Why is there so much plankton near the continental shelf?

Oh honey, let me break it down for you. Plankton love hanging out near the continental shelf because that's where all the party snacks are - nutrients from the land are constantly getting washed down and plankton are like, "Free buffet, woohoo!" Plus, the currents near the shelf keep things interesting, so plankton can mingle and reproduce like there's no tomorrow. It's basically the plankton version of a hot spot, minus the cocktails and fancy outfits.