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Mangroves occur in tropical and subtropical regions, including harsh arid areas. Little is known about how the environmental conditions of deserts influence the ecology of mangrove seedlings. The seedlings of the mangrove Avicennia marina were examined in situ in a natural stand of the southern Red Sea coast of Saudi Arabia to (1) estimate and compare the growth rate of A. marina between selected microhabitats with different tidal exposures, and (2) examine the influence of sandstorms on the growth and survival of the seedlings. Samplings were conducted in four zones established according to their tidal exposure: low tidal exposure (Z1), medium tidal exposure (Z2), high tidal exposure with numerous burrows (Z3), and high tidal exposure with a few or no burrows (Z4). Vertical growth and mortality of the seedlings and selected environmental variables were quantified. The results show that seedling growth rates differed significantly between the sampling zones, the highest growth being found in the high tidal regions (Z3 followed by Z4) and the lowest growth in Z1. Growth rate followed a significant decreasing pattern over time, coinciding with increasing air temperature and decreasing relative humidity. Sandstorms showed a marked increase in July, leading to massive dust deposition that caused extensive mortality of the seedlings by burial. Our study highlights that seedling growth can be affected by the extent of tidal inundation and that sandstorms act as a natural stressor., Los manglares proliferan en regiones tropicales y subtropicales, incluidos los desiertos. Sin embargo, se sabe poco acerca de cómo las condiciones ambientales de los desiertos influyen en la ecología de las plántulas de manglares. Las plántulas del manglar Avicennia marina se examinaron in situ en un manglar natural de la costa sur del Mar Rojo de Arabia Saudita para (1) estimar y comparar la tasa de crecimiento de A. marina entre microhábitats seleccionados con diferente exposición a las mareas, y (2) examinar la influencia de las tormentas de arena en el crecimiento y supervivencia de las plántulas. Los muestreos se realizaron en cuatro zonas establecidas en función de su exposición a las mareas: exposición a las mareas bajas (Z1), exposición a las mareas medias (Z2), exposición a las mareas altas con numerosas madrigueras de cangrejos (Z3) y exposición a las mareas altas pero con pocas o ninguna madriguera (Z4). Se cuantificó el crecimiento vertical y la mortalidad de las plántulas, así como las variables ambientales seleccionadas. Los resultados muestran que las tasas de crecimiento de las plántulas difirieron significativamente entre las zonas de muestreo con el mayor crecimiento encontrado en las regiones de marea alta (Z3 seguida de Z4) y el crecimiento más bajo en Z1. La tasa de crecimiento siguió un patrón decreciente significativo a lo largo del tiempo, que coincidió con el aumento de la temperatura del aire y la disminución de la humedad relativa. Las tormentas de arena aumentaron en julio, causando una deposición masiva de polvo que enterró a las plántulas, desencadenando una gran mortalidad. Nuestro estudio destaca que el crecimiento y la supervivencia de las plántulas pueden verse afectados por la extensión de la inundación de las mareas y las tormentas de arena, actuando como factores de estrés natural.

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 7493–7505, doi:10.1002/2015JC010996., A variety of data based on hydrographic measurements, satellite observations, reanalysis databases, and meteorological observations are used to explore the interannual variability and factors governing the deep water formation in the northern Red Sea. Historical and recent hydrographic data consistently indicate that the ventilation of the near-bottom layer in the Red Sea is a robust feature of the thermohaline circulation. Dense water capable to reach the bottom layers of the Red Sea can be regularly produced mostly inside the Gulfs of Aqaba and Suez. Occasionally, during colder than usual winters, deep water formation may also take place over coastal areas in the northernmost end of the open Red Sea just outside the Gulfs of Aqaba and Suez. However, the origin as well as the amount of deep waters exhibit considerable interannual variability depending not only on atmospheric forcing but also on the water circulation over the northern Red Sea. Analysis of several recent winters shows that the strength of the cyclonic gyre prevailing in the northernmost part of the basin can effectively influence the sea surface temperature (SST) and intensify or moderate the winter surface cooling. Upwelling associated with periods of persistent gyre circulation lowers the SST over the northernmost part of the Red Sea and can produce colder than normal winter SST even without extreme heat loss by the sea surface. In addition, the occasional persistence of the cyclonic gyre feeds the surface layers of the northern Red Sea with nutrients, considerably increasing the phytoplankton biomass., Saudi ARAMCO Marine Environmental Centre of King Abdullah University of Science and Technology (KAUST); Saudi Aramco Oil Co., 2016-05-19

Throughout 2003 and 2004 continuous autonomous observations of surface temperature, conductivity and chlorophyll fluorescence were recorded on the P&O "Pride of Bilbao" ferry between Portsmouth, UK and Bilbao Spain. Different conditions over the shelf, slope and deep waters along the route were detected and studied - from eutrophic harbour waters to the southern Bay of Biscay, which is oligotrophic in summer. During the two years, 21 manned crossings on the ferry provided information on nutrients, phytoplankton biomass and speciation. Measurements include chlorophyll a concentrations (calibration of the fluorimeter is discussed), High Performance Liquid Chromatography (HPLC) determined pigments concentrations, phytoplankton species abundance (biomass and identification) and nutrients. Data was also available from satellite images for estimates of chlorophyll (SeaWIFS), zooplankton abundance from CPR (Continuous Plankton Recorder) tows, wind speed and direction and irradiance. This has enabled phytoplankton populations to be related to-: (1) nutrient supply (2) grazing pressure (3) fresh water influences, (4) hydrography and (5) climatic conditions. The distributions of hydrographic properties and of plankton were analysed on the basis of four generalised regions (i) well-mixed, (ii) northern summer stratified, and (iii) southern summer stratified on the shelf and (iv) oceanic region in the Bay of Biscay water. There were differences between the two years in the timing of seasonal changes and in the abundance of phytoplankton species. Chlorophyll a values were generally higher in shelf waters compared to oceanic water in both years. The spring phytoplankton bloom reached its peak during March 2003 in the Bay of Biscay and during April on the continental shelf with maximum chlorophyll values of 2- 4 mg m-3. Whereas, the strong SW wind in Bay of Biscay in winter 2004 may have