This paper is carried out in the coastal area of Bahía Creek and its surroundings, highlighting 15 km to the west Caleta de los Loros. This area is located on the coast of Río Negro province, which is part of the San Matías gulf. Bahía Creek is located precisely at 41º 05´S, 63º 56´ W. It belongs to the department of Adolfo Alsina and it is located 70 km SW of Viedma city, capital of the province and 70 km E of San Antonio Oeste port (Fig. 1). The main objective of this work is a morphological classification of the dunes present in the dunefield of Bahía Creek, based on the proposed classifications by McKee (1979), Lancaster (1995), Hesp (2011) and Sanjaume and Gracia (2011). For this it is necessary to observe satellite images and aerial and field photographs, together with the study of wind data. With this information it is also possible to know the factors that can condition the location of the dunes, their migration, their mobility index according to Lancaster (1988) and the sand drift potential (DP), the resulting drift direction (RDD), the resulting drift potential (RDP) and the directional variability of the wind through the RDP/DP relationship through the methodology proposed by Fryberger (1979). The used material consisted of aerial photographs from 1986 from the Servicio Geológico Minero Argentino, scale 1:80.000; the digital elevation model (DEM) of the ALOS satellite and Landsat 8 images from 2017, the latter of 30 m of spatial resolution. The images available in Google Earth, Earth Engine and Bing Maps were also used. The wind data used correspond to the records of the Servicio Meteorológico Nacional weather stations located in the towns of Viedma and San Antonio Oeste (SAO). Within these winds, those capable of mobilizing the material available in the study area (effective wind), of an average grain size of 0.25 mm (Toffani, 2018), are those that reach speeds equal to or greater than 6.7 m/s. This value was calculated using the equations proposed by Bagnold (1954). The effective wind was recorded in 34% of the total measurements within Viedma and SAO stations. In Viedma (Fig. 2) the main effective wind directions are NW (13.9%), and SW (10.1%), while in SAO (Fig. 2) the NW direction (18.8%) also predominates, followed by WNW (10.4%). These values suggest that the net displacement of the dunes occurs from NW/SW to SE/NE. Subsequently, applying the mobility index, it was obtained that the dunes, on average, correspond to active except in the interdune, with a value of 124. The annual value of DP is 1090, the RDP 392 and the annual RDD direction is 76 o, indicating a displacement of the sediments towards the ENE (Fig. 3). The directional variability of the wind regime, characterized by the RDP/DP ratio, shows the value of 0.36. This means that Bahía Creek is located within a high energy environment, with a wind regime between complex and bimodal. The annual rate of migration for the dunes studied, which are located within fields of dunes 2, 5 and 7, between 1986 and 2017 was 6.02 ± 0.3 m/ year (Fig. 4), towards NE - SE. The dunefield is transgressive and is characterized by a gentle relief that goes from 0 to 60 - 90 meters above sea level from the beach towards N and E. The active dunes rest on a field of stabilized dunes and this in turn is located on an old dissected alluvial plain. The dunes can reach a relative height of 16 m and are composed of medium to fine sands, generally very well sorted, with the exception of some well sorted. Within the classification itself (Fig. 5), the dune fields 1 (Fig. 6a), 3 (Fig. 6c), 5 (Fig. 8a) and 6 (Fig. 8b) are characterized by the predominance of crescentic dunes. Field 2 has mainly linear and reversible crest dunes (Fig. 6b). Field 4 is characterized by star dunes (Fig. 6d). Field 7 is composed of symmetric, asymmetric and lateral coalescence parabolic dunes (Fig. 8c - d). While field 8 is represented by embryonic dunes (Fig. 9a - b), field 9 by climbing dunes (Fig. 9c) and field 10 by hanging dunes (Fig. 9d). Echo dunes (Fig. 10a), falling dunes from the cliff (Fig. 10b) and enveloping dunes (Fig. 10c) were also recorded in the field. In addition, within the different sectors mentioned, the formation of nebkas occurs (Fig. 10d). The wavelengths vary between 30 m and 350 m, the lowest values are after the creek, that is where the dunefield begins, and in the most distal part, east of the dune field 6. This sector is also the one that records the highest values. This distribution is coherent, since the first accumulations are of smaller size and close to each other, in general they are growing and having greater wavelength, until reaching a 57 maximum. Where transport begins to decrease they acquire smaller sizes. The greatest lengths, up to 1 km, due to the development of its arms, are reached by the parabolic dunes. The smallest, 10 m, are those presented by the barchans. Regarding the width, the latter are also those that have smaller sizes, 10 m, while the largest correspond to coalescent parabolic dunes and transverse or barchanoid ridges, which are between 500 m and 600 m. It is also observed that the larger the size of the dunes in terms of length and width, the wavelength is greater. Variations in wind and sand transport rate at different time and space scales appear to be the most important control of their size and spacing. These factors, together with vegetation, humidity, input of sand, topography and constructions or anthropogenic processes, influence the distribution of the active dunes and at the same time in the location of the different types of dunes. The most relevant for the population of Bahía Creek are the constructions that act as an obstacle to the transport of sediments by the wind. They difficult the passage of winds coming mainly from the S, which contribute to the movement of the dunes towards the NE, leaving them more relative weight to the winds of the W and the NW. The latter cause the fastest advance of the dunes towards the E and SE, that is, where the buildings are. Bahía Creek dunefield, due the types of dunes and their distribution, shows great complexity, mainly due to the variations in the effective winds, and that over time generate compound and complex dunes. In Argentina, coastal dunefields with similar characteristics are develop, for example, around San Antonio Oeste and Este, in Río Negro province (Carbone et al., 2007); in the south and east of Buenos Aires province (Barrera Medanosa Austral y Oriental) (Bértola and Cortizo, 2005; Cortizo and Isla, 2007, 2012; Bértola et al., 2009); and in Península Valdés, Chubut province (del Valle et al., 2008). However, Bahía Creek has exceptional characteristics due to the possibility that offers to appreciate a natural environment with different geomorphological features with virtually no anthropic disturbance. Among these are beaches, cliffs and mainly the vast dunefield, which enters the continent with a concentration and striking diversity of dunes. It is a site that is not yet highly exploited by urbanization and tourism and allows visitors to access an almost virgin and pristine environment, which includes Caleta de los Loros, Pozo Salado and Punta Mejillón Protected Area. This last one is conformed to a greater extent by a tidal plain, which added to the rest of the coastal environment and to the dunefield, makes the area have a great diversity of species. In addition, the importance of the study of the dunefield lies in its proximity to the seaside town of Bahía Creek, which acquires more visitors over the years and is affected by the migration of the dunes, which sometimes have already covered houses or arrived at a distance very close to them and continue to move in that direction.

