Alkenones in the northwestern Mediterranean Sea

C37 alkenone fluxes were measured with sediment traps at 200 m depth over the years 1989/1990 and 1993/1994 to assess the interannual variability of the alkenone flux from the surface waters of the Mediterranean Sea. Fall and spring were identified as the high flux periods. SST estimates derived from the UK'37 index indicated 50 m and 30 m as major production depths in spring and fall, respectively. Althought interannual variation of alkenone fluxes was notable, the seasonality and depth of production appeared to be recurrent features of the coccolithophorid cycle of production. Alkenone fluxes at 1000 m measured over the year 1993/1994 were about 5 times lower than at 200 m and show no evidence of preferential preservation relative to the organic carbon between these depths. SST predicted at 200 m and 1000 m indicated a remarkably good transfer of the surface temperature signal to deeper layers.

Composition of Upper Quaternary bottom sediments from the Syrian area of the Mediterranean Sea

Results of a lithological study of bottom sediments in the Syrian region of the Mediterranean Sea during Cruise 27 of R/V Vityaz (1993) are reported. Suspended sediment discharge of the Nile River are of the greatest importance for terrigenous sedimentation in the SE part of the Mediterranean Sea, especially in deep-sea areas. Suspended load entering from the Syrian catchment area plays an important role in formation of recent shelf and slope deposits. Supply of aerosols from Syrian and Arabian deserts was distinguished by the patchiness of surface distribution of quartz. During Late Quaternary accumulation of terrigenous material supplied from both the Syrian and the Nile drainage areas was irregular. Sedimentation was remarkably enhanced during sapropel formation 7000-9000 years BP.

A comprehensive analysis of tidal notches in the Mediterranean Sea

Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology. Our results suggest that, considering 'the development of tidal notches the consequence of midlittoral bioerosion' (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development. Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them.

Sapropels in the Mediterranean Sea

Eastern Mediterranean sediments are characterized by cyclic deposition of organic-rich sediments known as sapropels. Enhanced primary productivity combined with bottom water oxygen depletion are thought to be the main drivers for sapropel deposition. We selected sapropel layers from a suite of ODP-Leg 160 cores, and applied a set of geochemical proxies to determine paleo-productivity variations, redox conditions of the water column during deposition, and provenance of detrital material. High sedimentary Ba/Al and Corg contents indicate enhanced primary production, whereas the sedimentary La/Lu ratio, points to an enhanced contribution from a North African riverine source, during sapropel formation. These features are especially pronounced on Sapropels S5 and S7, deposited during a particularly warm climatic interval. This indicates a more intense North African drainage/weathering and consequently run-off for those sapropels that have the most enhanced expression of productivity too. Correspondingly, the latter has also resulted in bottom water redox conditions that have been more severe during these sapropels than during others. Deepwater formation from Adriatic and Aegean areas, thought to be mainly controlled by sustained cooling of preconditioned surface waters, triggers the onset of bottomwater ventilation, thus sapropel duration. Our data, therefore, suggest that the intensity of sapropel formation is determined by the North African monsoonal system, whereas their duration is directed by northern borderlands climatic conditions.

Hydrography and water chemistry of the open Mediterranean Sea

On a cruise from the eastern into western Mediterranean Sea in November/December 1978 a total of 126 samples were collected from 8 vertical profiles and 7 coastal stations for trace metal analysis. The sampling, processing and analysis was performed under strict "clean room" conditions. The concentration of the open-sea samples are close to oceanic results gathered under similar conditions. The grand averages from all profiles (± st. dev. of the individual samples) of 0.40 ± 0.16 µg/l Zn, 17.4 ± 7.4 ng/l Cd, 0.21 ± 0.07 µg/l Cu, 0.21 ± 0.13 µg/l Mn and 0.25 ± 0.09 µg/l Fe indicate that a "metal problem" does not exist in the open Mediterranean. A biologically mediated deplition in surface waters or correlation with nutrients have not been observed under the conditions established on this cruise. This is probably due top low primary production and seasonal advection processes prevailing in this sea. The data for manganese show generally higher values in the surface layer (0-75 m) than in deep waters. This could evidently proved in the nearshore profile indicating a terrigenous source for manganese.

