Outbreaks, coexistence, and life cycle of jellyfish species in relation to abiotic and biological factors along a South American coast

Olindias sambaquiensis and Rhacostoma atlanticum are the most abundant species of macrohydromedusae on the southern coast of Brazil; the first is associated with outbreaks of stings in bathers during the summer, and the second with interference in fishing. Due to their direct relationship with human activities, their life cycles were investigated, using laboratory cultivation and study of their cohorts in the field, as well as the patterns of abundance in light of the abiotic and biotic factors of the study area. The coexistence of the two species is possible due to differences in their life cycles, duration of the polyp phase, and the formation of well-defined cohorts. Variations in abundance of the species from one year to another cannot be explained by abiotic variables alone, such as seawater temperature, but may also be associated with the balance between these and other biotic forces, such as local production and, possibly, effects of competition between species. However, on a monthly scale, the aggregations of O. sambaquiensis in southern Brazil appear to be associated with the lowest frequency of north quadrant winds, which could, in addition to promoting resurgence processes, lead to dispersion of the organisms off the coast.