Uruguayan Coast Research Articles

Una Fauna Local Lujanense (Pleistoceno Superior–Holoceno Inferior) del sur de Uruguay: Santa Regina, Departamento de Colonia

A Lujanian Local Fauna (Upper Pleistocene–Lower Holocene) from southern Uruguay: Santa Regina, Colonia Department. On the southwestern coast of Uruguay, in the Colonia and San José departments, sedimentary rocks that correspond to the Neogene and Quaternary are found. Herein we describe the fossiliferous locality of Santa Regina, located on the east coast of the department of Colonia. The stratigraphic profile shows at the base grayish-green sandy rocks belonging to the Camacho Formation (Upper Miocene). Overlying this unit, there is a tough yellowish-greenish siltstone in net contact, in which several pieces of a Notiomastodon platensis specimen were found. Towards the upper part, a thicker greenish-brownish bed is observed, ranging upwards from conglomerates to siltstones. The lower part of this bed includes disarticulated and fragmentary remains of Lestodonarmatus, Glyptodon reticulatus, Pampatheriidae indet., Toxodon cf. T. platensis, Morenelaphus sp., and Lycalopex gymnocercus, and to the top large portions of carapaces of Glyptodon sp. and Panochthus sp. The aforementioned mastofaunistic assemblage corresponds to the Lujanian Mammal Age or regional Stage (Upper Pleistocene-Greenlandian). The lithostratigraphy allows us to refer the two upper levels to the Dolores Formation, a characteristic unit of the Quaternary of southern Uruguay, and not to the Raigón Formation, as indicated in some previous reports for this locality. The presence of Lestodon armatus, Glyptodon reticulatus, Notiomastodon platensis, Lycalopexgymnocercus, and the probable presence of Toxodon platensis, allow us to infer landscapes of open or semi-open areas, with a predominance of grasslands and shrubs during the genesis of the deposits. Keywords: LatePleistocene–Early Holocene, land mammals, stratigraphy, Uruguay.

Relationship between sea surface temperature anomalies in the Southwestern Atlantic Continental Shelf and atmospheric variability on intraseasonal timescales

The intraseasonal (IS) variability of the sea surface temperature (SST) in the Southwestern Atlantic Continental Shelf (SWACS, 45–33° S—70–50° W), and its relationship with that in the atmosphere, was studied for the austral warm season. SST satellite data (11-km resolution NOAA CoastWatch Program) and data of different atmospheric variables (Reanalysis1 NCEP/NCAR and ERA-Interim) were used. Data were filtered using a 10–90 day filter to isolate the IS variability. A Principal Component analysis was applied then to the filtered SST anomalies (SSTA) and the activity of the leading modes was described through the corresponding temporal series. The first three modes are significant. EOF1 (25.7% of variance) exhibits SSTA of opposite sign to the north/south of 42° S. EOF2 (9.0%) and EOF3 (5.1%) are related with centers of SSTA of opposite sign located off the Uruguayan coast and in the middle shelf. Composites of SSTA and of key atmospheric variables were made considering the days in which the main modes were active. They show that the SSTA described by the three modes are associated with distinctive regional sea level pressure anomalies that, in turn, seem to be related to atmospheric Rossby wave trains extending from the Australia area towards South America. The corresponding atmospheric wave sources vary depending on the mode. These results show, therefore, that the SSTA in the SWACS exhibit significant IS variability that is, in part, locally and remotely influenced by atmospheric anomalies oscillating on similar timescales. These ocean–atmosphere teleconnections could help to improve ocean predictability at those timescales in the future.

Alongshore Classification and Morphometric Analysis of Developed Coastal Belts: An Example from Uruguay, South America

