I am of average height. I am well aware that I am dwarfed by many animals, like elephants and giraffes. In the oceans, organisms can even grow bigger than terrestrial animals as they are not limited by gravity like land critters; the water carries their body weight. As a result, whales are one of the biggest animals that ever lived on the Earth. Body size is an interesting phenomenon, as it varies with many other aspects of a species. For example, number of offspring in a lifetime, energy use per unit weight, oxygen consumption, abundance, etc. all relate to body size.
In the deep sea, most animals are small as food availability is limited in the deep sea. This is because even down here, most organisms depend on photosynthesis, the process of producing new organic material by using the sun’s energy. This material is produced by the phytoplankton in the upper water layers. However, dead organisms, excreted material and other debris will sink to the ocean floor and serve as a food source for the organisms living here. This flux will get smaller with depth; thus the deeper you go down the less food there is. Being small means you are more likely to find a meal that is big enough to sustain you and your species.
However, that does not mean that there cannot be giants here. These giants grow at a very slow pace, patiently waiting for food to come by. And they can live for hundreds of years, if not thousands! Bamboo coral is one of these giants, being able to grow several meters high. We had the luck and opportunity to find a very large one and bring it up. It barely fitted in the tool tray of ISIS, our Remotely Operated Vehicle. And when we finally got it in our hands, it towered even above the tallest of us! It was amazing, such an old creature dwarfing the whole team. And do not be deceived by the smiles and think that it was a nice thing to handle – it fights back with its tiny, but sharp, spines!