ICES standard for phytoplankton primary production measurements
One of the most important marine processes is the formation of organic material resulting from the interaction of carbon dioxide, water and sunlight, a process known as photosynthesis. The ability to measure this process is of great importance when assessing marine pelagic systems. In practice the best way to measure photosynthesis is to look at the absorption of carbon dioxide. The high sensitivity of carbon dioxide absorption measurements allows to use this method under all circumstances. Neither low or very high algal concentrations nor low light conditions and low temperatures are restrictions for this method. Based on the 14C method, using the absorption of the radio-active 14C isotope of carbon (Steemann-Nielsen, 1952), the ICES Incubator is the ICES standard for phytoplankton primary production measurements.The incubator shown here has been mainly developed for monitoring purposes. It should be used preferably for water samples taken from a mixed water layer with a fixed temperature. Measurements of the amount of phytoplankton (based on chlorophyll-a concentration measurements) should be carried out for interpretation purposes. The ICES Incubator consists of an illuminated transparent plexiglass tank incorporating a turning wheel on which 12 experimental bottles can be clamped. The tank is filled with water which is set in motion by an adjustable circulating pump. Thus the turning wheel is set in rotation at speeds up to 10 rpm with the experimental bottles acting as paddles. Tank connections for a second water circulation allow for temperature adjustments of the water by using external tempering equipment. The 12 experimental bottles of 50 ml capacity each have different optical coatings, so that each bottle has individual transmission rates and thus generating a number of 12 different irradiance (or light intensity) levels. The illumination unit is equipped with 10 fluorescent tubes with a wave spectrum according to ICES specifications, each can be switched individually. For higher irradiance levels a second illumination unit can be mounted onto the ground plate of the ICES Incubator.