Structural and physiological effects of chromium uptake in the seagrass Halophila stipulacea

•Halophila stipulacea can act as a bioindicator of ambient Cr (VI) bioavailability.•Cr can be toxic to seagrasses at environmentally relevant Cr (VI) concentrations.•Actin filaments and endoplasmic reticulum are sensitive markers of Cr (VI)•Regression models describe the relationship effect onset vs. Cr (VI) exposure.•Uptake rate rather than tissue concentration relates to the onset of toxic effects. This work aims to provide insight on the effects of chromium (Cr) uptake in seagrasses at environmentally relevant exposure concentrations; information on this issue can further increase the utility of marine angiosperms as indicators of trace metal contamination. Cr uptake kinetics, effects on physiological and structural cell traits, and the uptake-effects relationship in Halophila stipulacea leaves incubated in 0.01–10 mg L−1 (0.2–200 μM) of Cr (VI) were examined. An initial uptake was followed by a decrease at 0.01–0.5 mg L−1 (0.2–10 μM); at higher exposures, the fit of uptake data to a Michaelis-Menten-type equation was significant (p