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The biomagnification of Hg and Se was studied using nitrogen stable isotope analysis during four seasons in a coastal lagoon of the eastern central Gulf of California. This lagoon receives agricultural, municipal, and shrimp aquaculture effluents. The species were categorized into organism groups and presented a significant accumulation of Hg and Se with respect to the sources, while the concentration of both elements in sediment and suspended particulate matter (SPM) was low. Our data confirms the positive transfers (biomagnification factors >1) of Hg and Se in the entire studied food web, and it was structured in five trophic levels across all seasons. Additionally, there were no linear correlations between the molar Se:Hg ratios and the trophic levels of the organism groups. However, the Se:Hg ratios among organism groups were >1, which indicates that there is an excess of Se and that it is not a limiting factor for the detoxification of Hg. [ABSTRACT FROM AUTHOR]

We aimed at characterizing the methylmercury (MeHg) exposure through fish consumption in two populations (common general and fishing-related population (FRP)) using a probabilistic health risk assessment in children, women of childbearing age, and adults in Mazatlán. The hazard quotients (HQs) were obtained from fish consumption, defined through a survey, and the levels of mercury in fishery products, obtained from published information. The average fish ingestion rate (IRfood) was higher in the FRP (167.85 g d−1) than in the general population (GP) (140.9 g d−1). However, HQs were significantly (p< 0.05) higher in the GP (ranging from 0.18 to 10.91) compared to the FRP (0.20 to 2.48); significant differences were also found among groups of both populations. Remarkably, children in both populations exhibited the highest proportions of risk, reaching up to 97% in GP. For all populations, fish consumption was the most important variable influencing MeHg exposure. Overall, for MeHg exposure, there is no safe level of fish consumption without risk, and actions should be taken to mitigate possible risk; further research with current data is needed to assess potential health risks associated with MeHg exposure, particularly in children. [ABSTRACT FROM AUTHOR]

The article offers information on the marine species condition at Upper Gulf of California. Topics discussed include concern for extinction of vaquita porpoise, most endangered marine mammal of Mexico; reduction of freshwater flow into the Upper Gulf of California (UGC) due to damming and diversion of the Colorado River, cause decline in vaquita; and collaborative efforts required among fishermen, the seafood supply chain, and environmental and fisheries agencies for conservative solution.

Microplastics (MPs, < 5 mm in size) are highly bioavailable to many taxa within the marine ecosystem, either ingested directly or indirectly through trophic transfer from polluted prey. The ingestion analysis of these MPs from top predators, such as pinnipeds in Mexico, is relatively unexplored. Forty-eight scats from California sea lions were collected on six rookeries along the Gulf of California. From these scat samples, 294 suspected MPs particles were classified and chemically analyzed; 34% were synthetic and semi-synthetic, and 66% were non-synthetic. Blue-colored polyethylene terephthalate fibers were the most common type of MP registered. During laboratory work, multiple contamination control measures were implemented. Although the ingestion pathway is still unknown, our results support the other authors that suggest the potential trophic transfer of MPs to top predators and incidental ingestion while foraging. The particles documented here provide important baseline information for future MP research in the Gulf of California. [Display omitted] • 294 suspected microplastic particles were classified and chemically analyzed. • 34 % of particles analyzed were of synthetic and semi-synthetic origin. • Blue-colored PET fibers were the most common type of microplastic registered. • Our results infer that California sea lions are exposed to microplastics. [ABSTRACT FROM AUTHOR]

Supralittoral and high intertidal coastal zones are exposed to pollution from both marine and terrestrial sources and undergo higher deposition rates than the subtidal zone. It is therefore important to identify organisms for this section of the coastal area that can be tolerant to contaminants. The aim of this study was to determine if supralittoral isopods of the genus Ligia can be used as biomonitors, since they are abundant and widely distributed. For this purpose, concentrations of trace elements were determined in Ligia isopods in toto from 26 locations across the Gulf of California and Pacific coast of the Baja California peninsula, which were collected during the summers of 2009 and 2010. The concentrations of trace elements followed the order of; Zn≥Cu>As>Cd>Pb>Hg. Elevated concentrations of copper (up to 1010 μg/g) were detected in Ligia from Santa Rosalía (SRo), a locality where industrial mining of copper has historically occurred. Industrial and municipal sewage discharges appear to have contributed to the high concentrations of zinc (326 μg/g) and lead (144 μg/g) found in organisms from Guaymas location. The high mercury concentration in organisms from Mazatlán (M) (2.01 μg/g) was associated with a thermoelectric plant. Natural sources of metals were also detected; coastal upwelling appears to be associated with high cadmium concentrations in Ligia from Punta Baja (PB) (256 μg/g) in the Pacific coast, whereas hydrothermal vents may have contributed to high concentrations of arsenic at Ensenada (E) (61 μg/g). Our results suggest that Ligia isopods reflect the natural and anthropogenic inputs of trace metals in the environment and could potentially be used as biomonitor organisms of the intertidal rocky shores of the Gulf of California and Pacific coast. [ABSTRACT FROM AUTHOR]

