should be conducted in order to validate the predictions made in this study as well as investigate the population dynamics of periphyton community on streams with moderate enriched nutrient conditions.