Gulf Of Guayaquil Research Articles

Biological and Fishery Aspects of Hake (Merluccius gayi, Guichenot, 1848) Caught with Trawl Nets in the Gulf of Guayaquil, Ecuador.

Biological and Fishery Aspects of Hake (Merluccius gayi, Guichenot, 1848) Caught with Trawl Nets in the Gulf of Guayaquil, Ecuador.

Social, Environmental and Techno-Economic Impact of Rural Electrification Isolated with Photovoltaic Systems

Objective: To analyze the social, environmental, and techno-economic impact of rural electrification through the implementation of photovoltaic systems in isolated communities, in order to improve the quality of life of the inhabitants and promote sustainable development. Theoretical Framework: Successful cases of off-grid rural electrification with photovoltaic solar energy in Latin America for the economic and social development of isolated communities are reviewed. The drivers and limitations of this technology in Latin America, the cost of energy and the contribution to local development are analyzed to promote its adoption and sustainability. Method: A qualitative documentary method is used to study the social, environmental and techno-economic impact of rural electrification with photovoltaic systems in rural and marginal communities in Latin America, focusing on the case study of the community of Masa 2 in the Gulf of Guayaquil. Aspects such as the adoption of solar systems, implementation costs, benefits for the inhabitants and the need for a management plan to guarantee the sustainability of the systems are evaluated. Results and Discussion: The results of the study show that isolated electrification with photovoltaic systems in the case study has had a positive impact on the development of the quality of life of the inhabitants, allowing access to basic services such as electricity and telecommunications and providing the possibility of receiving virtual classes and entertainment, among other benefits. The need for policies that promote the adoption of photovoltaic technology is emphasized, as well as the importance of considering technical, economic and social aspects to ensure the successful implementation of rural electrification. Research Implications: The paper discusses the importance of implementing photovoltaic systems with management plans, in addition to the positive impact on the quality of life of the inhabitants, economic savings and access to basic services and improving educational opportunities. Originality/Value: The multidisciplinary approach in addressing the social, environmental and techno-economic impact of implementing photovoltaic systems in isolated communities. The study also analyzes the benefits of rural electrification in terms of local development, access to basic services and improvement of the quality of life of the villagers, highlighting the horizontal analysis of the state of losses or gains.

Age and growth of larval Pacific flagfin mojarra (Eucinostomus currani) in coastal Ecuador based on otolith analysis

The flagfin mojarra (Eucinostomus currani) is an important subsistence fishery resource in local Ecuadorian markets; however, very little is known about the early life history and reproductive biology of this species. In 2016 and 2017, E. currani larvae were collected at 3 sandy beaches in the Gulf of Guayaquil, Ecuador, and identified using DNA barcoding. Standard lengths ranged from 4.00–15.78 mm. We also collected otoliths to better understand the early life history of E. currani. Otoliths were used to estimate the age, population growth rate (±SE), hatch dates, and reproductive period. On average, the fish were 16.5 ± 4.5 days old, while the average growth rate was 0.70 ± 0.05 and 0.22 ± 0.16 mm per day in March and May, respectively. In the Gulf of Guayaquil, most hatch dates and the presumed reproductive activity of E. currani occurred during the wet season (December–April) when warmer water prevailed. To our knowledge, this is the first study to estimate the hatch dates and larval growth rate for a species of the family Gerreidae in the Pacific Ocean.

Quantification of Heavy Metal Content in Anadara tuberculosa from the Gulf of Guayaquil Using ICP-OES: Assessing Marine Contamination

The present study was conducted to quantify the heavy metals cadmium, lead, copper, chromium, nickel, and zinc in the bivalve mollusk concha prieta (Anadara tuberculosa) using inductively coupled plasma optical emission spectroscopy (ICP-OES). This research aims to identify whether the bioaccumulated content of heavy metals exceeds the maximum limits established by various public health bodies such as the ONU, FAO, Codex Alimentarius, EEC, and NHI. Samples of the species were collected randomly from three locations in Puerto El Morro, Playas Municipal Market, and La Libertad Seafood Market in the Gulf of Guayaquil. Thirty-three soft tissue samples of Anadara tuberculosa were evaluated, and the values quantified in mg/kg were in the following order: Zn > Cu > Cd > Ni > Cr > Pb.