El presente trabajo se llevó a cabo en el área de Bahía Creek, en la costa sur de la provincia de Río Negro, NE de Patagonia, Argentina. El mismo consta de una clasificación morfológica de las dunas presentes en el campo eólico de Bahía Creek, junto con un estudio del índice de movilidad y el potencial anual de deriva de arena (DP), sumado a la dirección de deriva resultante (RDD) y al potencial de deriva resultante (RDP); además de la tasa de avance de las dunas entre los años 1986 y 2017 y características granulométricas de las arenas que las componen. Estas tareas fueron posibles gracias al uso de imágenes satelitales, fotografías aéreas y de campo, muestreo in situ, modelos de elevación digital y datos de viento recolectados en estaciones cercanas al área de estudio. Las dunas estudiadas se agruparon en diez sectores con características comunes, definidos por las morfologías dominantes. Dentro de estos destacan los referidos a dunas semilunares (barjanes y cordones barjanoides y transversales), lineales, estrella, parabólicas, embrionarias, remontantes y colgadas, junto con dunas oblicuas, reversas, nebkas y, a escala de campo, dunas eco, descendentes y envolventes. A su vez, dentro de cada sector hay dunas compuestas y/o complejas, pudiendo haber más de un tipo de duna. Teniendo en cuenta el índice de movilidad, las dunas resultan en promedio activas a excepción de la interduna, mientras que el potencial de deriva de arena calculado fue de 1090, con una dirección de deriva resultante de 76º y un RDD de 391. Asimismo la tasa de migración media entre los años estudiados (1986 - 2017) fue de 6,02 ± 0,3 m/año. Estos estudios, además de brindar una clasificación del campo de dunas de Bahía Creek, escasa hasta la actualidad, permiten tener un conocimiento sobre por qué las dunas en general se ubican en el área de estudio y cómo se produce la división de las mismas dentro del campo eólico. Esto último se debe a factores tales como la vegetación, la humedad, el aporte de arena, los vientos, la topografía y construcciones o procesos antropogénicos. Además se realizaron comparaciones con campos de dunas con similares características ubicados también en la costa Argentina.

RESUMO O objetivo deste estudo foi avaliar índices de crescimento do híbrido de Eucalyptus urograndis sob aplicação dos herbicidas triclopyr e fluroxipyr+triclopyr. Utilizou-se delineamento em blocos casualizados com quatro repetições em esquema fatorial (3x2x5), correspondendo aos herbicidas (triclopyr e fluroxipyr+triclopyr), ambos em duas doses (0,75 e 1,5% da concentração de 480 g.e.a L-1 para triclopyr e 80+240 g.e.a L-1 para fluroxipyr+triclopyr) mais uma testemunha (plantas que não receberam aplicação dos herbicidas) e cinco datas de avaliação aos 15, 30, 45, 60 e 75 dias após aplicação (DAA). Aos 45 dias após o transplante das mudas, foram realizadas aplicações com pulverizador costal pressurizado a gás carbônico, equipado com pontas bico (XR 110.02) com volume de calda de 200 L ha-1 e pressão constante de 35 kgf/cm2. Foram avaliados: área foliar (AF), área foliar específica (AFE), razão de área foliar (RAF), razão de peso de folha (RPF), taxa de crescimento absoluto (TCA), taxa de crescimento relativo (TCR) e taxa assimilatória líquida (TAL). A deriva dos herbicidas triclopyr e fluroxipyr+triclopyr no híbrido E. urograndis prejudica o desenvolvimento das plantas no início do estabelecimento. Aos 75 dias após a simulação da deriva dos herbicidas as plantas apresentam características de recuperação dos sintomas de intoxicação. É necessário a realização de estudos superiores a 75 DAA para comprovar a recuperação total dos sintomas de intoxicação de plantas do híbrido de E. urograndis resultante da deriva dos herbicidas em estudo.

ABSTRACT The aim of this study was to evaluate growth rates of E. urograndis under application of triclopyr and fluroxipyr+triclopyr herbicides. Was used a randomized block design with four replications in a factorial design (3x2x5), corresponding to herbicides (triclopyr and fluroxipyr+triclopyr), both with two doses (0.75 and 1.5% concentrations of 480 g and L-1 for triclopyr and 80+240 g and L-1 for fluroxipyr+triclopyr), plus one control (plants that did not receive herbicide application) and five evaluation dates at 15, 30, 45, 60 and 75 days after application (DAA). At 45 days after seedlings transplant, applications were performed with pressurized carbon dioxide backpack sprayer, equipped with beak tip (XR 110.02) with spray volume of 200 L ha-1 and constant pressure of 35 kgf/cm2. Were evaluated: leaf area (LA), specific leaf area (SLA), leaf area ratio (LAR), leaf weight ratio (LWR), absolute growth ratio (AGR), relative growth ratio (RGR) and net assimilatory ratio (NAR). The drift of triclopyr and fluroxipyr + triclopyr herbicide in the hybrid E. urograndis affect plant development in the beginning of the establishment. At 75 days after simulation drift of herbicides the plants showed characteristics of the symptoms of intoxication. It’s necessary to perform studies after 75 DAA to verify the complete recovery of the intoxication symptoms of E. urograndis hybrid plants resulting from the herbicide drift in the present study.

