Coastal response to late-stage transgression and sea-level highstand

Coastal morphologic features associated with past shoreline transgressions and sea-level highstands can provide insight into the rates and processes associated with coastal response to the modern global rise in sea level. Along the eastern and southern Brazilian coasts of South America, 6000 years of sea-level fall have preserved late-stage transgressive and sea-level highstand features 1-4 m above present mean sea level and several kilometers landward of modern shorelines. GPS with real-time kinematics data, ground-penetrating radar, stratigraphy, and radiocarbon dating within a 2-3-km-wide river-associated strandplain in central Santa Catarina (southern Brazil) uncovered a diverse set of late-stage transgressive and highstand deposits. Here, the highstand took the forms of (1) an exposed bedrock coast in areas of high wave energy and low sediment supply; (2) a 3.8-m-high transgressive barrier ridge where landward barrier migration was prohibited by the presence of shallow bedrock; and (3) a complete barrier-island complex containing a 5.2-m-high barrier ridge, wash-over deposits, a paleo-inlet, and a backbarrier lowland, formed in a protected cove with ample sediment supply from small local streams and the erosion of upland sediments. Similar signatures of the mid-Holocene highstand can be traced across all coastal Brazilian states. This study presents the first complete compilation of the diversity of these sedimentary sequences. They are broadly classified here as exposed bedrock coasts (type A), back barrier deposits (type B), transgressive barrier ridges (type C), and barrier-island complexes (type D), according to localized conditions of upland migration potential, wave exposure, and sediment supply. These Brazilian systems present a paradigm for understanding future coastal response to climate change and accelerated sea-level rise: the recognition of a minimum threshold sea-level-rise rate of similar to 2 mm yr(-1) above which transgression proceeded too rapidly for the formation of these stable accretionary shoreline features demonstrates the nonlinearity of coastal response to sea-level change, and the site specificity of conditions associated with the formation of each highstand deposit type, even within a single small embayment, demonstrates the non-uniformity of that response

Antimicrobial Activity, Acute Toxicity and Cytoprotective Effect of Crassocephalum Vitellinum (Benth.) S. Moore Extract in a Rat Ethanol-HCl Gastric Ulcer Model.

A decoction of Crassocephallum vitellinum (Benth.) S. Moore (Asteraceae) is used in Kagera Region to treat peptic ulcers. This study seeks to evaluate an aqueous ethanol extract of aerial parts of the plant for safety and efficacy. An 80% ethanolic extract of C. vitellinum at doses of 100, 200, 400 and 800 mg/kg body wt was evaluated for ability to protect Sprague Dawley rats from acidified ethanol gastric ulceration in comparison with 40 mg/kg body wt pantoprazole. The extract and its dichloromethane, ethyl acetate, and aqueous fractions were also evaluated for acute toxicity in mice, brine shrimp toxicity, and antibacterial activity against four Gram negative bacteria; Escherichia coli (ATCC 25922), Salmonella typhi (NCTC 8385), Vibrio cholera (clinical isolate), and Streptococcus faecalis (clinical isolate). The groups of phytochemicals present in the extract were also determined. The ethanolic extract of C. vitellinum dose-dependently protected rat gastric mucosa against ethanol/HCl insult to a maximum of 88.3% at 800 mg/kg body wt, affording the same level of protection as by 40 mg/kg body wt pantoprazole. The extract also exhibited weak antibacterial activity against S. typhi and E. coli, while its ethyl acetate, dichloromethane and aqueous fractions showed weak activity against K. pneumonia, S.typhi, E. coli and V. cholera. The extract was non-toxic to mice up to 5000 mg/kg body wt, and the total extract (LC50 = 37.49 μg/ml) and the aqueous (LC50 = 87.92 μg/ml), ethyl acetate (LC50 = 119.45 μg/ml) and dichloromethane fractions (88.79 μg/ml) showed low toxicity against brine shrimps. Phytochemical screening showed that the extract contains tannins, saponins, flavonoids, and terpenoids. The results support the claims by traditional healers that a decoction of C.vitellinum has antiulcer activity. The mechanism of cytoprotection is yet to be determined but the phenolic compounds present in the extract may contribute to its protective actions. However, the dose conferring gastro-protection in the rat is too big to be translated to clinical application; thus bioassay guided fractionation to identify active compound/s or fractions is needed, and use of more peptic ulcer models to determine the mechanism for the protective action

The interplay between gonadal steroids and immune defence in affecting a carotenoid-dependent trait

The hypothesis that sexual ornaments are honest signals of quality because their expression is dependent on hormones with immune-depressive effects has received ambiguous support. The hypothesis might be correct for those signals that are carotenoid-dependent because the required carotenoid deposition in the signal, stimulated by testosterone, might lower the carotenoid-dependent immune defence of the organism. Two pathways underlying this androgen-dependent honest signaling have been suggested. Firstly, androgens that are needed for ornament expression may suppress immune defence, a cost that only high-quality animals can afford. Alternatively, immune activation may downregulate the production of androgens in low-quality individuals. Which of these alternatives is correct, and to what extent these effects are mediated by the different metabolites of androgens, remain open questions. To provide answers to these questions, we manipulated the levels of testosterone (T), 5α-dihydrotestosterone (DHT), and 17-β-estradiol (E2) in diamond doves Geopelia cuneata, a species in which both sexes exhibit a carotenoid-dependent, androgen-regulated red–orange periorbital ring of bare skin. On the first day of the experiment (day 0), we inserted steroid-releasing implants into groups of birds and on day 14, we subjected half of the birds to an immunological challenge by immunizing them with sheep red blood cells (SRBC). In females, but not in males, androgen but not estradiol treatments reduced antibody production to SRBC. In addition, the immunological challenge reduced redness and size of the trait as well as androgens levels in both sexes and in all treatments. This indicates that an immunological challenge can lower circulating T at the cost of the trait expression. These findings are in accordance with both pathways postulated in the immunocompetence-handicap hypothesis, but do not entirely support the idea that the immunosuppressive effect of androgens yields honest signaling since both T and DHT were not immunosuppressive in males, for which sexual signaling is supposed to be especially important

