Colors in the Open Ocean: Hide and Seek without Structure
If you asked an elementary school student to draw an oceanscape, they would likely draw a vibrant coral reef ecosystem, full of colorful corals and shiny fishes. Although many coral reef ecosystems are losing this color and most reef ecosystems do not actually look like the reef structures in aquaria, coastal seas are typically characterized by this luscious vibe. On the contrary, the open ocean is more monotone and so are the organisms within it. Reef vs. Pelagic Ocean. Almost all animals that live in the open ocean have a dark dorsal (top) side and light ventral (bottom) side, a characteristic called countershading . Consider the below image of an Atlantic bluefin tuna ( Thunnus thynnus ). The dorsal side is a dark blue and the ventral side is white. The main purpose of this is to avoid predation in a 3-dimensional environment (many pelagic organisms in lakes have this as well). Predators hunting from below the tuna will have to look up at a light backdrop where the white ven...