Resumo Objetivo: Avaliou-se o efeito dos fatores ambientais sobre a estrutura da comunidade de ostrácodes perifíticos ao longo do sistema rio-planície de inundação do alto rio Paraná. Foi predito que quanto maior a distância a jusante da barragem de Porto Primavera, maior a diversidade e densidade de ostrácodes. Métodos Ostrácodes perifíticos (associados aos sistemas radiculares da macrófita flutuante Eichhornia spp) foram amostrados durante novembro de 2013 a maio de 2015. Três amostras foram coletadas em cada ponto de amostragem (canal principal do rio Paraná, tributários e lagoas). Plantas de Eichhornia foram removidas da água manualmente e colocadas em balde plástico. As raízes foram lavadas para a remoção dos ostrácodes, e as amostras foram filtradas através de uma rede de mão de 160 µm de abertura de malha. Resultados O levantamento faunístico registrou 44 espécies de ostrácodes e os estimadores de riqueza indicaram que o esforço amostral pareceu ser adequado para revelar a diversidade de ostrácodes nesta área de estudo. A maior riqueza e densidade foram observadas no trecho a jusante da barragem no canal principal do rio Paraná e nas lagoas. A diversidade beta não foi significativamente diferente ao longo do gradiente longitudinal a jusante e a maior similaridade na composição de espécies de ostrácodes foi observada nas lagoas localizadas no trecho a jusante da barragem. Conclusões Um aumento na riqueza e densidade de ostrácodes foram registrados nas seções do rio Paraná, a jusante da barragem, evidenciando a importância dos tributários não represados sobre alguns atributos da comunidade de ostrácodes. A similaridade da diversidade beta entre os pontos de amostragem pode ser devido à permanente conectividade hidrológica entre estes ambientes, favorecendo a troca de organismos principalmente através da deriva de macrófitas flutuantes livres, e devido a dispersão passiva dos ovos de ostrácodes resistentes a seca. Os fatores abióticos locais tiveram efeitos significativos sobre a abundância e distribuição de algumas espécies de ostrácodes.

Abstract Aim: We assessed the effect of environmental factors on the structure of periphytic ostracods communities along the river-floodplain system of the Upper Paraná River. We predict that the higher distance from Porto Primavera dam downstream would lead to higher diversity and density of the ostracods. Methods Periphytic ostracods (associated with root systems of the floating Eichhornia spp) were sampled during November 2013 to May 2015. Three samples were collected at each sampling site (channel of the Paraná River, tributaries and lakes). Eichhornia plants were removed from the water by hand and the plants were placed in a plastic bucket. Roots were washed for the removal of ostracods, and samples were filtered through a hand net with 160 µm mesh size. Results The faunistic survey recorded 44 ostracods species and richness estimators indicated that sampling effort appears to be suitable to reveal the diversity of ostracods in this studied area. The highest richness and density were observed in the stretch downstream of the dam in the main channel of Paraná River and in the lakes. Beta diversity was not significantly different along the longitudinal gradient downstream and higher similarity of ostracods species composition was observed in the lakes located in the stretch downstream of the dam. Conclusions An increase in the richness and density of ostracods were recorded in the sections downstream of the Paraná River, evidencing the importance of undammed tributaries on the ostracods community. The similarity of beta diversity amongst sampling sites may be owing to permanent hydrological connectivity amongst these environments, favouring the exchange of organisms mainly through the drift of free-floating macrophytes, and owing to the passive dispersal of drought resistant eggs of ostracods. Local abiotic factors had significant effects on abundance and distribution of some ostracod species.

Abstract: For several years now, national governments and international institutions have generated a set of strategies with the aim of reducing environmental problems by creating nature reserves. However, it is worth mentioning that under the conservation scenario, non-consensual actions do not resolve the environmental degradation due to the weakening of the social fabric necessary to start a process of sustainable community development, and, as a result, conservation becomes illegitimate to the local population, which hardens positions and makes it difficult to search for joint solutions. The latter is what has been happening recently with the fishermen of the Port of San Felipe, Baja California, who on a couple of occasions have closed the highway between the city of Mexicali and the port, and has gone so far to close the international border between Mexicali and Calexico. This social unrest that threatens to escalate further is the result of the refusal of the San Felipe fishermen (and now the Gulf of Santa Clara in Sonora) to modify their fishing gear according to the new official standard (NOM-002-SAG / PESC-2013).

Resumen: Desde hace varios años, los gobiernos nacionales y las instituciones internacionales han generado un conjunto de estrategias con el objetivo de disminuir los problemas ambientales, mediante la creación de reservas naturales. A pesar de ello, las acciones no consensuadas sobre la conservación no resuelven el deterioro ambiental, debido a que se debilita el tejido social necesario para impulsar un proceso de desarrollo comunitario sustentable; la conservación se trasforma en una actividad o interés ilegítimo para la población local, lo que endurece las posturas y dificulta la búsqueda conjunta de soluciones. Esto es lo que ha sucedido recientemente con los pescadores del puerto de San Felipe, Baja California, quienes en un par de ocasiones han cerrado la vía de comunicación terrestre entre Mexicali y el puerto, y se ha llegado al extremo de cerrar la garita internacional Mexicali-Calexico. Este malestar social, que amenaza con un mayor escalamiento, es el resultado de la negativa de los pescadores de San Felipe (y ahora también del Golfo de Santa Clara, en Sonora) para modificar su arte de pesca, acorde con lo que plantea la nueva norma oficial mexicana.

