Effects of PAHs on meiofauna from three estuaries with different levels of urbanization in the South Atlantic

Estuarine environments are suggested to be the final receivers of human pollution and are impacted by surrounding urbanization and compounds carried by the river waters that flow from the continent. Polycyclic aromatic hydrocarbons (PAHs) are among the contaminants that can reach estuaries and can directly affect marine conservation, being considered highly deleterious to organisms living in these environments. This research investigated the meiofauna of three estuaries exposed to different levels of urbanization and consequently different levels of PAH concentrations, in order to assess how these compounds and environmental factors affect the distribution, structure and diversity of these interstitial invertebrates. A total of 15 major meiofauna groups were identified, with Nematoda being the dominant taxon (74.64%), followed by Copepoda (9.55%) and Polychaeta (8.56%). It was possible to observe significant differences in all diversity indices studied in the estuaries. With the exception of average density, the diversity indices (richness, Shannon index and evenness) were higher in the reference estuary, Goiana estuarine system (GES). On the other hand, the Timbó estuarine system (TES) had the lowest Shannon index value and richness, while the Capibaribe estuarine system (CES) had the lowest evenness value. The latter two estuaries (TES and CES) presented intermediate and high levels of urbanization, respectively. The ecological quality assessment (EcoQ) in the studied estuaries was classified from Poor to Moderate and the estuary with the lowest demographic density in its surroundings, GES, showed a better ecological quality (Moderate EcoQ). A significant distance-based multivariate linear modelling regression (DistLM) was observed between the environmental variables and the density of the meiobenthic community, where PAHs and pH were the main contributors to organism variation. The sediments were characterized by predominance of very fine sand and silt-clay in the most polluted environments, while the control site environment (GES) was dominated by medium grains. The highest concentrations of PAHs were found in the most urbanized estuaries, and directly affected the structure of the interstitial benthic community. The metrics used in the present study proved to be adequate for assessing the environmental quality of the investigated estuaries

Toxic effects of phenanthrene intensify with an increase of temperature for the populations of a free-living nematode

Phenanthrene is one of the most common Polycyclic Aromatic Hydrocarbons (PAHs) in the marine environment. It has high lipoafinity and environmental persistence and tends to accumulate in benthic ecosystems. Exposure to phenanthrene can have severe impacts on a wide range of marine organisms, from nematodes to fish. These effects can be exacerbated with concurrent warming associated with climate change. In this study we in-vestigated the response of free-living nematode populations of the species Diplolaimelloides delyi following exposure to different phenanthrene concentrations under normal and increased temperature conditions (from 25 degrees C up to 35 degrees C). Phenanthrene was toxic to D. delyi, causing a decrease in population growth (at concentrations >_1 mu g ml(-1)) and negatively affecting their development times and reproduction (at concentrations >_2.5 mu g ml(-1)). The observed effects intensified with increasing temperature, leading to further reduced development and population growth rate, arrested reproduction, and even mortality in 100% of the populations exposed to phenanthrene concentrations over 5 mu g ml(-1) at the highest temperature used (30 degrees C). Thermal induced toxicity effects on marine populations can be significant, and current climate change and warming may have substantial implications for marine food webs and ecosystem functioning