Co-occurrence bloom of lipophilic toxic-producers in a hotspot Chilean fjord: Fine-scale distribution, toxins and fate in shellfish.

Abstract. Lake Tanganyika, the world's second-largest freshwater lake by volume, is a vital resource for millions in East Africa, providing water, food, and economic opportunities while supporting exceptional biodiversity. Chlorophyll a concentration (Chl a) is a key indicator of phytoplankton biomass. In Lake Tanganyika, Chl a is known to display strong spatiotemporal horizontal variability with an exceptionally low annual mean and wide ranges of concentrations compared to other tropical or temperate great lakes. This variability is influenced by the lake's hydrodynamic cycle driven by air temperature and wind seasonality. Phytoplankton biomass is suspected to be decreasing due to a strengthening of water column stratification induced by climate change. However, the particular spatiotemporal variability and trends in phytoplankton biomass have never been examined using a lake-wide, temporally continuous long-term record. This study bridges this gap by analyzing satellite remote sensing-derived Chl a data from the ESA Climate Change Initiative Lakes dataset across the entire surface of Lake Tanganyika over a 20-year period. It offers insight into the Chl a dynamics with an unprecedented timespan and spatial coverage. The analysis reveals distinct seasonal patterns in Chl a concentrations, with shallow regions (depth < 170 m) maintaining higher levels year-round, while deeper areas exhibit pronounced seasonality tightly linked to known wind patterns. To further explore these spatial differences in seasonal dynamics, the study identifies seven clusters of co-varying Chl a concentrations, each displaying distinct seasonal behaviours that reflect the lake's hydrodynamic cycle. Long-term trends indicate a decline in Chl a concentrations of −9 % per decade in deep regions, suggesting decreasing phytoplankton biomass. However, this overall decline is nuanced by monthly patterns. In deep regions, the low Chl a concentrations, mainly observed between November and April, tend to decrease over time at rates between -5 to −15 % per decade when averaged over entire clusters. In contrast, highest Chl a values recorded during the most productive months, from August to October, show increasing trends up to 25 %. Nearly all shallow areas, meanwhile, display year-round increases up to 35 % across the Chl a distribution, with particularly sharp rises in extreme values. The findings underscore the complexity of Lake Tanganyika's Chl a dynamics. The observed trends may have significant consequences for the lake's trophic structure and the communities dependent on its resources. Further research is needed to elucidate the underlying drivers of these changes and to assess their broader ecological and socio-economic impacts.

Influence of the Amazon River plume on upper water column stratification in the western tropical Atlantic Ocean during the last 30 ka

Along-River and Temporal Variation of Water Column Stability in the Balikpapan Estuary During Spring Tide Based on In-Situ Observations

In tropical lakes, thermal stratification is essential for oxygen dynamics and ecosystem function, and it responds sensitively to short-term weather variation. Using high-resolution temperature profiles and weather data in 2016–2017, this study examines the effects of meteorological variability on water column stratification and oxygen levels in Lake Maninjau, a eutrophic tropical lake in West Sumatra, Indonesia. The results show that seasonal drops in air temperature were the primary factor influencing stratification in 2016, while, wind speed and sunshine duration had a greater impact on its occurrence in 2017. Furthermore, in 2016, stratification breakdown triggered full-depth mixing and a sharp drop in dissolved oxygen (DO) from >3 mg/L to <2 mg/L at 5 m depth. Generally, stratification occurs at the minimum air temperature (Tmin) of above 20.25°C. At lower Tmin, the water column can either be stratified or mixed, notably when the average wind speed (Vave) exceeds ~2.75 m/s, in which stratification tends to break down. These findings highlight how thermal and mechanical forces contribute to weakening stratification and increasing the risk of hypoxia which are detrimental to aquaculture in floating net cages, and are linked to fish kills. Recognizing these thresholds can guide risk forecasting and adaptive management of tropical lakes.

