Seaweed vs Algae on the Shore: What's Underfoot?

In August 2014, thousands of tangled green ribbons piled up on the beaches of Qingdao, blocking swimmers and leaving one question hanging in the salty air-was it seaweed, or just ordinary algae? Both slither onto the shore looking slimy and green, and both grow in the sea. But seaweed is actually a type of large, multicellular algae-these are the big, leafy strips you see, like kelp or bladderwrack. Algae, on the other hand, is a broad group. Most algae are tiny and invisible, like the green scum you find in ponds or the floating clouds that make the sea turn murky. The green mats at Qingdao covered entire stretches, but up close, the difference shows: seaweed has holdfasts, like roots, and a clear structure, while microalgae are just slimy film. If it’s rubbery and leafy, it’s seaweed. If it coats your feet like paint, it’s algae. Remember-seaweed, you can hold; algae slips right through your fingers. The Qingdao mystery? It was a gigantic bloom of enteromorpha seaweed-proof that even the biggest mess isn’t always what it seems.