Impacts of dredging on biomarkers responses of caged bivalves in a semi-arid region (Ceará State, NE Brazil)

Chemical contamination affecting filter-feeding bivalves in no-take marine protected areas from Brazil

Marine protected areas (MPAs) are zones geographically delimited under pre-defined management goals, seeking to reduce anthropogenic threats to biodiversity. Despite this, in recent years reports of MPAs affected by chemical contamination has grown. Therefore, this study addresses this critical issue assessing legacy and current chemical contamination in filter-feeder bivalves obtained in very restrictive no-take MPAs from Brazil. The detected pollutants encompass polycyclic aromatic hydrocarbons (PAHs), linear alkylbenzenes (LABs), and persistent organic pollutants (POPs) like dichlorodiphenyltrichloroethane (DDTs) and polychlorinated biphenyls (PCBs). Despite protective measures, bivalves from nine MPAs exhibited high LABs (13.2-1139.0 ng g-1) and DDTs levels (0.1-62.3 ng g-1). PAHs were present in low concentrations (3.1-29.03 ng g-1), as PCBs (0.7-6.4 ng g-1), hexachlorobenzene (0.1-0.2 ng g-1), and Mirex (0.1-0.3 ng g-1). Regardless of the sentinel species, MPAs and management categories, similar accumulation patterns were observed for LABs, DDTs, PAHs, and PCBs. Based on the limits proposed by Oslo Paris Commission, the measured levels of PAHs, PCBs and were below the environmental assessment criteria. Such findings indicate the no biological effects are expected to occur. However, they are higher considering background conditions typically measured in remote or pristine areas and potential simultaneous exposure. Such findings indicate an influence of anthropogenic sources, emphasizing the urgency for monitoring programs guiding strategic management efforts to safeguard these areas.

Biochemical responses in Pacific oysters Magallana gigas (Thunberg, 1793): Tools to evaluate the environmental quality of aquaculture areas

The discharge of sanitary sewage into the bays of the Florianópolis Metropolitan Area (Southern Brazil), has led to the contamination of oyster farms. Consequently, linear alkylbenzenes (LABs) were quantified in the sediment, and the biochemical responses in gills and digestive gland of oysters from six farms were assessed. Our findings revealed elevated levels of LABs in the sediment of the Imaruim and Serraria farms. Additionally, alterations were observed in the antioxidant enzymes: catalase, glutathione peroxidase and superoxide dismutase in both oyster tissue from the Serraria, Santo Antonio de Lisboa and Sambaqui farms. Furthermore, correlation analyses indicated strong and moderate associations between biochemical responses, organic contaminants, and certain physicochemical parameters. Consequently, our results demonstrated the activation of the antioxidant system in oysters, representing a protective response to the presence of sanitary sewage and other contaminants. Therefore, we propose the utilization of biochemical biomarkers for monitoring the environmental quality of farms.

Genotoxicity of surface waters in Brazil

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000-2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil.

Microplastics and linear alkylbenzene levels in oysters Crassostrea gigas driven by sewage contamination at an important aquaculture area of Brazil

The levels of linear alkylbenzenes (LABs) and the occurrence of microplastics (MPs) in the oysters Crassostrea gigas were evaluated in six farming areas in southern Brazil. The results revealed higher concentrations of LABs in oyster tissue from the Serraria (1977 ± 497.7 ng g^-1) and Imaruim (1038 ± 409.9 ng g^-1) sites. Plastic microfibers were found in oysters from all locations with values from 0.33 to 0.75 MPs per oyster (0.27-0.64 MPs per gram) showing the ubiquitous presence of this contaminant in the marine environment, which could be considered a threat to farming organisms. In addition, elements such as Ti, Al, Ba, V, Rb, Cr, and Cu were found in the chemical composition of the microfibers, suggesting MPs as vectors of inorganic compounds. A positive correlation between LABs and thermotolerant coliforms suggests that sewage discharges are the main source of contamination in these oysters cultured for human consumption. The present study highlights the need for efficient wastewater treatment plants and the implementation of depuration techniques in oysters from farming areas.

