Micro and Nano-Plastics in the Environment: Research Priorities for the Near Future.

Plastic litter dispersed in the different environmental compartments represents one of the most concerning problems associated with human activities. Specifically, plastic particles in the micro and nano size scale are ubiquitous and represent a threat to human health and the environment. In the last few decades, a huge amount of research has been devoted to evaluate several aspects of micro/nano-plastic contamination: origin and emissions, presence in different compartments, environmental fate, effects on human health and the environment, transfer in the food web and the role of associated chemicals and microorganisms. Nevertheless, despite the bulk of information produced, several knowledge gaps still exist. The objective of this paper is to highlight the most important of these knowledge gaps and to provide suggestions for the main research needs required to describe and understand the most controversial points to better orient the research efforts for the near future. Some of the major issues that need further efforts to improve our knowledge on the exposure, effects and risk of micro/nano-plastics are: harmonization of sampling procedures; development of more accurate, less expensive and less time-consuming analytical methods; assessment of degradation patterns and environmental fate of fragments; evaluating the capabilities for bioaccumulation and transfer to the food web; and evaluating the fate and the impact of chemicals and microorganisms associated with micro/nano-plastics. The major gaps in all sectors of our knowledge, from exposure to potentially harmful effects, refer to small size microplastics and, particularly, to the occurrence, fate and effects of nanoplastics.

Yellow-legged gull eggs (Larus michahellis) as persistent organic pollutants and trace metal bioindicator for two nearby areas with different human impact.

The concentration of different persistent organic pollutants (POPs including chlorinated and brominated compounds) and trace metals and metalloids (As, Cd, Cu, Cr, Pb, Hg, Ni, and Zn) was examined in eggs from two colonies of yellow-legged gulls. The two colonies are established in Ría de Vigo, Northwest Spain, with a distance between them of only 10 km, one in Vigo town (industrial and harbour activities) and the other in the Cíes Islands in a Natural Park and Marine Protected Area -MPA- (with no known anthropogenic inputs). Statistically significant differences for the two colonies were observed for Hg, the sum of 7 CBs, the sum of DDTs y and the sum of 9 PBDEs, with values that could be causing some toxic effects in the area of the most anthropogenically influenced colony. The estimated isotopic niche was also calculated, based on δ15N and δ13C, for the two colonies, pointing to a wider diet in the Cíes colony when compared to the diet in the Vigo colony. The study supports the use of the yellow-legged seagull eggs as a bioindicator of pollution capable of differentiating pollution level even in geographically close areas.

Historical Profiles of Polycyclic Aromatic Hydrocarbons (PAHs) in Marine Sediment Cores from Northwest Spain.

The northwest coast of Spain is characterized by an irregular coastline rich in marine life and with the highest mussel production in Europe. Taking this into account, the characterization of the pollution levels and the sources involved appear necessary. Not only were parent Polycyclic Aromatic Hydrocarbons (PAHs) analysed but also their alkylated homologues. In total, 35 compounds were analyzed in 5 sediment cores. Sediments were collected using a box core dredge and extracted by (Pressurized Liquid Extraction) whilst the quantification of PAHs was performed using gas chromatography coupled to mass spectrometry (GC-MS). The total concentration detected varied from 49.6 to 2489 ng g-1 dry weight (d.w.) of which parent PAHs ranged from 44.5 to 2254 ng g-1 d.w. and alkylated PAHs varied from 5.04 to 317 ng g-1 d.w. Temporal and spatial evolution were outlined and pollution sources were identified along with a possible correlation between this pollution and local history and industry. Most of the PAHs from the superficial samples have a biomass and coal combustion profile, and some specific, localized events are reflected in the total PAH concentration evolution. Moreover, the study of the deepest layers of the sampled cores provides a baseline to develop background concentration values that will help in future sediment quality assessment.

Influence of mussel biological variability on pollution biomarkers.