Finkl, C.W. and Makowski, C., 2021. Alongshore classification and morphometric analysis of developed coastal belts: An example from Uruguay, South America. Journal of Coastal Research, 37(5), 906–922. Coconut Creek (Florida), ISSN 0749-0208. Approximately half of the 666-km long Uruguayan coastal belt length is characterized by continuums of developed urban centers that are associated with ports and harbors, residential, recreational, military, shore protection, and/or commercial facilities that occur in association with agricultural pursuits. Modification of the Biophysical Cross-shore Classification System (BCCS) to include such features of anthropogenic change along with naturally occurring coastalscapes permits classification of developed and undeveloped coastal belts based on interpretation of satellite imagery. Characterization of alongshore domains was based on conjoining archetypes into catenary sequences that typify coastal belts both alongshore and cross-shore. Based on interpretation of satellite imagery acquired from Google Earth Pro, Uruguayan coastal belts were divided into six separate departments (Rocha, Maldonado, Canelones, Montevideo, San Jose, Colonia) and characterized by the alongshore widths of archetypes that extended from offshore to several kilometers inland. Compilation of coastal belt catenas showed that promontories and headlands, which comprise resistant igneous and metamorphic rocks, function as anchor points along the shore and are widely interspersed by sedimentary (littoral) domains that contain mainland and barrier beaches that are backed by beach-dune couplets, wetlands, lagoonal flats, and developed upland archetypes. Typical alongshore super domains, which were concised from cross-shore archetypical consequences, include the following predominant types of sequences: Barrier-Beach-Dune, Beach-Dune-Lagoon, Beach-Dune-Wetland, Beach-Dune-Upland, Beach-Cliff-Upland, Beach-Wetland-Flat-Lagoon, and Rock-Cliff-Upland. Certain archetypes, such as rock and developed, were prevalent throughout the coastal belt codifications with their representative symbolizations appearing in the variable code sequences of domains and super domains. Morphometric analysis tables were also compiled with alongshore lengths of domains and super domains, as well as percentages of individual department and Uruguayan coastal belts. This examination of the Uruguayan coast showed for the first time that the BCCS can characterize anthropogenically developed units with naturally occurring biophysical features. Interpreted cross-shore transects, alongshore domains, and all-encompassing super domains allow for a comprehensive classification and morphometric analysis of offshore, inshore, and onshore components along Uruguay's natural and developed coastal belts.

Comprehensive wave climate analysis of the Uruguayan coast

Comprehensive wave climate analysis of the Uruguayan coast

Life history and demographic evolution: Comparative population genetics in sandy beach crustaceans

Studies comparing the distribution of genetic diversity may help revealing connectivity patterns in marine populations, as they allow identifying factors behind genetic population structure and elucidating the relationship between the habitat and resident species. The macrofauna of sandy beaches constitutes an interesting study subject, since it includes species with contrasting life histories and dispersal strategies, with potential implications on connectivity. In this work, COI sequences of three peracaridan species with direct development (the talitrid amphipod Atlantorchestoidea brasiliensis and the cirolanid isopods Excirolana braziliensis and Excirolana armata), and one decapod with planktonic larvae (the hippid mole crab Emerita brasiliensis), were compared in order to evaluate the influence of dispersal and historical processes in the distribution of their genetic diversity in the Uruguayan coast, covering both marine and estuarine beaches located along the Rio de la Plata. The hypothesis that species with similar life histories show similar geographic patterns of genetic diversity did not completely explain the genetic variability observed in these species. The intertidal Emerita brasiliensis and the supralittoral Excirolana braziliensis presented high genetic homogeneity, with evidence of population expansion originated at similar times. This shared pattern of genetic variability could be explained by their tropical origin and recent colonization of the Uruguayan coast. The intertidal Excirolana armata and the supralittoral Atlantorchestoidea brasiliensis presented high variability, although differences between them could be associated with the beach zone they inhabit. The role of salinity affecting connectivity patterns was important in Excirolana armata and Atlantorchestoidea brasiliensis, which showed genetic differentiation between estuarine and oceanic beaches. Results reinforce the concept that the distribution of genetic variability not always reflects contemporary population structure and that it is important to consider the evolutionary history of the species when studying connectivity in sandy beach populations. Finally, the accelerated rates of warming in the region could favor a demographic explosion of Emerita brasiliensis and Excirolana braziliensis, species with tropical affinities, which is coherent with the documented demographic history of both species.

