Environmental contaminants pose a global threat to humans and biodiversity conservation worldwide. Yet little is known about contaminant levels in tropical seabird communities located in key biodiversity points. French Guiana is a hotspot of biodiversity and is one of the regions experiencing a rampant increase in mercury (Hg) contamination. This review has the objective to summarize the results of (i) previous work on Hg contamination in seabirds from French Guiana and (ii) already published work on other environmental contaminant sources as persistent organic pollutants (POPs). Furthermore, previous research on Grand Connétable island, a key breeding site for Caribbean seabirds, reported high blood Hg concentrations in several seabirds, reaching the threshold of possible health concern for some species, particularly for the magnificent frigatebird Fregata magnificens. Because frigatebirds are experiencing massive mortality events of chicks caused by a herpesvirus disease that first appeared in 2005, this review further discusses a potential synergistic or additive interaction between food availability and Hg exposure in determining the recurrent disease outbreaks, a topic that has been often neglected in the literature. Here, we (i) summarize already published results from several years of research on this topic and (ii) suggest a potential connection between the occurrence of infectious diseases and cumulative effects of environmental stressors in marine top predators including birds, which clearly deserves further investigations. We also highlight the lack of studies on other sources of local pollution rather than Hg, and the need to take into consideration the cumulative effects of stressors on the health status of organisms, rather than focus on individual stressors or specific contaminants.