Blooms of this genus were recorded as early as 1937 in the Oslo Fjord (Braarud, 1945) an have occured more recently as G. sanguinum with concentrations up to 35 106 ind/l.
- Reid, P.C.; Lancelot, C.; Gieskes, W.W.C.; Hagmeier, E.; Weichart, G. (1990). Phytoplankton of the North Sea and its dynamics: a review. Neth. J. Sea Res. 26(2-4): 295-331