Phoxocephalidae G.O. Sars, 1891 (Crustacea: Amphipoda) collected by the R/V Almirante Saldanha off the coast of Uruguay and Argentina

Amphipods of the family Phoxocephalidae G.O. Sars, 1891 collected by the R/V Almirante Saldanha off the coast of Uruguay and Argentina in 1972 were examined. New records from the northern Argentine Sea and Uruguayan Sea include two species of the subfamily Harpiniinae Barnard and Drummond, 1978: Pseudharpinia jonesyi Andrade and Senna, 2020a, previously known from southeast/southern Brazil; and Pseudharpinia tupinamba Senna and Souza-Filho, 2011, recorded hitherto only from southeastern Brazil. Six species of the subfamily Phoxocephalinae G.O. Sars, 1891 were also recorded: Fuegiphoxus abjectus Barnard and Barnard, 1980, Fuegiphoxus fuegiensis (Schellenberg, 1931), Metharpinia dentiurosoma Alonso de Pina, 2003b, Metharpinia grandirama Alonso de Pina, 2003b, Metharpinia protuberantis Alonso de Pina, 2001, and Parafoxiphalus longicarpus Alonso de Pina, 2001. Redescriptions and discussion on distribution and morphological variations are presented.

First record of the non-native medusa Blackfordia virginica (Hydrozoa, Leptomedusae) on the coast of Uruguay, Southwestern Atlantic

First record of the non-native medusa Blackfordia virginica (Hydrozoa, Leptomedusae) on the coast of Uruguay, Southwestern Atlantic

Echolocation inter-click interval variation among specific behaviours in free-ranging bottlenose dolphins from the coast of Uruguay

To assess whether behaviour can be inferred from echolocation trains (inter-click intervals) this study examines acoustic recordings of free-ranging bottlenose dolphins using Passive Acoustic Monitoring (PAM). Inter-click intervals from 17 groups of free-ranging bottlenose dolphins were monitored over a 36 day period in an area within the Cerro Verde (Marine Protected Area), Uruguay. Simultaneous visual observations were made from shore nearby. Results show that inter-click intervals in the echolocation trains had significant differences for three specific behaviours: feeding, socialising and travelling. The natural environment was quiet, with no disturbances in the immediate vicinity from boats, drones or other man-made noises.

A note on minke whales (Cetacea: Balaenopteridae) in Uruguay: strandings review

The minke whale is the smallest of the living rorquals and is widely distributed in the tropical, temperate and polar waters of both hemispheres. In the western Southwest Atlantic Ocean there are two currently recognised species, the dwarf form of the common minke whale, Balaenoptera acutorostrata unnamed subsp. and the Antarctic minke whale B. bonaerensis. All stranding records and collected specimens of minke whale on the coast of Uruguay were reviewed and analysed. Between 1962 and 2018, 33 records were gathered in a non-systematic way, 22 specimens of B. acutorostrata and 11 of B. bonaerensis. It was found that most animals were discovered alive or recently dead and assigned as neonates/young calves. This supports the hypothesis that Uruguayan coasts are part of an important region for reproduction and breeding for the species.

Assessment of larval connectivity in a sandy beach mole crab through a coupled bio-oceanographic model

The biophysical mechanisms influencing larval distribution and their impacts on the metapopulation dynamics of sandy beaches, particularly the connectivity patterns associated with larval dispersal, are poorly understood. Here, we identify larval connectivity patterns of the mole crab Emerita brasiliensis in the coast of Uruguay. A biophysical individual based model (IBM) of larval transport was coupled to a regional high-resolution physical model to estimate the monthly and interannual variation of larval connectivity, as well as the impact of the length of the reproductive period on it. Larval connectivity showed marked interannual variations, which were mainly related to interannual changes in seasonal winds and associated ocean circulation patterns, particularly during La Niña years. The southernmost area where E. brasiliensis occurs only received larvae from the nearest release area in November and January spawning events during a strong La Niña year, characterized by intense northeasterly winds. The Uruguayan coast constitutes the leading (poleward) edge of the distribution of E. brasiliensis, where climate change effects are projected to intensify. Extrapolation of these results to a climate change scenario with stronger La Niña events, suggest that larval transport to southernmost beaches will become more probable.

Acceso a tierra de ganaderos familiares: análisis de la acción colectiva en el litoral norte uruguayo

