Coupling of phytoplankton and ciliate biomasses to environmental factors along the north coast of Sfax (Tunisia, Eastern Mediterranean Sea)

We discuss the structure of the present Hellenic subduction zone. We show that the present Hellenic subduction zone was formed at about 15 Ma when it started to consume the Mediterranean lithosphere and to form the large accretionary wedge that covers a large part of the eastern Mediterranean. We establish that there is independent evidence that the very large Hellenic Trough that it created was formed simultaneously. Shortly before, an 8–10 km thick backstop that extends 200 km southward, where it presently abuts the African margin, was put into place. We reconstruct the northern margin of the eastern Mediterranean Sea prior to the Hellenic subduction in a new and independent way. The faults recently identified by Sachpazi et al. (2016a . Geophysical Research Letters, 43: 651–658) and Sachpazi et al. (2016b . Geophysical Research Letters, 43: 9619–9626) within the Hellenic seismic slab are a key element of our reconstruction. This is because the slab, which is part of the Nubia plate, is rigid and the faults within it coincide with the lines of slip congruent with the relative motion of the Aegean block over it. These faults demonstrate that about 400 to 500 kilometers of eastern Mediterranean lithosphere have been subducted with essentially the same southwestward direction of motion during the last 15 Myr. Our reconstruction shows that before the onset of the Hellenic subduction, the northern margin of the eastern Mediterranean Sea coincided with a major Jurassic transform fault that limited the eastern Mediterranean to the north during its formation in the Jurassic and Early Cretaceous as proposed in part 1. We discuss the implications of this reconstruction on the Neogene evolution of the Anatolia–Aegea block and its geodynamics.

Download Full-text

Chlorophyll in the Eastern Mediterranean Sea: Correlations with Environmental Factors and Trends

Environments ◽

10.3390/environments6080098 ◽

2019 ◽

Vol 6 (8) ◽

pp. 98 ◽

Cited By ~ 1

Author(s):

Dionysia Kotta ◽

Dimitra Kitsiou

Keyword(s):

Wind Speed ◽

Environmental Factors ◽

Surface Temperature ◽

Mediterranean Sea ◽

Sea Level ◽

Eastern Mediterranean ◽

Sea Surface ◽

Sea Level Pressure ◽

Eastern Mediterranean Sea ◽

Mean Sea Level

The research on marine chlorophyll concentrations, as indicators of phytoplankton abundance, their relations with environmental parameters, and their trends is of global interest. It is also crucial when referring to oligotrophic environments where maintenance or increase in primary production is vital. The present study focuses on the Eastern Mediterranean Sea that is in general oligotrophic. Its primary goal is to explore possible relations between surface chlorophyll-a concentrations and environmental factors. The involved parameters are the sea surface temperature, the wind speed, the wave height, the precipitation, and the mean sea level pressure; their relation with chlorophyll is assessed through the calculation of the relevant correlation coefficients, based on monthly satellite-derived and numerical model data for the period 1998–2016. The results show that chlorophyll relates inversely with sea surface temperature; in general positively with wind speed and wave height; positively, although weaker, with precipitation; and negatively, but area and season limited, with mean sea level pressure. These correlations are stronger over the open southern part of the study area and strongly dependent on the season. A secondary aim of the study is the estimation of chlorophyll trends for the same time interval, which is performed separately for the low and the high production periods. The statistically significant results reveal only increasing local chlorophyll trends that, for each period, mainly characterize the eastern and the western part of the area, respectively.

Download Full-text