Impacts of 2015-2016 El Niño event in the Bay of La Paz, Gulf of California: Surface temperature and wind variability

The hydrogeochemical processes governing intertidal spring waters remain poorly understood because the potential sources and factors influencing their chemical and isotopic compositions are rarely documented. The northwestern coast of the Gulf of California hosts numerous geothermal intertidal springs. Hydrothermal systems are commonly associated with major fault zones. However, the occurrence of all springs near the shoreline is not entirely reported. Our study primarily focuses on four intertidal discharge zones: (i) San Felipe, (ii) Punta Estrella, (iii) El Coloradito, and (iv) Puertecitos. Using geochemical (major species and Rare Earth Elements [REE]) and isotopic data (δ 18 O, δD, 87 Sr/ 86 Sr, 143 Nd/ 144 Nd), we infer the sources of the intertidal springs, characterize water-rock interactions, and determine mixing processes among water types. Arid environmental conditions, evaporite dissolution, and reverse ion exchange primarily control the hydrogeochemical facies of the intertidal springs. Stable isotope data (δ 18 O and δD) demonstrate either mixing between meteoric and seawater components or influence from a major brine source originating in the southernmost basin, associated with inputs from the Colorado River. Solute inputs derived from bedrock weathering and lixiviation processes on the continent dominate the geochemistry of seawater from the upper Gulf of California. Mixing calculations using 1/Sr and 87 Sr/ 86 Sr ratios confirm that the intertidal spring waters are a mixture of seawater, meteoric water, and deep brines, with notable variations in the proportions and isotopic signatures of these end-members across the sites. Neodymium isotopes elucidate a more radiogenic input in waters from San Felipe, suggesting a connection to fluids leached from the Colorado River. Finally, we present hydrogeological models to integrate structural and geophysical information from the literature. • The occurrence of intertidal hot springs is controlled by several hydrogeological factors. • Various chemical and isotopic end-members associated with intertidal hot springs are presented. • The composition of coastal seawater is altered by inputs from the Colorado River • The hydrogeochemical facies are controlled by arid environmental conditions, evaporite dissolution, and reverse ion exchange. • The isotopic data reveal water-rock interactions and mixing processes among seawater, local freshwater, and deep sources from the Colorado River.

Thread herrings (Opisthonema spp.) are ecologically and economically important small pelagic fishes in the Gulf of California, yet their parasitic fauna remains poorly documented. Given their role in regional fisheries and marine food webs, clarifying the identity of anisakid nematodes infecting these fishes is relevant for food safety surveillance. In this study, we examined 306 individuals of Opisthonema libertate, 25 of O. medirastre, and 89 of O. bulleri collected from multiple fishing grounds between 2022 and 2023. A total of 140 third-stage anisakid larvae were recovered from O. libertate, whereas infections were rare in the other two host species. Molecular analyses of the ITS rDNA region confirmed the presence of Contracaecum bioccai and revealed an additional Contracaecum species that could not be assigned to species level. Although infection intensities were low, the occurrence of anisakid nematodes belonging to a genus that includes species associated with anisakidosis highlights the importance of continued monitoring of small pelagic fishes in the region. In addition to anisakids, the parasite assemblage of O. libertate was dominated by digeneans, and multivariate analyses revealed significant spatial variation in infracommunity structure across fishing grounds. Similar spatial patterns reported previously were also detected in the present survey, indicating reproducible interannual differences within the Gulf of California. These findings provide the first molecular confirmation of anisakid species infecting O. libertate in the region and underscore the complementary value of parasitological research for food safety and fisheries science.

Linking silicic plumbing systems and oblique rift tectonics: Petro-tectonic evolution along the eastern margin of the Gulf of California

A new species of the genus Stilipes Holmes, 1908, is described and illustrated from a single female specimen collected from the SW Gulf of California, Mexico, in 1500 m depth. Stilipes sp. nov. represents the sixth species of this genus worldwide, all documented from 200 to 1060 m depth. Characters that separate the new species from congeners include: head with eyes; first three pereonites subequal in length; presence of a conical subrostral lamina and a vestigial accessory flagellum of antenna 1; 6th coxa forming a very wide, rounded posteroventral lobe; epimeral plate 2 acute, directed posteriorly; epimeral plate 3 rounded; telson length and width subequal. A comparative table of diagnostic characters among species of Stilipes is provided, including the depth range and geographic distribution of each species.