Molecular changes in oysters Crassostrea gigas (Thunberg, 1793) from aquaculture areas of Santa Catarina Island bays (Florianópolis, Brazil) reveal anthropogenic effects

Anthropogenic activities in coastal regions cause risks to the environmental and human health. Due to the carcinogenic and mutagenic potential, polycyclic aromatic hydrocarbons (PAH) are considered priority for monitoring. Most of the Brazilian production of Crassostrea gigas oysters are placed in the Bays of Santa Catarina Island. The aim of this study was to evaluate molecular responses (phase I and II of biotransformation and antioxidant defense) of C. gigas from six oyster farming areas potentially contaminated by sanitary sewage in Florianópolis Metropolitan (SC, Brazil): Santo Antônio de Lisboa, Sambaqui, Serraria, Caieira, Tapera, Imaruim. We evaluated the transcript levels of CYP1A1-like, CYP2-like, CYP2AU2-like, CYP356A1, GSTA1A-like, GSTO.4A-like, SULT-like, SOD-like and CAT-like by qRT-PCR. Only oysters from Caieira showed levels of thermotolerant coliforms allowed by the law. Chemicals analyses in soft tissues of oysters showed low to average levels of PAH in all monitored areas. Enhanced transcript levels of phase I (CYP1A1-like, CYP3564A1-like, CYP2-like and CYP2AU2-like) were observed in oysters from Serraria and Imaruí, suggesting higher biotransformation activity in these farming areas. Regarding phase II of biotransformation, GSTO.4A-like was up-regulated in oysters from Imaruí compared to Caieira and Santo Antônio de Lisboa. An upregulation of SOD-like and CAT-like were observed in oysters from Imaruí and Serraria, suggesting that oysters from these sites are facing higher prooxidant conditions compared to other areas. By integrating the biological and chemical data it is suggested that human-derived contaminants are affecting the oyster metabolism in some farming areas.

Levels, source appointment, and ecological risk of petroleum hydrocarbons in tropical coastal ecosystems (northeast Brazil): Baseline for future monitoring programmes of an oil spill area

We reviewed 20 years of levels, sources, and environmental risks related to the main petroleum hydrocarbons in the northeast region of Brazil. The aim of this study was to conduct a systematic review to serve as a comprehensive baseline for future monitoring programmes related to the oil spill disaster in 2019/2020. Most contamination levels of both PAHs and AHs were classified as low, except those in specific areas influenced by human activities, such as ports, highly urbanised mangroves, or rivers of medium-sized cities with inadequate liquid and solid waste treatment. Most hydrocarbons were linked to natural sources and burning processes, except in regions of extraction activities and petrochemical facilities as well as highly urbanised areas, where degraded petroleum and oil hydrocarbons predominated. Only 2.5% of the samples exceeded threshold effect levels for ∑_16-PAHs and no samples exceeded probable effect levels. When regional threshold levels were used, however, the probable effect for the ∑_16-PAHs measured was high, ranging from 5.8 to 6.1%. The few studies reporting biological responses showed that hydrocarbons from anthropogenic sources can induce adverse effects on marine organisms even at low to moderate levels. As the region has recently received a considerable quantity of crude oil, studies should be prioritised for a more precise assessment of the impact of this oil spill.

