Jellyfish
Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus "Cassiopea" typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. The tiny creeping jellyfish "Staurocladia" and "Eleutheria" cannot swim, and "walk" around on seaweed fronds or rocky bottoms on their tentacles. Most hydromedusae and scyphomedusae that live in coastal habitats find themselves on the bottom periodically, where they may stop swimming for a while, and certain box jellyfish species also rest on the sea bed in shallow water. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.
Warm core ring
Many fish species’ life cycle involves two distinct habitats. The adults live in warmer temperate waters south of Cape Hatteras, NC while the juveniles are found in estuaries of cooler waters north of Cape Hatteras. Warm Core Rings play an important role in the transport of larvae between the two habitats. Species like the bluefish (Pomatomus saltatrix) and pearly razorfish (Xyrichtys novacula) spawn near the western edge of the Gulf Stream just south of Cape Hatteras. Because of the convergence of the Gulf Stream from the south and cooler coastal water current from the north, most water around Cape Hatteras flows into the Gulf Stream. The larvae released near this convergence is swept into the Gulf Stream and flows north. Since the larvae are planktonic, they don’t swim into the center of the Gulf Stream but stay near the western edge. This is beneficial for when warm core rings form. Warm core rings are formed when the crest of a meander breaks off from the Gulf Stream. Any larvae in the crest of the meanders are then entrapped in the warm core ring. Once the warm core ring breaks way, it takes a southwesternly path towards the coast. The interaction between warm core rings and the continental shelf creates a weakening of the ring and enables the larvae to escape and continue their journey to nearby estuaries. The warm core rings formed along the northeastern states can last between 4 and 5 months. During this time the larvae grow so that by the time they reach the estuaries, they are able to swim away from the warm core ring into the estuaries.