Framvaren Fjord, Norway

The Framvaren fjord is located in southwestern Norway. With sulfide levels in the bottom water 25 times greater than those in the Black Sea, the fjord represents the extremes of anoxicity and contains the highest levels of H2S (6,000 µM) ever reported for an open anoxic basin. Our sampling site is located in the central basin of the Framvaren Fjord with a water depth of about 180 m. Samples for our protistan diversity studies were collected at three different depths: The oxic-anoxic boundary layer (18 m in May 2004), the pycnocline and upper H2S boundary (23 m in May 2004) and the upper layer of the anoxic intermediate deep water, characterized by steep chemical gradients (36 m in May 2004). At the latter depth, the H2S concentrations (0.6 mM) are already twice as high as in the deep water (> 1000 m) of the Black Sea and even 30 times higher than in the Cariaco bottom water (1200 m), which is the world’s largest truly marine permanently anoxic deep-sea basin.