The effects of inflow of agricultural biogas digestate on bivalves' behavior

This study focused on the reaction of bivalve molluscs to biogas digestate, which is a waste product of an increasingly developing biogas production in rural areas worldwide. The effects of biogas digestate on aquatic organisms are not fully known, and neither this substance nor any types of manure were tested in the monitoring based on valvometry, which is a biomonitoring method based on bivalve behavior. The change in bivalves functioning in biogas digestate inflow was studied using three different diluted digestate concentrations. Exposure to the highest concentration of digestate induced a decline of mean shell opening and activity time of Unio tumidus species. A significant difference in behavioral patterns was recorded during the first 10 min after exposure to the digestate. A Gradual decreasing tendency of shell opening levels was apparent under the highest concentration reaching 55% compared to the pretreatment value. Also, a decreasing tendency was observed under the medium concentration (82.4% of initial level) after 2 h, while an increase in shell opening levels was recorded in the most diluted digestate. This research work proved that the inflow of biogas digestate has significant impact on bivalves' behavior. Unio tumidus is a sensitive indicator of biogas digestate inflow in the aquatic environment. Moreover, it proved that the opening and closing activities over time depend on the concentration of the digestate. Therefore, the mollusk bivalves might be utilized in early warning systems to detect organic pollutants in water.

Dredging impacts on the toxicity and development of sediment quality values in a semi-arid region (Ceará state, NE Brazil)

Sediment dredging impacts coastal environments by promoting the resuspension of fine particles and remobilization of contaminants that may trigger toxic effects. In this study, we evaluated the sediment quality in harbor areas of Mucuripe bay, a semi-arid ecosystem located in Ceará state (Brazil), which is subject to dredging activities. A sampling survey was conducted right after dredging operations and data compared to another survey performed prior dredging. Sediments were analyzed for fine particles, organic carbon, nutrients, metals, hydrocarbons, and tributyltin (TBT). Toxicity of whole-sediment and liquid phase exposures were also determined. The concentrations of Cd, Cr, Cu, and Zn decreased after dredging, which was confirmed by the geoaccumulation index. Levels of TBT dropped while phosphorus, aliphatic and polycyclic aromatic hydrocarbons increased. Toxic effects persisted, indicating a post-dredging recontamination combined with other sources such as urban runoff, wastewater discharges, harbor activities, and antifouling particles. Data from Mucuripe and Pecém harbors were compiled and site-specific sediment quality values (SQVs) were developed by using multivariate methods. The threshold values proposed by our study were lower and more effective to predict toxicity compared to international guidelines, indicating levels of contamination for this tropical region in which toxic effects may occur. Considering the large geographic area with different sediment characteristics of the Brazilian coast, this study represents a significant contribution to sediment toxicity assessment of dredging activities in semi-arid environments.

Effects of pollution on marine organisms

This review covers selected 2019 articles on the biological effects of pollutants, including human physical disturbances, on marine and estuarine plants, animals, ecosystems, and habitats. The review, based largely on journal articles, covers field, and laboratory measurement activities (bioaccumulation of contaminants, field assessment surveys, toxicity testing, and biomarkers) as well as pollution issues of current interest including endocrine disrupters, emerging contaminants, wastewater discharges, marine debris, dredging, and disposal. Special emphasis is placed on effects of oil spills and marine debris due largely to the 2010 Deepwater Horizon oil blowout in the Gulf of Mexico and proliferation of data on the assimilation and effects of marine debris microparticulates. Several topical areas reviewed in the past (e.g., mass mortalities ocean acidification) were dropped this year. The focus of this review is on effects, not on pollutant sources, chemistry, fate, or transport. There is considerable overlap across subject areas (e.g., some bioaccumulation data may be appeared in other topical categories such as effects of wastewater discharges, or biomarker studies appearing in oil toxicity literature). Therefore, we strongly urge readers to use keyword searching of the text and references to locate related but distributed information. Although nearly 400 papers are cited, these now represent a fraction of the literature on these subjects. Use this review mainly as a starting point. And please consult the original papers before citing them.

Data on hydrocarbons in sediment samples, and its body burden levels in tissues of Anomalocardia flexuosa from toxicity testing

The analysis of hydrocarbons in terms of individual compounds is relevant to understand the origin and source of these substances, as well as its distribution in environmental compartments, including sediments and biota. Hydrocarbons concentrations were determined in sediments and in whole-body soft tissues of the tropical clam Anomalocardia flexuosa in sediment toxicity testing using samples of Mucuripe bay (Ceará State, NE Brazil) collected in 2011 during dredging events [1]. Data of target compounds included aliphatic (AHs) and aromatic hydrocarbons (PAHs), and linear alkylbenzenes (LABs). AHs compounds were determined on gas chromatography with flame ionization detector (GC-FID), while PAHs and LABs were determined on gas chromatography coupled to a mass spectrometer (GC/MS) in a selected ion mode (SIM). The potential of this dataset is baseline information on hydrocarbons contamination in sediments from a semi-arid region and the bioaccumulation of organic contaminants in marine organisms that can be used as models in ecotoxicological studies.

