Contributions of Atmospheric Deposition to Pb Concentration and Isotopic Composition in Seawater and Particulate Matters in the Gulf of Aqaba, Red Sea.

Lead concentrations [Pb] and isotope ratios (206Pb/207Pb, 208Pb/207Pb) have been measured in samples of total suspended particulate (TSP) aerosols, seawater, and suspended and sinking particles in the Gulf of Aqaba (GOA), Red Sea. Isotope ratios of Pb in seawater and in the soluble fraction of Pb in atmospheric TSP were similar suggesting that TSP is an important source of Pb in this area. Pb concentrations in seawater measured in this study (max 76.8 pmol kg-1) were much lower than those recorded at the same location in 2003-2004 (up to 1000 pmol kg-1). Changes in Pb isotope ratios in TSP depositions in these years indicate that leaded gasoline was responsible for the high dissolved Pb in GOA more than a decade ago and that recent regulation reduced Pb contamination. The similarity in Pb isotope ratios in suspended and sinking particles implies close interactions between these two size fractions. This study demonstrates the effect of the phasing out of leaded gasoline on TSP and seawater Pb chemistry in the Northern GOA; the rate of change in dissolved Pb concentrations in the GOA is faster than that reported for the open ocean possibly due to higher particle scavenging and the relatively short residence time of deep water in the Basin.

The FORCIS database: A global census of planktonic Foraminifera from ocean waters.

Planktonic Foraminifera are unique paleo-environmental indicators through their excellent fossil record in ocean sediments. Their distribution and diversity are affected by different environmental factors including anthropogenically forced ocean and climate change. Until now, historical changes in their distribution have not been fully assessed at the global scale. Here we present the FORCIS (Foraminifera Response to Climatic Stress) database on foraminiferal species diversity and distribution in the global ocean from 1910 until 2018 including published and unpublished data. The FORCIS database includes data collected using plankton tows, continuous plankton recorder, sediment traps and plankton pump, and contains ~22,000, ~157,000, ~9,000, ~400 subsamples, respectively (one single plankton aliquot collected within a depth range, time interval, size fraction range, at a single location) from each category. Our database provides a perspective of the distribution patterns of planktonic Foraminifera in the global ocean on large spatial (regional to basin scale, and at the vertical scale), and temporal (seasonal to interdecadal) scales over the past century.

Elevated temperatures reduce the resilience of the Red Sea branching coral stylophora pistillata to copper pollution.

Copper (Cu) is a common marine pollutant of coastal environments and can cause severe impacts on coral organisms. To date, only a few studies assessed the effects of Cu contamination in combination with elevated seawater temperatures on corals. Furthermore, experiments focusing on coral recovery during a depuration phase, and under thermal stress, are lacking. The present study investigated the physiological response of the common and thermally tolerant scleractinian coral Stylophora pistillata from the northern Red Sea to Cu contamination (2.5, 5 or 10 µg L - 1) in combination with thermal stress (5 °C above local ambient temperatures (26 °C)) for 23 days, and assessed the impact of elevated temperatures on its ability to recover from such pollution during a one-week depuration period. Variation in coral photo-physiological biomarkers including antioxidant defense capacity, were dose, time and temperature-dependent, and revealed additive effects of elevated temperatures. Successful recovery was achieved in ambient temperature only and was mediated by antioxidant defenses. Elevation of temperature altered the recovery dynamics during depuration, causing reduced Cu bioaccumulation and photosynthetic yield. The present study provides novel information on the effects of elevated temperature on the resilience (resistance and recovery processes) of a scleractinian coral exposed to a common marine pollutant. Our findings suggest that ocean warming may alter the resilience strategies of corals when exposed to local pollution, an impact that might have long-term consequences on the chances of survival of reefs in increasingly populated and warming coastal environments.

The Oligo-Miocene closure of the Tethys Ocean and evolution of the proto-Mediterranean Sea.

The tectonically driven Cenozoic closure of the Tethys Ocean invoked a significant reorganization of oceanic circulation and climate patterns on a global scale. This process culminated between the Mid Oligocene and Late Miocene, although its exact timing has remained so far elusive, as does the subsequent evolution of the proto-Mediterranean, primarily due to a lack of reliable, continuous deep-sea records. Here, we present for the first time the framework of the Oligo-Miocene evolution of the deep Levant Basin, based on the chrono-, chemo- and bio- stratigraphy of two deep boreholes from the Eastern Mediterranean. The results reveal a major pulse in terrigeneous mass accumulation rates (MARs) during 24-21 Ma, reflecting the erosional products of the Red Sea rifting and subsequent uplift that drove the collision between the Arabian and Eurasian plates and the effective closure of the Indian Ocean-Mediterranean Seaway. Subsequently, the proto-Mediterranean experienced an increase in primary productivity that peaked during the Mid-Miocene Climate Optimum. A region-wide hiatus across the Serravallian (13.8-11.6 Ma) and a crash in carbonate MARs during the lower Tortonian reflect a dissolution episode that potentially marks the earliest onset of the global middle to late Miocene carbonate crash.

A drop in Sahara dust fluxes records the northern limits of the African Humid Period.

Northern and eastern Africa were exposed to significantly wetter conditions relative to present during the early Holocene period known as the African Humid Period (AHP), although the latitudinal extent of the northward expansion of the tropical rain belt remains poorly constrained. New records of 230Thxs-normalized accumulation rates in marine sediment cores from the Red Sea and Gulf of Aden are combined with existing records of western Africa dust and terrestrial records across the Sahara Desert, revealing that fluxes of dust transported east from the Sahara decreased by at least 50% during the AHP, due to the development of wetter conditions as far north as ~22°N. These results provide the first quantitative record of sediment and dust accumulation rates in the Red Sea and the Gulf of Aden over the past 20 kyrs and challenge the paradigm of vast vegetative cover across the north and northeastern Sahara Desert during the AHP.