The study locations ( Figure 1 ) were selected from scientific literature reporting the presence of hydrocarbons in water, sediment, or soft tissue of the organisms in the Gulf of Mexico (Botello et al., 2014; Hernández-Martínez and Ferrari, 2017). For a reliable result of the evaluation of potential marker genes in response to hydrocarbon exposure, at least 30 individuals of Crassostrea virginica were selected per sampled lagoon and 15 from a sample of individuals exposed to light hydrocarbon under laboratory conditions at the facilities of the Universidad Tecnológica del Mar de Tamaulipas Bicentenario (La Pesca, Soto La Marina, Tamaulipas).

The procedures used to get the hydrocarbon extracts in soft tissue from individuals of C. virginica sampled in the different lagoons of the Gulf of Mexico, as well as from water and sediment, were based on Murphy et al. (2012) and Glaser et al. (1981). In the case of tissue samples, each lagoon consisted of three independent pools (n = 3), with each pool consisting of 15 organisms. In the case of sediment, three replicates (n = 3) were used, and three volumes (n = 3) of 1.8 L in the case of water. All samples were stored in precleaned amber glass jugs. Water samples were saturated with a mercuric chloride solution and refrigerated at 4°C until analysis. López-Landavery et al. (2019) reported more details about the processing of the samples. Organisms from all lagoons were included in the assessment of hydrocarbons, except those from Las Enramadas, which were used only in the expression analysis.

Diagnostic ratios were calculated to identify possible sources of hydrocarbons in the different matrices (water, sediment, and soft tissue) collected from the Gulf of Mexico’s coastal lagoons. Carbon preference index (CPI), the terrigenous/aquatic ratio (TAR), the ratio between lower-molecular weight and higher-molecular weight compounds (LMW/HMW), and the natural n-alkane ratio (NAR)) were calculated to n-alkanes. LMW indicates the sum of n-alkanes from n-C₉ to n-C₃₂, while HMW indicates the sum of n-alkanes from n-C₂₄ to n-C₃₆. Equations described to continuation were reported previously by Hernández-Guzmán et al. (2021).

In the case of PAHs, the most used diagnostic ratios are phenanthrene/anthracene (Phe/Ant), fluoranthene/pyrene (Fla/Pyr), and the ratio between lower-molecular weight and high-molecular weight compounds (LMW/HMW) (Nassar et al., 2011; He et al., 2014). LMW/HMW indicates the concentration ratio of 2-3 ring PAHs to 4-6 ring PAHs.

About 30 mg of the digestive gland from the collected organisms were used for RNA extraction. All samples were fixed with RNAlater (Ambion, Austin, TX, USA) and stored at -80C until RNA purification. Following the manufacturer’s recommendations, the total RNA was extracted with the RNeasy Mini Plus^® kit (Qiagen, Valencia, CA, USA). The total RNA was eluted with 50 μL of DNase-free water and quantified by absorbance using a Nanodrop ND-2000 spectrophotometer (Thermo Scientific, USA). The RNA integrity was confirmed by electrophoresis using a 2% agarose gel.

RNA samples were treated with DNase (DNase I, RNA Free, Qiagen) to remove the residual genomic DNA and thus prevent it from interfering with the evaluation of the expression of potential marker genes. After DNA elimination, the total RNA was quantified with a Qubit fluorometer^® 3.0 using a Qubit™ RNA Broad Range assay (Life Technologies, USA), and its integrity was assessed through electrophoresis. Effective DNase treatment was confirmed by verifying no-amplification after PCR when using the housekeeping gene rpl19 (Ribosomal Protein subunit Large 19) ( Table 1 ).

For cDNA synthesis, we proceeded to synthesize 1 µg of total RNA treated with DNase from each sample. For this, the Impron-II Reverse Transcriptase (Promega) Kit was used. cDNA synthesis was confirmed through PCR using the housekeeping gene rpl19. The correct amplification of the rpl19 gene showed a single amplification band when it was analyzed in 2% agarose electrophoresis.

