Sandy Intertidal

Do beaches have low or high primary productivity? Do they have little or lots of organic matter for consumption?

They have low primary productivity but lots of organic matter for consumption

Why do beaches have low productivity?

This is because there is lack of stable holdfasts for macroalgae and near constant sediment motion that can be damaging to macro algae or grasses that are trying to establish themselves. There is also damaging wave stresses that prevent anything from rooting onto the bottom of beaches

What brings abundant organic matter onto the beach?

Stokes drift produces shoreward flux of detritus

What is Stokes Drift?

It is the drift of water that occurs because waves are moving a little bit faster at the top of their orbitals than they are at the bottom because those orbital velocities get lower and lower as you go deeper in the water

Does the detritus flow back out with the water? What happens once it’s there?

No it stays stranded on the beach where bacteria will break this organic matter down. Detritivores will then feed on the decaying organic matter