Protecting ecological integrity of aquatic systems and reducing years of nutrient increase are major goals of the Clean Water Act. Reference streams serve as comparisons to streams with questionable ecological status, with reference criteria being set based on remaining at or below the 25th percentile from the desired chemical concentrations. Middle Georgia, within EPA region IV, has criteria set for total phosphorus (TP) and total nitrogen as 0.037 mg/L and 0.69 mg/L, respectively. Algae are sensitive bioindicators, having short generation times and significant bottom-up control. The goals of this study were to compare water quality indices for two low-impact streams in Middle Georgia. Tobler Creek, enclosed within the property of the historic Andalusia Farm, is a recovering stream after years of agricultural activities stopped in 1980. Closely positioned, Murder Creek is located within the Oconee National Forest, which is protected. In 2011, Tobler Creek met reference criteria for nitrate nitrogen, but not for TP, it took another 11 years to meet reference criteria for both nutrients. Periphyton samples from both streams were collected in 2022 following standard protocol and assessed with community indices. Diatoms dominated primary communities. Species richness was significantly higher in Tobler Creek 2022 than in 2011 (χ2=42.09, p<0.01), but for both years stayed below species richness and diversity documented for Murder creek. Estimating total ecological health, the Multi-Metric Index was significantly lower for Tobler Creek (χ2=18.46, p<0.01), indicating that despite a 42-year recovery from agricultural use, the stream has not achieved regional expected criteria. For the recovering stream, % SSN (surirelloid, nitzschoid, naviculoid) taxa were significantly higher (χ2=101.25, p<0.01), indicating that ecological degradation was driven by sedimentation and not nutrients. These findings suggest that while limiting nutrients can help improve trophic status of a stream, other factors could decrease water quality in those dynamic aquatic habitats.

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