Resumo É comum a ocorrência de flutuadores extraviados, provenientes de redes de pesca do tipo emalhe. Geralmente apresentam-se quebrados e apresentam sinais de terem sido reparados. A análise desses flutuadores e entrevistas com pescadores sugerem duas causas principais para o extravio. Primeira, colisões entre equipamentos ativos, as redes de arrasto camaroeiras, ou equipamentos passivos, as redes de emalhe para peixes, com destruição e perda de materiais em ambos os casos. Como segunda causa destaca-se o método precário com que flutuadores são inseridos na tralha superior das redes de emalhe na época em que os recursos-alvo são predominantemente pelágicos. Tal inserção ocorre para substituir unidades danificadas ou perdidas ou ainda, em caráter sazonal, as que foram removidas na época em que a pesca era dirigida a recursos demersais. Este trabalho descreve um novo desenho de flutuador e testa sua eficácia, visando aumentar a retenção nos cabos e reduzir a perda.

Abstract Plastic floats from fishing nets are commonly found washed up on beaches in southern Brazil. They are usually broken and show signs of having been repaired. Characteristics of floats and interviews with fishermen suggest two main causes of float loss. First, collisions between active gear, bottom trawl nets for shrimp, and passive gear, drift nets for fish, destroy nets and release fragments of them, including floats. Second, the difficulty with which floats are inserted on the float rope of the nets when they are used near the surface. Floats are inserted to replace damaged or lost floats, or they may be removed if it is desired that the nets be used in deeper waters. Floats may thus be poorly fixed to the cables and lost. Here a new float design that offers greater safety in use and for the replacement of floats is described and tested.

O controle de plantas daninhas é comumente feito com roçadas na entrelinha associada a aplicações dirigidas de glyphosate na linha de plantio de culturas arbóreas, acarretando risco de deriva ou aplicação acidental do herbicida, que pode afetar a cultura de interesse. O objetivo foi avaliar a resposta dos clones C219, GG100, I144 e I224 de eucalipto (Eucalyptus grandis x E. urophylla) a doses de glyphosate de 0, 18, 36, 72, 180, 360 e 720 g de equivalente ácido por hectare. Os clones apresentaram padrões de crescimento distintos no que se refere a altura da planta, número de folhas, massa seca do caule, taxa de crescimento relativo, taxa de assimilação líquida e taxa de crescimento foliar relativo. Os clones I144 e GG100 foram mais suscetíveis ao glyphosate, sendo as doses necessárias para reduzir a massa seca em 50% de 113,4 e 119,6 g ea ha-1, respectivamente. Os clones C219 e I224 foram menos suscetíveis ao glyphosate, sendo as doses necessárias para reduzir a massa seca em 50% de 237,5 e 313,5 gae ha-1, respectivamente. Clones de eucalipto respondem diferentemente à exposição ao glyphosate, e entre I224, C219, GG100 e I144 a suscetibilidade é aumentada.

Weed control is commonly performed by the inter-row mechanical weeding associated to intrarow glyphosate directed spraying, causing a risk for drift or accidental herbicide application, that can affect the crop of interest. The objective was to evaluate the response of clones C219, GG100, I144, and I224 of eucalypt (Eucalyptus grandis x E. urophylla) to glyphosate doses of 0, 18, 36, 72, 180, 360, and 720 g of acid equivalent per hectare. The clones showed different growth patterns with regard to height, leaf number, stem dry weight, relative growth rate, net assimilation rate, and relative leaf growth rate. The clones I144 and GG100 were more susceptible to glyphosate, showing the doses required to reduce dry weight by 50% of 113.4 and 119.6 g acid equivalent per hectare, respectively. The clones C219 and I224 were less susceptible to glyphosate, showing the doses required to reduce dry weight by 50% of 237.5 and 313.5 g acid equivalent per hectare, respectively. Eucalyptus clones respond differently to glyphosate exposure, so that among I224, C219, GG100, and I144, the susceptibility to the herbicide is increasing.

Barriers and barrier islands can form from the reworking of coastal plains, non-operative deltaic plains, or by the growing of complex spits. They change their shape in relation to the sedimentation rates and the evolution of the sea level, but they are also very sensitive to man-made interventions, mostly when they cause variations in the littoral drift or sediment budgets. The barrier of Patagones is located in Northern Patagonia, and spans from the estuary of the Negro River to the former delta of the Colorado River; a coast dominated by a northward littoral drift. Part of the barrier is hanged on top of coastal cliffs, part is growing towards the depressed area of Anegada Bay, and the northern portion is being reworked from the former delta (Fig. 1). Landsat and CBERS images from different years, ALOS Palsar images and aerial photographs were analyzed in order to estimate morphologic changes of the dunes composing these barriers. Analogic and digital processes were applied to understand the evolution of both barriers. Climate (wind and rain) is the main factor that diminishes the sand supply to these dunes. Winds from the SW and W have a potential drift higher than 400 with a net transport towards the NE. The maximum migration rate of the dunes was 9 m a-1 (interval 1973-2005), higher than the migration rates estimated at other sand barriers of Buenos Aires Province. Near San Blas village, non-vegetated transverse-barchanoid dunes moved to the east (Fig. 3). Cliff-top dunes are present in Faro Segunda Barranca (Fig. 4). A great variation in the shape of parabolic dunes was observed between Punta Redonda and Punta Rasa (simple and compound) with a length-width relationship of 3 for simple elongated shapes (Fig. 5). Digital processing of Landsat images allowed calculating vegetation indices (NDVI) and change-detection maps, showing the fixation of 772 ha of dunes at the Punta Redonda- Punta Rasa area (1989-2005 period; Fig. 6). Prior to the Holocene transgression, several tectonic depressions were scattered on top of the plateau; two allochtonous rivers, the Colorado and Negro, crossed it. During the maximum highstand, the Negro River valley became flooded while a delta established where the Colorado River discharged into Anegada Bay (Fig. 9). In Jabalí Island, Upper Pleistocene marine terraces composed mostly of gravel were partially reshaped into beach ridges. In the last 6000 years, significant changes occurred. The avulsion of the Colorado River channels made it to discharge to the north during historic times. The delta became reworked by marine processes. The northward longshore drift accumulated the sand delivered by the Negro River that climbed on top of former cliffs along the segment between Faro Segunda Barranca and Punta Redonda. Westerly winds reinforced this eastwards sediment transport either as barchans or parabolic dunes. At the end of that littoral drift, at Jabalí Island, the sand transport induced dunes to climb on top of former Holocene beach ridges. The barrier islands of the north have been related to a decrease in the littoral transport, and an increase of the tidal prism that induced the stability of the tidal inlets.

