Unfortunately, seagrasses are under threat and seagrass coverage is being lost globally at a rate of 1.5 percent per year or 2 football fields an hour. Seagrass loss occurs naturally due to storms and herbivore grazing, however much of the reduction is due to human activities.
The most widespread cause of seagrass decline is a reduction in available light through reduced water quality. Processes that reduce light penetration to seagrass include floods, enhanced suspended sediment loads, pollution and elevated nutrient concentrations. Phytoplankton and fast-growing macro algae are better competitors for light, and if their growth is accelerated by increased nutrients in the water their biomass can shade seagrass, resulting in progressive eutrophication.
Image: Photograph of scars on the seagrass meadows from watercraft activities taken during a recent segrass survey. The red arrows point to scars.
In addition, coastal development reduces habitat area, anchoring and boat props and watercraft scar the seabed and uproot the seagrass (see image above), and over-fishing upsets the ecosystem balance, resulting in further seagrass decline. Pollution washed off the land may have toxic effects on seagrass species. These local and regional threats to seagrass all exist within a backdrop of global issues such as of climate change.
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