Assessing climate change impacts for small-scale fisheries in the Gulf of California using deep learning

Seasonal changes in neritic and oceanic zooplankton community structure during 2022–2023 in a deep subtropical bay of the Gulf of California

This study characterizes the phytoplankton assemblage within a cyclonic eddy confined in the Bay of La Paz, Gulf of California, integrating high-resolution hydrographic data and water samples collected in August 2017 complemented by satellite observations. The eddy featured a distinct cold core with elevated chlorophyll- a concentrations and supported a diverse phytoplankton community of 151 species, dominated by dinoflagellates (37,780 cells L -1 ) and diatoms (35,780 cells L -1 ). Notable taxa included Planktoniella sol , Pseudo-nitzschia subfraudulenta , Coscinodiscus asteromphalus , Protoperidinium punctulatum , Gyrodinium fusiforme , Protoperidinium robustum , Dictyocha fibula, Mesodinium rubrum , and Trichodesmium hildebrandtii . Horizontal distribution patterns revealed significant spatial heterogeneity, with species composition diverging between the eddy core and periphery in response to temperature and density gradients. Multivariate analysis identified temperature as the primary driver of community abundance. Furthermore, our findings suggest that a previously undocumented predator-prey dynamic between autotrophic and heterotrophic species may exert an additional influence on these patterns. These findings clarify how cyclonic eddies structure phytoplankton communities and provide critical insight into regional primary production, biogeography, and the distribution of species, some of which capable of forming harmful algal blooms. • This study identified a total of 151 phytoplankton species. • The circulation pattern was characterized by a well-defined cyclonic eddy. • Some species were found to be more abundant near the center of the eddy. • Other species were more abundant at the periphery of the eddy.

Spatial richness patterns of large pelagic fishes in the Eastern Pacific Ocean.

Abstract Objective: Analyze the Pacific hake (Merluccius productus) fishery in the northern Gulf of California from 2010 to 2021 to evaluate fleet performance, profitability, and implications for a quota system. Design/methodology/approach: Information on fleet composition, fishing effort, catch efficiency, and economic indicators was analyzed for small and large vessels. Net cash flow, cost-benefit ratio, and return on investment were calculated. A break-even analysis was conducted to estimate the minimum harvest required to sustain fleet operations. Results: Small vessels were more numerous and active, while large vessels showed 1.5 times higher efficiency. Average catch per vessel rose from 30 t in 2010 to 108 t in 2021, and CPUE in large vessels increased from 2 t/d to 6 t/d. In 2021, small vessels recorded negative returns (net cash flow: -MX$176,604; C/B=0.90; ROI=-10%), while large vessels achieved positive outcomes (MX$337,735; C/B=1.13; ROI=12%). Break-even analysis indicated that sustaining half the fleet required 7,798 t, equal to 75% of the proposed TAC. Limitations/Implications: Market price variability and environmental fluctuations may affect results beyond the study period. Findings/Conclusions: Quota systems must consider efficiency disparities. Implementing quotas, monitoring, and stakeholder participation is essential to prevent overfishing and ensure sustainability.

The green sea turtle (Chelonia mydas) is listed as an endangered species in Mexico and presents significant conservation challenges due to its changing migratory patterns throughout its life stages and the thousands of kilometers it travels between its birthplace and foraging grounds. To understand the natal origins of green sea turtle populations of the Baja California peninsula, samples were collected over two years from two populations at opposite sides in the Baja California peninsula, with one located in the middle of the Gulf of California (Bahía de Los Ángeles [BLA]) and the other on the Pacific Western coast (Complejo Lagunar Ojo de Liebre [CLOL]), both located in Mexico. The mitochondrial DNA control region was sequenced and compared with potential source populations in the Pacific Ocean. The mixed-stock analysis indicated that both Baja California populations originate from nesting sites in the Eastern Pacific, primarily from the Revillagigedo Islands and the coast of Michoacán. Statistical analysis was used to evaluate the contribution of turtles originating from the Revillagigedo Islands and the coast of Michoacán to both sites, which found that statistically both Revillagigedo and Michoacán contribute the same number of individuals to the BLA and CLOL zones (Bayes Factor <1.9 for both populations [1.59 and 1.14, respectively]).

Studies of deep-sea hydrothermal vent systems have generated a spectrum of hypotheses concerning the origin of life on Earth. The present paper integrates recent literature surrounding three separate hydrothermal vent systems (Lost City in the mid-Atlantic, Guaymas Basin in the Gulf of California, and 9°50′ N on the East Pacific Rise) to provide biological, chemical, and geophysical support for these origin-of-life hypotheses. Comparisons between deep-sea hydrothermal vents and impact-generated hydrothermal vent systems may provide further insights into the origin of life. Impact-generated hydrothermal vent systems may have cradled early life. A comprehensive review of studies conducted at Lonar Lake, the Haughton impact structure, and the Chicxulub impact crater provide evidence of long-term hydrothermal activity conducive to the formation of early life, as well as potentially unique DNA structures found in sediment samples—opening the discussion for further investigations into the possible origin (or origins) of life both on Earth and other planetary bodies.