Harmful algal blooms (HABs) in reservoir tributaries are a global concern, yet their regulating mechanisms remain unclear. We hypothesized that the variation in relative water column stability (RWCS) is a critical driver of when and where HABs develop in reservoir tributaries. We tested this by intensive field sampling and CE-QUAL-W2 hydrodynamic modeling in three transects (S1, S2, S3) of Pengxi River, a tributary of the Three Gorges Reservoir (TGR), from April 17 to May 20, 2021. Each transect had unique hydrological conditions affecting RWCS. Transect S3 (downstream), most affected by backwater intrusion and thermal stratification, exhibited prolonged surface density layer (SDL) gradients and the highest chlorophyll-a (Chl-a) levels, with HAB development dominated by the Ceratium hirundinella. Surface-layer Chl-a at S3 peaked at 262.6 µg L−1, ∼86.4% higher than upstream (S1). Water mixing influenced dissolved total phosphorus (DTP) at S1; SDL formation corresponded with surface-water DTP reduction at midstream (S2) and downstream (S3), while backwater intrusion enriched bottom-water DTP at S3. This study identifies RWCS, as reflected by the presence and persistence of SDLs, as a key driver of HAB development in reservoir tributaries. These findings support early warning and targeted management of HABs in high-risk downstream backwater-influenced tributary reaches.

Abstract Scientists are closely monitoring the effects of global warming on the oceanic conveyor belt because of its central role in maintaining global climate stability. As the oceans warm up and become more stratified, processes driven by salinity are becoming increasingly important in shaping surface circulation, despite traditionally being considered less significant than wind forcing and sea-level gradients.
This study examines salinity-driven dynamics in the Central Mediterranean Sea (CMed) using an integrated approach combining in-situ observations (Argo floats and gliders), satellite data and model reanalysis. The CMed is a critical region where the zonal and meridional branches of the Mediterranean overturning circulation converge and deep convection and dense water formation occur. Over recent decades, the region has experienced significant warming and salinification, with salinity levels rising sharply since 2012. This enhanced salinity has directly affected the circulation field and the vertical stability of the water column.
In the Southern Adriatic Gyre, the vorticity field is primarily driven by wind forcing and its interannual variability, but is also strongly influenced by horizontal advection from adjacent regions. After 2012, the baroclinic term of the vorticity equation associated with salinity-induced density gradients became increasingly significant, reaching magnitudes comparable to wind stress. Together with advection, these effects shaped the circulation. In the North Ionian Sea, rising upper-layer salinity has intensified the centre–edge salinity gradient during the inflow of fresher, Atlantic-origin waters. This has led to a weakening of the vorticity field and increased water-column stability.
These findings highlight the growing importance of salinity in driving thermohaline variability and surface circulation, with significant implications for the dynamics of the Mediterranean Sea in the context of ongoing climate change.

Baihua Reservoir, a typical large waterbody in the karst region of southwestern China and an essential drinking water source, is characterized by a high carbonate buffering capacity that profoundly shapes the structure and function of its phytoplankton community. This study systematically elucidates the multi-dimensional driving mechanisms underlying seasonal phytoplankton community assembly in karst reservoirs by integrating multiple analytical models-including the Neutral Community Model, β-diversity decomposition, co-occurrence network analysis, XGBoost-SHAP machine learning, and Partial Least Squares Path Modeling-based on monthly sampling at five sites from 2020 to 2024. The results revealed that: (1) Stochastic processes dominated community assembly across all four seasons, while deterministic processes played a crucial role in local species turnover. (2) The co-occurrence network structure showed significant seasonal dynamics, with the composition of keystone species adaptively shifting in response to changing environmental conditions. (3) The key environmental factors influencing the phytoplankton community exhibited clear seasonal patterns, primarily pH, NH3-N, and CODMn in spring; water temperature, CODMn, and NH3-N in summer; TN, TP, and pH in autumn; and pH, water temperature, and DO in winter. To support the sustainable management of karst reservoirs, we propose seasonally differentiated strategies derived from our phytoplankton community analysis: target CODMn reduction in spring and summer, focus on TN and TP load control in autumn, prioritize water column stability in winter, and maintain hydrological connectivity and pH monitoring year-round. This approach enhances phytoplankton community stability, safeguards drinking water safety, and provides a targeted management model for similar reservoir ecosystems globally.

