He led an expedition in 1889 on the steamboat National from Kiel to southern Greenland in the north to as far as near the mouth of the Amazon in Pará, Brazil in the south to study whether plankton can be found more in tropical waters than cold waters.
He led an expedition in 1889 on the steamboat National from Kiel to southern Greenland in the north as far as near the mouth of the Amazon in Pará, Brazil in the south to investigate if plankton is more prevalent in tropical waters than cold waters.