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.

Disentangling natural vs. anthropogenic induced environmental variability during the Holocene: Marambaia Cove, SW sector of the Sepetiba Bay (SE Brazil).

Multiproxy approach based on textural, mineralogical, geochemical, and microfaunal analyses on a 176-cm-long core (SP8) has been applied to reconstruct the Holocene paleoenvironmental changes and disentangling natural vs. anthropogenic variability in Marambaia Cove of the Sepetiba Bay (SE Brazil). Sepetiba Bay became a lagoonal system due to the evolution and development of the Marambaia barrier island during the Holocene and the presence of an extensive river basin. Elemental concentrations from pre-anthropogenic layers from the nearby SP7 core have been used to estimate the baseline elemental concentrations for this region and to determine metals enrichment factors (EF), pollution load index (PLI), and sediment pollution index (SPI). Record of the core SP8 provides compelling evidence of the lagoon evolution differentiating the effects of potentially toxic elements (PTEs) under natural vs. anthropic forcing in the last ~ 9.5 ka BP. The study area was probably part of coastal sand ridges between ≈ 9.5 and 7.8 ka BP (radiocarbon date). Events of wash over deposited allochthonous material and organic matter between ≈ 8.6 and 7.8 ka. Climatic event 8.2 ka BP, in which the South American Summer Monsoon was intensified in Brazil causing higher rainfall and moisture was scored by an anoxic event. Accumulation of organic matter resulted in oxygen depletion and even anoxia in the sediment activating biogeochemical processes that resulted in the retention of potentially toxic elements (PTEs). After ≈ 7.8 ka BP at the onset of the Holocene sea-level rise, a marine incursion flooded the Marambaia Cove area (previously exposed to subaerial conditions). Environmental conditions became favorable for the colonization of benthic foraminifera. The Foram Stress Index (FSI) and Exp(H'bc) indicate that the environmental conditions turned from bad to more favorable since ≈ 7.8 ka BP, with maximum health reached at ≈ 5 ka BP, during the mid-Holocene relative sea-level highstand. Since then, the sedimentological and ecological proxies suggest that the system evolved to an increasing degree of confinement. Since ≈ 1975 AD, a sharp increase of silting, Cd, Zn, and organic matter also induced by anthropic activities caused major changes in foraminiferal assemblages with a significant increase of Ammonia/Elphidium Index (AEI), EF, and SPI values and decreasing of FSI and Exp(H'bc) (ecological indicators) demonstrating an evolution from "moderately polluted" to "heavily polluted" environment (bad ecological conditions), under variable suboxic conditions. Thus, core SP8 illustrates the most remarkable event of anthropogenic forcing on the geochemistry of the sediments and associated pollution loads and its negative effect on benthic organisms.