As part of the “Abyss” group, we might wonder what things look like down there, in the deep ocean. As you probably already experienced, diving in water comes with (uncomfortable) changes of temperature and pressure. And that’s only a few meters! The conditions keep changing going deeper in the water column (more than freezing toes!). In oceans, the abyssal waters represent the part lying between 2000 m and 6000 m under sea level. At these depths, the temperature is constant around 0-4°C, the pressure is up to 200-600 atmospheres, and there is no light. And light is not only useful to see around but it is also the energy for photosynthesis and hence life sustenance at the surface of the Earth. Yet, although very poorly known, these depths allow life to exist. And what comes out of discoveries is sometimes very interesting or unexpected!
Life has to adapt to these difficult conditions of low temperature, high pressure, absence of light and scarcity of nutrients. The result is not exactly what we are used to, evolution sometimes leads to cool physical and morphological features! Let’s have a look at some inhabitants of the abysses.
Beyond 100 m in the dark cold water, plants disappear, life in the deep sea is 100% animal, likely because photosynthesis is impossible. With disappearance of light at depth, numerous species evolved to be blind or, conversely, grew big, globular eyes in the attempt to catch any remaining light like our very cute friend in Figure 1.