Physical oceanography of the GOIN project in the Mediterranean Sea (1987-1990)

This set provides 1779 CTD profiles of temperature and salinity measured with a russian "Zond-Bathometer" by the research vessels Yakov Gakkel and Vladimir Parshin, of the former Soviet Union, during 1987-1990. It is dedicated to the memory of Professor Ivan Ovchinnikov (1931-07-14 to 2000-06-10) who initiated the soviet program of research of the Mediterranean Sea and contributed significantly to the investigation of physical processes in the Mediterranean Sea.

Surface time series of nitrate, silicate and chlorophyll a (1999-2011) and CTD profiles (1999) at the PhytoCly station, Bay of Calvi, Corsica, Mediterranean Sea

This work is based on a long time series of data collected in the well-preserved Bay of Calvi (Corsica island, Ligurian Sea, NW Mediterranean) between 1979 and 2011, which include physical characteristics (31 years), chlorophyll a (chl a, 15 years), and inorganic nutrients (13 years). Because samples were collected at relatively high frequencies, which ranged from daily to biweekly during the winter-spring period, it was possible to (1) evidence the key role of two interacting physical variables, i.e. water temperature and wind intensity, on nutrient replenishment and phytoplankton dynamics during the winter-spring period, (2) determine critical values of physical factors that explained interannual variability in the replenishment of surface nutrients and the winter-spring phytoplankton bloom, and (3) identify previously unrecognized characteristics of the planktonic ecosystem. Over the >30 year observation period, the main driver of nutrient replenishment and phytoplankton (chl a) development was the number of wind events (mean daily wind speed >5 m s-1) during the cold-water period (subsurface water <13.5°C). According to winter intensity, there were strong differences in both the duration and intensity of nutrient fertilization and phytoplankton blooms (chl a). The trophic character of the Bay of Calvi changed according to years, and ranged from very oligotrophic (i.e. subtropical regime, characterized by low seasonal variability) to mesotrophic (i.e. temperate regime, with a well-marked increase in nutrient concentrations and chl a during the winter-spring period) during mild and moderate winters, respectively. A third regime occurred during severe winters characterized by specific wind conditions (i.e. high frequency of northeasterly winds), when Mediterranean "high nutrient - low chlorophyll" conditions occurred as a result of enhanced crossshore exchanges and associated offshore export of the nutrient-rich water. There was no long-term trend (e.g. climatic) in either nutrient replenishment or the winter-spring phytoplankton bloom between 1979 and 2011, but both nutrients and chl a reflected interannual and decadal changes in winter intensity.

Subsurface time series of chlorophyll a at the PhytoCly station, Bay of Calvi, Corsica, Mediterranean Sea

The development of the winter-spring phytoplankton bloom was investigated in the Bay of Calvi (Corsica, Ligurian Sea, northwestern Mediterranean) in 1979, 1986, 1988, 1997 and 1998. A drastic reduction of phytoplankton biomass was evidenced over the last 2 decades, in relation to long-term changes in climatic and environmental conditions. Between 1979 and 1998, the monthly averaged chlorophyll a concentrations at 1 m decreased by about 80% during February, March and April. Simultaneously, major changes to hydrodynamic conditions include warmer water, overall decrease of salinity at 10 m depth, longer periods of bright sunshine and lower wind stress. The changes in environmental conditions were large enough to affect the vertical stability of the water column during the winter-spring period and to reduce nutrient replenishment of the surface layer prior to the usual period of phytoplankton growth. Until 1986, the main factor driving nutrient replenishment was the winter upward mixing of nutrient-rich deep waters, while the progressive reduction of mixing from 1988 induced nutrient limitation of surface waters in the last decade. The following hypotheses on changes in the development of the winter-spring phytoplankton bloom are made: (1) Until 1986, phytoplankton peaks took place in relatively high-nutrient waters and were diatom-dominated. (2) Between 1986 and 1988, decreasing Si availability led to Si limitation which caused a reduction in diatom abundance. This resulted in the disappearance of the diatom-dominated pulses and in lower phytoplankton biomass and was accompanied by a shift toward non-siliceous phytoplankton. (3) In 1988, 1997 and 1998, decreasing nitrate availability led to nitrate limitation, thus explaining the progressive reduction in non-siliceous phytoplankton biomass. Other, associated changes in benthos assemblages and ichthyofauna are documented. The conclusions from the Bay of Calvi are extended to the whole western Corsican coast. This confirms that the Mediterranean reacts rapidly to external perturbations, which are driven by climate change in that particular area.