A deep-learning automated image recognition method for measuring pore patterns in closely related bolivinids and calibration for quantitative nitrate paleo-reconstructions

Eutrophication is accelerating the recent expansion of oxygen-depleted coastal marine environments. Several bolivinid foraminifera are abundant in these oxygen-depleted settings, and take up nitrate through the pores in their shells for denitrification. This makes their pore density a possible nitrate proxy. This study documents three aspects related to the porosity of bolivinids. 1. A new automated image analysis technique to determine the number of pores in bolivinids is tested. 2. The pore patterns of Bolivina spissa from five different ocean settings are analysed. The relationship between porosity, pore density and mean pore size significantly differs between the studied locations. Their porosity is mainly controlled by the size of the pores at the Gulf of Guayaquil (Peru), but by the number of pores at other studied locations. This might be related to the presence of a different cryptic Bolivina species in the Gulf of Guayaquil. 3. The pore densities of closely related bolivinids in core-top samples are calibrated as a bottom-water nitrate proxy. Bolivina spissa and Bolivina subadvena showed the same correlation between pore density and bottom-water nitrate concentrations, while the pore density of Bolivina argentea and Bolivina subadvena accumeata is much higher.

Marine litter and social inequities entangle Ecuadorian mangrove communities: Perceptions of plastic pollution and well-being concerns in Puerto Hondo and Isla Santay, Ecuador

Mangrove forests of Ecuador’s Gulf of Guayaquil are ecologically, culturally, and economically important to local communities relying on them for artisanal fishing, ecotourism, and related businesses. However, these ecosystems have experienced significant degradation by anthropogenic impacts such as anthropogenic marine debris. On one hand, plastics have improved the ease of life and safety for local people of the region; however, plastic pollution threatens the health of the mangrove ecosystem and these communities. This interdisciplinary study explores perceptions of marine litter and its impacts on community well-being based on surveys conducted in Puerto Hondo and Santay Island, two mangrove communities in the Gulf of Guayaquil, in 2019 and 2021. Santay Island respondents expressed that marine litter is an extreme issue affecting their well-being, while Puerto Hondo respondents reported less concern. Authors suggest Puerto Hondo’s geographic link to Guayaquil city has transitioned the community into a “peri-urban” landscape, where community members increasingly look inland for basic needs. Conversely, Santay Island, isolated by estuarine water, is physically linked to the mangroves. It is suggested that as communities spend less time in the mangroves, whether geographically or socially separated, marine litter becomes “out of sight, out of mind” despite its ongoing impacts on local food security and historical heritage. This work illustrates the complexities of plastic use and marine debris. To foster equitable plastic waste governance for exposed coastal Ecuadorian communities, policies must not only account for these intricacies but also actively engage with and listen to local perspectives.

