Can environmental pollution by metals change genetic diversity? Ucides cordatus (Linnaeus, 1763) as a study case in Southeastern Brazilian mangroves

Contamination acts as a genotype-dependent barrier to gene flow, causing genetic erosion and fine-grained population subdivision in Mussels from the Strait of Istanbul

This study provides evidence of fine-grained genetic structuring in Mediterranean mussels (Mytilus galloprovincialis) from the Strait of Istanbul, caused by barriers to gene flow via contaminant-mediated selection. In this study, mitochondrial D-loop sequences were analyzed in mussels from 8 localities, all less than 30 kilometers apart, with differing contaminant loads. The results were: 1) Intra-population genetic differentiation (ΦST) between sites with high and low contaminant loads was high (up to 0.459), even at distances of only a few kilometers. 2) Genetic diversity was negatively correlated with the contaminant load ("genetic erosion"). 3) There was evidence of selection, based on haplotype frequencies and neutrality tests (Tajima's D), with purifying selection at the most contaminated site and balancing selection at the least contaminated. 4) Genetic distance was not correlated with geographic distance (no isolation-by-distance), but was correlated with contaminant load at each site. 5) Population dendrograms and Bayesian estimators of migration indicated that gene flow between sites was affected by contamination. For the dendrograms of the sampling sites, the clades clustered according to contaminant load more than geographic distance. Overall, these results suggest that 1) contamination may serve as a genotype-dependent dispersal barrier (i.e., contamination may not affect total number of migrants, just the relative proportions of the haplotypes in the established immigrants), leading strong population differentiation over short distances, and 2) genetic erosion may occur by a combination of selection and altered patterns of haplotype-specific gene flow. These effects may be more pronounced in the Strait of Istanbul than in other locations because of the riverine nature and strong, uni-directional current of the strait.

Distribution, toxicity and bioaccumulation of trace metals in environmental matrices of an estuary in a protected area

Mangroves are productive ecosystems that are highly threatened by anthropogenic activities. We investigated the environmental quality of the Serinhaém river estuary located in a legally protected area. Through chemical analysis of sediments and tissues of Cardisoma guanhumi, in addition to bioassays with elutriate involving Nitokra sp. and Thalassiosira pseudonana, we determined the contamination status and risk factors related to trace metals in the estuary. For the sediment, the concentrations of Cr and Ni were above the limit established by CONAMA n° 454/2012 in the "City" site, and Cr above the TEL in all sampling sites. Ecotoxicological tests showed high toxicity in samples from "City" and "Tributary". The elements Cr, Mn, Ni and Zn were also higher in crabs from these sites. Cr levels exceeded the Brazilian limit for food consumption. The bioaccumulation factor was not significant. However, the overall analysis proved that this estuary is increasingly impacted by anthropogenic pressure.

Geospatial modeling and ecological and human health risk assessments of heavy metals in contaminated mangrove soils

Heavy metal-contaminated wastes can threaten mangrove forests, one of the most biodiverse ecosystems in the world. The study evaluated the geospatial distribution of heavy metals concentrations in soils, the ecological and human health risks, and metal contents in soil fractions and mangrove organisms in the Botafogo estuary, Brazil, one of the most environmentally impacted estuaries in the country. The metal concentrations exceeded by up to 2.6-fold the geochemical background; 91%, 59%, 64%, 31%, and 82% of the soils were contaminated with Cr, Zn, Pb, Cu, and Ni, respectively. Adverse effects to the biota may occur due to Cr, Cu, Ni and Pb exposures. Contents of clay and organic matter were the main factors governing the distribution of metals in soil, contributing to up to 63% of the total variability. However, the geospatial modeling showed that the predictive ability of these variables varied spatially with the metal and location. The ecological and human health risks assessments indicated that the metal concentrations in soils are safe for the environment and human beings. There was a low transfer of metals from the soil to the biota, with values of sediment-biota accumulation factor (SBAF) and biological accumulation coefficients (BAC) lower than 1.0, except for Zn (SBAF = 13.1). The high Zn bioaccumulation by Crassostrea rhizophorae may be associated with the concentrations of Zn in the bioavailable fractions.