Con el objeto de analizar y describir la morfometría y dinámica de la barrera medanosa e islas de barrera del partido de Patagones, se utilizaron imágenes satelitales Landsat y CBERS de diferentes períodos, así como fotografías aéreas escala 1:20.000 e imágenes radar ALOS Palsar. Siguiendo procedimientos analógicos y digitales se lograron establecer los procesos evolutivos relacionados con la configuración de ambas barreras. La variación de los vientos y precipitaciones incidieron en un menor volumen de material sedimentario que indujeron cambios en la morfología de dunas. Los vientos de mayor velocidad, principalmente del SO y O, determinaron un potencial de deriva de arena relativa superior a 400, principalmente hacia el NE. Las tasas de migración promedio de dunas alcanzaron valores máximos de 9 m a-1, superando las estimadas en otros sectores costeros de Provincia de Buenos Aires, y aumentando su movilidad durante la primavera. Una gran variedad de formas parabólicas (simples, y compuestas) fueron descriptas en el sector comprendido entre punta Redonda y punta Rasa con una relación largo-ancho mayor a 3 para dunas parabólicas simples elongadas. En este sector se estimó un aumento en la fijación natural de dunas de 772 ha durante el lapso 1989-2005. En las cercanías de San Blas los médanos barjanoides libres se mueven hacia el E, mientras que existen otros médanos vegetados que cubren mayor superficie. Las islas de barrera del norte están relacionadas a un menor transporte litoral y al aumento del prisma de mareas que incrementó la estabilidad de los canales de mareas.

O presente trabalho apresenta uma estimativa, por modelagem numérica, dos padrões de dispersão de sedimentos causados pela incidência de ondas em cinco distintos contornos de linhas de costa da planície deltaica do Rio Jequitinhonha durante o Holoceno Tardio. Para isso, um modelo de clima de ondas baseado na construção de diagramas de refração de onda, em função das condições de contorno atuais, foi definido e assumido ser válido para as cinco linhas de costa. A modelagem numérica, a partir dos diagramas de refração, foi feita considerando o ângulo de aproximação e a altura da onda ao longo da linha de costa. O trabalho permitiu reproduzir os padrões pretéritos e atuais da deriva litorânea efetiva de sedimentos, definidos por um modelo conceitual desenvolvido a partir da integração de testemunhos de sedimentos, interpretação de fotos aéreas e datações de C14, bem como por indicadores geomórficos de deriva. Estes resultados mostram que, em média, em relação à região leste-nordeste brasileira as condições de onda atuais parecem ter permanecido com as mesmas características desde aproximadamente 5.100 anos A.P. até o tempo atual. Esse tipo de informação pode ser importante para tentativas de simulação de possíveis situações futuras em termos do comportamento genérico de longa duração das regiões costeiras leste-nordeste brasileira.

Using numerical modeling, this work estimates sediment dispersion patterns caused by the incidence of waves in five distinct coastline contours of the Jequitinhonha River delta plain during the Late Holocene. For this study, a wave cliate odel based on the construction of ave refraction diagras relative to the current boundary conditions as defined and assumed to be valid for the five coastlines. Numerical modeling from the refraction diagrams was carried out considering the angle of incidence and wave height along the coastline. This work has allowed us to reproduce past and current patterns of net longshore sediment drift defined by a conceptual model developed from the integration of sediment cores, aerial photograph interpretation, C14 datings and geomorphic indicators of longshore drift. These results show that, on average, current wave conditions in the east-northeastern Brazilian region seem to have remained characteristically the same from approximately 5100 years BP until the present time. This type of information can be important when attempting to simulate possible future situations in terms of the long-term general behavior of the east-northeastern Brazilian coastal region.

En la zona próxima a la costa del área de estudio, el movimiento de la arena a lo largo de la costa es debido a la acción de las olas y las corrientes. El movimiento del sedimento a lo largo de la línea de costa del área de estudio es principalmente gobernado por fuerzas asociadas a las olas entrantes a la costa y la disponibilidad de sedimentos en la zona. Esta investigación fue realizada para estudiar el movimiento del sedimento en relación a la actividad de las olas a lo largo de la costa. La dirección del transporte de sedimento a lo largo de la costa es mayor hacia el Norte que hacia el Sur. Las condiciones normales para el movimiento anual del sedimento se encuentran en aguas someras y en la playa. Las olas y la corriente de oleaje generan una deriva litoral de las arenas a lo largo de la playa y costa afuera. La erosión natural en el área de estudio (exepto Kanyakumari) entre Marzo y Octubre es debido a la prevalencia del gran oleaje desde la dirección Sur y Sureste. Introduction

In the nearshore zone ofpresent study area, the movement ofsand alongshore is due to the action ofwaves and currents. The sediment movement along the shoreline ofstudy area is mainly governed by the forces associated with the incoming wavesandtheavailabilityofsedimentswithinthearea. Thepresentinvestigationhasbeenmadeasanattempttoappreciate the sediment movement in relation to wave activity along the coast. The longshore sediment transport is higher in the northerly direction as compared to southerly direction. The normal condition is for and to be moved annually or more frequently in the shallows and on the beach. Waves and wave-driven currents cause longshore drift ofsand alongthe beach and offshore. The net erosive nature of the study area (except Kanyakumari) from March to October is due to the prevalence ofhigh waves from S and SE directions.