This study deals with the identification and characterization of biological variables that may affect some of the biological responses used as pollution biomarkers. With this aim, during the 2012 mussel survey of the Spanish Marine Pollution monitoring program (SMP), at the North-Atlantic coast, several quantitative and qualitative biological variables were measured (corporal and shell indices, gonadal development and reserves composition). Studied biomarkers were antioxidant enzymatic activities (CAT, GST, GR), lipid peroxidation (LPO) and the physiological rates integrated in the SFG biomarker (CR, AE, RR). Site pollution was considered as the chemical concentration in the whole tissues of mussels. A great geographical variability was observed for the biological variables, which was mainly linked to the differences in food availability along the studied region. An inverse relationship between antioxidant enzymes and the nutritional status of the organism was evidenced, whereas LPO was positively related to nutritional status and, therefore, with higher metabolic costs, with their associated ROS generation. Mussel condition was also inversely related to CR, and therefore to SFG, suggesting that mussels keep an "ecological memory" from the habitat where they have been collected. No overall relationship was observed between pollution and biomarkers, but a significant overall effect of biological variables on both biochemical and physiological biomarkers was evidenced. It was concluded that when a wide range of certain environmental factors, as food availability, coexist in the same monitoring program, it determines a great variability in mussel populations which mask the effect of contaminants on biomarkers.

PAHs and trace metals in marine surficial sediments from the Porcupine Bank (NE Atlantic): A contribution to establishing background concentrations.

Little is known about pollutant concentrations in marine remote areas such as the Porcupine Bank in the NE Atlantic Ocean. Remote locations are much less studied than the more readily accessible coastal areas, nevertheless, are of great importance both to unveil how far human influence has reached and, are more challenging, to infer background concentrations (BCs) of naturally occurring and/or anthropogenic pollutants. Knowledge of contaminant background levels are critical for establishing remediation and management strategies; in addition, background assessment is heavily emphasised in legislative monitoring requirements. Obtaining suitable sampling locations to assess background concentrations can be challenging, as samples should match characteristics to the target area and not be impacted by historical or current inputs of the chemical substances of study. Anthropogenic impacts generally deem local-based sampling to be unsuitable to infer background pollution values. Sampling in remote areas such as the Porcupine Bank better fulfils low impact and pressure requirements making them more suitable for the derivation of background concentration estimates for organic compounds and metals. The total concentrations of polycyclic aromatic hydrocarbons (PAHs) and metal(loid)s in deep sea sediments were evaluated and both an environmental status and a set of concentration data were adequate to derive BCs concentrations is presented. Concentration data indicated, in comparison with previous published data, trace level presence of PAHs and metal(loids) in sediments from the Porcupine Bank. These values will provide a valuable tool to identify the natural presence of organic and inorganic compounds and be the basis to perform a sound environmental assessment.

Linking chemical contamination to biological effects in coastal pollution monitoring.

To establish the connection between pollutant levels and their harmful effects on living resources, coastal monitoring programmes have incorporated biological tools, such as the scope for growth (SFG) in marine mussels and benthic macrofauna community indices. Although the relation between oxygen-depleting anthropogenic inputs and the alteration of benthic communities is well described, the effects of chemical pollutants are unknown because they are not expected to favour any particular taxa. In this study, the combined efforts of five research teams involved in the investigative monitoring of marine pollution allowed the generation of a multiyear data set for Ría de Vigo (NW Iberian Peninsula). Multivariate analysis of these data allowed the identification of the chemical-matrix combinations responsible for most of the variability among sites and the construction of a chemical pollution index (CPI) that significantly (P < 0.01) correlated with biological effects at both the individual and the community levels. We report a consistent reduction in the physiological fitness of local populations of mussels as chemical pollution increases. The energy balance was more sensitive to pollution than individual physiological rates, but the reduction in the SFG was primarily due to significantly decreased clearance rates. We also found a decrease in benthic macrofauna diversity as chemical pollution increases. This diversity reduction resulted not from altered evenness, as the classic paradigm might suggest, but from a loss of species richness.

Post-incident monitoring to evaluate environmental damage from shipping incidents: chemical and biological assessments.