In vivo experimental study to investigate cytogenotoxicity of a contaminated estuary from Southeastern Brazilian Coast

The aim of this study was to evaluate cytogenotoxicity in mammalian cells induced by ingestion of superficial water from SESS. For this purpose, surface water was collected from two points of SESS: São Vicente Channel (SVC) and Piaçaguera Channel (PIC). Four groups (n = 5) of adult male Wistar (8 weeks old) received for 5 days: (a) filtered tap water (water control), (b) tap water with 2.4% of NaCl (saline control), (c) estuarine water from PIC and (d) estuarine water from SVC. Results demonstrated that Ki67 immunoexpression was higher in hepatocytes exposed to both sampling site, while caspase-3 demonstrated downregulation in rat liver exposed to estuarine water. There was also significant increase in micronuclei frequency in bone marrow cells and hepatocytes, and DNA damage in blood and liver of rats exposed to estuarine water from SVC and PIC. In summary, studies with complex mixtures, such as contaminated estuarine water are important since this work confirmed by experiments using in vivo mammalian cells of rats that SESS water are genotoxic, mutagenic and cytotoxic, denoting concern for environmental health.

Biomarkers and occurrences of heavy metals in sediment and the bioaccumulation of metals in crabs (Ucides cordatus) in impacted mangroves on the Amazon coast, Brazil

In this study, we analyzed biomarkers and heavy metals in Ucides cordatus specimens caught in mangrove areas [A1 = reference (low impact area); A2, A3 and A4 = port complex (potentially impacted area)] of the Amazonian northern coast of Brazil. Sediments and crab muscles sampled from the potentially impacted mangroves showed high levels of metals. Additionally, catalase and glutathione S-transferase enzymes in the gills and hepatopancreas of the collected crabs were elevated in crabs from A2, A3 and A4 relative to those from A1. The histological characteristics of the gills and hepatopancreas differed in crabs collected from A2, A3 and A4 compared with those collected from A1. The crabs were larger and heavier in the rainy season in A1 and A3 and heavier in the dry season in A4. Heavy metal analyses of sediments, crab muscles and biological responses indicated that the animals are subjected to stress levels differentiated in the mangroves due to a gradient (A4>A3>A2>A1) of anthropogenic pressure in São Marcos Bay. In conclusion, the analyses of metals in the sediment and in the muscles of crabs, as well as the biochemical biomarker and histological analyses, suggest that crabs from mangroves in the port complex region are subject to pollutants that compromise their health.

In vivo and in vitro analysis of cytogenotoxicity in populations living in abnormal conditions from Santos-Sao Vicente estuary

The aim of the study was to evaluate cyto- and genotoxic effects in populations living in subnormal clusters in Santos São Vicente estuary. For in vivo study, samples of buccal mucosa and peripheral blood cells were collected. Micronucleus assay and single-cell gel (comet) assay were performed. For in vitro study, Chinese ovary hamster (CHO) cells were exposed to contaminated water. The results showed that people living in the contaminated estuary have increased DNA damage in oral mucosa and peripheral blood cells, as detected in the micronucleus and comet assays respectively. In addition, estuarine water was able to promote cytotoxicity at the highest concentrations, as well as decrease the number of cells in the G1 phase. In summary, our results indicate that water from the Santos-São Vicente estuary is capable of inducing cytogenotoxicity in mammalian cells in vivo and in vitro.

