Impact of an intense water column mixing (0-1500 m) on prokaryotic diversity and activities during an open-ocean convection event in the NW Mediterranean Sea

Abstract. Data obtained during the monthly cruises of the DYFAMED time-series study (northwestern Mediterranean Sea) in the period 1995–2007 were compiled to examine the hydrological changes and the linked evolution of some biogeochemical characteristics. A regular increase of temperature and salinity (0.005 °C y−1, 0.0022 psu y−1) was recorded in deep waters of the NW Mediterranean Sea (2000 m depth) during 1995–2005. In February 2006 an abrupt increase in T (+0.1 °C) and S (+0.03 psu) was measured as the result of successive intense winter mixing events during the 3 previous years. The February 2006 event led to the mixing of the whole water column (0 to > 2000 m) and increased salt and heat content of the Western Mediterranean Deep Water by mixing with saltier and warmer Levantine Intermediate Water. The deficit in fresh water inputs to the western Mediterranean basin in three successive years (2003–2005) was suspected to be the major cause of this event since an increase of salinity in surface waters was monitored during these years. The measured phytoplankton biomass was specifically high after the periods of intense mixing. Chlorophyll a integrated biomass reached 230 mg m−2 in 1999, 175 mg m−2 in 2003, and 206 mg m−2 in 2006. The high levels of biomass were related to the particularly high increases in nutrients content in surface layers following the intense water column mixing and the subsequent development of a diatom bloom (as seen by fucoxanthin content). The frequency of extreme events (high mixing, high nutrients, and high biomass) increased in recent years. Our results suggested that the NW Mediterranean Sea could have an increased productivity and was not deriving towards the decreased productivity predicted by models.

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Effects of hydrostatic pressure on microbial activity through a 2000 m deep water column in the NW Mediterranean Sea

Marine Ecology Progress Series ◽

10.3354/meps183049 ◽

1999 ◽

Vol 183 ◽

pp. 49-57 ◽

Cited By ~ 19

Author(s):

O Tholosan ◽

J Garcin ◽

A Bianchi

Keyword(s):

Hydrostatic Pressure ◽

Mediterranean Sea ◽

Water Column ◽

Microbial Activity ◽

Deep Water ◽

Nw Mediterranean ◽

Nw Mediterranean Sea

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Hydrological changes in the Ligurian Sea (NW Mediterranean, DYFAMED site) during 1995–2007 and biogeochemical consequences

Biogeosciences ◽

10.5194/bg-7-2117-2010 ◽

2010 ◽

Vol 7 (7) ◽

pp. 2117-2128 ◽

Cited By ~ 81

Author(s):

J. C. Marty ◽

J. Chiavérini

Keyword(s):

Mediterranean Sea ◽

Water Column ◽

Heat Content ◽

Subsequent Development ◽

Western Mediterranean ◽

Intermediate Water ◽

Ligurian Sea ◽

Hydrological Changes ◽

Nw Mediterranean ◽

Nw Mediterranean Sea

Abstract. Data obtained during the monthly cruises of the DYFAMED time-series study (northwestern Mediterranean Sea) in the period 1995–2007 were compiled to examine the hydrological changes and the linked variation of some biogeochemical characteristics (nutrients and pigments). A regular increase of temperature and salinity (0.005 °C y−1, 0.0022 psu y−1) was recorded in deep waters of the NW Mediterranean Sea (2000 m depth) during 1995–2005. In February 2006 an abrupt increase in T (+0.1 °C) and S (+0.03 psu) was measured at 2000 m depth as the result of successive intense winter mixing events during the 3 previous years. The February 2006 event led to the mixing of the whole water column (0 to >2000 m) and increased salt and heat content of the Western Mediterranean Deep Water by mixing with saltier and warmer Levantine Intermediate Water. The deficit in fresh water inputs to the western Mediterranean basin in three successive years (2003–2005) was suspected to be the major cause of this event since an increase of salinity in surface waters was monitored during these years. The measured phytoplankton biomass was specifically high after the periods of intense mixing. Chlorophyll a integrated biomass reached 230 mg m−2 in 1999, 175 mg m−2 in 2003, and 206 mg m−2 in 2006. The high levels of biomass were related to the particularly high increases in nutrients content in surface layers following the intense water column mixing and the subsequent development of a diatom bloom (as seen by fucoxanthin content). The occurrence of extreme events (high mixing, high nutrients, and high biomass) increased in recent drought years (2003 to 2006). Our results indicated that the NW Mediterranean Sea productivity is increasing.