Continental block motion in the Northern Andes from GPS measurements

SUMMARYNorthwestern South America is a plate boundary zone where the Nazca, Caribbean and South American plates interact to produce a wide area of active continental deformation from the Gulf of Guayaquil (latitude 3°S) to Venezuela. Previous studies have identified a ∼2000-km-long continental sliver, referred as the North Andean Sliver (NAS), squeezed between the Nazca, Caribbean and South American plates and escaping at ∼1 cm yr−1 northeastward with respect to South America. Subduction of the Nazca Plate beneath the NAS has produced a sequence of large and great earthquakes during the 20th century along the coast of Ecuador and Colombia. Large crustal earthquakes up to magnitude 7.7 have been documented along the proposed eastern boundary of the NAS. However, active tectonics data, historical and recent earthquakes all indicate active fault systems within the NAS, possibly resulting from the interaction of several tectonic blocks. Here, we derive an extensive horizontal velocity field using continuous and episodic GNSS data from 1994 to 2019.9, covering northern Peru, Ecuador, Colombia, Panama and Venezuela. We model the GNSS velocity field using a kinematic elastic block approach that simultaneously solves for rigid tectonic block rotations and interseismic coupling along the subduction interfaces and along major crustal faults. In contrast to previous results that considered a single rigid NAS, our dense GNSS velocity field demonstrates that the NAS undergoes significant internal deformation and cannot be modelled as single rigid block. We find that block kinematics in the northern Andes are well described by the rotation of 6 tectonic blocks, showing increasing eastward motion from south to north. The Eastern boundary of the sliver is defined by a right-lateral transpressive fault system accommodating 5.6–17 mm yr−1 of motion. Fragmentation of the NAS occurs through several fault systems with slip rates of 2–4 mm yr−1. Slow reverse motion is found across the sub-Andean domain in Ecuador and northern Peru at 2–4 mm yr−1, marking a transitional area between the NAS and stable South America. In contrast, such a transitional sub-Andean domain does not exist in Colombia and western Venezuela. At the northwestern corner of Colombia, fast (∼15 mm yr−1) eastward motion of the Panama block with respect to the NAS results in arc-continent collision. We propose that the Uramita fault and Eastern Panama Deformed Zone define the current Panama/NAS boundary, accommodating 6 and 15 mm yr−1 of relative motion, respectively. A fraction of the Panama motion appears to transfer northeastward throughout the San Jacinto fold belt and as far east as longitude ∼75°W. Along the Caribbean coast, our model confirms, slow active subduction at ∼4.5 mm yr−1 along the South Caribbean Deformed Belt offshore northern Colombia and a relatively uniform rate of ∼1–2 mm yr−1 offshore northern Venezuela. Along the Nazca/NAS subduction interface, interseismic coupling shows a first-order correlations between highly locked patches and large past earthquake ruptures. These patches are separated by narrow zones of low/partial coupling where aseismic transients are observed. Compared to previous studies, our interseismic coupling model highlights the presence of deep coupling down to 70 km in Ecuador.

Cranial variation between coastal and offshore bottlenose dolphins, Tursiops truncatus (Cetacea: Delphinidae) in Ecuador and the Mediterranean: a three-dimensional geometric morphometric study

Abstract Skull shape analysis provides useful information on wildlife ecology and potential local adaptations. Common bottlenose dolphins (Tursiops truncatus) often differentiate between coastal and offshore populations worldwide, and skull shape analyses can be particularly useful in this context. Here we quantify skull shape variation between coastal populations from the Gulf of Guayaquil (Ecuador) and the Mediterranean Sea, compared to offshore specimens from multiple oceans. We analysed skull shape differences using 3D models from museum specimens through geometric morphometrics (3DGM). Two complementary landmark approaches included single-point semi-landmarks in homologous features, as well as pseudo-landmarks placed automatically. Results show skull shape distinction between both coastal populations and offshore specimens. Offshore specimens showed little differentiation between distinct locations. Skull shape patterns mostly diverged in the shape and length of rostrum, as well as the shape of the ascending processes of the maxilla, pterygoids, and occipital bones. However, both coastal populations differed in the patterns and direction of change of those features and were also morphologically distinct. Our results are consistent with local data on site fidelity and social structure in the coastal populations. Skull shape changes suggest divergent feeding and sound production patterns are potential drivers, probably specific to the local environment of each community.

First record of the invasive dwarf surf clam Mulinia lateralis (Say 1822) in the eastern Pacific Ocean

Mulinia lateralis is a native bivalve from the Western Atlantic Ocean, distributed from the Gulf of Saint Lawrence in Canada to Yucatan in Mexico. Based on morphological and genetic data of specimens collected in shrimp farms, in this work, we confirm the presence of M. lateralis in the Gulf of Guayaquil, Ecuador. Presence and its consequences of this invasive bivalve in the region is discussed.

