Environmental Health Assessment Using Sentinel Species near Placencia Lagoon, Belize

Unexplained bird deaths discovered around Placencia Lagoon, Belize over a 2-year period sparked an investigation into the environmental health of the lagoon and two of its major tributaries. In this study, conducted from January 23 to February 28, 2018, we assessed avian health within two commercial aquaculture facilities, each with a substantial outflow into the lagoon; a shrimp farm and a tilapia farm. Birds were chosen as our study subjects not only because of previous bird deaths, but also as sentinel species to assess overall possible contamination. Both facilities had previously been affected by die-offs of their cultivated product. The variety of sampled bird species, both year-round and winter residents, fed on small fish, airborne insects, mud-dwelling invertebrates and/or plant material, i.e. seeds and fruits, thereby sampling air, soil and water as possible bioaccumulation vectors. We trapped birds in, or nearby outflow containment ponds which emptied into the lagoon. Additionally, we assessed avian health at two reference locations on Placencia Penninsula, not known for avian health problems. Birds from multiple families representing different ecological niches were captured using two net types. We conducted standard ornithological assessments, measured hematocrit, made an evaluation of ectoparasite load and types, and for shorebirds, examined fecal swabs for parasites. Measured values were compared to published data and a previously established database from data collected elsewhere in the Caribbean. For each of the major sites, an extensive period of evaluation was later followed with a shorter, second evaluation at each location. Except for a single, second-year, Brown Pelican (Pelicanus occidentalis) evaluated one day at the close of the study, 257 birds were found to be healthy on all parameters including hematocrit and parasite load. We observed that the pelican had not been present previously and inferred that its health problems were acquired at another site. This conclusion was corroborated by the concurrent discovery of dead or dying pelicans along the Belize coast near the end of this investigation