In the past years, gelatinous zooplankton blooms became more frequent in coastal areas causing several impacts on ecosystems dynamics and socio-economic activities. Many of these blooms are from non-indigenous species which may be of greater concern due to the unpredictable effects on the invaded area. The impact of these species on estuarine/marine nursery areas and their food webs became an important object of study because most them rely on early stages of fishery resources. However, routine observations on their diet composition revealed to be more diversified. Therefore, species belonging to class Hydrozoa (Blackfordia virginica), Scyphozoa (Catostylus tagi), Cubozoa (Copula sivickisi) and phylum Ctenophora (Mnemiopsis leidyi) were subject of feeding ecology studies based on gut content analysis, selectivity feeding experiments, biomarkers (stable isotopes ratios) and ecophysiological condition (RNA:DNA index) analysis. Those studies revealed that allocthonous food sources also contribute to sustain the jellies blooms especially in estuarine ecosystems where the connectivity between terrestrial and marine ecosystems are more crucial.