Many ocean ecosystems ar ethought to be heading towards a domiance of gelatinous organisms. However, gelatinous zooplakton has been largely understudied and the absence of quantitative long-term data for the studied area impeded drawing conclusion on the potential increasing densities. This study gives a comprehensive overview of the spatio-temporal distribution patterns of gealtinous zooplankton in terms of diversity and density bewteen March 2011 and February 2012 in the Belgian part of the North Sea and the adjacent Westerschelde estuary, based on monthly and seasonal samples respectively.

The lack of gelatinous blooms data reveals scant attention to such phenomena due to their irregular occurrence (Boero et al. 2008), to modern publication trends that give no importance to observations (Boero 2013b), to current monitoring programs that usually do not cover jellyfish (Riisgård et al. 2012) and to the lack of remote sensing tools to detect jellyfish. From 2009 the Italian project Occhio alla Medusa started involving citizens to record sightings of gelatinous organisms. In 2010 till 2015, the Italian popular science magazine FOCUS supported the campaign dedicating a webpage and releasing a smartphone app to upload records.