Seagrass are the basis of a complex ecosystem supporting some of our most iconic marine creatures including turtles and dugongs. Seagrass is their primary food source, with turtles consuming around 2-4kg a day and dugongs consuming a staggering 40kg per day.
As dugongs and turtles graze on seagrasses, organic matter is stirred up, aerating the sediment. Turtles eat the seagrass leaves, whereas dugongs remove the whole plant.
Dugongs specifically prefer the succulent root stalks (rhizomes) of Halophila ovalis and Halodule uninervis, which are found growing primarily over the eastern banks of Moreton Bay and in certain areas within the Broadwater. Scientists believe that these species are targeted because of their greater nitrogen content and lower concentrations of fiber (read more here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4941767/).
Dugongs are known to garden the seagrass meadows in a process known as ‘cultivation grazing’. As they feed they remove whole plants, leaving patches of bare sediment. This in turn creates good conditions for the fast growing, pioneer seagrass species to grow in the disturbed area. The more grazing, the more the disturbance they create, encouraging their preferred species of seagrass to grow.
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