Long-beaked common dolphins ( Delphinus capensis) in the Gulf of California have been exposed to persistent contaminants that originated in large agricultural areas near the coast. Live common dolphins were sampled by remote dart biopsies to determine concentrations of tDDT in blubber. Life stage and initial gender identification was determined by field observations. Gender was confirmed by genetic analysis of the skin. Concentration of tDDT in blubber was analyzed by gas chromatography. The 16 samples collected consisted of: 2 adult males, 6 adult females, and 8 juveniles. 4,4′-DDE was detected in most of the samples with 4,4′-DDD and 4,4′-DDT under detection levels. Concentrations of DDE varied from non-detectable to 87.3 µg/g lipid weight with a median of 16 µg/g lipid weight. The highest concentration was detected in an immature female. No differences were detected between gender or life stage but this could be attributed to small sample size. We recommend continued sampling of D. capensis blubber biopsies from the Gulf of California in order to relate these levels with affected in vitro biomarkers such as mixed function oxidase activity. [ABSTRACT FROM AUTHOR]

Abstract: Salinity has affected the Colorado River for more than five decades: agriculture, mining and urban sprawl have exacerbated the problem, with the most severe impacts occurring in its southern basin and Mexico. However, moderate salinities (2.6gL−1 Total Dissolved Solids) and constant average flows (4m3 s−1) from a U.S. agriculture drain, have allowed the establishment of a 6500ha cattail (Typha domingensis) dominated wetland in the mudflats of the upper Gulf of California in Mexico, called “Cienega de Santa Clara” (Cienega). This wetland could now be threatened due to the operation of the Yuma Desalting Plant (YDP). Operations will result in reduced flows and salinity increases in the canal that feeds the wetland. From 2006 to 2011 we monitored water quality conditions at the Cienega as part of a binational effort. Monthly monitoring of field parameters was made at the inflows and at 28 stations inside the wetland. In 2010, 4 automatic loggers were installed inside the wetland to take half an hour readings of temperature and salinity. At the center of the Cienega from 70 to 80% of salinity variations depended on salinity from the main inflow; this response was observed with both monthly data and daily data, indicating a rapid response from salinity inflows. The YDP demonstration run at 10% capacity caused a mean salinity increase from 3.0 to 3.3gL−1 TDS at the center of the wetland and from 3.8 to 5.2gL−1 TDS salinity increase at the periphery. During the YDP pilot run at one-third capacity, mean salinity increased from 3.2 to 4.3gL−1 TDS at the center of the wetland and from 4.3 to 8.3gL−1 TDS at the periphery. There was no evidence of upper Gulf of California tidal intrusion into the wetland. Salinity concentrations at the main inflow should not exceed 3.0gL−1 TDS in order to prevent a reduction in cattail growth inside the wetland. Nevertheless, our recommendation is to maintain salinities at 2.6±0.2gL−1 TDS at the main inflow, in order to preserve vigorous cattail stands. Operation of the YDP plant at 10%, one-third, two-thirds and full capacity without replacement water, will have negative effects on the vegetation. Future efforts should be oriented to compensate for possible salinity increases. [Copyright &y& Elsevier]

To assess the safety for human consumption of commercially important bivalves harvested from areas with or without mining activities, we compared the levels of heavy metals in mollusks collected from different coastal environments along the Gulf of California. We sampled the mussel Mytilus edulis and the clams Laevicardium elatum and Megapitaria squalida (June 2004) and the clam Chione californiensis (November 2006). Concentrations of cadmium, lead, nickel, zinc, iron, copper, and manganese in the soft tissue of the mollusks were measured by atomic absorption spectrophotometry. Based on dry weight, the highest average concentrations of iron, copper, and cadmium were found in clams from Loreto (572, 181, and 4.66 mg/kg, respectively); that of nickel, in mussels from San Luquitas (12.2 mg/kg); that of zinc, both in mussels from San Luquitas and in clams from Golfo de Santa Clara (94.3 and 91.8 mg/kg, respectively); and those of lead and manganese in clams from the Golfo de Santa Clara (9.2 and 3.68 mg/kg, respectively). Although mollusks were taken from coastal areas of the Gulf of California, which are considered to be contaminated by mining activities, the heavy metals in the sediments apparently were in a chemical form that had low bioavailability for the bivalves feeding in those areas. The interplay of oceanographic conditions and the chemical composition of anthropogenic inputs into the environment is not well understood. Thus, these factors or their interaction could potentially result in increased concentration and bioavailability of such metals in areas without effluent generated by mining activities. [ABSTRACT FROM AUTHOR]

