ABSTRACT Background. The euphotic zone (EUZ) is the most superficial section of the water column where solar radiation is sufficient to produce photosynthesis. In situ depth is measured using light profiler probes but can also be monitored using remote sensing. Objective. To determine the temporal and spatial variability of Bahía de Banderas Euphotic Zone (EUZ) and its relationship with other variables that contribute to turbidity. Methods. Different data sources (OceanColor, Copernicus, NOAA, CONAGUA) were used to obtain time series (2003 to 2020) of particulate inorganic matter (PIM), Chlorophyll-a (Chl-a), diffuse attenuation coefficient at 490 nm (Kd490), depth of the Secchi disk (ZSD), ZEU, daily precipitation and water level of the Ameca and Pitillal rivers and a correlation analysis was made between these variables, and a cluster analysis to determine if there are spatial differences in the bay, as well as scatter plots to observe trends among environmental parameters. Two seasonal maps (rainy and dry season) were drawn based on the climatic medians of ZEU and the prevailing geostrophic currents. Results. The euphotic zone (EUZ) was deeper from June to August (48.54 ± 21.93 m) and shallower from February to April (22.95 ± 12.98 m); the cluster analysis determined that the bay is divided into two areas: the north, whose ZEU is shallower (higher correlation with MIP and Chl-a), and the south, where it is deeper (higher correlation with Chl-a). Conclusions. The parameter that has the greatest effect on the depth of the ZEU is the Chl-a, and only the area closest to the mouth of the Ameca and Pitillal rivers presents an inverse relationship between the ZEU with the MIP and the Chl-a.

RESUMEN Antecedentes. La zona eufótica (ZEU) es la sección más superficial de la columna de agua donde la radiación solar es suficiente para producir fotosíntesis. La profundidad in situ se mide usando sondas perfiladoras de la luz, pero también se puede monitorear utilizando percepción remota. Objetivo. Determinar la variabilidad temporal y espacial de la zona eufótica (ZEU) de Bahía de Banderas y su relación con otras variables que contribuyen a la turbidez. Métodos. Se utilizaron distintas fuentes de datos (OceanColor, Copernicus, NOAA, CONAGUA), para obtener series de tiempo (2003 al 2020) de materia inorgánica particulada (MIP), Clorofila-a (Chl-a), coeficiente de atenuación difusa a 490 nm (Kd490), profundidad del disco de Secchi (ZSD), ZEU, precipitación diaria y nivel hídrico de los ríos Ameca y Pitillal, se hizo un análisis de correlación entre estas variables. A partir de lo anterior, se realizó un análisis de conglomerados para determinar si existen diferencias espaciales en la bahía, así como diagramas de dispersión para observar las tendencias entre los parámetros ambientales. Se realizaron dos mapas estacionales (lluvias y secas) con base a las medianas climáticas de ZEU y a las corrientes geostróficas predominantes. Resultados. La profundidad de la zona eufótica (ZEU) fue mayor de junio a agosto (48.54 ± 21.93 m) y menor de febrero a abril (22.95 ± 12.98 m); el análisis de conglomerado determinó que la bahía se divide en dos áreas: la norte cuya ZEU es más somera (mayor correlación con la MIP y Chl-a), y la sur, donde es más profunda (mayor correlación con la Chl-a). Conclusiones. El parámetro que tiene mayor efecto sobre la profundidad de la ZEU es la Chl-a, y solamente el área más cercana a la desembocadura de los ríos Ameca y Pitillal presenta relación inversa entre la ZEU con la MIP y la Chl-a.

