Turkish Journal of Agriculture and Forestry
Abstract
Anthropogenic pressures on freshwater ecosystems have increased metal contamination in riparian zones; however, biological thresholds that distinguish tolerable exposure from ecologically significant accumulation remain poorly defined. This study investigated species-specific thresholds for heavy metal uptake in riparian macrophytes to establish a biologically grounded framework for ecological risk assessment in impacted streams. A gradient encompassing five sites was used to sample four dominant macrophyte species: Typha latifolia, Phragmites australis, Lythrum salicaria, and Persicaria lapathifolia. Concentrations of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn) in aboveground plant biomass were examined in relation to their corresponding concentrations in stream water using piecewise regression to identify threshold points (τ). These thresholds mark significant changes in the relationship between environmental metal availability and metal accumulation in aboveground biomass, indicating a shift in uptake dynamics. Identified threshold values ranged from 2.05 to 5.99 µg L⁻¹ (Cd), 1.91–70.5 µg L⁻¹ (Cr), 0.05–42.3 µg L⁻¹ (Cu), 75.2–555 µg L⁻¹ (Fe), 0.05–24.2 µg L⁻¹ (Ni), 0.29–30.9 µg L⁻¹ (Pb), and 1.55–244 µg L⁻¹ (Zn), with regression models explaining up to 81% of the observed variation in uptake. Thresholds were highly species-specific. For instance, the sensitive species Persicaria lapathifolia exceeded its calculated thresholds in 75–100% of observations. In contrast, the generally tolerant Typha latifolia showed an early threshold response specifically for Cu. Phragmites australis responded primarily under high exposure, except for Zn, for which its threshold was notably low. By integrating species-specific threshold determination with exceedance frequency analysis, this study provides a practical framework to distinguish zones requiring early biological warning from those subject to long-term accumulation. Furthermore, by establishing the first species-specific thresholds for macrophyte metal uptake in Türkiye, this study provides a scientifically grounded tool for selecting appropriate plant species for phytoremediation and watershed restoration initiatives.
DOI
10.55730/1300-011X.3493
Keywords
Riparian macrophytes, metal uptake thresholds, ecological risk assessment, threshold exceedance, watershed management
First Page
641
Last Page
654
Publisher
The Scientific and Technological Research Council of Türkiye (TÜBİTAK)
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
SAĞLAM, R, & GÖKBULAK, F (2026). Species-specific metal uptake thresholds in riparian macrophytes: A biological framework for ecological risk assessment. Turkish Journal of Agriculture and Forestry 50 (5): 641-654. https://doi.org/10.55730/1300-011X.3493
