Centre for Geobiology

Macroorganisms living around hydrothermal areas

The macrofauna that is found around hydrothermal areas is dominated by species that live by filtering food particles from the water. These organisms include anemones (Cnidaria), sea lilies (Haliometra sp, from the phylum Echinodermata) and basket stars (Gorgoncephalus sp., phylum Echinodermata). Their presence in these areas indicates that there are food particles to be found in the circulating water. It also emphasises the currents that exist here due to the streaming out of the water from under the sea floor and the chimneys.

In addition to these dominant species, researchers studying these northern hydrothermal areas have found species that are also found in the deep water habitats of more temperate latitudes. During this summer's cruise, biologists will collect samples of these organisms to compare them with samples from more temperate areas.

Researchers in Pacific hydrothermal and seep ecosystems have found unique communities of organisms including tubewormes, mussels, crabs and shrimps, which have high growth rates. The tubeworms are nourished through a symbiotic relationship with sulphur oxidising bacteria (similar to the symbiotic relationship between coral and the algae zooxanthellae in tropical reefs).

Thus far it seems that the vent fauna is different in the north Atlantic. There are not any impressive ones as are found in the Pacific. As yet researchers have only found organisms that can be considered rather ‘typical' of the north Atlantic in general, such as a blind shrimp.

There are a number of reasons why organisms around hydrothermal vents in the north Atlantic may be different from those in the Pacific. One is that the Atlantic Ocean is a much younger ocean; its origins date to only 130 million years ago. The Pacific Ocean is much older and thus organisms living there have had a much longer time to evolve and become specialised.

Another is that, thus far, hydrothermal vents north of Island have only been found in relatively shallow waters (up to 700m deep). Further south in the Atlantic they have been found at depths up to 2950m and in the Pacific up to 3600m. The environment in very deep water is very stable with respect to light, temperature and water movement. As a general rule, one finds many different species in the deep sea, each with its own niche. However, because there is relatively little competition between species, one tends to find rather low populations of each.

Hydrothermal vents have particular ecosystems because they create environments that have unique conditions: temperature, presence of toxic chemicals etc. Interestingly, high levels of plankton have been found in the waters around the Atlantic hydrothermal vents. As a result, researchers have also found high numbers of predator organisms such as shrimp around the Atlantic hydrothermal vents south of Island. Interestingly, these organisms were not found around the north Atlantic vents.

Researchers would like to know more about the plankton species present, so scientists will conduct plankton trawls during the cruise in order to identify the species present, and to carry out biomass estimates. The technology available on the GOSars will also make it possible to carry out acoustic studies of the plankton fauna in parallel with the trawls so that it will be possible to tentatively identify the plankton in future acoustic studies.