Abstract Integrating intricate environmental data within a unified analytical framework for extensive conservation and monitoring initiatives encounters several challenges. These challenges encompass defining a conceptual model outlining cause-and-effect relationships, addressing dissimilarities in data source quantity and information content, grappling with missing or noisy data, fine-tuning model optimization, achieving accurate predictions, and tackling the issue of imbalanced observations across factors. In the context of the Santos project, dedicated to comprehending the spatio-temporal dynamics of benthic, pelagic, and physical systems for the facilitation of conservation and monitoring programs, the application of machine learning’s random forest (RF) technique for modeling univariate data offers notable advantages. This approach adeptly handles non-linearity, covariation, and interactive effects among predictors. For modeling multivariate data sets, a hybrid strategy combining a self-organizing map (SOM) and RF is harnessed to effectively tackle the challenges. Addressing missing values, the bagging imputation technique demonstrated superior performance compared to other methods. Both machine learning techniques discussed herein exhibit resilience against the impact of noisy data, yet the identification of noisy data remains feasible based on model outputs. In scenarios of imbalanced data sets, we investigate the correlation between the RF model’s overall statistics and those of individual classes. The joint interpretation of these statistics aids in comprehending model limitations and facilitates discussions on the environmental mechanisms shaping observed patterns. We propose two analytical workflows that not only enable the exploration and enhancement of model accuracy but also facilitate the investigation of potential cause-and-effect relationships inherent in the data. Furthermore, these workflows lay the foundation for implementing long-term learning algorithms, a pivotal increment for monitoring initiatives. Notably, these workflows, alongside the discussed analytical challenges, can be seamlessly implemented within iMESc, an open-source application. causeandeffect cause effect content finetuning fine tuning optimization predictions factors project spatiotemporal spatio temporal benthic pelagic programs learnings s (RF advantages nonlinearity, nonlinearity non linearity, linearity non-linearity covariation predictors sets selforganizing self organizing SOM (SOM values methods outputs models classes patterns Furthermore longterm long term algorithms Notably iMESc opensource open

Abstract The Gulf of California is known for its high productivity, diversity, and unique oceanography. Based on old and recent contributions, we estimate a richness of 160 copepod species in this province. This work seeks to identify latitudinal and seasonal patterns of the copepod composition, abundance, and diversity in the Gulf of California during 1985. Differences between four zones of the gulf (NGC, CGC, SGC, EGC) and between the cold and warm seasons were hypothesized, based on taxonomic and ecological data. Samples were collected during the CORTES cruises (1985), which also measured salinity, temperature, and dissolved oxygen at each station. We analyzed the latitudinal and seasonal variation of the copepod community with multivariate analyses (NMDS-PCA) and correlated these with the environmental data (CCA). Seventy-nine copepod species were identified, averaging 265,649 and 98,885 ind/10 m3 in the cold and warm seasons, respectively. Only 53 of these occurred in both seasons, indicating seasonal change in species composition. Composition and diversity varied latitudinally in the cold season (P < 0.05 in all comparisons but CGC vs. SGC), but not in the warm season (except NGC vs. the rest of the gulf). There was seasonal change in the composition and the abundance (P < 0.005 cold vs. warm season). Richness and diversity were negatively correlated with salinity (decreasing from the north of the gulf); the abundance and composition were mainly affected by the shift in temperature. These patterns also match the phytoplankton abundance and size structure in the gulf, probably the main factors affecting copepod distribution.

Abstract The Antarctic region has experienced recent climate and environmental variations due to climate change, such as ice sheets and ice shelves loss, and changes in the production, extension, and thickness of sea-ice. These processes mainly affect the freshwater supply to the Southern Ocean and its water masses formation and export, being crucial to changes in the global climate. Here, we review the influence of the glacial freshwater input on the Antarctic Peninsula adjacent ocean. We highlight each climate process’ relevance on freshwater contribution to the sea and present a current overview of how these processes are being addressed and studied. The increase of freshwater input into the ocean carries several implications on climate, regionally and globally. Due to glacier melting, the intrusion of colder and lighter water into the ocean increases the stratification of the water column, influencing the sea-ice increase and reducing ocean-atmosphere exchanges, affecting the global water cycle. This study shows the role of each hydrological cycle processes and their contributions to the regional oceanography and potentially to climate.

