After the Earth Summit in Rio, 1992 and the adoption of the Convention on Biological Diversity, the term biodiversity has become a component of research policy in many countries and international bodies and initiatives. Biodiversity however, is not a concept but an umbrella term the content of which is quite diverse as can be inferred by definitions provided in many different texts The distinction between diversity and biodiversity is also fairly unclear in many studies in biology. As with most other issues in Ecology and Evolution, paradigms dominating the study of biodiversity on both global and regional scales come mainly from the terrestrial environment despite the marked distinctive features of marine biodiversity and the fact that the aquatic (freshwater & marine) environment occupies more than two thirds of the Earth’s surface). Marine organisms play crucial roles in many bio-geochemical processes that sustain the biosphere, and provide a variety of products and functions which are essential to mankind’s well-being, including the production of food and natural substances, the assimilation of waste and regulation of the world’s climate. The rate and efficiency of any processes that marine organisms mediate, as well as the range of goods and services that they provide, are determined by interactions between organisms and interactions between organisms and their environment; and therefore by biodiversity