The assumptions of normality and homoscedasticity were evaluated with the Shapiro-Wilk and Levene tests, respectively. A one-way ANOVA was used to determine statistical differences in the presence of hydrocarbons between the lagoons for each matrix (water, sediment, and soft tissue). Also, a one-way ANOVA was used to detect significant differences in the relative expression values between lagoons, with a significance value of 0.05. For both cases (bioaccumulation and gene expression analyses), when there were significant differences between lagoons, a Tukey’s honestly significant differences (HSD) test was applied with P< 0.05. The analysis was carried out in R version 3.6.3 (R Core Team, 2019).

The chromatography analysis confirmed the presence of aliphatic hydrocarbons (AHs) and aromatic hydrocarbons (PAHs) in the water and sediment of the different lagoons of the Gulf of Mexico. For water, the highest concentrations of AHs (F = 70.14, P*** =8.14e-11) were found in Tamiahua and Laguna de Términos with 0.50 and 0.43 ng/mL, respectively ( Supplementary material (SM) , Figure S1A ). The lagoons with the lowest levels of AHs in water were Cármen, La Pesca, and Mecoacán, with values below 0.05 ng/mL. In the PAHs case (F = 64.97, P*** = 2.86e-08), the highest concentrations were registered in Tampamachoco and Laguna de Términos, with values greater than 0.06 ng/mL ( Figure 2A ). La Pesca and Mecoacán registered the PAHs’ lowest levels with 0.002 and 0.009 ng/mL, respectively. The most abundant PAH components in water were phenanthrene > pyrene > fluoranthene.

For sediment, the Tamiahua and Tampamachoco lagoons presented the highest concentrations of AHs (F = 31.9, P*** = 2.17e-07) with values close to 2.5 μg/g dry weight (SM, Figure S1B ). On the other hand, the lagoons with the lowest levels (< 0.5 μg/g dry weight) were La Pesca and Mecoacán, with 0.44 and 0.68 μg/g dry weight, respectively. In the PAHs case (F = 37.47, P*** = 9.30e-09), the analysis showed that Tamiahua, Cármen, and Tampamachoco had the highest values (66.57 – 75.61 ng/g dry weight), while in Pajonal was registered the lowest concentration with 2.35 ng/g dry weight ( Figure 2B ). In sediment, perylene > indene(1,2,3)pyrene > benzo(a)pyrene represented the most abundant PAH components.

The levels of AHs (F = 15.34, P*** = 5.23e-06) in the soft tissue of C. virginica were higher in the organisms of the natural environment than those exposed to hydrocarbons under laboratory conditions (data not shown). Within the sampled lagoons, Pajonal, Tampamachoco, and Alvarado had the highest concentrations with values above 10 μg/g dry weight (SM, Figure S1C ). In comparison, La Pesca recorded the lowest value with 3.62 μg/g dry weight, although it did not present significant differences with Tamiahua, Laguna de Términos, Cármen, and Mecoacán (P > 0.05). In the case of PAHs (F = 7.45, P*** = 4.56e-04), the highest concentrations were obtained for La Pesca, Cármen, and Mecoacán, with values between 200 and 250 ng/g dry weight. A previous study reported a concentration of PAHs of 230 ng/g dry weight in the soft tissue of organisms collected in La Pesca (López-Landavery et al., 2019). On the other hand, the lagoon with the lowest PAH concentration was Alvarado in the state of Veracruz, with a value of 65 ng/g dry weight ( Figure 2C ). The most abundant PAH component detected in the soft tissue of individuals from the Gulf of Mexico was perylene, except for Alvarado. Other abundant PAH components were phenanthrene and naphthalene.