Abstract The formation of dense water masses at polar regions has been largely influenced by climate changes arising from global warming. In this context, based on ensemble simulations with a coupled model we evaluate the meridional shift of a climate signal (i.e., a cold and fresh water input pulse generated from melting of positive Antarctic sea ice (ASI) extremes) towards the Tropical Atlantic Ocean (TAO). This oceanic signal propagated from Southern Ocean towards the equator through the upper layers due to an increase in its buoyance. Its northward shift has given by the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) flows, that inject cold and fresh mode/intermediate waters from into subtropical basin. The signal has reached low latitudes through the equatorial upwelling and spreads out southwards, through the upper branch of southern subtropical gyre. We concluded that 10 years of coupled simulations was enough time to propagate the climate signal generated by ASI positive extremes melting, which reached TOA around 2 year later. The oceanic connection between Southern Ocean and TAO is indeed established within the timescale analyzed in the study (10 years). Nonetheless, the period needed to completely dissipate the disturbance generated from ASI seems to be longer.

Abstract The Brazil Current (BC) is a western boundary current, with an average vertical extension of 500 m, which occupies the southwestern margin of Atlantic Ocean. Recently, the South Brazil Bight - SBB (23º S - 28º S) has been intensively explored by the oil and gas industries, which brought a high demand in operational oceanography and ocean state monitoring. In this study we present a new technique based on the vertical dynamic modes of oscillation, to extrapolate velocity profiles in the SBB, with potential applications to data acquired by Vessel Mounted Acoustic Doppler Current Profilers (VMADCP). Using four quasi-synoptic crosssectional velocity data, acquired by Lowered Acoustic Doppler Current Profilers (LADCP), we observed that the mean circulation of this region can be characterized as a 2-dynamical mode system. This mean circulation is mainly dominated at surface by the BC and at intermediate levels by the Intermediate Western Boundary Current (IWBC), which flows northward. Furthermore, observed mesoscale vortical features in the SBB, such as eddies and meanders, are shown to be primarily barotropic-mode dominated. In our extrapolation methodology, the use of an independent set of velocity time series obtained by four moorings has shown to be a valid way for obtaining the relative contribution of each dynamical mode in the velocity field in the SBB. Normalized mean squared errors below 10% and radar diagrams show that the presented methodology was able to reproduce the main dynamic features observed by LADCP transects. Also, with this technique, we extrapolated three VMADCP sections and the results agreed with previous observations.

RESUMEN Con el objetivo de generar insumos para el manejo del Santuario de Flora y Fauna Malpelo, la Dirección Territorial Pacífico de Parques Nacionales Naturales de Colombia, inició en 2006 un monitoreo de condiciones oceanográficas en el área. En la actualidad este monitoreo cuenta con una malla de muestreo de solo seis estaciones ubicadas a 0,93 km (0,5 millas náuticas) y 1,85 km (1 milla náutica) desde la isla, por lo que es poco eficiente debido a la reducida distancia entre estaciones e insuficiente dada la gran extensión del Santuario. Por lo tanto, se diseñó una malla de muestreo con base en datos de temperatura superficial del mar (TSM) tomados in situ, derivados del sensor remoto MODIS-Aqua. Se analizó la estructura de autocorrelación espacial a través de una función de semivarianza. La decisión para elegir la mejor malla de muestreo entre los diferentes tamaños, fue basada en la disimilitud entre estaciones asociada al modelo de semivarianza, en la varianza del error de predicción, en el patrón de corrientes marinas predominante durante el ciclo anual, y en aspectos logísticos relacionados con las limitantes de desplazamiento de las embarcaciones que realizan los monitoreos oceanográficos en el SFF Malpelo. Como resultado de considerar estas variables, se obtuvo una malla de muestreo con estaciones cada 7,41 km (4 millas náuticas) compuesta por ocho estaciones nuevas y las seis de la malla de muestreo histórica.