Desembocaduras são ambientes bastante dinâmicos e sujeitos à complexa interação entre fatores estabilizadores e desestabilizadores. Dependendo dessa interação, desembocaduras podem apresentar a tendência de migração ao longo de barreiras arenosas. Um dos mecanismos mais eficientes de transporte de sedimento paralelo à costa, e consequentemente migração de canais, são as correntes longitudinais geradas pelas ondas se aproximando obliquamente à costa. A motivação do presente trabalho é entender o comportamento morfodinâmico do sistema de desembocadura do rio Itapocú, localizado no centro-norte de Santa Catarina (SC), frente aos processos forçantes que atuam na sua migração ao longo da linha de costa. A morfologia dos pontais arenosos foi obtida a partir de levantamentos morfológicos com o uso de DGPS. Para analisar a refração de ondas foi utilizado o modelo numérico MIKE 21 SW, sendo considerados como condições de contorno os dados de ondas referentes ao ano de 2002 e os dados de ondas previstos referentes ao período de coleta. Os dados de saída do modelo foram utilizados para estimar a deriva litorânea potencial na região. Os resultados morfológicos obtidos demonstraram uma migração da desembocadura para o norte durante o período analisado, sendo mais intenso durante o inverno e o verão. Ondas incidentes do quadrante sul sofreram mais o fenômeno da refração e as ondas de leste apresentaram menor variação angular ao se aproximarem à costa. A deriva litorânea potencial anual para os dados de ondas de 2002 apresentou sentido norte-sul, com inversão de sentido durante o outono. Utilizando os dados de ondas previstas para o período dos levantamentos, a deriva litorânea potencial estimada apresentou sentido sul-norte, concordando com a migração observada. Na região próxima a desembocadura, nos pontais arenosos, a deriva potencial apresentou direção para o norte durante todas as estações. Os dados de descarga fluvial não apresentaram influência na migração do canal, porém apresentaram uma relação com a largura do mesmo sazonalmente.Os dados de morfologia juntamente com os dados de deriva litorânea referentes às ondas de 2004/2005 mostraram claramente a migração do canal para o norte sendo a deriva a principal contribuinte para a migração da desembocadura.

Inlets are highly dynamic environments subjected to the complex interaction between stabilizing and destabilizing factors. Depending on this interaction, inlets have a tendency to migrate along sandy barriers. One of the most effective mechanisms for transporting sediment alongshore and consequently controlling the migration of inlets, are currents generated by waves approaching the coast at an angle. The motivation of this study is to better understand the morphodynamic behavior of the Itapocú inlet, at the northern Santa Catarina (SC) coast. The morphology of the sandy spits that enclose the inlet was obtained from morphological surveys conducted with the use of DGPS. To analyze the wave refraction the numerical model MIKE 21 SW has been applied to the region. Boundary conditions have been set based on a one-year long database (2002) and predicted waves for the studied period. The model output has been used to estimate the potential longshore drift in the region. Results show the migration of the inlet to the north during the analyzed period, with higher migration rates during winter and summer. Waves incoming from the south are the most influenced by the refraction process, while the less refracted waves are those coming from the east. The net longshore drift obtained when using the 2002 database is southwards, presenting slight inversions during autumn. When using the predicted wave data for the studied period, the potential longshore drift is dominated by northward direction, in agreement with the observed inlet migration. The Itapocú river discharge does not present any relation with the observed inlet migration rates, although there seems to be a relation with the seasonal channel width variability. The surveyed morphological evolution is well related to the potential longshore drift for the 2004/2005 waves, indicating that during the monitored period, the northwards inlet migration is being controlled by the wave generated longshore drift.

Este trabalho mostra que a localização dos recifes de coral ao longo dos litorais leste e nordeste do Brasil, em uma aproximação de primeira ordem, parece ser controlada pelo déficit de sedimentos no sistema costeiro. O padrão de transporte de sedimentos definido por modelagem numérica a partir de diagramas de refração de ondas, representando cerca de 2000 km dos litorais leste e nordeste do Brasil, permitiu a reprodução, em escala regional, de várias células de deriva litorânea efetiva de sedimentos. Essas células de deriva podem razoavelmente explicar os segmentos costeiros que representam superávit, ou deficit de sedimentos que correspondem, respectivamente, a regiões onde existe deposição e erosão ou pouca/nenhuma deposição de areia. O deficit de sedimentos propicia a exposição e manutenção de substratos rochosos livres de sedimento, uma condição favorável para a fixação e desenvolvimento das larvas de coral.

This paper shows that the location of the shoreface bank reefs along the northeastern and eastern coasts of Brazil, in a first order approximation, seem to be controlled by the deficit of sediment in the coastal system. The sediment transport pattern defined by a numerical modeling of wave refraction diagrams, representing circa 2000 km of the northeastern and eastern coasts of Brazil, permitted the regional-scale reproduction of several drift cells of net longshore sediment transport. Those drift cells can reasonably explain the coastal sections that present sediment surplus or sediment deficit, which correspond, respectively, to regions where there is deposition and erosion or little/no deposition of sand. The sediment deficit allows the exposure and maintenance of rocky substrates to be free of sediment, a favorable condition for the fixation and development of coral larvae.

O presente trabalho apresenta uma estimativa, por modelagem numérica, dos padrões de dispersão de sedimentos causados por ondas ao longo de quatro distintos traçados da linha decosta durante o Holoceno Tardio na planície deltaica do Rio Doce. Para tanto, foi definido um modelo de clima de ondas baseado na construção de diagramas de refração de ondas, em função das condições de contorno atuais, que foi assumido como válido para as quatro linhas de costa. A modelagem numérica foi realizada a partir dos diagramas de refração, levando-se em conta o ângulo de aproximação e a altura da onda ao longo da linha de costa. Os resultados obtidos mostraram-se compatíveis com os dados existentes relativos aos sentidos da deriva litorânea efetiva de sedimentos estimados a partir da integração de testemunhos de vibração, interpretação de fotos aéreas e datações por C. Esse fato aparentemente sugere que, em média, as condições de contorno atuais parecem ter permanecido com as mesmas características gerais desde 5.600 cal yr BP até o atual, bem como que a abordagem aqui utilizada poderá ser útil para a avaliação de padrões de dispersão de sedimentos durante o Holoceno Tardio na região costeira leste-nordeste brasileira.