For n-alkanes ( Table 3 ), the CPI values were higher than one (1.06 - 7.01), except for samples water in Tampamachoco (0.63) and Pajonal (0.71); and in soft tissues of individuals from Laguna de Términos (0.46). In the case of TAR, sediments from different lagoons predominantly had values higher than one (1.36 - 15.30), while NAR had values lower than one in all matrices collected along the Gulf of Mexico. Considering the lower- and higher-molecular weight compounds, water and sediment had values predominantly lowers than one, while soft tissues had values higher than one (1.56 - 217.98), except for Tampamachoco (0.48).

Based on diagnostic ratios for PAHs ( Table 3 ), Phe/Ant had values higher than one for all matrices (1.39 – 27.16), except for water at Pajonal (0.01). In contrast, the Fla/Pyr ratio values were lower than one in water and soft tissue, except for Tamiahua (matrix = soft tissue, value = 1.77). Interestingly, PAHs of 2-3 rings predominated on PAHs of 4-6 rings in water. However, that relationship was inverse in sediment and soft tissues, with a predominance of PAHs of 4-6 rings, probably due to the sediment’s chemical characteristics and the physiology of oysters presenting a low rate of elimination of PAHs.

Like HKGs, potential GOIs had an optimal melting temperature of around 60°C. Also, the dissociation curve confirmed the specificity of each primer, and the standard curves (SM, Figure S3 ) indicated efficiency values between 82.0 (Metalloproteinase inhibitor) and 104.8% (Flavin monooxygenase) ( Table 1 ).

The relative expression analysis of the GOIs was carried out using the previously selected HKGs (tubα, rpe, and ef1α) and the biological replicates of the Crassostrea virginica individuals sampled in the Gulf of Mexico lagoons ( Table 2 ). In this section, results are described considering three gene categories: master regulators of the stress response (hif-1α, ahr, and arnt), biotransformation and excretion of xenobiotics (cyp302a1, cyp10, gstΩ1, fmo, sult4a1, and mdrd1), and response to oxidative stress and redox process (cat, ggt1, ttr3, and meti4).

For this group of genes ( Figure 4 ), hypoxia-inducible factor (hif-1α), hydrocarbon receptor (ahr), and AHR nuclear translocator (arnt) showed significant differences between lagoons (hif-1α: P***< 0.0001, ahr: P* = 0.037, arnt: P* = 0.038). The lowest levels of hif-1α occurred in La Pesca. In this context, all the evaluated lagoons presented significant differences concerning La Pesca, while the highest levels of expression were shown in Las Enramadas and Mecoacán. For organisms exposed to hydrocarbons under laboratory conditions (200 µg/L during 21 days), differences in expression were detected after 21 days of exposure (T3). In the case of ahr, the lowest level of expression occurred in organisms exposed to hydrocarbons at 14 days (T2), while Las Enramadas presented the highest levels of expression. For arnt, Cármen was the lagoon with the lowest expression level, while Las Enramadas again showed the highest expression levels.

The process of biotransformation and excretion of xenobiotics is divided into three phases. During phase I, the cytochrome P450 (CYP) family has been reported to participate in this response. In this study, the expression levels for two CYP members ( Figure 5 ) were significant between lagoons (cyp302a1: P***< 0.0001, cyp10: P** = 0.0002). The lowest expression values for cyp302a1 were obtained in Laguna de Términos, Mecoacán, Tampamachoco, and Cármen, significantly different from those of La Pesca (P*< 0.05). In the case of organisms exposed under laboratory conditions, the differences concerning La Pesca occurred at 14 days of exposure (P*< 0.05). For cyp10, the highest levels of expression occurred in organisms exposed under laboratory conditions, and the values were significantly different from those found in Laguna de Términos (P*< 0.05).