ABSTRACT In order to generate inputs for the management of the Sanctuary, the Pacific Territorial Directorate of National Natural Parks began in 2006 a monitoring of oceanographic conditions in the area. Currently, this monitoring has a sampling network of only six stations located 0.93 km (0.5 nm) and 1.85 km (1 nm) from the island, so it is not efficient due to the reduced distance between stations, and insufficient given the large extension of the Sanctuary. Therefore, a sampling network was designed based on Sea Surface Temperature (TSM) data taken in situ and derived from the Modis-Aqua remote sensor. The spatial autocorrelation structure was analyzed through a semi-variance function. The decision to choose the best sampling network among the different sizes was based on the dissimilarity between stations associated with the semi-variance model, on the variance of the prediction error, on the predominant pattern of marine currents during the annual cycle, and on aspects logistics related to the movement limitations of the vessels that carry out oceanographic monitoring in the SFF Malpelo. As a result of considering these variables, a sampling network was obtained with stations every 7.41 km (4 nm) , composed of eight new stations and six of the historical sampling network.

Abstract The Irrawaddy dolphin (Orcaella brevirostris) is an endangered, small cetacean species which is widely distributed in rivers, estuaries, and coastal waters throughout the tropical and subtropical Indo-Pacific. Despite the extensive distribution of this species, little is known of individual movements or genetic exchange among regions in Thailand. Here, we evaluate the genetic diversity and genetic structure of O. brevirostris in the eastern, northern and western Gulf of Thailand, and Andaman Sea. Although phylogenetic relationships and network analysis based on 15 haplotypes obtained from 32 individuals reveal no obvious divergence, significant genetic differentiation in mitochondrial DNA (overall FST = 0.226, P < 0.001; ΦST = 0.252, P < 0.001) is apparent among regions. Of 18 tested microsatellite loci, 10 are polymorphic and successfully characterized in 28 individuals, revealing significant genetic differentiation (overall FST = 0.077, P < 0.05) among the four sampling sites. Structure analysis reveals two inferred genetic clusters. Additionally, Mantel analysis demonstrates individual-by-individual genetic distances and geographic distances follow an isolation-by-distance model. We speculate that the significant genetic structure of O. brevirostris in Thailand is associated with a combination of geographical distribution patterns, environmental and anthropogenic factors, and local adaptations.

Abstract At age 101, Walter Munk passed away in 2019. His groundbreaking discoveries will still guide and amaze oceanography students for years to come. Here, we perceive patterns in rotating tank with Munk's circulation theory aided by a Lagrangian particles tracking algorithm and numerical modeling. From information captured by video, we track the trajectories of drifters, and then objectively mapped the streamfunction to obtain the mean circulation pattern. We were able to reproduce the wind-forced anticyclonic and asymmetric gyre, including the western boundary intensification and its retroflection. The latter phenomenon was predicted by the non-linear version of Munk's model and observed in real subtropical gyres as small recirculation regions. We have configured two numerical model simulations mimicking the physical experiment, with linear and non-linear terms. The comparison between the numerical and physical experiments confirmed the effect of non-linear distortion of the gyre. Geophysical fluid dynamics is often hard to visualize, and counter-intuitive in a rotating system. We present this set of experiments as a tool for oceanography teaching. Besides studying general ocean circulation theories and observations through practical examples, this experiment provides an opportunity to develop basic image processing and geophysical modelling skills.

Resumo Marta Vannucci é considerada uma das mais importantes cientistas brasileiras. O artigo explora a trajetória internacional da pesquisadora, destacando sua atuação na Organização das Nações Unidas para a Educação, a Ciência e a Cultura (Unesco) no âmbito do projeto regional sobre mangues na Ásia e no Pacífico. Produto da sua atuação nesse programa, a autora publicou Os manguezais e nós, que é objeto de análise crítica neste artigo.