Oil and chemical spills in the marine environment are an issue of growing concern. Oil exploration and exploitation is moving from the continental shelf to deeper waters, and to northern latitudes where the risk of an oil spill is potentially greater and may affect pristine ecosystems. Moreover, a growing number of chemical products are transported by sea and maritime incidents of hazardous and noxious substances (HNS) are expected to increase. Consequently, it seems timely to review all of the experience gained from past spills to be able to cope with appropriate response and mitigation strategies to combat future incidents. Accordingly, this overview is focused on the dissemination of the most successful approaches to both detect and assess accidental releases using chemical as well as biological approaches for spills of either oil or HNS in the marine environment. Aerial surveillance, sampling techniques for water, suspended particles, sediments and biota are reviewed. Early warning bioassays and biomarkers to assess spills are also presented. Finally, research needs and gaps in knowledge are discussed.

The seasonal cycle of micro and meso-plastics in surface waters in a coastal environment (Ría de Vigo, NW Spain).

Marine litter is an emerging environmental problem. In this study, micro and mesoplastics were determined for the first time in seawater in Ría de Vigo (Spain) identifying their concentration, annual cycle, size, shape and polymer composition. Besides, temporal variations at an annual scale were also established. The Ría de Vigo is well known for the important industry related to marine activities (fishing, mollusc culture, shipyards, and tourism). Three sampling stations were selected along the transverse axis of Ría and were monthly sampled for one year. Seawater samples were collected using a manta trawl and analyzed with ATR-FTIR, and Raman spectroscopy to determine plastic polymer type. The mesozooplankton community (0.2-20 mm) was also studied. The samples were collected with bongo nets in the same sampling stations as plastics. Manta trawl net (330 µm) was used to collect 32 samples (identifying 854 plastic particles; 677 microplastics and 177 mesoplastics). The mean concentration across all sites was 25.4 ± 13.4 items·km-2. The microplastics abundance was greater than that of mesoplastics (79%, and 21%, respectively). Around 30% of plastics analyzed were Polyethylene (PE), 19% were acrylates, 18% were Polypropylene (PP) and 10% were Polystyrene (PS). The main shapes of both micro and mesoplastics were fibers followed by paint sheets being black the main colour in both cases. The results showed high seasonal variability by micro and mesoplastics but similar spatial distribution. This seasonal heterogeneity can have effects on a future monitoring program. Furthermore, it was demonstrated that pollution by mesoplastics cannot be estimated through the microplastics abundances. Regarding the values of microplastics-zooplankton, they present a great negative correlation.

From the coast to the shelf: Microplastics in Rías Baixas and Miño River shelf sediments (NW Spain).

Microplastics (<5 mm; MPs) are globally recognized as an issue of emerging concern in the marine environment. In this study, MPs were determined for the first time in sediments from Rías Baixas and Miño river shelf, to show the baseline contamination levels. The Rías is well known for its intense fishing and shellfish harvesting activities. The sampling stations were selected due to their different exposure to anthropogenic activities and/or pressures. Sediment samples were collected using a box corer dredge and analyzed with density separation and µF-TIR analysis to determine polymer type. The results showed MPs pollution in all stations. The mean concentration was 70.2 ± 74.2 particles/kg DW. The main MPs shape was fibers (88.8%) followed by fragments (5.80%). Regarding the polymers, the most abundant were PP (43%) and HDPE (29%). Once again, MPs are ubiquitous all along Rías and Miño river mouth as previously shown in different works.

Plackett Burman design for microplastics quantification in marine sediments.

Microplastics are gaining worldwide attention due to their omnipresence. The marine environment is one of the most affected systems; especially the sediment compartment. Microplastic separation from the sediment matrix is the first step to evaluate its abundance and availability. Nevertheless, a lack of consistency in extraction protocols is a fact. This paper describes the optimization of the microplastic extraction procedure from marine sediments. The Plackett-Burman saturated factorial design was used to identify the significant factors and to select optimum working conditions. With this purpose, the following variables were studied: the number of extractions; the amount of sediment; the settling time; the density separation solution volume; the agitation time and the suitability of using wet or freeze-dried sediment. The Plackett-Burman design has revealed that the most statistically significant variables were sediment mass and agitation time. The optimized method was applied for two marine sediments collected in the Mar Menor Lagoon.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) occurrence in Sparus aurata exposed to microplastic enriched diets in aquaculture facilities.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are highly stable and bioaccumulative, and microplastics (MPs; plastics <5 mm) are ubiquitous in the marine environment. In this study we report the levels of a selection of pollutants in liver and muscle of juvenile gilthead seabream (Sparus aurata) exposed to virgin and weathered MP enriched diets during three months and followed by one month of MP depuration. In general, a major concentration of pollutants in liver was observed. According to OCPs, total DDTs was two or three times higher in liver. Levels in muscle suffer higher variability between treatments and sampling periods. The MP index was negatively correlated to HCB and positively to p,p'DDT in liver. Levels of pollutants are correlated to biological parameters such as total size and total weight. Our results suggest that the bioaccumulation is subjected to the molecular structure of the pollutants and that MPs are correlated with the detoxification system.