This study aims to elucidate the depositional characteristics of the Qingshankou Formation shales in the Qian'an area of the Songliao Basin and establish a new paradigm for organic-matter enrichment governed by the coupled effects of salinity, water depth, and primary productivity. A total of 54 core samples from Well QY2 were analyzed for total organic carbon (TOC), pyrolysis parameters (S1, OSI, Tmax), and trace-element proxies [Sr/Cu, Sr/Ba, Ba/Al, V/(V+Ni), δU], enabling a comparative assessment of oil content, organic-matter type, thermal maturity, and depositional environmental indicators between the first and second members of the formation. The results demonstrate that Member 1 exhibits systematically higher TOC, stronger hydrocarbon-generation potential (reflected by elevated S1 and OSI values), more favorable kerogen compositions (predominantly Type I), and higher thermal maturity. Trace-element signatures reveal that the Qingshankou shales were deposited in a semideep-to-deep lacustrine setting under semihumid-to-semiarid paleoclimatic conditions, characterized by mildly brackish-to-moderately brackish water, relatively great paleowater depth, high lake productivity, and overall weakly oxic-to-reducing conditions. Specifically, Member 1 is marked by higher salinity (Sr/Ba > 1.0-1.5), greater paleowater depth (Ba/Al > 30-35), enhanced primary productivity (EFMo > 3), and slightly stronger reducing conditions, all of which correspond well with its elevated TOC values. In addition, volcanic eruptions and episodic marine incursions strengthened nutrient influxes and promoted water-column stratification, thereby further enhancing the organic-matter preservation. Collectively, the findings indicate that organic-matter enrichment in the Qingshankou shales was jointly controlled by the coupled interplay among salinity, water depth, and productivity superimposed by extrinsic events such as volcanism and marine incursions. This integrated "salinity-water depth-productivity" framework provides a new conceptual basis for evaluating shale-oil sweet spots and predicting favorable target intervals in the region.

Glacial meltwater is a major contributor to stratification in polar waters, particularly in glacial fjords where it is contained by fjord topography. Stratification from glacial meltwater input impacts both light and nutrient availability, altering the timing and magnitude of phytoplankton blooms and peak in secondary productivity. Ice conditions can further impede near-surface circulation and trap low-density meltwater plumes, amplifying stratification. Whilst stratification is a critical process in the initiation of phytoplankton blooms, reduced mixing can impede nutrient resupply in the euphotic zone, reduce productivity, and alter the formation processes of marine snow. Here, using a combination of optical and acoustic instrumentation, we investigated how different stratification conditions in two adjacent fjords of northwest Greenland (Petermann Fjord, PF, and Sherard Osborn Fjord, SOF) impact the vertical distribution of two key components of Arctic pelagic ecosystems: marine snow and copepods. We show that the amplified stratification caused by ice damming outside SOF was associated with lower indices of primary and secondary production. Stratification also reduced concentrations of marine snow and resulted in an altered vertical distribution of small sphere particles that were likely fecal pellets in the top 100 m of SOF. Zooplankton distributions in both fjords were centered below the fluorescence peak but were more tightly coupled with the chlorophyll maximum in SOF than in the well-mixed PF. Feeding conditions in SOF were poorer, while in the more productive PF zooplankton were distributed deeper where risks of predation are likely reduced. Although small and large copepod densities were comparable between fjords, the low numbers of nauplii in SOF further suggest mismatch conditions not suitable for their survival. We demonstrate that sea ice conditions are linked to local physical water column stratification that has cascading effects on productivity and the abundance, distribution, and types of marine snow and copepods. Future conditions in glacial fjords are not clear because thermal stratification and glacier runoff will increase, but the number of ice damming events could decrease.

We present a millennial-scale multi-proxy reconstruction of changes in properties of the upper water column near the East Antarctic ice shelf based on planktonic foraminifera from a unique sedimentary archive spanning the glacial period from 75,000 to 20,000 years. Our results imply that variations in the thermohaline structure between Antarctic Surface Water and Warm Deep Water (WDW) may have resulted in either strengthening the stratification of the upper water column or promoting polynya formation (convective overturning). Oceanic subsurface warming during glacial Antarctic stadials and periods of low obliquity, combined with increased salinity and nutrient content, suggests the breakdown in stratification and polynya presence. This glacial polynya formed off Dronning Maud Land (DML) reflects a hybrid coastal-open-ocean polynya mode. We attribute the development of the Glacial DML Polynya to sea-ice induced subsurface warming of WDW and a decrease in density stratification in combination with circulation changes in the atmosphere and ocean. The polynya-driven oceanic heat release during the glacial stadials may have increased the moisture supply to Antarctica and thus promoted the accumulation of ice and the thickening of an advancing ice sheet at the continental shelf margin.