Abstract Marta Vannucci is held to be one of Brazil’s most important scientists. Her international trajectory is explored, highlighting her work with the United Nations Educational, Scientific and Cultural Organization (Unesco) in the ambit of the regional project on mangroves in Asia and the Pacific. As a result of her work for this program, Vannucci published The mangroves and us, which is the object of critical analysis in this article.

Abstract The Gulf of Mexico (GoM) is a large marine ecosystem that has unique oceanographic dynamics, as it shows important spatio temporal variations in the configuration of its surface waters. Several studies have used the thermal and biological features to subdivide the GoM, while other had provided subdivisions using circulation features. Nevertheless, none of those works have produced a dynamic regionalization that consider biological and physical features of the GoM simultaneously. The goal of this work was to propose a dynamic division of the GoM which considers physical and biological features and to analyze the monthly spatial evolution of regions in an average year. We used statistical multivariate analysis to recognize the underlying structure of the data, to generate a monthly expression of clusters and to test the robustness of the achieved regionalization. We obtained 18 regions called oceanographic units (UO) that merged unique surface characteristics of the GoM and that had a monthly spatial configuration. We observed two main groups of UO: those that are mainly related with circulation properties and those that were defined by its biological and thermal associations. Fifteen UO were present all year long, while three of them were only present some months. All UO have monthly internal variations and their boundaries displayed seasonal spatial variation; however, they remained well differentiated from each other. This study offers a novel way to divide an oceanic system, which provides quantitative and pragmatic parameters that can help to develop monitoring systems considering the intrinsic ocean dynamics. The information about oceanographic unit variability provides valuable information to promote marine resources management, in concordance to their temporal association with certain water masses. These results also provide the basis to analyze interannual variations of oceanographic units to offer information about the sea surface dynamics and to help understanding a complex system such as Gulf of Mexico.

Resumen El Golfo de México (GoM) es una región oceánica de una dinámica y complejidad particular, que se evidencia en las variaciones espacio temporales de la configuración de sus aguas superficiales. Varios estudios han utilizado las características superficiales térmicas, biológicas o de circulación para proponer subdivisiones estáticas del GoM; sin embargo, ninguna investigación ha regionalizado la zona integrando distintos aspectos oceanográficos de forma dinámica. El objetivo de este trabajo fue proponer una división del GoM que considerara las características físicas y biológicas y que permitiera analizar la evolución mensual espacial de las unidades en un año promedio. Utilizamos análisis multivariados para reconocer la estructura subyacente de los datos, para generar una expresión espacial mensual de los conglomerados y para probar la robustez de los resultados. Se obtuvieron 18 regiones denominadas unidades oceanográficas (UO) que condensan diversas características superficiales del GoM. Se observaron dos grupos de UO: aquellas que están relacionadas con las propiedades de circulación y aquellas que fueron definidas por la asociación de las características biológicas y térmicas. Quince UO están presentes a lo largo del año, mientras que dos tienen presencia únicamente en verano. Todas las UO tienen variaciones temporales tanto en sus características biofísicas como en su expresión espacial. Este estudio propone una manera novedosa de particionar un sistema marino y aporta parámetros cuantitativos interpretables de las UO propuestas. La representación de la variabilidad de unidades oceanográficas homogéneas provee información valiosa para el manejo diferenciado de recursos marinos asociados temporalmente a masas de agua especificas. Los resultados obtenidos proveen también bases robustas para analizar de manera condensada la dinámica de largo plazo de un sistema tan complejo como es el GoM.

