Gas exchange in many sharks depends on 

Adult Ascidiacea (sea squirts) feed similarly to sponges, by pumping water through their bodies and filtering out the tiny microorganisms and other organic particles (although sponges are more efficient at capturing the very tiny bacteria-sized particles).

One advantage of diminished populations of green turtles is that sea grass blades are allowed to grow longer, benefitting not only the plants, but also the entire ecosystem

Based on Joe Connell’s experiments to investigate the distribution of large and small barnacles in the rocky intertidal, what happened when the small barnacles were transplanted lower in the intertidal?

Peak diversity at intermediate levels of disturbance is a result of both r and K selected species, as well as species with intermediate life histories, being present simultaneously in the   community.

Dominant structure-providing organisms were consumed by very large herbivores until humans consumed too many of those large herbivores.

Reflecting their more ancient evolutionary history, a greater proportion of shark species than of boney fish species reproduce by spawning eggs and sperm into the water  column.

sea snakes 

Sediment in channels of mangrove swamps and salt marshes, where the water movement is slow and calm is more likely to be   

corals