Aquatic ecosystems are major reservoirs of antibiotic resistance genes (ARGs) and hubs for microbial interactions that can facilitate their spread through horizontal gene transfer (HGT). While mobile genetic elements (MGEs), including plasmids and viruses, are recognized as important drivers of ARG mobility, the extent to which water column stratification constrains their vertical dissemination remains unresolved. Here, we analysed depth-resolved metagenomic data from stratified freshwater and marine systems to assess the role of HGT in ARG spread. We found that ARG diversity is consistently lower in marine than freshwater environments and that only a small fraction of ARGs is mobilized by plasmids and viruses. Importantly, we detected no evidence for recent HGT-mediated dissemination of ARGs across depth layers, despite genetic compatibility among co-occurring bacteria. Instead, ARGs appear largely confined to lineage-specific inheritance and within-layer persistence. These findings suggest that stratification acts as a barrier, limiting vertical ARG transfer while promoting within-layer accumulation. Given projections of intensified and prolonged stratification under climate change, our results imply reduced vertical connectivity of ARGs in aquatic environments, with potential consequences of further mitigation in its dynamics by water stratification.

Understanding how climate influences phytoplankton dynamics is crucial for anticipating temporal trends and cascading consequences on ecosystem functioning under climate change. This study explores long-term dynamics in contrasted Mediterranean lagoons and investigates the effects of climatic (air temperature, rainfall, wind speed) and nutrient (inorganic nutrient concentrations) drivers on phytoplankton chlorophyll a, abundances, and pigment composition. 17years of summer monitoring were analyzed using univariate trend tests and multivariate approaches to highlight changes and to disentangle the contributions of abiotic factors to phytoplankton variability. Our results revealed contrasts among lagoons in physicochemical conditions and phytoplankton community, which strongly structured their temporal trends. Climatic drivers significantly influenced phytoplankton, but their importance was context-dependent. In nutrient-enriched systems, phytoplankton dynamics were primarily controlled by inorganic nutrient concentrations, while climatic effects were weak by comparison. Conversely, in nutrient-poor systems, climatic signals became more visible and influential: wind events were associated with higher chlorophyll a, warmer conditions with increases in phycoerythrin-rich picocyanobacteria, and rainfall with higher picoeukaryote abundances, potentially through indirect effects on water column stability and nutrient and light availability. However, under nutrient limitation, abundances remained low and dominated by small cells, suggesting that nutrient control exerts the strongest influence on phytoplankton, which may explain why nutrient control tends to mask diffuse climatic signals. Yet, climate change modulates physicochemical patterns and may progressively shape lagoon functioning. This study emphasizes the need to account for lagoon features and vulnerabilities, and supports adaptive and site-specific management strategies to safeguard coastal lagoons under future changes.

Abstract Harmful phytoplankton blooms driven by climate warming and nutrient pollution are a growing threat to freshwater ecosystems worldwide. Predicting these blooms is critical for managing water resources. However, process‐based models often struggle to capture the complex nonlinear dynamics of phytoplankton. Although machine learning (ML) offers powerful predictive capabilities, its “black‐box” nature has limited its adoption for management. In this study, we applied four ensemble ML algorithms, Extreme Gradient Boosting (XGBoost), Random Forest (RF), Gradient Boosting Machine (GBM), and Categorical Boosting (CatBoost), to model phytoplankton dynamics in two adjacent drinking‐water reservoirs. All models performed similarly; however, the XGBoost algorithm achieved the best performance in both reservoirs, with a root mean square error (RMSE) of 2.4–6.6 μg/L chlorophyll a and a Pearson correlation coefficient (r) of 0.83–0.86. To enhance the interpretability of these ML models, we applied explainable artificial intelligence (XAI) techniques, including Shapley Additive Explanations (SHAP) and partial dependence analyses (PDPs). Our XAI analysis revealed reservoir‐specific dynamics, with deep dissolved oxygen and water temperature more influential in one reservoir, whereas seasonality and water column stability were more critical in the other. We also observed opposing effects of thermal stratification, with high water temperatures and strong stratification stimulating phytoplankton in one reservoir and suppressing it in the other. Stability analyses confirmed that the SHAP explanations were robust to perturbations, boosting confidence in their interpretability. This study demonstrates the application of a stability‐constrained XAI framework to provide transparent and trustworthy ecological insights, offering a robust approach for data‐driven water quality management and forecasting.

