Pacific Ocean width at about 5°N latitude, where it stretches approximately from Indonesia to the coast of Colombia—halfway around the world, and more than five times the diameter of the Moon. The lowest known point on Earth—the Mariana Trench—lies below sea level. Its average depth is , putting the total water volume at roughly . Due to the effects of plate tectonics, the Pacific Ocean is currently shrinking by roughly per year on three sides, roughly averaging a year. By contrast, the Atlantic Ocean is increasing in size. Along the Pacific Ocean's irregular western margins lie many seas, the largest of which
Ocean acidification in the Arctic Ocean which play an important role in the food-web of various ecosystems. Since they harbour an aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO₂ emissions.Laboratory tests showed that calcification exhibits a 28% decrease at the pH value of the Arctic ocean expected for the year 2100, compared to the present pH value. This 28% decline of calcification in the lower pH condition is within the range reported also for other calcifying organisms such as corals. In contrast with sea urchin and bivalve larvae, corals and marine shrimps are more severely impacted by