Epipelagic Zone

The epipelagic zone extends from surface to 200m - the depth where enough light penetrates to power photosynthesis. Ninety percent of marine biomass lives here. Sunlight fuels phytoplankton, which feed zooplankton, which feed everything else. This is where tuna, sharks, marlin, and dolphins hunt.

Sunlit, oxygen-rich (from surface exchange), variable temperature (warmer near surface), salinity fluctuates with rainfall and evaporation.

Phytoplankton (diatoms, dinoflagellates, cyanobacteria) form the primary producers. Zooplankton (copepods, krill) form the grazers. Fish, marine mammals, and seabirds are the top consumers.

Countershading (dark back, pale belly) for camouflage. Fast swimming for pursuit or escape. Sharp vision. Migratory behavior to follow food.

Overfishing (most commercial fishing targets epipelagic species). Plastic pollution accumulating in gyres. Climate-driven acidification.