Comparison of water velocity profiles through morphologically dissimilar seagrasses measured with a simple and inexpensive current meter

The influence of seagrass morphology on water flow was studied by measuring water velocity profiles through natural seagrass meadows. An array of eight solid-state electronic current meters was used to obtain profiles through meadows of Amphibolis griffithii (Cymodoceaceae), a seagrass which possesses a profusely-branched erect stem with terminal leaf clusters, and two strap-like seagrasses, Posidonia australis and P. sinuosa (Posidoniaceae). Significant differences were observed in the shapes of velocity profiles of the different seagrass species; in particular, a region of high water velocity was observed beneath the leafy canopy of Amphibolis, but not in the Posidonia canopy. There is a strong correlation between the water velocity profile of Amphibolis plants and the distribution of leaf biomass, highlighting the influence of the 'stem-and-leaf cluster' morphology on the velocity profile. The unusual velocity profile of Amphibolis has implications for the ecology of these ecosystems, and sediment stability in particular. The solid-state electronic current meters used in this study were found to be an effective and inexpensive means of measuring water velocity profiles in seagrass canopies