This paper presents a numerical modeling estimation of the sediment dispersion patterns caused by waves inciding through four distinct coastline contours of the delta plain of the Doce River during the Late Holocene. For this, a wave climate model based on the construction of wave refraction diagrams, as a function of current boundary conditions, was defined and was assumed to be valid for the four coastlines. The numerical modeling was carried out on basis of the refraction diagrams, taking into account the angle of approximation and the wave height along the coastline. The results are shown to be comparable with existing data regarding the directions of net longshore drift of sediments estimated from the integration of sediment cores, interpretation of aerial photographs and C14 datings. This fact apparently suggests that, on average, current boundary conditions appear to have remained with the same general characteristics since 5600 cal yr BP to the present. The used approach may prove useful to evaluate the sediment dispersion patterns during the Late Holocene in the Brazilian east-northeast coastal region.

Utilizando-se as direções médias das principais frentes-de-onda que se aproximam do trecho costeiro do nordeste brasileiro compreendido entre as localidades de Rio Real (Sergipe) e Galinhos (Rio Grande do Norte) - coincidentes com aquelas dos principais ventos que ocorrem na área - e de seus períodos, nós definimos um modelo de clima de ondas baseado na construção de diagramas de refração. O modelo resultante de transporte de sedimentos, obtido por modelagem numérica feita a partir dos diagramas de refração, considerando o ângulo de aproximação e a altura das ondas ao longo da isóbata de 10m, foi capaz de reproduzir os padrões de dispersão de sedimentos fornecidos pelos indicadores geomórficos de deriva litorânea. Toda essa região costeira, com cerca de 900km de extensão, caracteriza-se por se constituir em uma grande zona de divergência no sentido da deriva litorânea efetiva dos sedimentos, cuja intensidade potencial aumenta consideravelmente de valor, por quase toda a sua extensão, de uma maneira contínua, no sentido de sotamar. Este fato implica em um défict crescente de sedimentos no sentido de sotamar, o que pode explicar a maior ou menor suscetibilidade, de longa duração, para a erosão ao longo do trecho costeiro aqui estudado, durante o Quaternário.

By using the mean directions of the wave-fronts approaching the Brazilian northeastern coastal stretch comprised between the localities of Real river (Sergipe State) and Galinhos (Rio Grande do Norte State) - coincident with those of the main winds occurring in the area - and their periods, we have defined a wave climate model based on the construction of refraction diagrams. The resulting model of sediment transport, as obtained by numerical modelling from the refraction diagrams, taking into consideration the angle of approach and waves heights along the 10-m isobath, was capable of reproducing the patterns of sediment dispersion provided by geomorphic indicators of the longshore drift. All this coastal region, approximately 900 km in length, is characterized by a significant divergence zone in the direction of net longshore drift of sediments, the potential intensity of which increases considerably in value, in almost its entire length, continuously toward downdrift, which might explain the greater or lesser long term susceptibility to erosion, during the Quaternary, along the coastal stretch studied.

This investigation is a contribution to the geological kowledge of the Argentine marine shelf. The study area is a sector of the internal shelf up to 25 m of depth, along a coastal zone extending approximately from Bahía Blanca estuary to Anegada bay (Fig. 1). The purpose of this report is to define, through the analysis of surface sediments and the marine subbottom, the present sedimentological conditions and establish the coastal sedimentary paleoenvironments that characterized the last transgressive holocene period. The specific oceanographic tasks, carried out with the research vessel El Austral, comprised the extraction of sedimentological samples (surface and core samples) and 3.5 kHz seismic survey (Fig. 2). The sediments were analyzed both in their texture (sieve and/or pipette) and their mineralogical contents (microscopy and X-ray difractometry). Generally, in bottom surface sediments, the psammitic fraction (medium-fine) is predominant, albeit important concentrations of silt-clay are found on the coastal region, while the gravel-type sizes (biogenetic remains, sandstone and “patagonic pebbles”) appear in the more external sector. The 3.5 kHz seismic survey, together with the cores, indicate that the shelf subbottom adjacent to the west and northwest coast is formed by a sequence of fine sediments (silt clay-fine sand), determined acoustically up to a depth of 7 m. Both texture and mineralogy, show lateral continuity towards the inner Bahía Blanca estuary. The seismic records determine a facies with a reflective configuration of the parallel-subparallel type and hummocky, associated with conditions of uniform sedimentation and to a shallow low energy palaeoenvironment, in marked contrast with the present hydraulic regime and sedimentation. During a period when the sea level was lower than the present one, the coastal palaleogeographic configuration would have determined restricted marine conditions, with a relevant continental contribution silt-clay type sediments. This ancient river-estuary sedimentary environment, defines seismically up to Anegada bay, would be formed by channels of various dimensions, as is evident from the seismograms. The silt-clay materials found on the shelf subbottom are thus associated with a wide deltaic palaleoenvironment, which may be put into correlation with the ancient drainage basin of the Colorado river, where marine conditions were influential only due to the effect of tides. It is to be noted that south of the present Colorado river mouth an ancient river bed of it is defined in the subbottom. The transgressive holocene process originated an important increase in the energy of the transport agent. Consequently, sandy material, with pebbles and bioclasts of different sizes and fragmentation, cover in erosive unconformity the silt-clay materials of the subbottom. In the cores, the thickness of this surficial sandy stratum is on the order of 40-50 cm, although towards greater depths seismic information establishes that it increases. Terraces and topographic slopes, together with the presence of pebbles and concentrations of heavy minerals and biogenic remains, represent morphosedimentological relict elements, belonging to periods of stabilization in the marine ascent and to ancient coastal environments. The regional distribution of the bottom sedimentary facies, as well as certain morphological marine features, are thus valuable indicators for inferring the present sedimentary dynamics. On the basis of the textural and statistical results, sedimentological evaluations were carried out to infer transport and sedimentation modes. Likewise, as part of the mineralogical analysis of the sediments, the regional distribution or tendency of the diverse mineral species was also taken into account, since through their different specific weights and differential hydrodynamic behavior, they point to sedimentary sources and/or energy conditions that operate on the shelf investigated. It then emerges from these observations the predominance of the bedload sediment transport in the more external sector of the study area. Contrarily, on the more coastal zone, the influence of silt-clay coming from the inner Bahía Blanca estuary and the Colorado river contribution is evident. In the latter case, considering the textural areal analysis of the sediments, the “sedimentary plume” developed starting on the west coast, adjacent to the Colorado river mouth, and extending northeastward, is remarkable. The distributive tendency of the heavy mineral concentration clearly points to an important source of sedimentary contribution, related to the ferrotitaniferous deposits present on the shores of the study area, from San Blas bay up to the Negro river mouth. These sediments would be affected by an intense coastal drift towards the zone of the present work. On the other hand, the bed forms, particularly sand waves, tend to reach an equilibrium state relative to the dominant flux conditions. The asymmetry of these geoforms is then an indicative feature of the sedimentary dynamics and circulation as bedload transport. The morphological evaluation of the sand waves found in the northern and southern sectors of the area investigated, in conjunction with analysis of the distribution of the sedimentary surface facies (textural-mineralogical), support the conclusion that the sedimentary bottom dynamics in the shelf environment studied is represented by a northward net bedload sediment transport.