Sampling bottles for shallow estuarine waters, constructed using inexpensive recyclable materials

Sampling water from shallow estuaries, rivers, or lakes, particularly where access is difficult, can be problematic. In estuaries at low tide, water depths can be less than a meter, and therefore conventional samplers based on vertical tubes of plastic or metal, such as Nansen and Niskin bottles, are inappropriate. During three consecutive years (2017–2019) whilst studying eutrophication in the shallow waters of the marginal Estero Salado (ES, Gulf of Guayaquil, Ecuador), a range of tubular water samplers were designed, constructed, and tested. Six of these designs are presented here and all use inexpensive recyclable and locally available materials. The sampling bottles were mainly made from readily available plastic components, including non-returnable drinking water bottles, acrylic/PVC pipes, tweezers, elastic bands, discarded gym weight plates, and closures made from plumbing items. Up to 80% of the materials used were recyclable. Costs ranged from 5 to 35 US$, and the time to design and construct was up to two days. The horizontal sampling bottles proved strong enough for rigorous field conditions. Sampling at depths <1 m, the bottles did not show any sign of collapsing due to either the hydrostatic pressure when empty nor the weight of the water sample. Three samplers are submerged with open ends to the depth required, and then moved sideways or allowed to align with the current to flush the interior. Then, a messenger or pulling on a line closes the bottle. A simple tap or direct dispensing is used to transfer the water into storage bottles. Two of the designs (with one end open) can be used to sample right through the very surface layer. Two of the designs that enter the water with closed ends were inter-compared with a standard Niskin water sampler and gave statistically comparable results. The lightest sampler was tested at various depths down to 5 m in a lake with no operational issues, and nutrient data from samples gave a coherent vertical profile. Two of the designs (with one end open) can be used to sample the very surface layer. The water samplers reported here are highly appropriate for laboratories with very limited resources and can be used in very shallow waters under a wide range of environmental conditions. Results from samples collected with the described samplers show that the inner estuarine branches of the ES are now under perennial hypoxic, acidic, and hypereutrophic conditions with extremely high total and fecal coliform loads.

Design of a Graphic Recipe Book to Improve Eating Habits Practices Based on the Local Cuisine of the Bellavista Commune of Guayaquil Gulf, Ecuador

ObjectivesThe purpose of this study was to design a digital graphic recipe book by optimizing food preparations to develop new culinary skills and improve the eating habits of the families that integrate the Bellavista community in the Gulf of Guayaquil. MethodsA descriptive-observational non-experimental cross-sectional study was carried out with a sample of 15 mothers over 18 years of age. All the participants accepted to be part of the study through signing an informed consent. An anthropometric nutritional evaluation, a socioeconomic questionnaire, a KAP questionnaire on knowledge, attitudes, and practices in nutrition, three nutritional educational interventions, and a practical workshop were carried out. To evaluate the effectiveness of the nutritional educational interventions the KAP questionnaire was applied at the beginning and at the end of the study among the participants. The before and after of KAP results were analyzed by a paired t-test considering a significant p-value < 0.05 using the RStudio software. After all the information was collected a graphic recipes book was designed. ResultsOnce the intervention was completed, an improvement in the participants’ learning was observed, evidenced in the preparation of dishes with a better arrangement of macronutrients, as well as a 70% improvement in their attitudes regarding health and nutrition. The paired t-test confirmed that there was an improvement in knowledge acquisition and that the educational talks had a positive effect (p-value < 0.05), with a confidence interval of 40.5%–79.4%. ConclusionsA digital graphic recipe book is an important tool in the communication and nutritional education strategy, which creates a positive impact on the nutrition of the members of the Bellavista community. Funding SourcesNone.

Cartographic scripts for seismic and geophysical mapping of Ecuador

This research describes a script-based method of Generic Mapping Tools (GMT) for mapping the seismicity, geophysics, geology and topography of Ecuador. The advances of GMT include the following points: (1) automation of workflow; (2) refined aesthetics of graphics; (3) speed console-based mapping; (4) multi-format data handling; (5) advanced syntax. An explanation of scripting with the examples of code snippets is provided. The results present six new maps of Ecuador. The distribution of geophysical phenomena and seismicity is compared to the terrain elevation, showing remarkable correlations with the topography and geoid. The data demonstrated low values in the depression of the Andes, the Gulf of Guayaquil, and the Peru-Chile Trench. The peaks in gravity are representative for the Andean topography. Local decreases in gravity correspond to the depressions in the coastal shelf and the Gulf of Guayaquil. The increase in seismicity is detected along the tectonically active areas. The GMT is appropriate to the geological risk assessment of Ecuador.