Mangrove wetlands in northwestern Mexico have been highlighted due to their ecological relevance and ecosystem services. This study evaluated the mortality and natural regeneration of mangroves located in six coastal lagoons in Sinaloa, considering five plots each (400 m2), during a warm–strong (2015–2016) and cold–weak (2017–2018) El Niño–Southern Oscillation. The highest mean mortality was recorded in Huizache–Caimanero—the southern coastal lagoon—during the second stage (390 stems ha−1; 22% corresponding to logging). While an increasing latitudinal (north–south) mortality trend was observed, differences between sites and stages were not statistically significant. Natural recovery was also observed due to higher abundance of seedlings, e.g., the largest increase from one stage to another was recorded in Santa María–La Reforma. Mortality and seedling regeneration are discussed in this study, particularly in relation to anthropogenic stressors, logging, and climate variability.

ABSTRACT Environmental DNA (eDNA) marker gene sequencing, or metabarcoding, can be a powerful tool for monitoring marine biodiversity. Traditional eDNA sampling methods involve manual water collection and active filtration to collect DNA. This process can be laborious and require expensive filtration equipment. To explore the possibility of making eDNA a more accessible tool, we investigated the efficacy of passive eDNA capture during citizen science SCUBA diving in the Gulf of California, Mexico. Rather than actively collecting and filtering water samples, filters that passively collected eDNA from seawater were attached to citizen scientist divers as they carried out visual surveys on fish species. eDNA metabarcoding from these filters was amplified using MiFish primers (12S rRNA gene) and sequenced to assess fish community composition and compare to visual surveys. We also investigated marine mammal detection with mitochondrial D‐loop metabarcoding primers on some of the samples. Sequencing results initially yielded 64 fish species, compared to 183 fish species observed by the divers, and shared similar biogeographic assemblage patterns. However, 95 visually observed species lacked publicly available reference sequences. To address this, we generated reference sequences for 64 fish species vouchers obtained from the Scripps Institution of Oceanography Marine Vertebrate Collection. Dedicated barcoding efforts yielded eDNA detections of 15 additional species. We discuss the relative advantages and disadvantages of this passive eDNA collection method for marine fish detection. Marine mammal sequencing results only yielded 3 species; however, one was the Guadalupe fur seal, a threatened species, which highlights the potential of eDNA for rare or threatened marine mammal detection. Our results suggest that passive capture of eDNA can be used as a tool for citizen scientists to supplement visual surveys for marine species detection and is particularly useful for species that are rare or visually inaccessible to divers.

The upper Miocene Boleo Formation (Baja California Sur, México) provides a record of tectonic controls on mixed evaporite-siliciclastic sedimentation in a transtensional pull-apart basin during continental break-up and onset of seafloor spreading in the central Gulf of California. The thin basal limestone, recently dated at 6.35 ± 0.21 Ma, records abrupt onset of subsidence and rapid marine transgression over a formerly emergent landscape. The siliciclastic member contains coarsening-up mud-sand-gravel parasequences that record progradation of fan deltas into a saline shelf. The laterally equivalent gypsum member consists of shallowing-up parasequences formed by evaporative drawdown in the distal evaporite depocenter. Thin, laterally extensive mudstone and breccia units, which host Cu-Co-Zn stratiform ore deposits, record short-lived pulses of marine transgression, fault activity, hydrothermal activity, and mineralization. Growth strata, internal unconformities, and paleocurrent data record NE tilting on a network of NW-striking syn-depositional normal faults during sediment transport to the northeast. Our results support a model for syn-basinal growth of a large monocline above the tip of a propagating oblique-dextral normal fault at the southwest margin of the Santa Rosalía basin. Large-scale displacement across the monocline was the primary mechanism of subsidence, which likely was enhanced by loading related to mafic intrusions and seafloor spreading in the adjacent Guaymas basin. We propose that marine flooding was geologically instantaneous within existing age uncertainties (± 0.2 m.y.) for &amp;gt;1000 km along the Pacific−North America plate-boundary fault system, consistent with models for rapid acceleration of transtensional strain when the plate boundary became localized in the modern Gulf of California at ca. 7−6 Ma.