Integrated assessment of water quality of the Costa da Morte (Galicia, NW Spain) by means of mussel chemical, biochemical and physiological parameters.

The aim of this study was to assess environmental quality at some of the sites most severely affected by the Prestige oil spill off 2 years after the spillage (April and November 2004). For this purpose analyses of polycyclic aromatic hydrocarbons (PAH) and several biochemical (antioxidant enzymes catalase, glutathione reductase, glutathione peroxidase, superoxide dismutase and DT-diaphorase and lipid peroxidation) and physiological [scope for growth (SFG)] biomarkers were determined on wild mussel populations (Mytilus galloprovincialis) collected at four points along the Costa da Morte and compared with those of a reference site not affected by the oil spill. Results showed that PAH contents had markedly decreased 17 months after the accident, although they were higher in April than in November, when they showed values similar to background levels reported for this area. Nevertheless, the predominance of chrysene on PAH profiles, similarly to findings obtained immediately after the spill, indicated the Prestige as their main source. In spite of the low PAH levels recorded, antioxidant activity levels (explained through the integrated antioxidant response-IAR) were higher in the Costa da Morte than at the reference site either in April and November. In April IAR seems to be related to PAH levels found 3 months after the accident (February 2003), suggesting the persistence in the environment of oxidative stress-producing components from the spill. However, evidence of oxidative stress was not reflected at physiological level by scope for growth, with only very slight differences being observed between values from the reference site and those from Costa da Morte sites. In conclusion, although 2 years after the spill PAHs bioaccumulated by mussels from the Costa da Morte had decreased to background levels, biochemical parameters showed signals of oxidative stress in mussels from this area. However, SFG reflected a good health status for the mussel populations studied and did not reveal evidence of physiological disturbance either 17 or 24 months after the Prestige spill.

Biomarker considerations in monitoring petrogenic pollution using the mussel Mytilus galloprovincialis.

Mussels are worldwide bioindicators in pollution monitoring since they fulfil the requirements for being good sentinels. However, some methodological concerns arise in the use of particular biomarkers, particularly those displaying low enzymatic rates and/or limited responsiveness to chemicals and biological-related variability. In the present study, the suitability of oxidative stress and detoxification parameters when using mussels as sentinels of polycyclic aromatic hydrocarbon (PAH) pollution is addressed. Present results show that the S9 subcellular fraction of the digestive gland in mussels is an adequate and convenient matrix where to measure most pollution-related biomarkers. Furthermore, this work constitutes the first evidence of the potential suitability of using particular carboxylesterase (CE) activities in determining PAHs exposure in mussels. This fact could imply the replacement of more controversial cytochrome P450 components (phase I oxidation), which are only measurable in microsomal fractions, by CEs (measured in S9 fractions) as good alternatives for phase I reactions in PAH-exposed mussels. Some methodological considerations, such as the need of including commercial purified proteins in biomarker determinations for quality assurance, are evaluated.

Identification of contaminants of emerging concern with potential environmental risk in Spanish continental shelf sediments.

