The cruise is a core project of a Collaborative Research Center (CRC) funded by Deutsche Forschungsgemeinschaft (DFG) on the Roseobacter clade, a globally important group of marine bacteria. The CRC started in January 2010 and enters its second funding period in January 2014, which lasts until December 2017. One major aim of this CRC is to assess the significance of this group of bacteria in the North Sea. Our previous work has already shown that subgroups of this bacterial clade are prominent components of the bacterioplankton in the North Sea.
The aim of this cruise is to assess the abundance, diversity and physiological activity of members of the Roseobacter clade during a phytoplankton bloom in the northern or central North Sea. Remote sensing of chlorophyll a and previous studies have shown that such phytoplankton blooms regularly occur in the northern North Sea, usually in May and June. The location, however, can vary considerably. Therefore, we can not precisely identify the exact working area until shortly before the cruise starts. We need to examine satellite images for the chlorophyll distribution to spot a bloom shortly before the start of this cruise. Then we want to steam to the area of the bloom and study the response of the Roseobacter
clade to this bloom in the water column and in surface sediments. We plan to collect samples at various depths in the water column and in the sediment along a transect from the German Bight to the bloom area and in and outside the bloom area for about 10 days. The samples will be analysed for the composition of the phytoplankton, the bacterioplankton with special emphasis on the Roseobacter clade, and for organic and inorganic nutrients. Samples on the transect will be collected at stations appr. every 50 nm and in time series in and outside the bloom area in areas of appr. 10x10 nm.
This cruise is a follow up to similar cruises conducted in September 2005, May 2006 and July 2011.
Meinhard Simon (Institute for Chemistry and Biology Of The Marine Environment)