Adaptative responses of myenteric neurons of Sphoeroides testudineus to environmental pollution

Contamination in estuarine regions affects the local biota damaging the ecosystems and reaching humans. The gastrointestinal tract is a dynamic environment capable of obtaining nutrients and energy from food while it protects the host against harmful toxins and pathogens from the external environment. These functions are modulated by the enteric nervous system and changes in its structure can result in gastrointestinal disorders. The objective of this study was to evaluate if the environmental contaminants have effects on the myenteric neuronal plasticity of pufferfish Sphoeroides testudineus. Animals were collected in Barra do Una River, located at Jureia-Itatins Mosaic of Protected Areas (reference area - RA) and in the Santos Estuarine System (impacted area - IA). Morpho-quantitative analyses of the general and metabolically active myenteric neuronal populations of the proximal and distal intestine were made. Disarrangement was observed in the general organization of the myenteric plexus, with an expressive reduction of the neuronal groups (nodes) in the animals of IA. The vulnerability of the myenteric plexus was evidenced by a decrease in density and cellular profile of the general neuronal population, followed by an increase of the metabolism of the remaining neurons, which in turn was verified by a growth of the area of the cellular and nuclear profiles of the metabolically active neuronal population. Through these analyses, we concluded that animals inhabiting polluted regions present alterations in the myenteric neuronal plasticity, as a way of maintaining the functions of the gastrointestinal tract.

Limited impact of several years of pretreated wastewater discharge on fauna and vegetation in a mangrove ecosystem

It was hypothesized that mangroves, tropical wetlands, could be used for the finishing treatment of domestic wastewaters. Our aim was to determine if a nutrient-stressed mangrove could tolerate long-term discharges of pretreated wastewater (PW). Since 2008, in an in situ experimental system set up in Mayotte Island (Indian Ocean), domestic PW are discharged into two impacted areas (675 m²) dominated by different species of mangrove trees. Anthropogenic inputs during > 4.5 years led to an increase in vegetation growth associated with an increase in leaf pigment content, leaf surface and tree productivity. A marked increase in tree mortality was observed. There was no effect on crabs and meiofauna densities, but significant modifications of community structures. These effects may be directly linked to PW inputs, or indirectly to the modifications of the environment associated with higher tree growth. However, our results indicate that there was no major dysfunction the ecosystem.

Metal toxicity assessment by sentinel species of mangroves: In situ case study integrating chemical and biomarkers analyses

Globally, there is a lack of knowledge about tropical ecotoxicology dealing with the potential impact of metal contamination in mangrove ecosystem. This habitat is considered a nursery for several animal species, among them the "uçá"-crab (Ucides cordatus), known as a key species due to its biological and economical importance. This study evaluated the association involving metal contamination (Cd, Cu, Pb, Cr, Mn and Hg) in water, sediment, red-mangrove vegetation (Rhizophora mangle) and tissues of uçá crab, together with its geno-cytotoxic responses, based on micronucleated hemocytes frequency and the retention time of neutral red in lysosomes. We assessed six mangrove areas with distinct pollution levels in São Paulo State, Brazil, where the water and sediment contamination by metals were associated with accumulation of these pollutants in biotic compartments (mangrove leaves and crab). In U. cordatus, metal accumulation was best explained by metal concentration found in leaves of R. mangle than in the water or sediment, indicating that feeding drives metal exposure in this organism. Mercury (Hg) concentration in sediment, copper (Cu) concentration in hepatopancreas of U. cordatus and lead (Pb) in water and green leaves of R. mangle showed a significant correlation with genotoxic impact in U. cordatus. However, copper concentration (in green/senescent leaves and hepatopancreas) and lead (in sediment), were the major metals affecting lysosomal membrane integrity. Therefore, representatives of all compartments were associated with cyto and genotoxicity in this species, thus requiring a holistic approach to issues related to sublethal damage. Probability estimates of cytogenetic impacts related to metal concentration in abiotic compartments (significantly correlated with known biomarkers: Hg in sediment; and Pb in water and sediment) are also presented. Our results highlight the need for environmental restoration of mangroves areas contaminated with metals, responsible for cytogenetic injuries and revealing a pre-pathological condition in this sentinel species, in addition to ecological disturbances.