But life in these alien environments can also exist without symbionts as Ian MacDonald from Texas A&M University, Corpus Christi US has demonstrated. His observations of the fauna around coastal margin hydrocarbon seeps in the Gulf of Mexico have revealed a habitat rich in biological activity and without a need for symbionts to extract nutrients.

MacDonald found that the productivity of deep-water seeps is overwhelmingly based on chemosynthesis (deriving energy from chemical compounds instead of light) and also some chemoautotrophic symbiosis (using a symbiont to derive energy from chemical compounds). However some communities of deep-sea corals associated with many seeps are probably filter feeders. Recent research findings indicate that the corals around the seeps may be much more widespread at seeps than previously realised. This fact adds to the biological diversity and ecological complexity of seep communities.

Underwater mud volcanoes In the Nile deep-sea fan, mud volcanoes were discovered in the mid-1990s and they are still being investigated by a EUROMARGINS project. In the Gulf of Cadiz, the first mud volcanoes were discovered in 1999. The deepest mud volcano in this area is located at 3890m.

Luis Pinheiro from the University of Aveiro in Portugal participated in the 1999 cruise when mud volcanoes were first discovered. Pinheiro and his team have been investigating this area in close collaboration with Spain, France and Belgium. So far they have mapped 40 mud volcanoes, some as big as over 4km across and a few hundred meters high supporting characteristic ecosystems with particular faunal communities, living directly or indirectly on methane, some of which appear to represent completely new species to science.