Las transformaciones ocurridas en los últimos años en Uruguay han desafiado al Estado para encontrar herramientas adecuadas para la aplicación de políticas y apoyos diferenciados a productores familiares. Una estrategia ha sido el fomento de procesos asociativos, impulsados con programas ministeriales desde la Dirección General de Desarrollo Rural (dgdr) y el Instituto Nacional de Colonización (INC), para el acceso colectivo a la tierra. Con el fin de comprender los procesos de acción colectiva de los ganaderos familiares del litoral norte del país, se identificaron y analizaron las experiencias de acceso colectivo a tierras del INC en Artigas, Salto, Paysandú y Río Negro. La investigación incluyó la revisión de fuentes secundarias y un relevamiento de campo a través de entrevistas a informantes calificados y referentes de cada una de las experiencias. Se identificaron 38 experiencias con acceso a la tierra mediante dos niveles de asociatividad: 27 casos en donde los beneficiarios gestionan una fracción en común, que han sido generados de forma exógena y se encuentran en procesos de consolidación organizativa; y 11 casos que disponen de bienes para uso común, que tienen varios años de trayectoria, siendo organizaciones de primer grado con estructuras conformadas. Entre ambos tipos se observan diferencias contrastantes en los modos de coordinación y construcción de la acción colectiva, debido a las necesidades e intereses comunes para obtener beneficios individuales y colectivos.

Changes in the Littoral Drift System of the Uruguayan Coast during the Holocene and its Influence in the Continuing Erosion in Southern Brazil

Dillenburg, S.R.; Barboza, E.G.; Rosa, M.L.C.C.; Caron, F., and Bitencourt, V.B., 2020. Changes in the littoral drift of the Uruguayan coast during the Holocene and its influence in the continuing erosion in southern Brazil. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 453–457. Coconut Creek (Florida), ISSN 0749-0208.In northern Uruguay and southern Brazil, a littoral drift system dominates from southwest to northeast. This littoral drift is a consequence of higher wave-energy, generated in southern latitudes and that has been operating on a long-term scale, playing an important role not only in the evolution of coastal barriers of this region during the Holocene but also in coastal erosion that presently occurs in some parts of this coast. From La Coronilla to Cabo Santa Marta, which is a coastal sector 750 km - along the coast is gently undulating, showing gentle projections located to the south of gentle reentrances, that are dominated by transgressive/stationary and regressive barriers, respectively. In general, the regressive barriers have been developed by sediments brought into the reentrances by long-shore currents. The main source of these sediments had been the transgressive/stationary barriers that occur along the coastal projections. This differentiation of barrier behavior started at around 6-5 ka, at the end of the Postglacial Marine Transgression (PMT), when all rivers were drowned, finishing the delivery of new coarse sediments to the coast. Also, at this time the large rock promontories of the Uruguayan coast were formed and started to retain sediments of the littoral drift system, triggering a long-term coastal erosion in the southernmost coastal projection. Regarding erosion that is occurring in this stretch of coast the important issue to be considered in future coastal planning is that erosion will continue to operate in the long-term but will also be (and certainly has been already) amplified by sea-level rise in the next centuries as projected by the Intergovernmental Panel on Climate Change (IPCC).

Assessing the origin of a massive cyanobacterial bloom in the Río de la Plata (2019): Towards an early warning system

The Río de la Plata estuary drains the second largest river basin of South America. The occurrence of frequent cyanobacterial blooms of the Microcystis and Dolichospermum complex in the Uruguayan coast are associated with high flows of Uruguay River due to rainy years. In summer 2019, a massive cyanobacterial bloom reached up to the Uruguayan Atlantic coast. This study seeks to unveil the origin and the environmental conditions that favored the occurrence of the last cyanobacterial bloom in the Río de la Plata, and to contribute with the development of an early warning system of cyanobacterial scum on Montevideo beaches. A complementary approach was applied with Sentinel-2 imagery, environmental data of monitoring programs of Salto Grande Reservoir and Montevideo beaches, hydro-meteorological information, and hydroelectric dam operation. Images were analyzed with the Normalized Difference Chlorophyll Index (NDCI), which allowed evaluating several water bodies within the same ranges. Positive anomalous rainfall increased river flows, particularly that of Uruguay and Negro rivers, which caused the opening of the dam spillways. NDCI maps showed that areas with high values (NDCI>0.06) in Salto Grande reservoir kept a similar surface area before and after the prolonged overflow period (8.7–7.8 km2, before and after). In the Río Negro reservoirs, however, NDCI>0.06 coverage remarkably changed (62.5 km2, Palmar reservoir), with a subsequent 56-fold reduction in the post-discharge of surface water. Twenty days after opening the spillways, Montevideo beaches were closed to swimming and the NDCI>0.06 surface reached 51.7 km2 in the Río de la Plata coast. The dynamics of NDCI areas, the downstream bloom discharge, and the predicted Río de la Plata residual currents, suggest that the cyanobacterial bloom originated in the Negro River (Palmar reservoir). This bloom event was one of the worst that occurred in the Río de la Plata in last 20 years, circulated along the Uruguayan sub-corridor to the Atlantic coast along 690 km from its origin, and lasted three months on Montevideo coast. This is the first study that addresses the impact of cyanobacterial blooms from the Negro River reservoirs on the Río de la Plata estuary. Therefore, the Negro River basin is where the main efforts should be directed to mitigate massive cyanobacterial blooms.

