The effects of water velocity and morphology on the photosynthetic rate of the aquatic macrophytes Vallisneria americana and V. spiralis

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Invasive macrophyte species are generally associated with negative ecological impacts. However, the physiological and morphological characteristics that successfully allow macrophytes to establish in new ecosystems have yet to be determined. In organisms, such as terrestrial angiosperms, algae, and corals morphology, surface area to volume ratio, and water velocity are determining factors in influencing the rate of an individual’s physiological processes. Two aquatic macrophytes, Vallisneria americana and Vallisneria spiralis, were used to determine whether leaf morphology influences the photosynthetic rate of aquatic macrophytes in both high (0.026 m s-1) and low (0.001 m s-1) freestream water velocities. Neither O2 flux (mol m-2 s 1) nor O2 production (mol) significantly differed between species or freestream velocities. However, O2 flux was observed to be highest for V. americana at low water velocity. In contrast, O2 flux was highest for V. spiralis at high water velocity. This distinction in observed O2 flux implies the morphological difference between V. americana and V. spiralis affects photosynthetic rate. Further research must be completed to determine physiological causes in this observed difference.