In phase II, the enzymes involved are glutathione S-transferases (GST), monooxygenases (FMO), and sulfotransferases (SULT4A1). Of the genes that code for these enzymes, only gstΩ1 (P***< 0.0001) and fmo (P***< 0.0001) had significant differences in expression levels when comparing lagoons. In the case of gstΩ1, the highest levels of expression occurred in organisms exposed to hydrocarbons for 21 days and in Las Enramadas, whose values were significantly different from those of La Pesca ( Figure 5 ). Likewise, the lowest expression values were presented in Mecoacán, La Pesca and organisms exposed to hydrocarbons for 14 days. An interesting behavior of expression levels was observed for fmo ( Figure 5 ), where the lowest values were presented in Las Enramadas and La Pesca. In contrast, the highest values were obtained in Tampamachoco, Cármen, and Mecoacán. The values found in Tampamachoco, Cármen, and Mecoacán were significantly different from those of La Pesca, Las Enramadas, and Laguna de Términos (P*< 0.05). The expression values for sult4a1 not shown significant differences (P = 0.806, data not shown).

During phase III, multidrug resistance proteins are associated with detoxification processes. In the case of mdrd1 (P***< 0.0001), the highest levels of expression occurred in the population of Las Enramadas and organisms exposed to hydrocarbons for 14 days (T2_200). The expression values of Las Enramadas and T2_200 were significantly different from those found in Laguna de Términos, Mecoacán, Tampamachoco, and Cármen (P*< 0.05, Figure 6 ). So far, it can be seen that most of the genes evaluated are down-regulated concerning the population of Las Enramadas, which could indicate a chronic condition due to the presence of contaminants.

Among the genes associated with oxidative stress, we have catalase (cat) and glutathione hydrolase (ggt1). For both genes, the expression values between lagoons shown significant differences (cat: P***< 0.0001, ggt1: P***< 0.0001). In the case of cat, the highest levels of expression occurred in Tampamachoco, Cármen, and Las Enramadas, being, in turn, significantly different concerning La Pesca (P*< 0.05). Of all the lagoons, La Pesca presented the lowest level of expression. For ggt1, Las Enramadas and Tampamachoco again showed the highest expression levels, significantly different from those found in Mecoacán and Laguna de Términos (P*< 0.05). In La Pesca, it only presented significant differences with Las Enramadas (P*< 0.05). For the trr3 gene (P***< 0.0001), which is involved in regulating redox processes and is essential for correct signaling, the highest levels of expression occurred in organisms exposed to hydrocarbons for 21 days (T3_200) and in Las Enramadas. The expression levels of these lagoons were significantly different from the values found in La Pesca, Mecoacán, and Tampamachoco (P*< 0.05). In general, La Pesca presented the lowest level of expression for trr3. Expression levels for meti4, associated with response to environmental stress, did not shown significant differences (P = 0.057, data not shown)

The coastal lagoons used in the present work were selected from previous studies that have reported the presence of hydrocarbons in water, sediment, or oyster tissue of the Gulf of Mexico, from Tamaulipas in the north to Campeche in the southeast (Botello, 2005; Montaño-Vera et al., 2017; Botello et al., 2019). In water, aliphatic hydrocarbons (AHs) and aromatic hydrocarbons (PAHs) were found in all the lagoons included in the present study; with the highest levels found in Tamiahua-Laguna de Términos and Tampamachoco-Laguna de Términos, respectively. Celis et al. (1985), in a review of different studies on the concentration of hydrocarbons in water from various bodies of water in the Gulf of Mexico, found that Laguna de Términos and the Tuxpan river presented the highest concentrations (20-48 μg/L). Laguna de Términos, located in the state of Campeche, is a lagoon complex situated in the area of marine oil platforms and receives discharges of particulate and dissolved organic matter from the Grijalva-Usumacinta river system (Paez-Osuna et al., 1987; Botello, 2005). In the case of the Tamiahua and Tampamachoco lagoons, in addition to being in an area of high oil exploitation and having influence from the Tuxpan river and, to a lesser extent, the Panuco river, they have a high annual maritime traffic (Botello and Calva, 1998). The factors mentioned above could explain comparatively the concentrations of hydrocarbons found in water in Laguna de Términos, Tamiahua, and Tampamachoco concerning other coastal lagoons of the Gulf of Mexico.