Complete genome sequence and analysis of a novel lymphocystivirus detected in whitemouth croaker (Micropogonias furnieri): lymphocystis disease virus 4

A novel lymphocystivirus causing typical signs of lymphocystis virus disease in whitemouth croaker (Micropogonias furnieri) on the coast of Uruguay was detected and described recently. Based on genetic analysis of some partially sequenced core genes, the virus seemed to differ from previously described members of the genus Lymphocystivirus. In this study, using next-generation sequencing, the whole genome of this virus was sequenced and analysed. The complete genome was found to be 211,086 bp in size, containing 148 predicted protein-coding regions, including the 26 core genes that seem to have a homologue in every iridovirus genome sequenced to date. Considering the current species demarcation criteria for the family Iridoviridae (genome organization, G+C content, amino acid sequence similarity, and phylogenetic relatedness of the core genes), the establishment of a novel species (“Lymphocystis disease virus 4”) in the genus Lymphocystivirus is suggested.

Diagnosis of lymphocystis disease in a novel host, the whitemouth croaker Micropogonias furnieri, associated with a putatively novel Lymphocystivirus species (LCDV-WC).

In 2015, an episode of lymphocystis disease (LCD) was detected in wild and cultured populations of whitemouth croaker Micropogonias furnieri off the coast of Uruguay. Fish of both origins were collected for histopathological and molecular investigations. Macroscopically, multinodular tumorlike masses were observed in the skin. Histological examination of these masses revealed enlarged cells with a hyaline capsule and basophilic inclusion bodies in the cytoplasm. The inclusion bodies were further examined by electron microscopy and showed icosahedral virions with a median diameter of 182 nm. Routine molecular investigations targeting the DNA polymerase and major capsid protein genes showed the presence of the DNA of an unknown lymphocystis disease virus (LCDV) in all specimens showing external signs of LCD. Subsequently, 4 other core genes were amplified and sequenced from the viral genome. Phylogenetic tree reconstruction based on the concatenated sequence of 6 core genes indicated that the virus undoubtedly belongs to the genus Lymphocystivirus. However, the core gene sequences of the whitemouth croaker LCDV differ markedly from those of the 3 known LCDVs, putatively representing a fourth LCDV species.

Spatiotemporal characterization of summer coastal upwelling events in Uruguay, South America

This study analyses the spatial and temporal characteristics of coastal upwelling events in the Uruguayan coast using satellite data and the output of an atmospheric reanalysis. We focus on the most intense upwelling events which occurred on synoptic time scales during the summer season. We were able to distinguish two upwelling configurations associated to different wind conditions due to the coast orientation: an upwelling mainly located in the Río de la Plata estuary which responds to easterly winds, and an oceanic upwelling located in the eastern (oceanic) coast of Uruguay associated to northeasterly winds. Moreover, the frequency of occurrence of upwelling events on interannual time scales was found to depend on the phase of El Niño Southern Oscillation.

Comparing cnidocyst sizes among populations of Bunodosoma (Cnidaria: Actiniaria: Actiniidae) from the South Atlantic west coast

The simplicity of a sea anemone polyp hinders the differences between species and populations, as very few external and internal morphological characters vary enough to distinguish closely related groups. Variations in size of different cnidocyst types could be an important way to characterize populations of sea anemones. We aim to identify which cnidocyst types could be useful to distinguish the variation between sea anemone populations, tested for two species of genus Bunodosoma from the South Atlantic west coast: Bunodosoma caissarum from the Brazilian coast, and Bunodosoma cangicum from the Brazilian and Uruguayan coasts. We measured cnidocysts in several parts of the sea anemones: acrorhagi, external and internal tentacles, column, actinopharynx and filaments, comprising a total of 35,593 measured capsules. Comparisons between cnidocysts lengths from each tissue type were performed by Generalized Linear Models. In B. caissarum, basitrichs from external and internal tentacles were found to be useful for detecting differences between populations and may indicate a latitudinal gradient. For B. cangicum, these aspects should be further analyzed in basitrichs from external tentacles, holotrichs from acrorhagi and microbasic b-mastigophores from the filaments. The basitrich from tentacles were found to be the most informative cnidae type in both species for population studies in a latitudinal sense.