Seaweed cultivation offers a potentially sustainable solution for biomass production. However, in Norway, biomass quality at kelp farms is affected by biofouling, typically from encrusting bryozoans, such as Membranipora membranacea and Electra pilosa. This study investigated the drivers of bryozoan biofouling at a kelp farm in the coast of central Norway in 2022 and 2023. Environmental variables (temperature, salinity, turbidity, light, nutrients and wind), phytoplankton concentrations (chlorophyll a and size structure), and bryozoan (cyphonautes) larval size, abundance and recruitment on the kelp species, Saccharina latissima, were monitored. Phytoplankton biomass and size structure were monitored because cyphonautes are planktotrophic, therefore, phytoplankton was used as a proxy for food availability. Spring phytoplankton blooms (up to∼6mg chlorophyll a m-3) followed increased irradiance and reduced mixing, with cyphonautes larvae showing two main abundance peaks - in April (∼200-400 ind m-3), 1-2 weeks after the onset of the bloom - and in June (∼450 ind m-3). Larval abundance was associated with low salinity (value∼32), stratified, fresher coastal waters. Membranipora membranacea larvae were generally more abundant and reached larger sizes (up to 0.6mm in length) during the spring settlement period (late April-June). Larval size, rather than abundance alone, was most closely related to subsequent colony settlement, highlighting the importance of larval maturity for predicting biofouling risk. Colony abundance, size, and areal coverage were higher in earlier-deployed kelp (October 2022 versus January 2023) and increased exponentially from May (<1%) to late June (up to 11%). Recruitment peaked during a sharp increase in temperature (1-2°C in a few days) and was low during a period with high wind speed (up to 15ms-1). Our findings demonstrate that food availability, water column stability, rapid temperature increases and cyphonautes size structure are the dominant factors influencing bryozoan biofouling on kelp.

This work provides an explicit, accurate, and physically interpretable formulation of the waveguide invariant (WI) for the shallow-water Pekeris model with a finite-impedance seabed, addressing limitations of existing approximations in the low-frequency regime. This is achieved by deriving an approximate closed-form expression for the intermodal WI based on the physically intuitive cycle-distance formula for modal group velocities. Its accuracy is established through comprehensive validation against full-wave KRAKEN simulations, showing close agreement with the benchmarks and a rapid decay of error beginning immediately above the modal cutoff. Three key analytical insights are derived. First, a rigorous lower bound-confirming that finite seabed impedance elevates the WI above its ideal baseline-is formally established and experimentally supported by large WI values from seabed-dominated, low-frequency data. Second, a compact closed-form expression is obtained for the limit as the grazing angle approaches zero, helping to explain the stability of far-field interference structures. Third, a continuous angular-dependent approximation for adjacent-mode WIs is presented. Experimental analysis further defines the framework's operational boundary, confirming its optimal use where seabed effects dominate over water-column stratification. Together, the derived formulation, analytical insights, and experimental evidence constitute a refined framework for understanding modal interference in shallow-water waveguides.

Oceanic deoxygenation linked to enhanced water column stratification in the eastern Tethys during Cretaceous Oceanic Anoxic Event 2

Late Permian paleoenvironmental instability and recurrent biotic crises coincided with enhanced marine organic-carbon burial, yet ocean-circulation dynamics have remained underappreciated as a key driver. In particular, for the Wuchiaping Formation along the eastern margin of the Paleo-Tethys Ocean, the presence, variability, and mechanistic impact of upwelling—and its coupling with water-column redox structures—have not been systematically constrained, limiting a process-based understanding of organic-matter enrichment. Here, we integrate sedimentological, mineralogical, and multi-proxy geochemical data to investigate the dominant controls on organic matter enrichment in the Wuchiaping Formation shale succession from the northeastern Sichuan Basin. The Lower Wuchiaping Formation consists mainly of clay-rich shales deposited under oxic, shallow-water, and weakly stratified conditions, as indicated by low Ni/Co ratios (average 1.88), limited uranium enrichment (UEF = 0.21), low Ba/Al ratios, and sparse biogenic debris. Biomarker indices (gammacerane index = 0.35; Pr/Ph = 1.91) suggest unfavorable preservation conditions, resulting in a low mean TOC of 0.78%. In contrast, the Upper Wuchiaping Formation is dominated by siliceous shales with elevated Ni/Co ratios (average 15.83), moderate uranium enrichment (UEF = 2.48), abundant framboidal pyrite, radiolarian–planktic foraminiferal assemblages, and laminated apatite. High Ba/Al and Cd/Mo ratios, higher gammacerane values, and low Pr/Ph ratios (&lt;1) indicate enhanced water-column stratification and bottom-water anoxia, leading to efficient organic matter preservation and a high mean TOC of 9.2%. Biomarker compositions reveal a shift from terrestrial-dominated organic matter in the Lower Wuchiaping Formation to algal- and plankton-derived inputs in the Upper Wuchiaping Formation. Collectively, these results indicate that intensified upwelling—rather than tectono-magmatic forcing alone—was the primary driver of enhanced productivity, strengthened redox stratification, and organic matter enrichment in the Upper Wuchiaping Formation. Our findings highlight the importance of upwelling–redox coupling as a key mechanism linking Late Permian ocean-system reorganization to spatially and stratigraphically heterogeneous organic-carbon accumulation along the Paleo-Tethyan margin.

