Five years after the collapse of the Fundão Dam: lessons from temporal monitoring of chemistry and acute toxicity.

In November 2015, the Fundão Dam break released millions of tons of metal-rich tailings into the Doce River Basin (DRB), causing catastrophic damage and potential ecological effects that reached the Atlantic Ocean. This study aimed to evaluate the geochemistry and toxicity of water and sediments collected in the DRB from 2015 to 2019 and to determine the spatial and temporal trends. Water and sediment samples were analyzed for metals and As by inductively coupled plasma optical emission spectrometry (ICP-OES), and acute toxicity for Daphnia similis or D. magna. Results were explored using geochemical indices and correlation analyzes. Overall, higher concentrations of metals and As in water and sediments were observed immediately after dam breakage, but the levels exhibited a decreasing trend over time, although the levels of some elements such as As and Mn remained high in the upper DRB. The geochemical indices indicated mostly low to moderate contamination, and the enrichment factor (EF) demonstrated a higher enrichment of Mn in the upper DRB. Acute toxicity to water fleas (D. similis and D. magna) was occasionally observed in waters and sediments, but the reference samples were toxic, and the short-term effects were not correlated with metals and As. Overall, the results showed limited bioavailability of metals and As and a decreasing trend in their concentrations, indicating an ongoing recovery process in DRB. These results are important to decision-making regarding the disaster and actions for environmental restoration.

Ocean warming and CO2-driven acidification can alter the toxicity of metal-contaminated sediments to the meiofauna community.

Interactive effects of trace metal contamination, ocean warming, and CO2-driven acidification on the structure of a meiofaunal benthic community was assessed. Meiofauna microcosm bioassays were carried out in controlled conditions in a full factorial experimental design which included three fixed factors: metal contamination in the sediment (3 levels of a mixture of Cu, Pb, Zn, and Hg), temperature (26 and 28 °C) and pH (7.6 and 8.1). Metal contamination caused a sharp decrease in the densities of the most abundant meiobenthic groups and interacted with temperature rise, exacerbating deleterious effects for Nematoda and Copepoda, but mitigating effects for Acoelomorpha. CO2-driven acidification resulted in increased acoelomorphs density, but only in sediments with lower levels of metals. Copepod densities, in turn, were lower in the CO2-driven acidification scenario regardless of contamination or temperature. The results obtained in the present study showed that temperature rise and CO2-driven acidification of coastal ocean waters, at environmentally relevant levels, interacts with trace metals in marine sediments, differently affecting the major groups of benthic biota.

Bioaccumulation of heavy metals in estuaries in the southwest Atlantic Ocean.

The southwestern Atlantic Ocean is home to highly productive regions, composed of a mosaic of both protected and anthropogenically impacted areas, including the estuaries of Paranaguá, Cananéia, and Santos. In this study, concentrations of metals were measured in sediments and in marine organisms, collected from these three Brazilian estuaries. The higher concentrations of metals in the sediments from the Santos estuary are due to having the greatest intensity of anthropogenic activities. There is bioaccumulation of As, Cu, Ni, and Pb in benthic invertebrates, As in fish, and Se and Zn in all studied trophic groups. Comparing the biota among estuaries, levels were highest for Cr, Cu, Pb, Se, and Zn in Paranaguá, As in Cananéia, and Ni in Santos; results justified due to anthropogenic activities, natural sources, and geochemical and hydrodynamics characteristics of each region that affect the bioavailability of metals. The results showed that these regions of the Atlantic present higher levels of metals in the biota than several coastal regions worldwide, and signal that food security may be compromised. Highlighting the need for better impact assessment, monitoring, and managing is deemed necessary as these regions are globally recognized as hotspots of biodiversity and are considered priority areas for conservation.

Genotoxic effects of silver nanoparticles on a tropical marine amphipod via feeding exposure.

Silver nanoparticles (AgNP) are widely used in several applications including as antifouling agents; therefore, they can end up in estuarine and marine environments. These nanoparticles tend to aggregate and to deposit in the sediment, where many organisms feed and reproduce. Parhyale hawaiensis is an epibenthic amphipod globally distributed in tropical zones, and has been considered a potential model for ecotoxicology. The aim of this study was to evaluate genotoxic effects of AgNP and Ag salt via feeding, as P. hawaiensis lives in the sediment where nanoparticles tend to accumulate. Organisms were cultivated in the laboratory, and adults were exposed to food containing both AgNP and Ag salt. We collected hemolymph after different times of exposure, and analysed the hemocytes for nuclear abnormalities (including micronuclei) and DNA damage using the standard alkaline comet assay. Conditions of both assays were developed/optimized to allow their successful application in marine invertebrates. Increased frequencies of micronuclei, nuclear buds and total abnormalities were detected in relation to concentration and time in organisms exposed to AgNP and Ag salt in comparison to the controls. No DNA damage was detected when the alkaline comet assay was applied. After 5 days of exposure, we observed higher micronuclei frequencies in Ag salt treatment in comparison with AgNP. After 13 days, micronuclei frequencies were similar for both silver forms. We believe that the Ag, in its ion form, is causing the mutagenic effect; therefore, more time would be needed for the release of the ion from AgNP, explaining the delayed mutagenic effect.

Assessment of crabs from Trindade, a Brazilian remote island: Support to marine studies.