Trace metal contamination in coastal lagoons of the Gulf of California (GC) represents a significant environmental and public health concern due to the persistence, toxicity, and bioaccumulative behavior of these elements in aquatic organisms. Among trace metals, mercury (Hg) is particularly hazardous because of its neurotoxicity and high biomagnification potential, whereas selenium (Se) may mitigate Hg toxicity through antagonistic biochemical interactions. This study evaluated total Hg and Se concentrations in different tissues of the clam Larkinia grandis, determined the Se/Hg molar ratio, and assessed potential human health risks associated with its consumption in Navachiste Lagoon (southeastern GC). Forty specimens were collected every 2months between August 2017 and June 2018 (n = 240). Average Hg concentrations (µg g⁻1 wet weight) followed the accumulation pattern: digestive gland (0.12 ± 0.02) ≥ gills (0.11 ± 0.01) > mantle (0.08 ± 0.01) > gonad (0.04 ± 0.01) ≥ muscle (0.03 ± 0.01), with all values below the maximum permissible limit (MPL < 1.0µgg⁻1 Hg). For Se, mean concentrations were highest in the digestive gland (1.67 ± 0.33), followed by gills (1.29 ± 0.20), mantle (0.90 ± 0.22), muscle (0.86 ± 0.19), and gonad (0.47 ± 0.17). The Se/Hg molar ratio ranged from 16.31 (mantle) to 115.68 (muscle), recorded in February 2018 and August 2017, respectively. The selenium health benefit index yielded positive values greater than 1 in all cases. In addition, the target hazard quotient for Hg (< 1.0) indicates that consumption of L. grandis poses a low risk to human health. These results provide baseline toxicological reference data for this arcid clam species in the southeastern GC.

Corals demonstrate vulnerability to environmental changes, exhibiting the capacity to substantially modify coral calcification. In this study, we estimated declines in the density of Pocillopora coral species in the Mexican Pacific. The samples utilized in this study encompass both recently collected corals and those stored in Mexican repositories collected in the northeastern and southern Mexican Pacific regions. Density estimates indicate a 28.6% decline in coral density over the past 23 years (-0.0227 g CaCO3 cm-3 y-1) in the southern Mexican Pacific, while at the entrance to the Gulf of California, density has decreased by 15.4% over the past 20 years (-0.017 g CaCO3 cm-3 y-1). A comprehensive evaluation of environmental data reveals that the observed decline in Pocillopora skeletal density in Mexican Pacific reefs is concomitant with decreases in Ωar and pH, and an increase in ocean temperature on a substantial regional scale. When considered in conjunction with the previously documented reductions in coral growth of Pocillopora spp. skeletons in the eastern Tropical Pacific, our findings indicate a potential decline in CaCO3 production within the region's reef systems. The results of this study underscore the significance of generating long-term series of coral growth parameters for relevant reef-building species and the carbonate system in key and representative coastal areas, particularly those that are already challenging for coral survival and reef maintenance.

Abstract “Steinbeck Today” includes contemporary notes and mentions of John Steinbeck’s works and legacy of interest to scholars, fans, and general-interest readers. In the first half of 2025, Steinbeck’s enduring impact emerged through AMC announcing a television adaptation of The Grapes of Wrath; a touring production Of Mice and Men and a new production of Mother Road, which was inspired by The Grapes of Wrath; the Western Flyer’s return to the Gulf of California; and important developments for the Steinbeck House in Sag Harbor.

The Sharpchin Slickhead, Bajacalifornia burragei, is a rarely collected bathypelagic fish endemic to the eastern tropical Pacific Ocean, and its genetic diversity remains undocumented. This study characterizes mitochondrial diversity in a localized deep-basin collection from the Carmen Basin of the Gulf of California by sequencing complete mitochondrial genomes from four individuals collected simultaneously at 1300 m in a single Tucker trawl. A high-quality reference mitogenome was assembled using PacBio HiFi long reads, and three additional mitogenomes were generated from Illumina PE150 libraries mapped to this reference. The mitogenome of B. burragei exhibits the canonical 37 gene architecture and conserved gene order typical of teleost mitogenomes. Overall mitogenome divergence was low (Range: 0.21–0.29%), with most protein-coding and rRNA genes exceeding 99.5% identity. Slightly elevated variation occurred in atp8, nad6, and several tRNA genes. This study provides the first genetic characterization of B. burragei and establishes a baseline for evaluating mitochondrial diversity within a localized collection of individuals and provides a point of comparison for future studies assessing connectivity among deep basins.

Abstract Carbon mobilization and sulfur transformation play a significant role in deep carbon and sulfur cycling. However, sulfur biogeochemistry and its coupling with carbon and iron cycling remain poorly constrained in hydrothermal sediments. We investigated the effect of temperature on carbon‐sulfur‐iron diagenesis in subsurface sediments (≤370 m depth) of the Guaymas Basin, Gulf of California. Sediments have a low average carbon‐to‐sulfur ratio (∼1.6), especially at hydrothermal active sites (1.3–0.67). These values are well below the typical value of 2.8 for marine sediment and could reflect carbon release and relative sulfur enrichment. Elevated temperatures accelerate the thermal breakdown of sedimentary organic matter, leading to hydrocarbon expulsion, increased dissolved organic carbon release, and ultimately carbon loss. Elemental sulfur content correlates positively with reactive iron, indicating iron oxides facilitate elemental sulfur accumulation. These results highlight the temperature effect on carbon storage and iron redox chemistry control on sulfur dynamics in hydrothermal systems.