The ocean constitutes the largest actively exchangeable carbon reservoir in Earth’s surface system, with the ocean–atmosphere system functioning as an integrated entity that modulates atmospheric CO2 concentrations over geological timescales. While carbonate and organic-rich sedimentary carbon sinks have been the subject of extensive research, their synergistic roles in long-term carbon–climate feedback loops, as well as the degree to which microbial mediation links ocean hydrographic states to basin-scale carbon sequestration efficiency, remain poorly synthesized. Here, we develop a mechanistic framework comprising five intercoupled components: (1) driving factors (tectonic–climatic forcing and anthropogenic analogs); (2) ocean state controls (basin restriction, water column stratification, and redox conditions); (3) microbial processes (microbial carbon pump-mediated transformation of dissolved organic carbon and the modulating influence of microbial carbonate formation); (4) sedimentary carbon sinks (carbonate platforms versus organic-rich shales underpinning organo-mineral stabilization); and (5) Earth system feedback expressions (e.g., carbon isotope excursions and sustained perturbations in atmospheric CO2 levels). This framework is validated across three contrasting sedimentary basins, including the Western Tethys rift basins, the Cambrian South China platform system, and the Toarcian Lower Saxony restricted basin, and via three falsifiable propositions. Converging evidence from these case studies corroborates three key conclusions: (1) basin restriction and diminished water mass renewal foster water column stratification and hypoxic/anoxic conditions, thereby enhancing organic carbon preservation (P1); (2) the tectonic and depositional setting of a basin modulates the relative predominance of carbonate and organic carbon sinks (P2); and (3) post-extinction anachronistic facies record amplified microbial control over carbon burial pathways (P3). By emphasizing the context dependence of carbon sequestration processes and the significance of organo-mineral stabilization alongside particulate organic carbon export, this synthesis provides a transferable analytical framework for interpreting deep-time carbon cycle transitions and for contextualizing the impacts of modern ocean warming and deoxygenation on natural carbon sinks.

Introduction: Fish spawning aggregations (FSAs) are temporary concentrations of individuals of the same species that form for the sole purpose of reproducing. Objective: To document the species, times, and localities where FSAs occur in the Gulf of Chiriqui, Panamanian Pacific. Methods: From 2020 to 2025, SCUBA surveys and photographic documentation were conducted to identify FSAs within Coiba National Park (CNP) and the Islas Secas Archipelago (ISA) in the Gulf of Chiriquí. Environmental data, including temperature, salinity, and pH were collected using a YSI EXO2 multiparameter probe, and temperature was continuously recorded with a HOBO Water Temperature Pro v2. Results: The FSAs were recorded for three snapper species (Lutjanus peru, Lutjanus colorado and Lutjanus aratus); one jack (Caranx sexfasciatus); one grouper (Cephalopholis colonus); and one wrasse (Thalassoma lucasanum). Aggregations were observed at Bajo 20, Sacramento, Sueño del Pescador, and Montaña Rusa within CNP, and at Bajo Rizo in ISA. In the latter location, aggregations were recorded for T. lucasanum, C. colonus, and L. colorado. During aggregations, water column stratification was observed, associated with the intrusion of cold-water masses into the gulf, thermocline shoaling, and a decrease in dissolved oxygen concentrations, all correlated with temperature dynamics. Spawning events were most frequently observed in the morning hours. Conclusion: The number of reported species forming FSAs in CNP increased from three to seven, and FSAs were documented for the first time in ISA for three species.