Sediments serve as depositories of several sources of organic matter and hydrocarbons, and they can be used to assess the historical impact on the environment (Romero et al., 2015). Likewise, the type of organic matter and hydrocarbon that accumulates will depend on the primary productivity of the area, physical and chemical factors, and the nature of the sediment (Waterson and Canuel, 2008). In this study, Tamiahua, Tampamachoco, and Laguna de Términos had the highest levels of AHs, while Tamiahua, Cármen, and Tampamachoco had the highest concentrations of PAHs. In the case of Tamiahua, Tampamachoco, and Laguna de Términos, which also had the highest levels of hydrocarbons in water, the levels of hydrocarbons found in the sediment would reflect the effect of the oil activity carried out over many years in this area of the country and the fluvial influence mentioned above. In addition, in front of the Laguna de Términos (~80 km) are the PEMEX oil exploitation platforms that correspond to the Sonda de Campeche, whose contributions could reach the coast by the action of currents and winds (Botello, 2005). From a quantitative approach, Gogou et al. (2000) reported that areas with low concentrations of AHs had values between 562 and 5,607 ng/g, while, for PAHs, the range fluctuated between 14.6 and 158.5 ng/g. Based on the above ranges and the values found in the present study for both AHs and PAHs, it could be suggested that the coastal lagoons of the Gulf of Mexico have low concentrations of hydrocarbons in the sediments.

The degree of accumulation of pollutants, such as oil, in a marine organism will depend on the biological availability of its different fractions, the time of exposure to which the organism is subjected, and the ability of the organism to metabolize it (Van der Oost et al., 2003). In the present study, the organisms that presented a higher level of bioaccumulation of AHs corresponded to Tampamachoco, Pajonal, and Alvarado. In the case of PAHs, the organisms of La Pesca, Cármen, and Mecoacán had the highest concentrations. Pajonal is part of the Cármen-Pajonal-Machona lagoon complex located in an area of exploration, drilling, and transport of hydrocarbons (Gold-Bouchot et al., 1997), so it would reflect the concentrations of AHs found in this lagoon. The Alvarado lagoon, in addition to being located in an area of oil exploitation, has the influence of the Coatzacoalcos river, which would be an additive factor in the origin of the AHs. In the specific case of La Pesca, which presented low levels of AHs and PAHs in water and sediment, the values of PAHs in the organisms suggest the idea of the presence of higher concentrations concerning organisms from other lagoons with higher levels of AHs and PAHs found in both water and sediment. The above would seem like a discrepancy since organisms living in areas with higher levels of hydrocarbons would be expected to have higher levels of bioaccumulation in their tissues. However, Gobas et al. (1999) indicated that invertebrates have less ability to metabolize xenobiotics than vertebrates, and it could result in relatively high tissue bioaccumulation even when the contaminant has disappeared from the environment. The scenario described above is one of the main causes of why invertebrates are frequently used as indicators of contamination by organic components (Coates and Söderhäll, 2021). In the case of Mecoacán, the levels of PAHs found could be due to its proximity to the Dos Bocas oil terminal, cataloged within the top three either by traffic of oil vessels or by volume of crude oil shipped (INEGI, 2010).

In general, diagnostic ratios were used to identify the possible sources of n-alkanes and PAHs in the different matrices (water, sediment, and soft tissue) from the lagoons of the Gulf of Mexico. The CPI values indicate the possible predominance of odd n-alkanes, even n-alkanes, or not predominance. CPI values near one suggest no preference among odd and even n-alkanes and are associated with petrogenic inputs or anthropogenic sources (Sainakum et al., 2021). In the present study, CPI values from water (0.63-1.72) and soft tissues (0.46-1.92, except Mecoacán) suggest a predominant petrogenic contribution for n-alkanes. In individuals from Carmen, the CPI value (1.92) suggests a contribution from mixed sources, with the predominance of biogenic sources, probably phytoplankton (El Nemr et al., 2016; Sainakum et al., 2021). In contrast, for individuals from Mecoacán, the high CPI value (3.21) suggests the presence of n-alkanes from terrigenous sources (Leider et al., 2013), typically from C3 plants, important in the deposition of organic matter in estuaries (Lu et al., 2022).