The distribution of per- and polyfluoroalkyl substances (PFAS), alkylphenols, organotin compounds, phthalates, alkylated polycyclic aromatic hydrocarbons, current-use pesticides (CUPs) and personal care products (PCPs) was characterized in 29 surface sediments from two Spanish Iberian continental shelf areas (14 on the Atlantic and 15 on the Mediterranean coasts). Concretely, 115 organic contaminants were determined and a specific methodology was used for each contaminant group, including contaminants of emerging concern (CECs) and traditional ones, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorinated pesticides (OCPs). PAHs, alkylated PAHs, alkylphenols and phthalates were found in all samples, showing mean concentrations per group higher than 20 ng/g (16-4974 ng/g d.w.) in the subregions under consideration (Galician, Cantabrian, Levantine-Balearic and Strait-Alboran). CUPs and PCPs were found in the majority of samples at very low concentrations of ng/g (1.4-46.8 ng/g d.w.), whereas organotins and PFAS were found principally in sediments from the Mediterranean subregions (2.5-3.9 ng/g d.w.). Different distribution patterns were observed for the contaminant groups and subregions under consideration as a consequence of the diverse predominant sources (industrial, urban, transport and agricultural activities) and environmental behavior (mainly hydrophobicity and persistence). Risk assessment confirmed the impact of phthalates, alkylphenols, PAHs and PCBs on Atlantic ecosystems and of alkylphenols, chlorpyrifos, phthalates, TBT, PAHs, OCPs and PCBs on the Mediterranean ones. Furthermore, the presence of CUPs, PCPs and PFAS in sediments from the Spanish continental shelf located between 2 and 31 km from the coast suggested that those contaminants may also provoke adverse effects on coastal marine ecosystems between their sources and their depositional areas. CAPSULE: Alkylphenols, phthalates and organotins may provoke adverse effects on Spanish coastal marine ecosystems from their sources to the sediment depositional areas.

A new perspective on marine assessment of metals and organic pollutants: A case study from Bay of Santander.

Pollution assessment is worldwide generally performed based on 'Trend assessment' or 'Status assessment´, and usually requires monitoring programs that should be designed in terms of pollutants to be studied, frequency and locations. Five groups of pollutants: polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs) and trace metals, were selected to evaluate how actual monitoring programs are coping with the evaluation of anthropogenic activities affect the environment and whether use restrictions and laws that ban certain pollutants are being effective. Santander Bay, in Northern Spain, is an industrial area with 250,000 inhabitants and with several rivers discharging into the Bay; those characteristics made the area an adequate location to perform the study. Marine sediment was selected as the study matrix since it gives comprehensive information regarding the human activities in coastal areas. The study clearly shows that there can be some potential biological impacts on the marine environment due to PAHs (mainly BghiP), PCBs (mainly congener CB118) and metals. On the other hand all analysed OCPs and PBDEs presented values below the applicable guidelines and will therefore, in principle, not give rise to environmental problems. Consequently, even after decades of banning and use restrictions, the studied pollutants are still a main issue in coastal areas. Moreover, the present study helps in the definition of future monitoring programs providing a complete description about the current situation of the listed pollutants.

Occurrence and toxicological assessment of polycyclic aromatic hydrocarbons (PAHs) in marine sediments under mussel farming influence.

The use of marine resources for mussel culture has become increasingly important, particularly on the European Atlantic coast and notably in the Galician Rías in the northwest of Spain. Despite its importance, there is a lack of research and analysis in this area and of the potential problems that it could cause to the environment. This paper details the findings of a study that aimed to find the probable environmental impact of mussel culture activities and to evaluate the polycyclic aromatic hydrocarbon (PAH) content derived from this activity. The Ría de Arousa, where you can find over 70% of all installed rafts in Galicia, was selected for the present study, and nearly 40 marine sediment samples were collected there. The sediments were extracted by ASE (accelerated solvent extraction) procedure, and the quantification of PAHs was performed using gas chromatography coupled to mass spectrometry (GC-MS), with the aid of deuterated PAH internal standards. The total concentration of parental PAHs ranged from 11.66 to 30,272-ng g-1 dry weight (d.w.), with a mean value of 3907-ng g-1 d.w.; the concentration of alkyl PAHs varied from 3.72 to 1187-ng g-1 d.w., with a mean value of 205.1-ng g-1 d.w. Compositional patterns, principal component analysis (PCA) and hieratical cluster association (HCA) yielded a sediment classification where the mussel raft impact is pointed out. PAH ratios indicated a predominance of combustion sources, except in two samples, located in small harbors. Only one station showed total potential carcinogenic PAH values in the range that would frequently cause negative biological effects, and the toxic equivalent concentrations based on BaP equivalents identified another ten positions where biological effects would occur occasionally.