Se analizan sedimentos superficiales y subsuperficiales, y rasgos geomorfológicos de fondo, de un sector de la plataforma continental interior entre el estuario de Bahía Blanca y bahía Anegada. El objetivo es definir condiciones de sedimentación actual y paleoambientes costeros. Las tareas oceanográficas, realizadas con el B.O. El Austral, comprendieron extracción de muestras sedimentológicas, superficiales y de testigos, y relevamiento sísmico con 3,5 kHz. Se establece que el subsuelo se halla conformado por una secuencia de sedimentos finos (limo arcilla-arena fina). Los sismogramas determinan una facies reflectiva con estratificación paralela-subparalela y “hummocky”, relacionada a condiciones de sedimentación uniforme y a un paleoambiente somero de baja energía. Durante un período con nivel del mar por debajo del actual, la configuración paleogeográfica costera habría determinado condiciones marinas muy restringidas, con un relevante aporte continental de sedimentos limo arcillosos. Estos se asocian a un amplio paleoambiente de sedimentación deltaico, correlacionable a la antigua cuenca hídrica del río Colorado, donde el medio marino tuvo una influencia parcial, sólo por efecto de las mareas. El proceso transgresivo holoceno produjo un sensible aumento de la energía en el ambiente hidrodinámico de sedimentación, lo que originó la depositación de material arenoso sobre los sedimentos deltaicos. Terrazas y desniveles topográficos, junto a la presencia de rodados y concentraciones de minerales pesados y bioclastos, resultan elementos morfosedimentológicos relícticos de períodos de estabilización en el ascenso marino y antiguos ambientes litorales. Evaluaciones de las facies superficiales permiten establecer un dominio del transporte de sedimento como carga de fondo en el sector más extremo del área. En cambio, sobre la zona más costera se evidencia un aumento del transporte en suspensión, resultando notable la influencia de material limo-arcilloso proveniente del interior del estuario Bahía Blanca y del río Colorado. Los minerales pesados marcan un importante aporte por deriva costera, proveniente de las playas del sur del área investigada. Por último, las características morfológicas de grandes ondas de arena presentes en el área, conjuntamente con el análisis de la distribución de las facies superficiales (texturales-mineralógicas), conducen a definir la dinámica sedimentaria dominante sobre el ambiente de plataforma estudiado, representada por un transporte de sedimento como carga de fondo en dirección norte.

184 machos da Carcharchinus porosas foram capturados com rede de emalhar nas Reentrâncias Maranhenses, entre Cururupu (1º 20' S e 45º W) e São Luis (2º 241 30'' S e 44º W) no período de outubro de 1983 à janeiro de 1984 e de junho à setembro de 1984. O desenvolvimento dos machos desta espécie foi estudado através da relação peso-comprimento e do crescimento: dos claspers, dos testículos, dos epidídimos e do fígado. Com exceção dos claspers e do fígado, o crescimento dos órgãos em questão é contínuo. No crescimento dos claspers evidenciou-se 3 fases que correspondem: a fase juvenil, a fase de adolescência e a fase adulta. Demonstrou-se, também, que existe uma descontinuidade no crescimento do fígado no momento da passagem da fase de adolescência à fase adulta, e que esta se verifica quando se relaciona o peso deste órgão com o peso corporal. Esfregaços do conteúdo da visívula seminal mostraram que o líquido branco presente neste órgão é livre de espermatozóides até 70 cm. Com base no crescimento dos claspers e na produção de espermatozóides normais, estabeleceu-se o tamanho de primeira maturidade em 71 cm (fim da fase de adolescência) e o tamanho de 100% de maturidade em 75 cm (início da fase adulta).

184 males of Cancharhinus porosus were caught by drift net off the state Of Mara-nhão, between Cururupu (1° 20' S / 45° W) and São Luís (2° 24' 30" S / 44° W) during the periods from October 1982 to January 1984, and from June to September 1984.Development of the males was studied by observing the lenght-welght relationship and the growth of the claspers, testis, epididymis and liver. With the exception of the clampers and liver, the growth of these organs is continuous.Three phases were observed in the growth of the clampers: the juvenile, adolescent and the adult phase. A discontinuity in the growth of the liver was observed during the transition from adolescent to adult phase, as was shown by the relationship between liver weight and body weight.Smears of the contents of the seminal vesicle showed that the white liquid which occurs in this organ, does not contain sperms at fish lengths less than 70 cm.On the basis of craspers grouth and sperm production, first sexual maturity and end of the adolescent phase was established at cm, and full maturity and adult phase ocurred at 75 cm.