by Dhikra A. Dean

Created on: September 15, 2009

Estuaries and hydrothermal vents constitute two very different ecosystems, but they have a curious characteristic in common: in both, two different kinds of water meet, creating a unique environment. Their peculiar features favor the flourishing of many forms of life, and have therefore become important objects of study for many researchers. Hydrothermal vents, having been discovered in relatively recent years, are attracting the interest of many a scientist, especially since it was previously believed that life could not exist so deep in the oceans, due to the absence of sunlight.

Estuaries are the meeting point of fresh and salt water and they can be found where rivers pour their water into the ocean. Fresh and salt water mix, allowing for a high productivity. In this special environment salinity varies according to the ebb and flow of tides. Estuaries can vary in dimension and water depth, and they are generally protected by surrounding land or barrier islands, acting as nurseries for a large amount of organisms. In fact, many species of animals spend their youth in estuaries, developing in this protected environment, and migrating either to the sea or to the rivers when they reach their maturity.

Hydrothermal vents are very unusual environments found on the bottom of the oceans, where very hot water rich in chemicals springs out of the seafloor. This happens because at rift valleys and hot spots the internal activity of the Earth forms some breaches in the crust, where the water seeps in and comes back out overheated, bringing along many dissolved minerals. Chimneys formed by this water can vary in temperature and mineral content, and their dimension grows until they become too tall and they eventually collapse. Only in 1977, Dr. Robert Ballard and his team discovered that life was thriving at hydrothermal vents.

Whereas life in estuaries relies as customary on photosynthesis - which means that plants transform the energy of sunlight into food, and then animals feed on plants and other animals, in hydrothermal vents all this is not possible, since the sunlight cannot reach the depths of oceans. This is the reason why scientists were really surprised to find life in such an environment. Then they discovered that there are bacteria able to transform energy from chemicals into food, in a process called chemosynthesis. These bacteria are the producers at hydrothermal vents, instead of plants, which are the producers on earth and also in the superficial part

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