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Seagrasses may frequently experience a combination of velocity and light stresses, as elevated hydrodynamics often enhances turbidity and the subsequent light reduction. The objective of this study is to investigate the effects that these stressors induce on morphometric and dynamic seagrass features depending on the initial biomass partitioning. For that purpose, a factorial mesocosm experiment was conducted on plants of Zostera noltii subjected to combinations of two contrasting light levels (2.5 ± 0.6 and 15.6 ± 2.5 mol photons m-2 d-1) and three unidirectional flow velocities (0.35, 0.10 and 0.1 m s-1). No interactive effects of both variables were recorded except for plant survival and leaf length, and generally, light effects prevailed over hydrodynamic ones. Plants responded to light reduction regardless the flow velocity treatments, showing low survival rates (which improved at high velocity), high aboveground/belowground biomass ratios (AG/BG) and a poorly developed root-rhizome system compared to plants under saturating light conditions. Plant morphometry only responded to hydrodynamic stress under saturating light: at high current velocity, plants allocated preferentially biomass into BG structures, bearing short leaves and high internode and root appearance rates. Overall, light reduction promoted similar responses in plants with different AG/BG biomass ratio, but dissimilarities were recorded for current velocity. Thus, it can be concluded that, under simultaneous light and hydrodynamic stresses, light effects prevailed to hydrodynamic ones in Z. noltii, while acclimation to hydrodynamics only occurred under saturating light.
Original languageEnglish
JournalMarine Ecology Progress Series
Journal publication date2010

ID: 214631