Fish at the top of the food chain bioaccumulate and biomagnify toxic metals including mercury (Hg), at a higher rate than nonpredatory fish. However, although some top predator fish species are important in the human diet, the risks for consumers in Mexico are difficult to evaluate due to the scarce baseline information available. In the present article, data on the total mercury (THg) concentrations found in edible tissues of different species of sharks, rays, large pelagic fishes and groupers from the Gulf of California are presented and compared with national and international health guidelines. During 2003 and 2004, 73 shark dorsal tissue samples, 52 ray samples, 66 large pelagic fish samples and 16 grouper samples were collected at different sites along the Gulf of California. Samples were digested in a microwave system and analyzed by cold vapor atomic absorption spectrophotometry. Thirty samples (14%) showed concentrations of Hg above the national statutory limit of 1 mg kg-1, from which 25 samples were sharks and 3 were large pelagic fishes. A positive correlation was found between the natural log of THg [ln(THg)] and total length (TL cm) in species of sharks, rays and groupers. The Teacapán estuary in Sinaloa was detected as a possible source of Hg into the Gulf of California due to historic mining in the watershed. Mean Hg concentrations exceeded the regulatory limit of 1 mg kg-1 in the following highly commercial shark species: smooth hammerhead, pelagic thrasher, pacific sharpnose shark, dusky shark, scalloped hammerhead, and whitenose shark, in that order. It is recommended that preventive food advisories be issued with respect to these species until further investigations are conducted. [ABSTRACT FROM AUTHOR]

Introduction: The life history of the California sea lion (Zalophus californianus) in the Gulf of California is marked by a series of important events influencing and modifying its population growth, distribution, and evolution. Despite the fact that this population has been studied since the 1950s, research has been rather punctual and fragmentary. Before 2010, there are only a few surveys conducted simultaneously in all rookeries, thus there is no reliable information on key aspects of life cycle, population trend and potential threats. In the present work we conducted a review of California sea lion life history and environmental changes in the Gulf of California thorough a collation of survey data encompassing the last 37 years. Objective: Our aim was focused on identifying short- and long-term processes potentially acting on the population, and hopefully improve knowledge about the population trend and status using different points of view. Methods: We collected and analyzed population survey data from different sources since the 1970s to 2018: published papers, master's and doctoral thesis, in addition to technical reports. The survey data are organized in sections corresponding with crucial population life history events. Results: Considering a long-time period the population size appears to be stable with zero growth. Cyclic interannual fluctuation seem to denote a certain dependence with climatic factors, not directly with El Niño, but with sea surface temperature anomalies that determine prey availability. However, many doubts persist about the incidence of different local environmental factors on gender and age, particularly related with juvenile recruitment and female survival rate. Conclusions: In conclusion, more information is required based on seasonal surveys, life cycle, regional environmental variation. Statistical errors need to be assessed and monitoring methods should be standardized and must be considered to ascertain short- and long-term population and colony spatial-temporal patterns. [ABSTRACT FROM AUTHOR]

The Gulf of California (GC) is an unique large ecosystem characterized by its rich biodiversity, high biological productivity and endemism of marine life. However, as many other large ecosystems worldwide, it is subject to diverse anthropogenic pressures (overfishing, climate change, losses of biodiversity and habitats, and pollution). We reviewed over 150 studies dealing with contaminants in water, sediments and representative organisms from the GC, and here we discuss the main issues associated to the presence of metals, metalloids, persistent organic pollutants (POPs, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), brominated diphenyl ethers (deca tri-a) (PBDEs), and several other pesticides), plastics, nutrients and algal blooms. The GC ecosystems have been subject to a wide range of pollution sources. Nevertheless, the pollution levels remain relatively low to moderate depending on the location and contaminant type. Contamination hotspots are found i) for metals and metalloids, in sites where mining spills have occurred and ii) for nutrients and pesticides, in wetlands that receive discharges from intensive agricultural and shrimp farming. We also identified sites where harmful algal blooms (HABs) have been observed. However, numerous coastal environments in GC, affected by pollution sources and events have yet been poorly studied. More detailed, extensive and comprehensive studies on the pollution levels and trends, transfer and toxic effects are still needed. [ABSTRACT FROM AUTHOR]