An overview of beach morphodynamic classification along the beaches between Ovari and Kanyakumari, Southern Tamilnadu Coast, India

Beach morphology relates the mutual adjustment between topography and fluid dynamics. The morphological makeup of beach systems is not accidental because the arrangement and association of forms occur in an organized contextual space and time. Since the classification derived by Wright and Short (1983) obtained from the analysis of the evolution in a number of Southern Tamilnadu beach sites, beach systems are comprehended in terms of three-dimensional morphodynamic models that include quantitative parameters (wave breaking height, sediment fall velocity, wave period and beach slope) and boundary conditions for definable form-processes association (e.g. presence or absence of bars as well as its type). This has lead to the classification of beaches into three main categories relating the beach state observations with the physical forcing (Short, 1999) dissipative, intermediate (from the intermediate-dissipative domain to the intermediate-reflective domain) and reflective modes. Morphodynamic classification of beach types was based on the equations of Wright & Short (1984) (Dimensionless fall velocity – Dean Parameter).Морфология берега отражает взаимное влияние топографии и динамики жидкости. При этом морфологическое строение береговых систем не является случайным, а определяется распределением и пространственно-временным взаимодействием береговых форм. Начиная с классификации, предложенной Райтом и Шортом (1983), основанной на анализе эволюции нескольких участков пляжа Южного берега Тамилнаду, пляжные системы рассматриваются в рамках трехмерных морфодинамических моделей, включающих количественные характеристики (высоту обрушения волн, скорость образования осадков, волновой период и уклон пляжа) и граничные условия для определенных взаимосвязей береговой динамики (т. е. наличие или отсутствие баров и их тип). Это привело к подразделению пляжей на три основные категории в соответствии с их поведением по отношению к внешним силам (Шорт, 1999) – рассеивающие, промежуточные (от промежуточно-рассеивающих до промежуточно-отражающих вариантов) и отражающие. Морфодинамическая классификация типов пляжей основана на уравнениях Райта и Шорта, 1984 (безразмерная скорость осадкообразования – параметр Дина).Морфологія берега відображає взаємний вплив топографії та динаміки рідини. При цьому морфологічна будова берегових систем не є випадковою, а визначається розподілом і просторово-часовою взаємодією берегових форм. Починаючи з класифікації, запропонованої Райтом та Шортом (1983), заснованої на аналізі еволюції декількох ділянок пляжу Південного берега Тамілнаду, пляжні системи розглядаються в рамках тривимірних морфодинамічних моделей, які включають кількісні характеристики (висоту обвалення хвиль, швидкість утворення опадів, хвильовий період та ухил пляжу) та граничні умови для певних взаємозв'язків берегової динаміки (тобто наявність або відсутність барів і їх тип). Це призвело до підрозділу пляжів на три основні категорії відповідно до їхньої поведінки відносно фізичних сил (Шорт, 1999) – розсіюючі, проміжні (від проміжно-розсіюючих до проміжно-відбиваючих варіантів) і відбиваючі. Морфодинамічна класифікація типів пляжів заснована на рівнянні Райта та Шорта, 1984 (безрозмірна швидкість осадоутворювання – параметр Діна)

Short- and long-term chlorophyll a variability in the shallow microtidal Patos Lagoon estuary, southern Brazil

In the shallow microtidal Patos Lagoon estuary, southern Brazil (32° 07′ S–52° 06′ W), chlorophyll a (Chl a) variability was studied at different time scales during the last 25 years (hourly–daily sampling in 1984/1985; weekly sampling in 1986 and from 1988 to 1990; monthly sampling from 1993 to 2008). Phytoplankton biomass variation seems to be most influenced by hydrology, which is primarily driven by meteorological factors like wind, rainfall, and evaporation. However, it was observed that the hydrological driving forces play different roles at different time scales. For instance, short-term Chl a variability is mainly controlled by winds, while long-term changes are related to the freshwater input by rainfall. Significant correlation was found between the total amount of rain in the year and the mean annual value of Chl a, though this relationship was linear until 1,500 mm of rain per year. After this threshold, mean annual Chl a values dropped significantly, probably due to a washout of the produced biomass from the estuary. Similarly, low rainfall levels and drought years lead to small phytoplankton biomass due to scarcity of nutrient, mainly silicate, or a possible inhibitory effect generated by high ammonium concentration. In this sense, large-scale Chl a variability would be related to the El Niño-Southern Oscillation climatic anomaly, which influences the rainfall levels in Southern Brazil, though sampling periodicity has also great influence on this relationship. No Chl a or nutrient enrichment was observed in the estuarine region along the last years, indicating that this estuary is not subject to an eutrophication process. In contrast, signals of an ongoing oligotrophication are observed, possibly a remote effect of the eutrophication in the Northern area of the lagoon where the phytoplankton nutrients uptake may act as a biological filter mechanism