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Short-term dynamics of microplankton abundance and diversity in NW Mediterranean Sea during late summer conditions (DYNAPROC 2 cruise; 2004)

Biogeosciences ◽

10.5194/bg-8-743-2011 ◽

2011 ◽

Vol 8 (3) ◽

pp. 743-761 ◽

Cited By ~ 15

Author(s):

S. Lasternas ◽

A. Tunin-Ley ◽

F. Ibañez ◽

V. Andersen ◽

M.-D. Pizay ◽

...

Keyword(s):

Mediterranean Sea ◽

Water Column ◽

Late Summer ◽

Taxonomic Composition ◽

Marine Phytoplankton ◽

Pigment Analysis ◽

Phytoplankton Communities ◽

Nw Mediterranean ◽

Nw Mediterranean Sea ◽

Abundance And Diversity

Abstract. Changes in marine phytoplankton communities at short-time scales have rarely been examined. As a part of the DYNAPROC 2 cruise (14 September–17 October 2004), conducted in the NW Mediterranean Sea, we daily sampled and determined taxonomic composition and abundance of the microphytoplankton and the dominant microzooplanktonic groups from both net and bottle sampling, during 4 cycles of 5 days. Hydrological conditions were characterised by the dominance of a stratified water column and nutrient-depleted conditions. However the stratification index revealed a destabilization of the water column from the beginning of the second cycle, related to a wind stress event accompanied with coastal water intrusion. This conducted to an increase of taxonomic richness and a general decrease of evenness, depicting the dominance of species with the best fitness. We also emphasised on the great interest of taxonomic studies, as able to provide valuable information on biogeochemical-important groups of species, potential water masses indicators and trophic aspects of the community that are ignored or largely underestimated with other kind of phytoplankton studies, such as pigment analysis.

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Distributions of carbonate properties and oxygen along the water column (0–2000m) in the central part of the NW Mediterranean Sea (Dyfamed site): influence of winter vertical mixing on air–sea CO2 and O2 exchanges

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/s0967-0645(02)00027-9 ◽

2002 ◽

Vol 49 (11) ◽

pp. 2049-2066 ◽

Cited By ~ 44

Author(s):

Claire Copin-Montégut ◽

Milena Bégovic

Keyword(s):

Mediterranean Sea ◽

Water Column ◽

Vertical Mixing ◽

Nw Mediterranean ◽

Nw Mediterranean Sea

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Role of environmental factors for the vertical distribution (0–1000 m) of marine bacterial communities in the NW Mediterranean Sea

Biogeosciences ◽

10.5194/bg-5-1751-2008 ◽

2008 ◽

Vol 5 (6) ◽

pp. 1751-1764 ◽

Cited By ~ 40

Author(s):

J. F. Ghiglione ◽

C. Palacios ◽

J. C. Marty ◽

G. Mével ◽

C. Labrune ◽

...

Keyword(s):

Community Structure ◽

Bacterial Community ◽

Mediterranean Sea ◽

Water Column ◽

Bacterial Communities ◽

Bacterial Community Structure ◽

Sampling Period ◽

Nw Mediterranean ◽

Nw Mediterranean Sea ◽

Bacterial Assemblages

Abstract. Bacterioplankton plays a central role in energy and matter fluxes in the sea, yet the factors that constrain its variation in marine systems are still poorly understood. Here we use the explanatory power of direct multivariate gradient analysis to evaluate the driving forces exerted by environmental parameters on bacterial community distribution in the water column. We gathered and analysed data from a one month sampling period from the surface to 1000 m depth at the JGOFS-DYFAMED station (NW Mediterranean Sea). This station is characterized by very poor horizontal advection currents which makes it an ideal model to test hypotheses on the causes of vertical stratification of bacterial communities. Capillary electrophoresis single strand conformation polymorphism (CE-SSCP) fingerprinting profiles analyzed using multivariate statistical methods demonstrated a vertical zonation of bacterial assemblages in three layers, above, in or just below the chlorophyll maximum and deeper, that remained stable during the entire sampling period. Through the use of direct gradient multivariate ordination analyses we demonstrate that a complex array of biogeochemical parameters is the driving force behind bacterial community structure shifts in the water column. Physico-chemical parameters such as phosphate, nitrate, salinity and to a lesser extent temperature, oxygen, dissolved organic carbon and photosynthetically active radiation acted in synergy to explain bacterial assemblages changes with depth. Analysis of lipid biomarkers of organic matter sources and fates suggested that bacterial community structure in the surface layers was in part explained by lipids of chloroplast origin. Further detailed analysis of pigment-based phytoplankton diversity gave evidence of a compartmentalized influence of several phytoplankton groups on bacterial community structure in the first 150 m depth.

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