The Chongón/Colonche orocline transrotational bending and the coeval opening of the Progreso basin in southwestern Ecuador

Integration of geological and geophysical studies of Progreso Basin in SW Ecuador provided a unique opportunity to propose an unorthodox model for the Progreso Basin opening within a strike slip regime. Shearing couple transrotation of the Chongón/Colonche (C/C) orocline bending accounted for the atypical, isosceles triangle shape, Progreso Basin opening during the Oligocene oblique convergence amid the Farallon and South America plates. Transrotation commenced with the sinistral strike slip reactivation of the Paleocene Chongón-Jipijapa-Jama (CJJ) Suture. This suture is inferred based on field kinematics of Cretaceous outcrops in the Santa Elena Peninsula and published high resolution potential field maps. The reactivated suture worked as the sinistral La Cruz (LCF) Fault and their “en echelon” synthetic Riedels C/CF, Consuelo (COF), and Carrizal (CAF) faults accommodated most of the basin heterogeneous transtension and transrotation. While the synthetic Riedels migrated northward along the La Cruz Fault, a narrow segment of the Paleogene foredeep and the intra-oceanic arc sequence of the C/C High attached to the Estancia Hills was scrapped off and rotated. The shearing couple between the “en echelon” Riedels enhanced the transrotation and transtension and triggered the counterclockwise crustal rotation of the C/C High. The subvertical block rotation involved significant lithospheric decoupling of this high that set off the C/C Orocline development and coeval opening of the Progreso Basin.Early Zapotal Formation deposition characterized by alluvial fan aggradation rapidly filled the graben between the Consuelo and Carrizal faults as the Consuelo Fault underwent strain hardening and confining. In doing so, the sediment input by the active alluvial fan complex spilled over the Carrizal Fault displaying down lapping and progradation along the hanging wall. Its listric behavior on other hand, set off the tilting of the pre-extensional Paleogene sequences, which in turn caused the onlapping and diachronous deposition of the Zapotal Formation toward the La Cruz Fault. Protracted marine incursion and deposition of a fine grained siliciclastic sequence that encompassed the whole Oligocene took place around the already opened basin toward the south.Early Miocene breakup of the Farallon Plate not only increased the convergence rate but also gradually changed the convergence from oblique to orthogonal. Multiple intraformational unconformities and high sedimentation and subsidence rates in the Dos Bocas Formation documented this change. Recurrent deposition of the diatomaceous Villingota Formation suggested episodic upwelling in the basin enriched by the high siliceous tuffs supply from the coeval Saraguro Arc volcanism in the Western Cordillera. Basin transtension terminated during Late Miocene inception of the Rodeo and Playas synthetic Riedels to the reactivated Pallatanga Suture known as the dextral Chingual-Cosanga-Pallatanga-Puna (CCPP) fault system. However, as this fault continued into the Gulf of Guayaquil, the transtension was transferred to this area. Hitherto, the Progreso Basin underwent a sagging phase characterized by the onlapping of the Subibaja and Progreso formations against the La Cruz Fault High as well as a localized, subtle tectonic inversion due to space problems linked to the synthetic Riedels inception.