Trindade is a remote island far from 1170 km of the Brazilian coast in the Atlantic Ocean, between South America and South Africa. The island has great biodiversity and scientific studies on the fauna and flora of Trindade are still scarce. Accordingly, since crustacean species of the island are also little known, this research features an unprecedented data set, which provides information on the level of potential toxic elements in two crab species: the Grapsus grapsus (herbivore) and the endemic species Gecarcinus lagostoma (omnivorous) which is in threatened status. Although Trindade has experienced contamination from human activities, mainly plastic debris, the element levels found in the samples suggest that there are no relevant inorganic sources into the island. Since minor and trace elements accumulated by marine invertebrates does not present a pattern behavior, our results can support other studies focused on the impact of global warming to the marine ecosystem.

Mercury in trophic webs of estuaries in the southwest Atlantic Ocean.

Anthropogenic activities have impacted the coastal region of Brazil. In the Paranaguá estuarine complex (PEC), Cananéia-Iguape estuarine-lagoon complex (CIELC), and Santos-São Vicente estuarine complex (SSVEC), such activities occur across differing scales. In these estuaries, the concentrations of mercury (Hg) and stable nitrogen isotopes (δ15N) were investigated in sediments and marine organisms including benthic macrofauna, fish and cetaceans. Hg bioconcentration occurred primarily in cetaceans, polychaetes and molluscs, and reflects the impact of anthropogenic activities in the regions studied (PEC and SSVEC > CIELC). Bioaccumulation occurred in most of the studied specimens, but biodilution of Hg was observed in the trophic webs of SSVEC and CIELC. Despite measuring lower Hg levels than in studies carried out in the northern hemisphere, the results highlight potential concerns for public and environmental health in these highly productive coastal regions in the southwestern Atlantic which are important for fishing and various economic activities.

Assessment of metal contamination in fish from estuaries of southern and southeastern Brazil.

Historically, the Brazilian coast has been impacted by urban, industrial, and port activities that have increased the input of chemical contaminants, such as heavy metals, to the ecosystem. The Paranaguá estuarine complex (PEC), Cananéia-Iguape estuarine-lagoon complex (CIELC), and Santos-São Vicente estuarine complex (SSVEC) (S-SE Brazil) are surrounded by urbanized cities and port areas characterized by various anthropogenic discharges comprising several potential pollutants, including heavy metals. Concerns about such contamination are paramount because these estuaries are important for traditional fishing communities and are categorized as World Heritage sites and biodiversity hotspots by UNESCO. In this study, metals (Cu, Cr, Ni, Pb, Zn, and Hg) and metalloids (As and Se) known to affect the health of marine life were evaluated in regional fishes. Muscle and liver tissues from three demersal teleosts (Stellifer rastrifer, Paralonchurus brasiliensis, and Isopisthus parvipinnis) were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), with a coupled vapor generated accessory (VGA). Irrespective of species, metal bioconcentration was significantly greater in fishes from the PEC and CIELC, which had higher As, Cu, and Zn concentrations, while Se levels were higher in fish from the PEC and SSVEC estuaries. Seasonality, fish species and maturation stage affected the accumulation of metals. Some metal levels, including As, Cr, Pb, and Se in all species across all estuaries, and Zn in the PEC, exceeded the maximum permitted level for seafood and might present a risk for daily human consumption. The results provide reference points for existing chemical contamination and should be used to guide monitoring programs and the sustainable development of these coastal regions, within a broader objective of maintaining public health.

Heavy metal concentrations in the benthic trophic web of Martel Inlet, Admiralty Bay (King George Island, Antarctica).

Knowledge of the metals behaviour in the Antarctic environment is important for conserving this continent, which can be impacted by local activities, such as research stations and by atmospheric and oceanic transport over long distances. As, Cd Cr, Cu, Hg, Ni, Pb and Zn levels and the nitrogen isotope ratio were investigated using benthic samples from Martel Inlet, Admiralty Bay. The results showed the biodilution of As and a tendency of increasing concentrations of Cd and Cu along the trophic web. Biomagnification was verified only for Zn, and this was attributed to its essentiality to the biota, and to the acting of metallothioneins proteins that participate in homeostasis, store and detoxify metals. These results can be used as baseline levels for the biota in the Antarctic region and assist the monitoring and management work developed by the Brazilian INCT-APA (National Institute of Science and Technology for Environmental Research Antarctic).

Bioaccumulation of heavy metals in marine organisms and sediments from Admiralty Bay, King George Island, Antarctica.

The Antarctic continent is considered a low-impact environment; however, there is a tendency to increase the contaminants' levels due to human activities in the research stations. In this study, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn levels in sediment and biota were determined in the environmental samples from Admiralty Bay (King George Island, Antarctica) collected in 2003. The results demonstrated high concentrations of Cu and Zn in the sediments. There was bioaccumulation of As in the biota from Admiralty Bay and bioaccumulation of Zn specifically in the biota from Martel Inlet. In addition, the results were useful in order to understand the heavy metal levels for the pre-accident condition of Comandante Ferraz Antarctic Station, where an accident occurred in 2012, and also for the comparison with current conditions within the monitoring work developed by INCT-APA (National Institute of Science and Technology for Environmental Research Antarctic).