Ontogenetic dietary shifts and bioaccumulation of diphenhydramine in Mugil cephalus from an urban estuary.

Though bioaccumulation of pharmaceuticals has received attention in inland waters, studies of pharmaceutical bioaccumulation in estuarine and marine systems are limited. Further, an understanding of pharmaceutical bioaccumulation across size classes of organisms displaying ontogenetic feeding shifts is lacking. We selected the striped mullet, Mugil cephalus, a euryhaline and eurythermal species that experiences dietary shifts with age, to identify whether a model base, diphenhydramine, accumulated in a tidally influenced urban bayou. We further determined whether diphenhydramine accumulation differed among size classes of striped mullet over a two year study period. Stable isotope analysis identified that ontogenetic feeding shifts of M. cephalus occurred from juveniles to adults. However, bioaccumulation of diphenhydramine did not significantly increase across age classes of M. cephalus but corresponded to surface water levels of the pharmaceutical, which suggests inhalational uptake to diphenhydramine was more important for bioaccumulation than dietary exposure in this urban estuary.

Predicted and observed therapeutic dose exceedances of ionizable pharmaceuticals in fish plasma from urban coastal systems.

Instream flows of the rapidly urbanizing watersheds and estuaries of the Gulf of Mexico in Texas (USA) are increasingly dominated by reclaimed waters. Though ionizable pharmaceuticals have received increasing attention in freshwaters, many research questions remain unanswered, particularly in tidally influenced urban coastal systems, which experience significant spatiotemporal variability in pH that influences bioavailability and bioaccumulation. The authors coupled fish plasma modeling of therapeutic hazard values with field monitoring of water chemistry variability and pharmaceutical occurrence to examine whether therapeutic hazards to fish existed within these urban coastal ecosystems and whether therapeutic hazards differed within and among coastal locations and seasons. Spatial and temporal fluctuations in pH within study sites altered the probability of encountering pharmaceutical hazards to fish. Significant water quality differences were consistently observed among traditional parameters and pharmaceuticals collected from surface and bottom waters, which are rarely sampled during routine surface water quality assessments. The authors then compared modeling predictions of fish plasma concentrations of pharmaceuticals to measured plasma levels from various field-collected fish species. Diphenhydramine and diltiazem were observed in plasma of multiple species, and diltiazem exceeded human therapeutic doses in largemouth bass, catfish, and mullet inhabiting these urban estuaries. Though the present study only examined a small number of target analytes, which represent a microcosm of the exposome of these fish, coastal systems are anticipated to be more strongly influenced by continued urbanization, altered instream flows, and population growth in the future. Unfortunately, aquatic toxicology information for diltiazem and many other pharmaceuticals is not available for marine and estuarine organisms, but such field observations suggest that potential adverse outcomes should be examined.

Bioaccumulation of human pharmaceuticals in fish across habitats of a tidally influenced urban bayou.

Though pharmaceuticals and other contaminants of emerging concern are increasingly observed in inland water bodies, the occurrence and bioaccumulation of pharmaceuticals in estuaries and coastal ecosystems are poorly understood. In the present study, bioaccumulation of select pharmaceuticals and other contaminants of emerging concern was examined in fish from Buffalo Bayou, a tidally influenced urban ecosystem that receives effluent from a major (∼200 million gallons per day) municipal wastewater treatment plant in Houston, Texas, USA. Using isotope dilution liquid chromatography-tandem mass spectrometry, various target analytes were observed in effluent, surface water, and multiple fish species. The trophic position of each species was determined using stable isotope analysis. Fish tissue levels of diphenhydramine, which represented the only pharmaceutical detected in all fish species, did not significantly differ between freshwater and marine fish predominantly inhabiting benthic habitats; however, saltwater fish with pelagic habitat preferences significantly accumulated diphenhydramine to the highest levels observed in the present study. Consistent with previous observations from an effluent-dependent freshwater river, diphenhydramine did not display trophic magnification, which suggests site-specific, pH-influenced inhalational uptake to a greater extent than dietary exposure in this tidally influenced urban ecosystem. The findings highlight the importance of understanding differential bioaccumulation and risks of ionizable contaminants of emerging concern in habitats of urbanizing coastal systems.

Water quality in the Dickinson Bayou watershed (Texas, Gulf of Mexico) and health issues.

The Dickinson Bayou watershed (near Houston, Texas, Gulf of Mexico) provides habitat for numerous coastally influenced communities of wildlife, including scores of birds and fish. Encroaching development and impervious surfaces are altering the habitat and degrading water quality. Herein we have defined the current health of the bayou using water quality data collected between 2000 and 2006. Elevated bacteria (fecal coliform, Escherichia coli and Enterococcus) and depressed dissolved oxygen concentrations (often <3mgl(-1)) are the two major impairments to this ecosystem. While nutrient ratios indicate primary productivity may be nitrogen limited, concerns of eutrophication persist because the bayou has a low intrinsic flushing rate. Consistent with this is the magnitude of algal blooms (ca. 100microg chll(-1)) which often occur in spring/summer. The findings of this study will assist with the understanding of the influence of urban development on small watersheds.