Marine sponges - in common with many other sessile marine invertebrates seemingly devoid of obvious physical forms of defence against predators, e.g. spines or shells - are the sources of a diverse array of organic chemical compounds known as marine natural products or secondary metabolites. Recent research has indicated that the production of natural products via cellular secondary metabolic pathways in some sponge species may not occur within the sponge cells themselves, but rather in microbial endosymbionts which inhabit the surface and interstitial spaces within the sponge tissue. Regardless of their biosynthetic origin, the bioactivity, e.g. toxicity, of many of these marine natural products may be utilised by sponges as chemical feeding deterrents to discourage predation or to provide a chemical anti-fouling competitive edge in the intense competition for living space amongst filter-feeders on space-limited benthic reefs. Paradoxically, a small number of sponge natural products have serendipitously shown potential as new pharmaceuticals, e.g. novel anti-cancer drugs. Marine biodiscovery (or bioprospecting) is the search for new pharmaceuticals from marine organisms. Exploration of the taxonomy, natural products chemistry and biomedicinal potential of the rich diversity of South African latrunculid sponges (family Latrunculiidae), at Rhodes University, the South African Department of Environmental Affairs and the University of the Western Cape has continued unabated for over a quarter of a century as part of a collaborative marine biodiscovery programme. A short review of this multidisciplinary latrunculid sponge research is presented here. SIGNIFICANCE: • Research into the taxonomy, chemistry and microbiology of latrunculid sponges is the most comprehensive, multidisciplinary investigation of any group of African marine sponges. • The potent cytotoxicity of the pyrroloiminoquinone alkaloid pigments isolated from latrunculid sponges may have biomedical applications. • This review underlines the importance of conserving and protecting South Africa's unique marine invertebrate resources.

ABSTRACT Salinity is a key variable for ecological processes in estuaries. Acartia tonsa is a typical estuarine copepod whose responses to salinity have been thoroughly studied in the laboratory. However, results cannot be extrapolated to the field, and formal comparisons between lab and field responses to salinity were not attempted. Here we compare lab-based with field copepod egg production rates (EPR) from the Río de la Plata estuary (RPE), with focus on A. tonsa. Field work was conducted between 2009 and 2011 in the mixing zone of the RPE. Water temperature, salinity and chlorophyll-a varied over ample ranges (temperature: 10.54 - 24.56ºC, salinity: 2.83 - 32.99, chlorophyll-a: 0.62 - 7.27 mg m-3). A. tonsa was the strongly dominant species. EPR ranged between 6.7 and 95.7 eggs female-1 day-1, and correlated to salinity, temperature (weakly), but not to chlorophyll. The relationship between A. tonsa’s EPR (EPRAT) and salinity was consistent with that obtained under laboratory conditions: a humped pattern with a maximum at intermediate salinities. However, differences were also evident, e.g., higher EPRAT was measured in the field. We speculate that discrepancies derive from nutritional differences between field and reference (laboratory) data sets. Besides salinity, food quality and quantity may be first order drivers of A. tonsa’s productivity in the RPE.

ABSTRACT Many microalgae are rich in lipid. Due to their low growth rates in the autotrophic culture, the best alternative is to cultivate cells under different conditions such as heterotrophic or mixotrophic, which results in the highest yield of biomass and lipid in the shortest duration. In this study, Dunaliela bardawil (UTEX 2538) green microalgae was cultivated under different culture conditions, autotrophic, heterotrophic and mixotrophic, and effects on cell concentration, lipid production and reactive oxygen species (ROS), total chlorophyll and beta-carotene concentrations were investigated. Due to very low cellular growth, this alga is not recommended for heterotrophic culture. In terms of mixotrophic conditions containing different concentrations of glucose or acetate, the highest cell growth and lipid production in 60mM glucose was similar to the control (autotrophic condition), while the concentrations of chlorophyll and beta-carotene decreased. However, at all concentrations of acetate, a slight increase in cell growth was achieved, while the lipid content decreased. Additionally, the concentrations of chlorophyll and beta-carotene increased. A positive correlation was observed between beta-carotene biosynthesis and lipid production, as well as levels of reactive species of oxygen and lipid production in the presence of glucose and acetate. This study showed that for D. bardawil the mixotrophic culture with 60mM glucose was the most suitable type of culture for increasing lipid content and cell growth rates in less time (one week).