An evaluation of fish and invertebrate mercury concentrations in the Caribbean Region.

Mercury is a ubiquitous pollutant of global concern but the threat of exposure is not homogenously distributed at local, regional, or global scales. The primary route of human exposure to mercury is through consumption of aquatic foods, which are culturally and economically important in the wider Caribbean Region, especially for Small Island Developing States (SIDS). We compiled more than 1600 samples of 108 unique species of fish and aquatic invertebrates collected between 2005 and 2023 from eleven countries or territories in the wider Caribbean Region. There was wide variability in total mercury concentrations with 55% of samples below the 0.23 µg/g wet weight (ww) guideline from the U.S. FDA/EPA (2022) for 2 or 3 weekly servings and 26% exceeding the 0.46 µg/g ww guideline consistent with adverse effects on human health from continual consumption, particularly for sensitive populations. Significant relationships were found between total mercury concentrations and taxonomic family, sampling country, fish length, and trophic level. The data analyzed here support the need for further sampling with concrete geospatial data to better understand patterns and mechanisms in mercury concentrations and allow for more informed decision making on the consumption of fish and invertebrates from the wider Caribbean Region as well as supporting efforts to evaluate the effectiveness of national, regional, and international mercury policies.

Global mercury concentrations in biota: their use as a basis for a global biomonitoring framework.

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention's progress to reduce the impact of global Hg pollution on people and the environment.

Assessing Freshwater Microbiomes from Different Storage Sources in the Caribbean Using DNA Metabarcoding.

Next-generation sequencing (NGS) and the technique of DNA metabarcoding have provided more efficient and comprehensive options for testing water quality compared to traditional methods. Recent studies have shown the efficacy of DNA metabarcoding in characterizing the bacterial microbiomes of varied sources of drinking water, including rivers, reservoirs, wells, tanks, and lakes. We asked whether DNA metabarcoding could be used to characterize the microbiome of different private sources of stored freshwater on the Caribbean Island nation of Antigua and Barbuda. Two replicate water samples were obtained from three different private residential sources in Antigua: a well, an above-ground tank, and a cistern. The bacterial microbiomes of different freshwater sources were assessed using 16S rRNA metabarcoding. We measured both alpha diversity (species diversity within a sample) and beta diversity (species diversity across samples) and conducted a taxonomic analysis. We also looked for the presence of potentially pathogenic species. Major differences were found in the microbiome composition and relative abundances depending on the water source. A lower alpha diversity was observed in the cistern sample compared to the others, and distinct differences in the microbiome composition and relative abundance were noted between the samples. Notably, pathogenic species, or genera known to harbor such species, were detected in all the samples. We conclude that DNA metabarcoding can provide an effective and comprehensive assessment of drinking water quality and has the potential to identify pathogenic species overlooked using traditional methods. This method also shows promise for tracing the source of disease outbreaks due to waterborne microorganisms. This is the first study from small island countries in the Caribbean where metabarcoding has been applied for assessing freshwater water quality.