Ecological Organization of the Sea

Two thirds of the Earth’s surface area are covered by the oceans and shelf seas and at first sight this vast marine living space appears ecologically homogenous compared to land. A closer look, however, reveals that the global ocean accommodates very different structurally and functionally complex communities that are formed by a great diversity of plant and animal species. All communities or ecosystems (the term is interchangeably used in the following chapter) are interconnected and depend upon each other. All of them have been providing a wealth of ecosystem goods and services that humans have been depending on and economically benefiting from. The following chapter aims at giving a general overview of the ecological organization of the global ocean, which is needed to understand and evaluate past and current impacts of human activities on marine communities. On the most general level, this chapter divides the marine living space and its inhabitants into the pelagic and the benthic zone. It introduces functionally important and widely distributed communities in both zones and highlights the dynamic biological, physical, and chemical processes or mechanisms that play an important role in the maintenance and functioning of these communities.