In petroleum hydrocarbons, the NAR ratio is close to zero and close to one for marine or higher terrestrial plants (El Nemr et al., 2016). In this study, except for La Pesca, the NAR ratio was close to zero in water and soft tissues, ranging from 0.02 to 0.23 in absolute value. The above values should indicate a substantial contribution of petrogenic sources in water and soft tissues collected from the Gulf of Mexico lagoons. In contrast, the NAR value in La Pesca (-1.00) suggests a strong contribution of hydrocarbons from higher terrestrial plants or marine plants. In sediment, NAR ranged from 0.31 to 0.67, indicating a moderate contribution of petrogenic sources or even a mixture of hydrocarbons from high vascular marine or terrestrial plants (Hernández-Guzmán et al., 2021). On the other hand, the TAR ratio helps to differentiate the terrestrial contribution from aquatic sources of n-alkanes based on long- and short-chain of odd compounds (Rielley et al., 1991; Jaffé et al., 2001). In this study, TAR values from sediment were greater than one (1.36-15.30), suggesting a predominant contribution of n-alkanes from the debris of higher terrestrial plants (Bourbonniere and Meyers, 1996). In contrast, the tendency of TAR values from water and soft tissues was lower than one, suggesting that the main contribution of n-alkanes was from aquatic sources (Keshavarzifard et al., 2020).

LMW/HMW values lower than one usually indicates n-alkanes produced from sources such as higher plants, marine animals, and sedimentary bacteria (Wang et al., 2006). Also, values close to one and greater than two suggest n-alkanes produced from petroleum and plankton and the presence of fresh oil input, respectively (Commendatore et al., 2000; Vaezzadeh et al., 2015). In this study, the LMW/HMW values in soft tissue (1.56-217.98, except for Tampamachoco) suggest that the predominant sources of n-alkanes are petroleum and fresh oil input. In contrast, LMW/HMW values in sediment were lower than one (0.08-0.46), reflecting the n-alkanes sources from higher plants, marine animals, and sedimentary bacteria. On the other hand, isoprenoids such as pristane (Pr) and phytane (Ph) are derived from the diagenetic processes of phytol, and they are not primary components in the terrestrial biota (Peters et al., 2005; Babcock-Adams et al., 2017). Furthermore, diagnostic ratios based on Pr and Ph have been used as markers of biodegradation for oil spills (Hernández-Guzmán et al., 2021). In this study, Pr/Ph values in soft tissues (data not shown) were close to one or slightly greater than one (0.90-1.67), except for Tamiahua (0.42). These values suggest that the predominant source of Ph is crude oil and corroborate the Ph nature because it is not commonly produced by biogenic sources (Caro-Gonzalez et al., 2020).