Impact of Shrimp Ponds on Mangrove Blue Carbon Stocks in Ecuador

Mangrove forests play an important role in mitigating climate change but are threatened by aquaculture expansion. The inclusion of mangroves in climate change mitigation strategies requires measuring of carbon stocks and the emissions caused by land use change over time. This study provides a synthesis of carbon stocks in mangrove and shrimp ponds in the Gulf of Guayaquil. In this study area, we identified 134,064 ha of mangrove forest and 153,950 ha of shrimp farms. Two mangrove strata were identified according to their height and basal area: medium-statured mangrove (lower height and basal area) and tall mangrove (greater height and basal area). These strata showed statistical differences in aboveground carbon stocks. In both strata, the most abundant mangrove species was Rhizophora mangle. For both strata, trees had a maximum height (&gt;30 m), and their density was greater than 827 ha−1. Total ecosystem level carbon stocks (measured to 1 m soil depth) were 320.9 Mg C ha−1 in medium-statured mangroves and 419.4 Mg C ha−1 in tall mangroves. The differences are attributable to higher basal area, soil organic carbon concentrations and salinity, tidal range, origin of allochthonous material, and herbivory patterns. Mangrove soils represented &gt;80% of the total ecosystem carbon. Ecosystem carbon stocks were lower (81.9 Mg C ha−1) in the shrimp farms, 50% less than in undisturbed mangroves. Our results highlight mangroves as tropical ecosystems with extremely high carbon storage; therefore, they play an important role in mitigating climate change. This research provides a better understanding of how carbon stocks in this gulf are found and can be used for design strategies to protect global natural carbon sinks.

Distribución del Ictioplancton y su interrelación con parámetros bióticos y abióticos en aguas costeras ecuatorianas

The biotic and abiotic conditions of the marine ecosystem affect the spawning grounds of fish and therefore the development and behavior of fish larvae in the Ecuadorian coast. During the cruise demersal fishing T 05/11 / 01D of November 2005, 44 zooplankton samples were collected with a simple conical network of 300 micron mesh. Ichthyoplankton distribution indicated a high density of larvae, 8800larvae / 10m2, in front of Muisne and 24 000 and 15 000 eggs / 10m2, in front of Cabuyal and Gulf of Guayaquil, respectively. The area between Cabo San Lorenzo until Cabuyal was the greatest diversity of fish larvae (4.26 bits) related with concentrations of diatoms and dinoflagellates, in an area characterized by mixingfresh water from the Chone River and oceanic warm waters of the Panama bay. The Gulf of Guayaquil was second in ichthyoplanktonic diversity associated with increased zooplankton, especially copepods and cladocerans (3.7 bits).Temperature, salinity, nutrients, and diatoms were the parameters of highest incidence in the distribution of larvae on the coast of Ecuador (r = 0.6 to 0.88). Interrelationships among phosphates, diatoms, zooplankton, fish larvae and adults fishes of Chloroscombrus orqueta, were observed.

Oceanic primary production trend patterns along coast of Ecuador

ABSTRACT Primary productivity (PP) is a vital oceanographic process generated by photoautotrophic organisms that transform inorganic carbon into organic macronutrients and micronutrients via photosynthesis. While in situ studies have shed light onto the spatial and seasonal variations of chlorophyll a (Chl a) concentration, and thus PP, in specific study sites, there are no comprehensive monitoring programs to assess its long-term variation nor its seasonal patterns in broader areas of coastal Ecuador. The main objective of the present study is to evaluate changes in Chl a concentration along the coast of Ecuador and examine how these changes correspond to changes in Sea Surface Temperature (SST). Eighteen offshore and nearshore sampling sites along the Ecuadorian coast were studied over 15 years, using satellite measurements of MODIS-Aqua and MUR. Results show mean Chl a concentration in coastal Ecuador is rather low (1.5 mg m−3) in comparison with other oceanic regions. Puerto Bolivar, Gulf of Guayaquil and Esmeraldas were characterized by the highest mean Chl a concentration; while Galera San Francisco Marine Reserve, Cojimies and Cabuyal were characterized by the lowest. A positive trend in Chl a concentration was detected at the southernmost (Puerto Bolivar and Gulf of Guayaquil) and northernmost (Esmeraldas) study sites, with a seasonal trend following the observed seasonal SST trend. Chl a is high in areas under the influence of both the Humboldt upwelling system and river discharge. The positive correlation between Chl a and SST is likely a response to increased precipitation during warmer months. These results highlight the importance of improving our understanding of the effects of climate change on coastal PP, and the potential for these effects to influence the health of commercial and threatened marine species. Further research should assess the implications of changes in PP and SST for species of commercial and conservation importance along the coast of Ecuador.