On the occurrence and ecology of Glaucus atlanticus Forster, 1777 (Mollusca: Nudibranchia) along the Southwestern Atlantic coast.

Unlike the majority of the nudibranchs, Glaucidae lives adrift at the sea surface within Tropical and Subtropical ocean basins, feeding on cnidarians or using them to attach their egg strings as a reproductive strategy. The latitudinal distribution of Glaucus atlanticus throughout the Brazilian Province is influenced by the Brazil current and, in its austral limit, by seasonal shifts in the Subtropical Convergence Zone (especially under the influence of ENSO El Niño events). Once over the shelf, seasonal wind patterns and meteorological events can force a passive displacement of the species towards the shore. Such onshore displacements may result on strandings of Glaucus spp. and other pleustonic species of the "blue plankton" community, like already reported worldwide and recently at the Southern Brazilian / Uruguayan coasts. Although fascinating, Glaucus spp. should be considered harmful to humans and people should thus avoid direct contact; if this accidentally occurs, short-term treatments can be implemented besides looking for medical attention. The current geographical distribution of Glaucus atlanticus over the Brazilian coast reveals some inaccuracy and gaps; the present study not only revises the ecology of this species but also evidences the occurrence of summer strandings and its austral distribution into subtropical shores.

A historical perspective of niche differentiation between two top predators in the Uruguayan coastal area

Context As top predators, marine mammals play a key role consuming in different trophic levels and the trophic niche characterization may help to understand how species utilize and share resources . On the coast of the Río de la Plata and the South-west Atlantic, the South American sea lion (Otaria flavescens) and the franciscana dolphin (Pontoporia blainvillei) are two important predators. Aims The present study investigated potential trophic overlap of both species by measuring stable carbon (δ13C) and nitrogen (δ15N) isotopes over two periods: historical (1959–79) and recent (2002–15) on the Uruguayan coast. Methods Bone samples of P. blainvillei and O. flavescens were used to determine the isotopic niche using the Stable Isotope Bayesian Ellipses in R (SIBER) analysis. Key results The isotopic niche did not overlap between species in any period. δ15N was higher in O. flavescens in both periods (20.29‰±0.73 in the historical and 19.95‰±1.0 in the recent period), indicating that it feeds at a higher trophic level than P. blainvillei. The δ13C was also significantly higher in O. flavescens than in P. blainvillei during the two periods (O. flavescens: –11.43±0.6‰ historic, –12.72±0.4‰ recent, and P. blainvillei: –12.69±1.1‰ historic, –13.84±1.3‰ recent). The isotopic niche areas of P. blainvillei in recent and historic periods confirmed they forage in 2 distinct environments, marine and estuarine, with low isotopic overlap. This overlap was higher in the recent period. Conclusions and Implications O. flavescens and both P. blainvillei groups were segregated in both periods, with a higher overlap in the recent. These species appear to reduce competition by using different resources in the same coastal habitat. O. flavescens preferentially feeds on benthic fish and showed wider trophic amplitude in both periods, whereas P. blainvillei has a more coastal–pelagic diet and included a greater variability of resources in its diet. The differences between species trophic niches can still be detected after both marine mammals species abundance has declined and after the development of fisheries.

Revisitando a Equação do Desenvolvimento de Sutcliffe

This study presents a review of the interpretation of the terms of the Sutcliffe’s equation and its contribution to the prediction of low and high pressure systems. For this reason, it was performed a case study of an extratropical cyclone that was associated with a cold wave in Brazil. The cyclone occurred on July 15, 2017 between the coast of Uruguay and Argentina. An intense horizontal gradient of surface air temperature and the horizontal advection of absolute vorticity at 500 hPa contributed to the formation of the low over the surface. The horizontal advection of absolute vorticity, according to the Sutcliffe’s equation, was important to the system manutention. On the other hand, this advection associated with the horizontal advection of air temperature were important to guide the displacement of the cyclone on the surface.