The Red Sea convergence zone (RSCZ) is formed by opposite surface winds blowing from northwest to southeast directions at around 18 ∘ -19 ∘ N between October and January. A reverse-oriented, low-level monsoon trough at 850 hPa, known as the Red Sea trough (RST), transfers moisture from the southern Red Sea to RSCZ. The positions of the RSCZ and RST and the intensity of the RST have been identified as important factors in modulating weather and climatic conditions across the Middle East. Here, we investigate the influence of the El Niño southern oscillation (ENSO) on the interannual variability of RSCZ, RST, and regional rainfall during winter months. Our results indicate that El Niño (warm ENSO phase) favours a shift of the RSCZ to the north and a strengthening of the RST in the same direction. Conversely, during November and December of La Niña periods (cold ENSO phase), the RSCZ shift to the south and the RST strengthens in the same direction. During El Niño periods, southeasterly wind speeds increase (20-30%) over the southern Red Sea and northwesterly wind speeds decrease (10-15%) over the northern Red Sea. Noticeable increases in the number of rainy days and the intensity of rain events are observed during El Niño phases. These increases are associated with colder than normal air intrusion at lower levels from the north combined with warm air intrusion from the south over the RSCZ. Our analysis suggests that during El Niño winters, warmer sea surface temperatures and higher convective instability over the Red Sea favour local storms conditions and increase rainfall over the Red Sea and adjoining regions.

Capsule Summary An integrated, high resolution, data-driven regional modeling system has been recently developed for the Red Sea region and is being used for research and various environmental applications.

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The Mediterranean Sea has the highest accumulation of microplastics in the world. Although numerous studies about microplastic’s abundance and distribution have been conducted, the majority sampled surface waters. Especially for the Eastern Mediterranean, there is no information concerning the deeper strata. This study fills this gap by studying the microplastic spatial and temporal distribution along the coasts of Cyprus, utilizing zooplankton samples collected from the entire 0–50 m depth layer. The average microplastics’ abundance was 41.31 ± 22.41 items/m3 indicating that the Eastern Mediterranean seems to be much more polluted than the western basin. The fibers outnumbered the abundance of the fragments by a factor of ten. Most fibers were sized between 0.5 and 1.0 mm, and 81.24% were transparent. The average area of the fragments was ≤0.05 mm2, and most of them were hard-rounded (53.38%). The microplastics to zooplankton ratio ranged between 0.021 and 0.241. A positive correlation was found between the abundance of microplastics and the total zooplankton, especially the copepods. Studies of microplastics in zooplankton samples taken from the water column are expected to provide better insights into the role of these pollutants in marine ecosystems.

This study provides elements on the spatial and temporal mesozooplankton variability during a three-year study, encompassing vertical hauls from 50 m deep to the surface from four coastal locations of Cyprus. The total mesozooplankton abundance fluctuated between 190.4 and 882.5 individuals m-3. A total of 90 holoplanktonic and meroplanktonic taxa were recorded. Copepods dominated in the community and accounted for 71.7% of the total mesozooplankton, followed by appendicularians, molluscs, cladocerans, and siphonophores, which contributed 8.04%, 5.48%, 4.60%, and 3.31%, respectively. There were no statistically significant differences among the four sampling sites for any of the mesozooplanktonic taxa, though seasonal and interannual differences were recorded for several of them. The community composition reinforced the evidence for a higher resemblance of the Cyprus mesozooplankton to the offshore communities of the northern and central Levantine Sea and those around Rhodes Island, instead of the northeastern Mediterranean coastal areas. Comparisons of the seasonal abundance variation of the mesozooplankton taxa with other coastal areas of the Levantine Sea are provided. Considering the seasonality of the mesozooplankton, there was a separation of the taxa into distinct groups representing the summer, the winter-spring, and the autumn periods. The temperature was the most important variable that shaped the formation of the distinct seasonal groups of taxa, while chlorophyll-α, dissolved oxygen, and salinity contributed to a lesser extent. Chlorophyll-α concentrations verified the oligotrophic character of the area and seem to be unaffected by inland inputs. The mesozooplankton community showed a spatial consistency, probably as the result of the open sea influence, and seems to be regulated mainly by the properties of the central Levantine pelagic waters and less by terrestrial inputs of inland waters.