Most of the stuff I want to filter out of the water tends to settle toward the bottom–but the filter inlet sits toward the top of the pool. If my kids and I don't stir the water by swimming, I have to mix the water around with a pool broom. The oceans suffer from a similar problem.
Oceans play a critical role in maintaining the habitability of Earth. They contribute significantly to the global water cycle and recycle nutrients that erode from continents. Additionally, they transfer heat from warm regions of the globe to cold regions and absorb carbon dioxide from the atmosphere and bury it in Earth's crust. A vibrant circulation pattern stands as a key requirement for the oceans to fulfill these vital roles. Scientists and nonscientists alike tend to view ocean currents, temperatures, and chemistry in terms of how they affect animals. However, recent research indicates that the opposite–how animals affect the oceans–is also true.
Jellyfish and other such creatures continually move through the oceans. Two Caltech scientists demonstrated that the movements of these creatures contribute to ocean stirring on a level similar to winds and the lunar and solar tides.
Given the critical nature of ocean circulation, a remarkable range of phenomena contribute to maintaining it. Atmospheric (temperature variations, wind, etc.), geological (erosion, continent placement, etc.) and now biological (swimming jellyfish, krill, etc.) conditions all work in harmony to ensure a vibrant, changing ocean environment. The dynamic and delicate interplay of such disparate forces argues for the work of a super-intelligent Designer.