The temperature average varies greatly across the marine biome because it is the largest biome on earth, covering over 70 percent of the planet. The lowest recorded monthly temperature was -40 degrees Fahrenheit, whereas the highest recorded monthly temperature was well over 100 degrees Fahrenheit.
Monthly temperature averages vary depending on where they are being measured in this massive biome. The marine biome is so large that it contains all four major oceans (Pacific, Atlantic, Indian and Arctic), as well as the Southern Ocean around Antarctica and a number of smaller gulfs and bays distributed across the globe. The average temperature is 39 degrees Fahrenheit, but again, the temperature varies wildly across the spectrum of this biome due to its immense size.
It is warmest in the waters near the equator and coldest around the North and South poles, as a direct result of how effectively sunlight can pierce the water. For example, in some cold regions near the poles, the water itself can freeze over, forming glaciers and ice. The temperature in the marine biome also depends on depth as well. Surface water is always markedly warmer than the water in the deepest trenches of the ocean, where sunlight cannot reach.