Do Norwegian deep-water coral reefs rely on seeping fluids?

Hundreds of large coral reefs up to 45 m high exist (A) on the continental shelf and (B) on morainic threshold ridges in fjords of northern, mid-, and southwest Norway. They occur in water depths between 400 and 40 m, and contain a large variety of megafauna. The most common frame-building coral is Lophelia pertusa (L.). The oldest reef found to date is 8600 calendar years old, determined by radiocarbon dating of buried Lophelia skeleton. Even though many of these reefs have been known to science for over 200 years, there is as yet no viable and unifying hypothesis to explain their existence in deep, cool waters, other than perhaps the ‘hydraulic theory’, presented by the author in 1990. It states that primary producers (mainly bacteria) are locally formed and concentrated at reef locations due to seepage of light hydrocarbons (mainly methane) on the continental shelf, and nutrient-rich groundwater in the fjords. The hydraulic theory is supported by the following topographic, reflection seismic, and geochemical indicators; for the continental shelf reefs (A): seaward-dipping sedimentary permeable strata, enhanced acoustic seismic reflectors, adjacent pockmark craters, locally elevated light hydrocarbon sediment content, locally elevated seawater methane content; for the fjord reefs (B): threshold morainic substratum rather than adjacent hardrock substratum, sub-surface dipping sedimentary layers, H2S smell of near-surface sediment samples. These indicators, or reef-associated observations, have been documented by German, British, and Norwegian researchers over the last 10–15 years. However, all the listed indicators do not necessarily occur at each of the respective shelf and fjord reef locations simultaneously.