PTERÓPODOS Y HETERÓPODOS DEL GOLFO DE GUAYAQUIL

From the analysis of 17 zooplankton samples, taken in the Gulf of Guayaquil, from 4 cruises corresponding to May 1973, February 1978, March 1982 and November 1983; 5 species of Pteropods and 2 of Heteropods were found, which are: Creseis chierchiae, C. virgula, C. acicula, Limacina trochiformis. L. inflata, Atlanta gaudichaudi and A. lesueuri.A general morphological description of the organism is given, highlighting its most important taxonomic characteristics of the species and are complemented with some ecological preferences of each one of them.a map with the stations of the different cruises and two tables showing the position and presence of the species in the different years are presented.

Stable isotope evidence for the origins of waters in the Guayas estuary and Gulf of Guayaquil

The Guayas estuary in Ecuador is the largest estuary system along the western coast of South America. It is formed by interactions of fresh waters from the Guayas River and numerous smaller rivers, and marine waters flowing through the Gulf of Guayaquil from the Pacific Ocean. To better understand the sources of waters and their distribution in the Guayas estuary, we collected a suite of water samples at the end of consecutive dry (December) and rainy seasons (May) from locations distributed across whole estuary system plus a limited amount of historical information about precipitation. The measured salinities together with oxygen (δ18O) and hydrogen (δ2H) isotopic ratios of these samples were used to characterize the end-member compositions of waters flowing into the Guayas estuary from the ocean and primary riverine sources, and to consider environmental factors that affect end-member compositions. Inverse relationships exist between the isotope ratios of river waters and the mean elevations of the drainage basins of the rivers, which are situated along the western flank of the Andes Mountains; δ18O and δ2H values of river waters were more positive at the end of the dry season than the end of the rainy season. Observed δ18O–salinity and δ18O–δ2H relationships confirm the Babahoyo River, and to a lesser extent, the Daule River (e.g., Salado sub-estuary), are principal sources of fresh water for the entire Guayas estuary. Spatial and temporal variations of the δ18O–salinity relationships of waters within five estuary regions indicate how river influx, tidal circulation, resultant mixing of waters from different sources, and evaporation affect these regions during dry and rainy seasons. TaxonomyEstuarine Circulations, Water Cycle

Spatio-temporal variability of Brachyura larval assemblages in mangroves of the Gulf of Guayaquil’s inner estuary

Mangroves are the dominant coastal vegetation in tropical estuaries and host a large diversity of brachyuran crabs. Crab larvae have adapted to dynamic hydrological conditions in estuaries using several physiological and behavioral strategies. Changes in crab larval assemblages can be monitored in time in order to detect ecological changes occurring within estuaries. For this study, we sampled quarterly crab larval assemblages in two sub-estuaries (Salado and Churute) of the Gulf of Guayaquil (GG) during 2016–2017. The largest community dissimilarities occurred between sub-estuaries, with Salado having higher morphological diversity and larval densities than Churute. Temporal patterns were only evident within each sub-estuary, and in relation to total and individual morpho-species density values. Ocypodidae larvae were dominant across samples; with zoea I of the red mangrove crab (Ucides occidentalis) showing maximal density values during spring tides. Hydrological parameters (i.e., turbidity, conductivity, salinity and temperature) contributed to only 19% of the variability in biota, demonstrating that crab larvae are physiologically adapted to a wide range of water conditions. This study established an ecological baseline for future studies using crab larval assemblages in the assessment of ecological changes occurring in mangrove tidal creeks of the GG. However, longer time-series monitoring data and description of new species and stages of crab larvae are necessary to better assess potential future changes.

Políticas de Conservación de Manglar en el Golfo de Guayaquil

During the last decade, the Ecuadorian government has designed and implemented a set of policies to improve mangrove forests conditions and their ability to provide ecosystem services. The present work aims to identify and explain current policies related to mangrove conservation in the Gulf of Guayaquil, which is a coastal region hosting more than 70% of Ecuador´s mangroves. The main assumption underlying this effort is the notion that mangrove conservation might be critically linked to subjective measures; these measures would better the welfare for populations that live in this ecosystem and depend on it. Based on the evidence of recent studies an institutional economic analysis was conducted; this analysis used the Situation, Structure and Performance framework. Results support the original assumption. Challenges were also identified for the continuity of current policies and new urgent needs for future research.