Biomarkers responses of the clam Anomalocardia flexuosa in sediment toxicity bioassays using dredged materials from a semi-arid coastal system

Few test organisms are employed for sediment toxicity assessments in Tropical regions, including Brazil. We assessed the ability of the clam Anomalocardia flexuosa to respond to contamination in sediment bioassays using dredging materials of a semi-arid region (Ceará State, NE Brazil), with attention to sublethal responses. Sediments were collected during and after dredging (survey 1 and 2, respectively) and animals exposed in laboratory over 28 days, with responses measured at 7 days. Bioaccumulation of contaminants was determined in whole-body soft tissues as a metric of bioavailability, and biomarkers' changes were monitored in terms of enzymes of phase I and II metabolism, acetylcholinesterase (AChE), and antioxidant responses, lipid peroxidation (LPO) and DNA damage (strand breaks). Clams accumulated aliphatic (AHs) and aromatic hydrocarbons (PAHs), and linear alkylbenzenes (LABs) compared to control conditions (day 0), with increased amounts of As, Cd, Cu, and Zn observed in some samples. The enzyme glutathione S-transferase was enhanced in animals exposed to samples, indicating activation of phase II metabolism. Changes observed in glutathione peroxidase (GPx), glutathione reductase (GR), LPO and strand breaks were related to oxidative stress. AChE enzymatic activity also changed, as an indicator of neurotoxicity caused by sediment exposure. The computed integrated biomarker response index (IBR) ranked sites according to the contamination status and proximity to its sources. Correlations found for biomarkers and bioaccumulation of hydrocarbons indicated the influence of harbor activities, effluent discharges, and urban runoff on the sediment pollution of Mucuripe Bay. Data also showed that SQGs are unable to predict bioaccumulation and subchronic effects. Based on our results we consider that biomarkers responses in A. flexuosa are important endpoints to be applied in sediment toxicity bioassays in tropical regions.

Biomonitoring of Mimachlamys varia transplanted to areas impacted by human activities (La Rochelle Marina, France)

The development of human activities on French Atlantic coastlines (La Rochelle) lead to chronic pollution of the environment by organic (pesticides, hydrocarbons, agrochemicals) and inorganic (heavy metals) contaminants. These past years, several regulations have been implemented to preserve coastal environments. The purpose of this study was to perform biomonitoring of bivalve species using an outdoor caging technique. The goal of our work was to assess the impact of harbour's trace elements on the state of health of the marine bivalve Mimachlamys varia. First, various molecular defence biomarkers were measured: SOD (oxidative stress), GST (detoxification process), MDA (lipid peroxidation), and Laccase (immune reaction). Thus, in April 2016, scallops were collected at three caging sites, which differ by their levels of pollution, after transplantation into port areas (fairing, rainwater) and a control site (marsh). Bivalve samples were taken at three sampling dates (D0, D07, D21). Biomarker assays were performed in the digestive glands due to their bioaccumulation properties. The second aim was to explore the impacts of inorganic pollutants placed in environmental harbour's sites. After 21 days, the biomarker response of transplanted bivalves revealed a SOD decrease, Laccase and GST stimulations, higher concentrations in Cu, Fe, As, Co, Mn, Zn, Sn and no significant variation of MDA concentration. Our ecological relevance of biomarker approaches opens interesting perspectives to identify M. varia such as a pertinent marine sentinel species. The several selected biomarkers determined could confirm their ability to appraise the water quality of hydro-systems located in French coastlines, such as port areas.