Diagnostic ratios were also used to assess the sources of PAHs. PAHs are persistent organic pollutants with pyrogenic, petrogenic, and biogenic sources (Liu et al., 2009; Kao et al., 2015; Vaezzadeh et al., 2015). Petroleum often contains PAHs that are thermodynamically more stable than others. For instance, Phenanthrene (Phe) is more stable than Anthracene (Ant), and the Phe/Ant ratio is high. Phe/Ant values from water in this study were greater than ten (12.13-27.16), except for Pajonal (0.01). The above suggests that PAHs source from the water in most of the coastal lagoons of the Gulf of Mexico is mainly petrogenic (Soclo et al., 2000). In contrast, sediment from all lagoons sampled in this study had Phe/Ant values lower than ten (1.39-6.51), suggesting a pyrogenic source for PAHs. Phe/Ant values for soft tissues in this study focused on bivalves, suggesting petrogenic and pyrogenic sources for PAHs. Oysters from Alvarado, Pajonal, and Mecoacán would be exposed to petroleum hydrocarbons, while oysters from La Pesca, Tamiahua, Tampamachoco, and Cármen would be impacted by combustion residues (Ünlü and Alpar, 2006). Another ratio for PAHs source identification is Fluoranthene/Pyrene (Fla/Pyr). Fla and Pyr are usually the most abundant PAHs in pyrolytic sources, with ratios greater than 1 indicating pyrolytic origin and ratios lower than one associated with petrogenic sources (Magi et al., 2002). In this study, Fla/Pyr values of water (0.24-0.97) and soft tissues (0.35-0.95, except for Tamiahua) suggest a petrogenic source for PAHs. More specifically, Fla/(Fla+Pyr) values (data not shown) suggest that the origin of PAHs from water in Mecoacán and PAHs of individuals from La Pesca, Pajonal, and Laguna de Términos is from petroleum combustion, while for other lagoons the PAHs source is petroleum (El Nemr et al., 2016). In sediment from Tamiahua and Cármen and individuals from Tamiahua, the Fla/Pyr values were higher than one and suggested a pyrolytic origin of PAHs, probably from coal combustion and wood (Yunker et al., 2002). LMW/HMW, defined as 2-3/4-6 ring PAHs, also indicates sources of PAHs from petrogenic and pyrogenic origins (Lu et al., 2022). PAHs from a petrogenic origin consist mainly of LMW (2-3 rings), while HMW (4-6) are predominant in PAHs with pyrogenic origin (Dashtbozorg et al., 2019). In this study, LMW/HMW values from the water of all lagoons sampled and individuals from Alvarado and Pajonal were greater than one and suggested that the origin of PAHs is petrogenic. Furthermore, in the sediment of all lagoons and individuals of La Pesca, Tamiahua, Tampamachoco, Carmen Mecoacán, and Laguna de Términos, LMW/HMW were lower than one, and it indicates a pyrogenic origin of PAHs.

This work is part of the Consorcio de Investigación del Golfo de México (CIGOM), the first multidisciplinary research group focused in to study the physical, chemical, and biological characteristics of this important oceanic basin on the Mexican side. CIGOM was founded in 2015 and it specializes in multidisciplinary projects related to possible environmental impacts of the oil and gas industry on the marine ecosystems of the Gulf of Mexico (https://cigom.org). The biological component, includes the study of the effects of hydrocarbons, mainly PAHs, on invertebrates, fish, turtles, and plankton and recently incorporated the problem of sargassum macroalgae (Sargassum spp.). Considering invertebrate monitoring as indicators of pollution in the coastal lagoons of the Gulf of Mexico, a similar and older initiative was established initially by the US Environmental Protection Agency, continued by the National Oceanic and Atmospheric Administration (NOAA), called “The Mussel Watch Program (MWP)” (Kimbrough et al., 2008; Bricker et al., 2014), and then it extended as a model around the world (Ramu et al., 2007; Thebault and Rodriguez y Baena, 2007; Cossa and Tabard, 2020). CIGOM and MWP reflect the need to assess the impact of anthropogenic activities on marine and estuarine ecosystems. In comparative terms and considering only the monitoring of contaminants, the MWP has a broader scope and intensive sampling than CIGOM. MWP monitors nearly 300 sites from the Atlantic, Pacific, and Great Lakes coasts, and measures more than 140 chemical contaminants (Beiras, 2018). In contrast, and on the same base, CIGOM includes more species such as oysters (Crassostrea virginica), benthic and pelagic teleost, Chondrichthyes, cetaceans, turtles, and plankton (https://escenarios.cigom.org/en/). In a complete scope, although CIGOM includes more components than MWP such as oil circulation modeling, biological connectivity, and sceneries of vulnerability, among others, it has the challenge of staying for many years just like MWP.