An Examination of the Current Knowledge of Contaminants in Mangroves: Hawaii and Globally

The geographic range of mangrove forests is shifting quickly as they expand poleward in response to climate change while simultaneously being removed from their native extent to clear space for anthropogenic land-uses. Mangrove forests are also known to be sinks for anthropogenic contamination. Yet contamination research is under-researched in mangrove ecosystems, specifically the environmental fate, effect on biodiversity, and risk to human populations from contamination in the context of these changing conditions requires further research. The goal of this thesis is to address this data gap through analysis of contamination in the literature and through an investigational survey of mangrove ecosystems in Hawaii. In chapter one, a review was completed for five classes of contamination in mangrove ecosystems, which was accomplished by summarizing other reviews and literature since those reviews. Four of these classes represent the most studied contaminants in mangrove literature, and include trace heavy metals, persistent organic pollutants, polycyclic aromatic hydrocarbons, and microplastics. The final category, pharmaceuticals and personal care products, is an emerging contaminant of concern that requires greater study in mangroves. This analysis identified several data-gaps that need to be addressed in the future. Pharmaceuticals and personal care products have received the least research despite biological activity at small concentrations. Research is concentrated in Asia and neglected in Africa and the Americas for all contaminant classes. Little discussion is given to whether the greater amount of research seen in Asia and Oceanic countries are due to the higher concentrations of mangroves in those regions of if there are other barriers preventing research. Some studies have noted that cost can be a prohibitive barrier to contaminant work, so efforts could be made to make contamination research more accessible. All contaminants were found to be widely present in mangrove ecosystems. Sources of contamination are correlated with proximity to waste water treatment plants, industry, and urbanized landscapes. Trace heavy metals and polycyclic aromatic hydrocarbons were found frequently at concentrations below the threshold to cause harm to plants, but may bioconcentrate in mangrove fauna. Persistent organic pollutants were found at levels that may cause harm to mangrove biota through long term exposure, and at some sites persistent organic pollutants were found at levels that might cause harm through short term exposure. Microplastics were found at variable levels, with some sites possibly being at concentrations that would cause harm to fauna, but more research is required in order to make that