Limpet (Patella sp) as a biomonitor for organic pollutants. A proxy for mussel?

The scarcity of the most widely used species for assessing marine pollution (mussels) in some areas brings out the need to test the use of a different organism. In this study, 11 sampling sites along the Atlantic Spanish coast were selected and both mussels (Mytilus galloprovincialis) and limpets (Patella sp.) were analysed for PAHs, PBDEs and PCBs. The concentrations of the different pollutants in both species followed the same general distribution allowing us to differentiate polluted and unpolluted sites using any of them. Although the concentrations found in limpets were generally lower than those measured in mussels, a good correlation was observed for most of the groups of pollutants and also for every individual congener. A conversion factor was proposed for most of the individual PAH and PCB congeners, allowing the conversion of limpet concentration into mussel concentration that can be directly applied in assessments using environmental criteria derived for mussels.

Effect of mussel reproductive status on biomarker responses to PAHs: Implications for large-scale monitoring programs.

Biomarkers are useful tools to assess biological effects of pollutants and have been extensively used in monitoring programs to determine ecosystem health. In these programs, a wide range of environmental conditions are covered and sometimes, obtained data are difficult to interpret because of natural variables are affecting biomarker responses. Among these variables, mussels reproductive status has been considered one of the most changing variables between sites in a monitoring survey. Thus, the main aim of this work was to identify the effect that mussel reproductive status has on biomarker responses. For that purpose, mussels sampled at two periods in the reproductive cycle (reproductive and resting stages) were conditioned to the same laboratory conditions and exposed to fluoranthene (FLU) for three weeks. Studied biomarkers covering a wide range of organism responses were included: bioaccumulation, physiological rates (clearance rate -CR-, absorption efficiency -AE-, respiration rate -RR- and their integration in the scope for growth -SFG-), antioxidant enzyme activities (superoxide-dismutase -SOD-, catalase -CAT-, glutathione reductase -GR-, glutathione peroxidase -GPx-, glutathione-S-tranferase -GST-) and biochemical damage responses (lipid membrane peroxidation -LPO-). The results obtained evidenced that the levels of the biomarkers studied (RR, SOD, CAT and GPx) were higher at reproductive than at resting stage. On the other hand, the effect of toxicant was observed in SFG, CAT and GPx but this effect was only detected during the resting period. Moreover, there was a deterioration of mussel gonadal tissue with FLU exposure during reproductive stage. FLU accumulation in mussel tissues was also dependent of the reproductive status with higher internal concentrations during resting than reproductive period. In conclusion, there was a strong effect of reproductive status on studied biomarkers which seems to mask the effect of FLU at reproductive stage. The present study evidences the need to include the measurement of mussel biological status in marine pollution monitoring programs for a correct interpretation of biomarker data.

Effect of diet quality on mussel biomarker responses to pollutants.

The effect of the quality of two microalgal species on select biological and biochemical responses used as indicators of pollution were assessed. Mussels were conditioned for 6 weeks with the diatom Chaetoceros neogracile and the dinoflagellate Heterocapsa triquetra, chosen for being two clearly different types of primary production quality that differ in both biometric and biochemical characteristics. After dietary conditioning, the mussels were exposed to a polycyclic aromatic hydrocarbon, fluoranthene (FLU), for 1 week followed by 1 week of depuration. Results showed higher FLU accumulation in mussels fed on C. neogracile compared to those fed on H. triquetra. Concomitantly, a greater impact of this toxicant was observed in the biomarker responses of mussels fed on C. neogracile. These mussels showed an increase in the percentage of dead hemocytes, an activation of phagocytosis and ROS production of hemocytes after exposure. Some enzymatic activities also increased upon FLU exposure (superoxide dismutase -SOD-, catalase -CAT-, and glutathione reductases -GR-) and after depuration (glutathione-s-transferase -GST-). Results suggest that FLU exposure as well as food quality influence biomarker responses, with higher values of SOD, CAT and GR in non-exposed mussels fed on C. neogracile. In addition, upon exposure to the same FLU concentration, GR response varied according to dietary conditioning, suggesting that diet could act as a confounding factor in biomarker responses to pollution. Consequently, trophic conditions should be considered in marine pollution monitoring programs for a better interpretation of biomarker responses.