Internal and Maternal Distribution of Persistent Organic Pollutants in Sea Turtle Tissues: A Meta-Analysis.

We aimed to identify patterns in the internal distribution of persistent organic pollutants (POPs) and assess contributing factors using sea turtles and their offspring as a case study of a long-lived wildlife species. We systematically synthesized 40 years of data and developed a lipid database to test whether lipid-normalized POP concentrations are equal among tissues as expected under steady state for lipophilic compounds. Results supported equal partitioning among tissues with high blood flow or perfusion including the heart, kidney, muscle, and lung. Observed differences in the brain, fat, and blood plasma, however, suggest the physiological influence of the blood-brain barrier, limited perfusion, and protein content, respectively. Polybrominated diphenyl ethers partitioned comparably to legacy POPs. Polycyclic aromatic hydrocarbons, meanwhile, partitioned more into the lung, colon, and muscle compared to the liver under chronic and acute field exposure. Partitioning ratios of individual POPs among tissues were significantly related to the lipophilicity of compounds (as estimated by Kow) in half of the observed cases, and significant differences between juveniles and adults underscore physiological differences across life stages. The comprehensive tissue partitioning patterns presented here provide a quantitative basis to support comparative assessments of POP pollution derived from biomonitoring among multiple tissues.

Sediment grain size determines microplastic exposure landscapes for sandy beach macroinfauna.

Despite the global occurrence of microplastic contamination on sandy beaches, evidence of microplastic distribution within beaches remains contradictory. When conflicting evidence is used to inform sampling surveys, it increases uncertainty in resulting data. Moreover, it hampers spatially explicit risk characterization of microplastic pollution to intertidal fauna. We aimed to guide sampling designs for microplastic monitoring on beaches, and to quantify macroinfauna exposure to microplastics. Microplastic abundance, quantified between 5 mm-66 µm, lacked a significant zonation across the top sediment layer of sub-terrestrial, upper and lower midlittoral, and swash zones at two sites with varying anthropogenic influence on a microtidal dissipative beach in Uruguay. Microplastic abundance decreased exponentially with increasing grain size, as revealed by Bayesian Poisson regression, although the decrease was less steep compared to prior knowledge regarding sediment - plastic interactions obtained for large (millimeter-sized) industrial pellets. Significant differences in microplastic contamination between the two sites with varying anthropogenic influence likely related to their proximity to a freshwater canal. Corresponding field measurements of body burdens of fibers and irregular particles were significantly lower for the polychaete Euzonus (Thoracophelia) furcifera, despite its preference for finer sediments with higher microplastic loads, compared to the isopods Excirolana braziliensis and Excirolana armata. Results provide critical insights toward representative sampling of microplastics within beach sites. Specifically, we caution against sampling limited to the drift line, and instead recommend: 1) reporting beach morphodynamic characteristics; 2) using clearly defined, ecologically-informed zonation schemes; and 3) accounting for sediment grain size as a covariate to normalize among reported contamination levels. The results contribute valuable baseline data toward realistic exposure landscapes relative to the sediment grain size preferences of macroinfauna, needed to inform laboratory experiments.

Maternal Transfer of Persistent Organic Pollutants to Sea Turtle Eggs: A Meta-Analysis Addressing Knowledge and Data Gaps Toward an Improved Synthesis of Research Outputs.

Maternal transfer of persistent organic pollutants (POPs) confronts developing embryos with a pollution legacy and poses conservation concerns due to its potential impacts unto subsequent generations. We conducted a systematic review focusing on: 1) processes of POP maternal transfer, 2) challenges and opportunities to synthesizing current knowledge on POP concentrations in eggs, and 3) a meta-analysis of patterns in current egg pollution data. Results suggest selective maternal transfer of individual compounds. These relate to biological factors such as the foraging and remigration behavior, and to the selective mobilization of POPs during vitellogenesis, such as increased diffusion limitation for lipophilic POPs and slower release and higher reabsorption of apolar POPs. A key gap relates to knowledge of further selective toxicokinetics during embryonic development, as research to date has mainly focused on initial uptake into eggs. Challenges in the synthesis of current data on egg contamination profiles relate to methodological differences, varying analytical approaches, restricted data access, and reporting transparency among studies. To increase opportunities in the use of current data, we propose best practice guidelines, and synthesize a database on POP concentrations within sea turtle eggs. The meta-analysis revealed a geographical and taxonomic bias on the West Atlantic Ocean, including the Gulf of Mexico and Caribbean Sea, with most studies conducted on green turtles. Concentrations of POPs show temporal patterns related to trends in usage, production, release, and persistence in the environment, often with regional patterns. The trophic level has the potential to influence POP patterns with higher concentrations in loggerheads compared to other species, but this is confounded by temporal and geographic trends. We argue for more mechanistically process-focused and methodologically comparable research. Environ Toxicol Chem 2019;39:9-29. © 2019 SETAC.

Profiles of environmental contaminants in hawksbill turtle egg yolks reflect local to distant pollution sources among nesting beaches in the Yucatán Peninsula, Mexico.

Knowledge of spatial variation in pollutant profiles among sea turtle nesting locations is limited. This poses challenges in identifying processes shaping this variability and sets constraints to the conservation management of sea turtles and their use as biomonitoring tools for environmental pollutants. We aimed to increase understanding of the spatial variation in polycyclic aromatic hydrocarbon (PAH), organochlorine pesticide (OCP) and polychlorinated biphenyl (PCB) compounds among nesting beaches. We link the spatial variation to turtle migration patterns and the persistence of these pollutants. Specifically, using gas chromatography, we confirmed maternal transfer of a large number of compounds (n = 68 out of 69) among 104 eggs collected from 21 nests across three nesting beaches within the Yucatán Peninsula, one of the world's most important rookeries for hawksbill turtles (Eretmochelys imbricata). High variation in PAH profiles was observed among beaches, using multivariate correspondence analysis and univariate Peto-Prentice tests, reflecting local acquisition during recent migration movements. Diagnostic PAH ratios reflected petrogenic origins in Celestún, the beach closest to petroleum industries in the Gulf of Mexico. By contrast, pollution profiles of OCPs and PCBs showed high similarity among beaches, reflecting the long-term accumulation of these pollutants at regional scales. Therefore, spatial planning of protected areas and the use of turtle eggs in biomonitoring needs to account for the spatial variation in pollution profiles among nesting beaches.

Sources and sinks of plastic debris in estuaries: A conceptual model integrating biological, physical and chemical distribution mechanisms.

Micro- and macroplastic accumulation threatens estuaries worldwide because of the often dense human populations, diverse plastic inputs and high potential for plastic degradation and storage in these ecosystems. Nonetheless, our understanding of plastic sources and sinks remains limited. We designed conceptual models of the local and estuary-wide transport of plastics. We identify processes affecting the position of plastics in the water column; processes related to the mixing of fresh and salt water; and processes resulting from the influences of wind, topography, and organism-plastic interactions. The models identify gaps in the spatial context of plastic-organisms interactions, the chemical behavior of plastics in estuaries, effects of wind on plastic suspension-deposition cycles, and the relative importance of processes affecting the position in the water column. When interpreted in the context of current understanding, sinks with high management potential can be identified. However, source-sink patterns vary among estuary types and with local scale processes.